JP2020156439A - Conversion method of farmland - Google Patents

Abstract

To provide a conversion method of farmland converting farmland from a dry field to a paddy field by using a water level adjustment system considering soil preparation.SOLUTION: A conversion method of farmland converting farmland used as a dry field to a paddy field comprises: a water level raising step of raising an underground water level using a water level adjustment system including a culvert pipe disposed at the underground of the farmland and forming a plurality of open holes at the circumference thereof, a sluice connected to the culvert pipe and adjusting the underground water level by use of the head pressure, and a feed part supplying the farmland with water; a seepage water reduction step performed after the water level raising step in which a ground surface of the dry field is compressed to reduce seepage water under the dry field; and a water supply step performed after the seepage water reduction step in which water is supplied to the ground surface by using the water level adjustment system.SELECTED DRAWING: Figure 9

Description

The present invention relates to a conversion method.

In recent years, agriculture has shifted significantly toward labor saving through mechanization and reduction of production costs by reducing chemical fertilizers and pesticides, reflecting the shortage of farmers, sluggish rice prices, and growing consumer safety preferences.
Under such circumstances, cost reduction of materials related to "soil preparation", whose effect is difficult to confirm in a short period of time, continues. The impact of this cost reduction is unlikely to become apparent in the short term, but as the period of cost reduction for soil prolongs, it is beginning to cast a shadow over recent agricultural production with significant climate variability, and it is expected that it will eventually become apparent. To.

Here, in Patent Document 1, as a method for converting a fallow field into a field, a porous body obtained by carbonizing solid waste fuel, which has been processed into a predetermined shape through crushing, drying and molding of waste, is described. A method of sprinkling a fallow field and then mixing and treating the sprinkled porous body and the surface layer portion of the fallow field is disclosed.
Further, in Patent Document 2, as a method of converting a poorly drained area such as a fallow field into a field, when improving the drainage property of the soil in a poorly drained area such as a fallow field to make a field, the area under the soil layer is described. Porous medium with a diameter of 2 mm or more, obtained by digging a hole and classifying the charcoal produced by drying and distilling solid waste fuel, which has been processed into a predetermined shape through crushing, drying and molding of waste in the hole. A method of covering a plurality of bodies with soil after charging a carbon-based water permeable body formed by connecting and integrating them with a binder is disclosed.
Further, Patent Document 3 has a subsoil having a function of pressing the side wall of a drilling ditch as a work method suitable for converting a paddy field into a field or improving a wet field into a dry field, thereby making a hydrophobic material. A filling groove for charging the material core material as one is formed, the material core material is charged while moving into the filling groove, and this is compressed from above by the compression ring moving in the filling groove. At the same time, it is disclosed that the soil is improved by forming a consolidated water-retaining layer in the soil layer by compressing it by the restored earth pressure of the side wall of the drilling ditch.

Japanese Unexamined Patent Publication No. 2003-41254 Japanese Unexamined Patent Publication No. 2003-261871 JP-A-2006-230417

The techniques of Patent Documents 1 to 3 described above do not convert farmland from farmland to paddy field in the first place.
By the way, the inventor of the present application judges that the situation where the cost is reduced in the above-mentioned "soil preparation" is "agricultural crisis", and it is not possible to continuously carry out "soil preparation". I think it is extremely important for future agriculture. In particular, we believe that it is important to promote agricultural production with excellent cost performance in consideration of the "three elements of physical, chemical and biological" necessary for revitalization of the mainland.
The techniques of Patent Documents 1 to 3 described above do not convert farmland from farmland to paddy field in the first place. Furthermore, these techniques are not proposals that take into account the "three elements of physicality, chemicality, and biologicalness" proposed by the inventor of the present application. Therefore, the above-mentioned techniques of Patent Documents 1 to 3 cannot realize the agricultural production proposed by the inventor of the present application.

An object of the present invention is to provide a farmland conversion method for converting farmland from farmland to paddy field by using a water level adjustment system in consideration of soil preparation.

The farmland conversion method of the first aspect of the present invention is a farmland conversion method for converting farmland used as upland into paddy fields, and is an underdrain that is arranged underground of the farmland and has a plurality of through holes formed on the outer periphery. The underground water level is adjusted by using a pipe, a water bar connected to the underdrain pipe and adjusting the underground water level using the head pressure, and a water level adjustment system provided with a supply unit for supplying water to the farm ground. A step of raising the water level and a step performed after the step of raising the water level, after the step of reducing the seepage water by pressurizing the ground of the field to reduce the seepage water under the field and the step of reducing the seepage water. This step includes a water supply step of supplying water onto the ground using the water level adjusting system.

The farmland conversion method of the second aspect of the present invention is the farmland conversion method, and in the seepage water reduction step, the ground of the field is pressurized by tightening the floor with a heavy machine.

The farmland conversion method according to the third aspect of the present invention is the farmland conversion method, and in the permeation water reduction step, the field is further scratched.

The farmland conversion method according to the fourth aspect of the present invention is the farmland conversion method, which is a step performed after the seepage water reduction step and before the water supply step, and the seepage water is generated in the seepage water reduction step. It includes an analysis step of performing a soil analysis of the reduced soil to identify the nutrients required to utilize the soil with reduced seepage water for paddy fields and the required amount of such nutrients.

The farmland conversion method according to the fifth aspect of the present invention is the farmland conversion method, in which the soil analysis is performed after removing residual nitrogen from the soil in which the seepage water has decreased.

The sixth aspect of the farmland conversion method of the present invention is the farmland conversion method, which is performed by scraping the soil with reduced seepage water.

The farmland conversion method according to the seventh aspect of the present invention is the farmland conversion method, which is a step performed after the analysis step and before the water supply step, and the seepage water is reduced in the seepage water reduction step. The fertilizer mixing step of mixing the soil with fertilizer corresponding to the required nutrient in the required amount specified in the analysis step is included.

The farmland conversion method according to the eighth aspect of the present invention is the farmland conversion method, and the fertilizer contains silicic acid.

The farmland conversion method according to the ninth aspect of the present invention is the farmland conversion method, in which the content of effective silicic acid in dry soil per 100 g is 20 mg or more in the soil mixed with the fertilizer.

The farmland conversion method according to the tenth aspect of the present invention is the farmland conversion method, wherein the content of humus in the soil mixed with the fertilizer is 3% by mass or more.

The farmland conversion method according to the eleventh aspect of the present invention is the farmland conversion method, and the fertilizer contains humic acid.

The farmland conversion method according to the twelfth aspect of the present invention is the farmland conversion method, which is a step performed after the fertilizer mixing step and before the water supply step, and lime nitrogen is sprayed on the residue of the field. The recharge step of cultivating the residue to which the lime nitrogen is sprayed together with the soil mixed with the fertilizer to recharge the soil fertilizer is included.

The farmland conversion method according to the thirteenth aspect of the present invention is the farmland conversion method, which is a step performed after the water supply step, and scratches the ground so that the water reduction depth per day is 2 cm to 3 cm. Includes a water reduction depth adjustment step.

The farmland conversion method according to the 14th aspect of the present invention is the farmland conversion method, and in the water level raising step, the underground water level by the water bar is adjusted so as to be at a depth of 50 cm or less from the ground. ..

The present invention provides a farmland conversion method for converting farmland from farmland to paddy field using a water level adjustment system in consideration of soil preparation.

It is a schematic diagram which shows the state which one farmland of two farmlands is used as a paddy field, and the other farmland is used as a field by using the groundwater level adjustment system of this embodiment. It is an overall view (schematic view) of the water lock of this embodiment. It is an overall view (schematic view) of the take-out member constituting the water lock of this embodiment. It is a partial cross-sectional view of the lower part of the water lock of this embodiment. It is a figure for demonstrating the state in which the slide cylinder which comprises the water lock of this embodiment is slid and fixed to the outer cylinder. It is a figure for demonstrating the state in which the telescopic cylinder (bellows) constituting the take-out member of this embodiment is expanded and contracted. It is a partial cross-sectional view of the lower part of the water stake of this embodiment, and is the figure for demonstrating the state (set state) in which the taking-out member is arranged in contact with an outer cylinder. It is a partial cross-sectional view of the lower part of the water shackle of this embodiment, and is the figure for demonstrating the state (offset state) which separated the taking-out member from an outer cylinder. It is an overall view (schematic view) of the water lock of this embodiment, and is the figure for demonstrating the state at the time of use. It is a partial cross-sectional view of the lower part of the water lock of this embodiment, and is the figure for demonstrating the flow of water at the time of use. It is a figure for demonstrating the case where the farmland is used as a paddy field and the case where the farmland is used as a field by using the water lock of this embodiment. It is a figure for demonstrating the flushing performed by moving the taking-out member of the water shackle of this embodiment from the position of a set state to the position of an offset state. It is a figure for demonstrating the movement of water of a farmland at the time of flushing described with FIG. 2K. It is a perspective view of the drainage device which comprises the groundwater level adjustment system of this embodiment. It is a side view of the drainage device of this embodiment. It is a figure in the case where the drainage device of this embodiment is used for a paddy field, and is the figure of the state in which water overflows from the drainage device arranged adjacent to the paddy field. It is a figure when the drainage device of this embodiment is used for a paddy field, and is the figure of the state which maintains the water level of a paddy field at a set water level which has a drainage device arranged adjacent to a paddy field. Is. It is a figure when the drainage device of this embodiment is used for a paddy field, and the drainage device arranged adjacent to the paddy field maintains the water level of the paddy field at a set water level lower than that in the case of FIG. 4B. It is a figure of the state of doing. It is a figure in the case where the drainage device of this embodiment is used for a paddy field, and is the figure of the state in which the drainage device arranged adjacent to the paddy field sets the set water level to 0 cm. It is a figure when the drainage device of this embodiment is used for a field. It is a figure when the drainage device of this embodiment is used for a field, and is the figure of the state which the drainage device constitutes a part of a culvert. It is a figure in the case where the drainage device of this embodiment is used for a field, and is the figure of the state in which the drainage device opens the earth retaining plate and drains the water from the culvert. It is an enlarged view of the part including the sluice and the drainer of the irrigation device used for the paddy field of FIG. It is a flow chart of the conversion method of this embodiment. It is a flow chart of a part of the conversion method of this embodiment (method of converting from paddy field to upland). It is a flow chart of a part of the conversion method (method of converting from a field to a paddy field) of this embodiment. It is a figure for demonstrating the characteristic of paddy soil and upland soil.

≪Overview≫
Hereinafter, a method of converting farmland from paddy field PF to upland TF or from upland TF to paddy field PF in this embodiment (hereinafter referred to as a conversion method of this embodiment) will be described with reference to the drawings. Here, as an example, the conversion method of the present embodiment is referred to as a water level adjusting system 10 (hereinafter, also referred to as a groundwater level adjusting system 10) or a water level adjusting device 20 (hereinafter, referred to as a groundwater level adjusting device 20) shown in FIG. It may be carried out using). Therefore, first, the function and configuration of the groundwater level adjusting system 10 of the present embodiment will be described. Next, the conversion method of the present embodiment will be described. The action and effect of this embodiment will be described in the description of the conversion method of this embodiment.
In all the drawings referred to in the following description, similar components are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

≪Overview≫
Hereinafter, the groundwater level adjustment system 10 (see FIG. 1) of the present embodiment will be described. First, the function and configuration of the groundwater level adjustment system 10 of the present embodiment will be described. Next, the action and effect of this embodiment will be described. In all the drawings referred to in the following description, similar components are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

≪Function and configuration of groundwater level adjustment system≫
In FIG. 1, using the groundwater level adjustment system 10 of the present embodiment, one farmland FL of two farmland FLs sandwiching the ridge RD is used as a paddy field PF, and the other farmland FL is used as a field TF. It is the schematic which shows the state which is. The groundwater level adjustment system 10 of the present embodiment easily adjusts the water levels of a plurality of (two locations in FIG. 1) farmland FL (water level on farmland FL and underground water level of farmland FL), and crops FP1 and FP2 ( The crop FP1 has a function of managing the water level according to the growth stage of rice (as an example, the crop FP2 is a vegetable such as wheat). In the following, one of the two farmland FLs will be described with reference to FIG. 1, which is an example of a state in which one farmland FL is used as a paddy field PF and the other farmland FL is used as a field TF. The groundwater level adjustment system 10 of the embodiment may utilize both of the two farmland FLs as paddy field PF or field TF.

As shown in FIG. 1, the groundwater level adjusting system 10 of the present embodiment includes a plurality of (two in FIG. 1) groundwater level adjusting devices 20 and a drainage pipe 30 as an example. The drainage pipe 30 is a liquid path into which water W (an example of a liquid) flowing out from each groundwater level adjusting device 20 flows in.

<Groundwater level adjustment device>
As shown in FIG. 1, each groundwater level adjusting device 20 includes a water lock 22, a supply mass 24 (an example of a supply unit), a waterway 26 in a farmland (an example of a waterway unit), and a drainage device 28. 29A and 29B (an example of a transportation pipe) are provided. A plurality of components (water lock 22, supply mass 24, farmland waterway 26, drainage device 28 and a plurality of outflow waterways 29A, 29B) constituting each groundwater level adjusting device 20 constitute a ridge RD and farmland FL. It is buried or fixed in the soil SO. While the groundwater level adjusting system 10 of the present embodiment has a function of managing the water level of a plurality of farmland FLs, each groundwater level adjusting device 20 of the present embodiment easily adjusts the water level of each farmland FL. It has a function of managing the water level according to the growth stage of crop FP1 or crop FP2.
Hereinafter, a plurality of components constituting each groundwater level adjusting device 20 will be described.

[Water lock]
The water level 22 of the present embodiment has a function of easily adjusting the water level of the farmland FL (the water level on the farmland FL and the water level under the farmland FL) by utilizing the head pressure. As shown in FIGS. 1, 2J, 2L and 6, the water rod 22 of the present embodiment is provided on the ridge RD so that the upper end thereof is substantially the same as the position of the surface (upper surface) of the ridge RD. It is supposed to be buried. Here, "substantially the same" in the present specification means, for example, about ± 5 cm in the vertical direction with respect to the surface of the ridge RD. In the drawing, the direction indicated by the arrow X is the vertical direction, the direction indicated by the symbol + X means the upper side in the vertical direction, and the direction indicated by the symbol −X means the lower side.

FIG. 2A is an overall view (schematic view) of the water lock 22 of the present embodiment. Further, FIG. 2B is an overall view (schematic view) of the take-out member 250 constituting the water lock 22 of the present embodiment.
As shown in FIGS. 2A and 2B, the water lock 22 of the present embodiment includes an outer cylinder 200, an inflow portion 210, an outflow portion 220, a slide cylinder 230, a lid 240, and a take-out member 250. ing.
Further, the water lock 22 of the present embodiment is, as a basic configuration, a bottomed cylinder embedded in the ridge RD with the bottom wall 204 facing downward, and is located at different positions in the vertical direction on the peripheral wall 202. An inflow portion fixed to the outer cylinder 200 in which the two through holes 206A and 206B are formed and the upper through hole 206A of the two through holes 206A and 206B to allow water W to flow from the outside to the inside of the outer cylinder 200. 210, an outflow portion 220 fixed to the lower through hole 206B of the two through holes 206A and 206B to allow water W to flow out from the inside, and a cylinder housed inside, from the inflow portion 210. At the same position as the outflow portion 220 on the lower side and away from the bottom wall 204 or at a position above the outflow portion 220, the lower end portion is in contact with the peripheral wall 202 over the entire circumference in the circumferential direction, and is expandable and contractible in the vertical direction. It includes a cylinder 252, a slide cylinder 230 that fits into the upper portion of the outer cylinder 200 and is slidable, and a lid 240 that is attached to the slide cylinder 230 and can open and close the upper opening of the slide cylinder 230. .. The slide cylinder 230 is positioned so that the vertical position of the lid 240 in the state where the opening is closed is substantially the same as the position of the surface of the ridge RD, and the upper end of the middle cylinder 252 is adjacent to the ridge RD. It is adjusted to the length that is the position of the water level required for the farmland FL.

<Outer cylinder>
The outer cylinder 200 is a bottomed cylinder (bottomed cylinder). That is, the outer cylinder 200 has a peripheral wall 202 and a bottom wall 204. The outer cylinder 200 has a cylindrical shape as an example. The outer cylinder 200 is embedded in the ridge RD with the bottom wall 204 on the lower side in the vertical direction (see FIGS. 1, 2A, etc.). Further, two through holes 206A and 206B are formed on the lower side of the peripheral wall 202 in the vertical direction, that is, the portion on the bottom wall 204 side (see FIG. 2C). The through hole 206A and the through hole 206B are formed at different positions in the vertical direction on the peripheral wall 202, that is, at positions offset in the vertical direction. As an example, the through hole 206A and the through hole 206B are opened in opposite directions in the radial direction of the peripheral wall 202.
The through hole 206A and the through hole 206B may be formed at different positions in the vertical direction on the peripheral wall 202, and may not be opened in opposite directions in the radial direction of the peripheral wall 202. Further, as shown in FIG. 2C, an inner wall 208 having an inner peripheral surface 208A whose diameter gradually decreases from the upper side to the lower side in the vertical direction is provided in the lower portion of the outer cylinder 200 in the vertical direction. Has been done. The technical meaning of the inner peripheral surface 208A will be described later.

<Inflow and outflow>
The inflow portion 210 is fixed to the upper through hole 206A in the vertical direction of the two through holes 206A and 206B, and is a member for allowing water W to flow from the outside of the outer cylinder 200 to the inner IS (FIG. 2A). , FIG. 2H, FIG. 2I, etc.). The inflow portion 210 has a tubular shape, and a portion on one end side thereof is fixed to the peripheral wall 202 of the outer cylinder 200 in a state of being fitted into the through hole 206A. The other end of the inflow portion 210 is connected to the waterway 26 in the farmland, which will be described later (see FIG. 1).
Further, the outflow portion 220 is fixed to the lower through hole 206B in the vertical direction among the two through holes 206A and 206B, and is a member for allowing water W to flow out from the internal IS of the outer cylinder 200 to the outside. (See FIGS. 2A, 2H, etc.). The outflow portion 220 has a tubular shape, and a portion on one end side thereof is connected to the peripheral edge of the through hole 206B in the upper part of the bottom wall 204 of the outer cylinder 200. The other end of the outflow portion 220 is connected to the outflow channel 29A, which will be described later (see FIG. 1).

<Slide tube and lid>
As an example, the slide cylinder 230 is a cylinder with both ends open. As shown in FIG. 2A, the slide cylinder 230 is arranged in the upper portion of the outer cylinder 200 in the vertical direction. Further, the slide cylinder 230 is fitted in a state where the outer peripheral surface of the outer cylinder 200 faces the inner peripheral surface thereof, and is slidable with respect to the outer cylinder 200 (see FIG. 2D). The slide cylinder 230 is fixed to the outer cylinder 200 by a fixing member (not shown) such as a screw within a slidable range. A female screw (not shown) for fixing the lid 240, which will be described later, is formed on the inner circumference of the upper end portion of the slide cylinder 230.
The lid 240 is attached to the slide cylinder 230 so that the upper opening of the slide cylinder 230 in the vertical direction can be opened and closed. A male screw (not shown) that fits with the female screw of the slide cylinder 230 is formed on the outer circumference of the lid 240.
With the above configuration, the slide cylinder 230 to which the lid 240 is attached (see FIG. 2A), that is, the slide cylinder 230 in a state where the opening of the upper end portion is closed by the lid 240, is the lid 240 as shown in FIG. The position in the vertical direction (the position of the upper end of the slide cylinder 230) is positioned to be substantially the same as the position of the surface (upper surface) of the ridge RD.

<Removal member>
As shown in FIG. 2A, the take-out member 250 is accommodated in the outer cylinder 200 and the internal IS formed by the slide cylinder 230 fitted in the outer cylinder 200, and the take-out member 250 is accommodated in the outer cylinder 200 and the take-out member 250. It is a member that can be taken out from the internal IS of the outer cylinder 200 and the slide cylinder 230. FIG. 2B is an overall view (schematic view) of the take-out member 250 taken out from the inner IS of the outer cylinder 200 and the slide cylinder 230. The take-out member 250 has a middle cylinder 252 and a shaft portion 254 as shown in FIG. 2B.

(Middle cylinder)
The middle cylinder 252 is housed in the inner IS of the outer cylinder 200 and the slide cylinder 230, and can be expanded and contracted in the vertical direction. The middle cylinder 252 is adjusted to a length whose upper end is the position of the water level required for the farmland FL adjacent to the ridge RD (see FIG. 1).
As shown in FIG. 2B, the middle cylinder 252 has a telescopic cylinder 252A, a lower cap 252B, an upper cap 252C, and a fixing screw 252D.

As an example, the telescopic cylinder 252A has both ends open and the peripheral wall is a bellows that can be expanded and contracted, as shown in FIGS. 2A and 2B.

The lower cap 252B is attached to the lower portion of the telescopic cylinder 252A in the vertical direction. Although the lower cap 252B is a columnar member in appearance (see FIGS. 2B and 2C), it is fixed to a hollow shaft 254A described later while penetrating in the vertical direction.
Further, a part of the lower cap 252B is an elastic member 252B1 whose diameter gradually decreases from the upper side to the lower side in the vertical direction. Here, in the present embodiment, the elastic member 252B1 is made of rubber as an example. When the middle cylinder 252 is used, the elastic member 252B1 which is the lower end of the telescopic cylinder 252A is in contact with the inner peripheral surface 208A of the inner wall 208 which is a part of the outer cylinder 200 over the entire circumference in the circumferential direction. , It is held in the outer cylinder 200 (see FIG. 2C). In this case, the position of the lower cap 252B in the vertical direction is lower than the upper through hole 206A in the vertical direction among the two through holes 206A and 206B formed in the outer cylinder 200 and the bottom wall of the outer cylinder 200. It is set to be at the same position as the through hole 206B separated from 204 or above the through hole 206B. That is, in this case, the vertical position of the lower cap 252B is set to be lower than the inflow portion 210 and above the outflow portion 220 separated from the bottom wall 204 of the outer cylinder 200. ..

The upper cap 252C is attached to the upper portion of the telescopic cylinder 252A in the vertical direction as shown in FIGS. 2A and 2B. Although the upper cap 252C is a columnar member in appearance (see FIGS. 2B and 2E), the upper cap 252C is fixed to the hollow shaft 254A, which will be described later, by the fixing screw 252D while penetrating in the vertical direction. It has become. Specifically, the upper cap 252C has the shaft adjusted to the length of the middle cylinder 252 at which the upper end of the middle cylinder 252 (the upper end of the upper cap 252C) is the position of the water level required for the farmland FL. It is designed to be fixed to the part.

(Shaft part)
The shaft portion 254 has a hollow shaft 254A, a slide shaft 254B, and a fastener 254C, as shown in FIG. 2B.

The hollow shaft 254A is fixed to the lower cap 252B as described above. In this case, the hollow shaft 254A is arranged at a position overlapping the shaft of the middle cylinder 252. The hollow shaft 254A is fixed to the lower cap 252B so that its lower end does not protrude downward from the lower cap 252B. Further, the length of the hollow shaft 254A is set to be longer than the length of the middle cylinder 252 in the state where the telescopic cylinder 252A is extended to the maximum length. Therefore, the hollow shaft 254A protrudes from the upper end of the middle cylinder 252 (the upper end of the upper cap 252C) regardless of the expansion / contraction length of the expansion / contraction cylinder 252A. In other words, a part of the hollow shaft 254A is arranged in the internal IS of the inner cylinder 252.

The slide shaft 254B is fitted inside the hollow shaft 254A and is slidable with respect to the hollow shaft 254A (see FIGS. 2B and 2E). Further, the slide shaft 254B can be fixed to the hollow shaft 254A by using the fixing member 254D.
The slide shaft 254B is usually fixed to the hollow shaft 254A in a state where the position of the lower end thereof is aligned with the position of the lower end of the hollow shaft 254A. On the other hand, when the slide shaft 254B is fixed at a predetermined position lower than the normal state, the hollow shaft 254A is in contact with the bottom wall 204 of the outer cylinder 200 and supported by the bottom wall 204. It is designed to support (see Fig. 2G). Along with this, the outer peripheral portion of the elastic member 252B1 of the slide shaft 254B is separated from the inner peripheral surface 208A of the inner wall 208 (see FIG. 2G).

[Supply mass]
Next, the supply mass 24 of the present embodiment will be described with reference to FIG. The supply mass 24 has a function of storing the water W supplied from the main liquid supply pipe MS and a function of supplying the stored water W to the farmland FL (paddy field PF). The supply mass 24 is connected to the main liquid supply pipe MS buried underground. In this embodiment, the supply mass 24 is arranged on the opposite side of the water lock 22 with the farmland FL in between.

[Waterways in farmland]
Next, the waterway 26 in the farmland of the present embodiment will be described with reference to FIG. The waterway 26 in the farmland connects the inflow portion 210 of the water lock 22 and the supply mass 24, and is used as a waterway for transporting water W from the supply mass 24 to the inflow portion 210. A part of the waterway 26 in the farmland is an underdrain pipe 26A arranged underground in the farmland FL. A plurality of through holes are formed on the outer periphery of the underdrain pipe 26A.

[Drainer]
Next, the drainage device 28 of the present embodiment will be described with reference to FIGS. 1, 3A and 3B. Here, FIG. 3A is a perspective view of the drainer 28, and FIG. 3B is a side view of the drainer 28.
As a basic configuration, the drainage device 28 of the present embodiment is arranged on the bottom plate 300, a pair of facing walls 310 arranged on both ends in the width direction of the bottom plate 300, and one end side in the depth direction of the bottom plate 300. It has a connecting wall 320 in which a through hole 322 is formed to connect the facing walls 310 to each other and allow water W flowing out to the drainage pipe 30 to pass through, and the other end side of the bottom plate 300 in the depth direction is directed toward the farmland FL. In the depth direction of the bottom plate 300, the main body 360 which is arranged adjacent to the farmland FL in the state, the shutter 330 which is arranged in the center of the bottom plate 300 in the depth direction and can slide up and down to change the position of the upper end. It is provided with an earth retaining plate 340 supported by a pair of facing walls 310 on the opposite side of the connecting wall 320 with the shutter 330 in between.
As shown in FIG. 1, the drainage device 28 of the present embodiment is arranged adjacent to the paddy field PF when the farmland FL is used as the paddy field PF, and is a culvert when the farmland FL is used as the upland TF. It is arranged at a position adjacent to the culvert OD on the opposite side of the paddy field TF with the OD in between. The drainage device 28 of the present embodiment has a function of adjusting the water level of the water W of the paddy field PF when the farmland FL is used as the paddy field PF, and from the culvert OD when the farmland FL is used as the field TF. It has a function of draining water W.

Further, the drainage device 28 of the present embodiment has the following functions when the farmland FL is used as a paddy field PF and is installed in the same paddy field PF together with the above-mentioned water lock 22.
That is, when the water level of the water W of the paddy field PF becomes higher (higher) than the water level set by the water lock 22 for some reason (for example, heavy rain), the drainer 28 sets the water level of the water W of the paddy field PF according to the setting. It has a function of preventing the water level from being above the defined water level (see the broken line drawn at the upper end of the second plate 334 in FIG. 6).

As shown in FIGS. 3A and 3B, the drainage device 28 of the present embodiment has a box shape in which a space is formed, and includes a bottom plate 300, a pair of facing walls 310, and a connecting wall 320. A shutter 330, an earth retaining plate 340, and an outflow portion 350 (an example of a connection portion) are provided. Here, the direction indicated by the arrow Z in the drawing is the depth direction of the drainage device 28, the direction indicated by the reference numeral + Z is the front side in the depth direction, and the direction indicated by the reference numeral −Z is the depth side. Further, the direction indicated by the arrow Y is the width direction of the drainage device 28, the direction indicated by the reference numeral + Y is the front side in the width direction, and the direction indicated by the reference numeral −Y is the back side in the width direction.
Hereinafter, the outline of each component (bottom plate 300, pair of facing walls 310, etc.) of the drainage device 28 will be described, and then the details of each component will be described.

(Overview of each component of the drainer)
The bottom plate 300 has a rectangular shape when viewed from above and below (see FIG. 3A).
The pair of facing walls 310 are arranged at both ends in the width direction of the bottom plate 300, and project from the upper surface of the bottom plate 300 to the upper side in the vertical direction and face each other (see FIGS. 3A and 3B).
The connecting wall 320 is arranged at the end of the bottom plate 300 on the depth side in the depth direction, and connects the ends of the bottom plate 300 on the depth side of each of the facing walls 310 constituting the pair of facing walls 310 (FIG. 3A). reference).
The shutter 330 is arranged in the center of the bottom plate 300 in the depth direction, and is fitted into a pair of facing walls 310 on both sides (both ends in the width direction of the bottom plate 300) and supported by the pair of facing walls 310 in the vertical direction. It is slidable (see FIGS. 3A and 4A-4D).
The earth retaining plate 340 is arranged at the end of the bottom plate 300 on the front side (opposite side of the connecting wall 320 with the shutter 330 in between) in the depth direction, and is supported by a pair of facing walls 310 (see FIG. 3A). The height (length in the vertical direction) of the earth retaining plate 340 is set lower (shorter) than the height (length in the vertical direction) of the pair of facing walls 310 and the connecting wall 320 (FIG. 3A). reference).
The outflow portion 350 has a cylindrical shape and is arranged so as to project further toward the depth side from the depth side surface of the bottom plate 300 in the connecting wall 320 in the depth direction, and is formed on the connecting wall 320 described later when viewed from the depth direction of the bottom plate 300. It surrounds the formed through hole 322 (see FIG. 3B).

As described above, the drainer 28 of the present embodiment forms an internal space surrounded by the bottom plate 300, the pair of facing walls 310, the connecting wall 320, and the earth retaining plate 340, and forms the bottom plate 300. A box is formed in which the front side in the depth direction and the upper portion in the vertical direction are open, and the back side is opened by the above-mentioned through hole 322. Further, the shutter 330 partitions the internal space at the center of the bottom plate 300 in the depth direction.
The drainage device 28 of the present embodiment is arranged so that the front side of the bottom plate 300 in the depth direction, that is, the earth retaining plate 340 side faces the farmland FL (see FIG. 1). Specifically, the drainage device 28 is arranged in a state where the earth retaining plate 340 is adjacent to the end of the paddy field PF when the farmland FL is used as the paddy field PF, and when the farmland FL is used as the field TF. Is arranged so that the earth retaining plate 340 is adjacent to the end of the culvert OD. Further, in the present embodiment, the combination of the bottom plate 300, the pair of facing walls 310, and the outflow portion 350 (an example of the main body 360) is, for example, an integrally formed hollow molded product. Further, the combination is formed of a resin such as polyethylene as an example.

Next, the details of each component of the drainage device 28 will be described.
(Bottom plate and pair of facing walls)
As described above, the bottom plate 300 has a rectangular shape when viewed from the vertical direction (see FIG. 3A).
On the front side of the bottom plate 300 in the depth direction and the upper portion in the vertical direction of the pair of facing walls 310, an inclined surface 314 that gradually approaches the front side in the depth direction of the bottom plate 300 from the upper end in the vertical direction toward the center side. Is formed. Therefore, each facing wall 310 has a shape in which the peripheral portion of one corner of the rectangular plate is cut out diagonally when viewed from the front side in the width direction of the bottom plate 300 (see FIG. 3B). ..
On the outer surface of each facing wall 310 in the width direction of the bottom plate 300, a plurality of (two as an example) recesses 312 are formed along the depth direction of the bottom plate 300. The two recesses 312 are linear along the vertical direction. In the present embodiment, of the two recesses 312, the length of the recess 312 on the front side in the depth direction of the bottom plate 300 is set to be shorter than the length of the recess 312 on the back side.
Further, a recess (not shown) for supporting the shutter 330 and the earth retaining plate 340 is formed on the inner surface of each facing wall 310 in the width direction of the bottom plate 300.

(Connecting wall and outflow part)
As described above, the connecting wall 320 connects the ends on the depth side of the bottom plate 300 in each facing wall 310 constituting the pair of facing walls 310 (see FIG. 3A). A circular through hole 322 is formed in the center of the connecting wall 320 in the width direction and the lower portion in the vertical direction of the bottom plate 300.
The outflow portion 350 is surrounded by the through hole 322 when viewed from the depth direction of the bottom plate 300, and projects further to the back side from the depth side surface of the bottom plate 300 in the depth direction of the connecting wall 320 (see FIG. 3B). ). A male screw for attaching the outflow channel 29B is formed on the outer peripheral surface of the outflow portion 350 (see FIG. 3B).

(shutter)
The shutter 330 is composed of two plates. Then, in the present embodiment, of the two plates, the plate arranged on the front side of the bottom plate 300 in the depth direction is referred to as the first plate 332, and the other plate is referred to as the second plate 334 (FIGS. 3A and 3A). See FIG. 3B). The second plate 334 is arranged on the back side of the bottom plate 300 in the depth direction in a state where at least a part of its own surface is in contact with the back surface of the first plate 332. The first plate 332 and the second plate 334 are slidable in the vertical direction while being supported by a pair of facing walls 310, respectively.
Further, a plurality of (three as an example) recesses 332A are formed on the front surface of the bottom plate 300 in the depth direction of the first plate 332. Each recess 332A has a linear shape along the width direction of the bottom plate 300 and is arranged in the vertical direction.

(Retaining board)
As described above, the earth retaining plate 340 is supported by a pair of facing walls 310 and can slide in the vertical direction. Specifically, the earth retaining plate 340 is slidable so that it can be attached to and detached from the pair of facing walls 310. Further, the earth retaining plate 340 is formed with a plurality of (two as an example) recesses 340A (see FIG. 3A). The two recesses 340A are linear along the width direction of the bottom plate 300 and are arranged in the vertical direction. In the present embodiment, it is assumed that a plurality of recesses 340A are formed in the earth retaining plate 340, but a plurality of through holes (not shown) may be formed instead of the plurality of recesses 340A.

In the drainage device 28 of the present embodiment, when the farmland FL is used as the field TF, the bottom plate 300 is located on the front side (earth retaining plate) of the bottom plate 300 in the depth direction on the culvert OD (see FIG. 5A, etc.) adjacent to the field TF. By forming a part of the culvert OD (a part of the side wall of the culvert OD) along the 340 side), it can be used as a drainage device for the culvert OD. In this case, as shown in FIGS. 5A to 5C, when the water W is discharged from the culvert OD, the retaining plate 340 is slid upward with the first plate 332 and the second plate 334 slid upward. Just let me do it.
From the above, in the drainage device 28 of the present embodiment, the farmland FL can be used as the paddy field PF and the upland field TF.

[Multiple runoff channels]
One end of the outflow channel 29A of the present embodiment is connected to the outflow portion 220 of the water lock 22 (see FIG. 2A and the like), and the other end is connected to the drainage pipe 30. Then, it constitutes a flow path of water W that flows out from the outflow portion 220 and flows into the drainage pipe 30.
Further, one end of the outflow channel 29B of the present embodiment is connected to the outflow portion 350 (see FIG. 3B) of the drainage device 28, and the other end is connected to the drainage pipe 30. Then, it constitutes a flow path of water W that flows out from the outflow portion 350 and flows into the drainage pipe 30.

The above is the description of the function and configuration of the groundwater level adjustment system 10 of the present embodiment. As described above, it can be said that the groundwater level adjusting device 20 of the present embodiment basically has a configuration in which a plurality of groundwater level adjusting devices 20 constituting the groundwater level adjusting system 10 are combined into one. Therefore, since the groundwater level adjusting device 20 of the present embodiment basically exhibits the same function as the groundwater level adjusting system 10 of the present embodiment, it can be regarded as an example of the groundwater level adjusting system of the present invention. ..

<< Conversion method of this embodiment >>
Next, the conversion method of the present embodiment (S10 and S in FIG. 7 mean steps (steps); hereinafter omitted) will be described mainly with reference to FIGS. 7 to 9. Here, FIG. 7 is a flow chart of the conversion method of the present embodiment. As described above, in the present embodiment, using the groundwater level adjusting system 10 (and the groundwater level adjusting device 20) of the present embodiment, each step described later (for example, the agglomeration step S23 in FIG. 8 and the fertilizer in FIG. 9) is used. By performing the mixing step S34 and the like), the farmland FL can be converted from the paddy field PF to the field TF, and the farmland FL can be converted from the field TF to the paddy field PF. In this way, in the conversion method of the present embodiment, the paddy field PF and the upland field TF can be repeatedly converted. In FIG. 7, after converting the farmland FL used as the paddy field PF to the upland TF (S20), the farmland FL converted to the upland TF is used for upland farming (S40), and then used as the upland TF. This means that after the farmland FL that has been converted to the paddy field PF (S30), rice cultivation is carried out using the farmland FL that has been converted to the paddy field PF (S60). Further, in the conversion method of the present embodiment, it is possible to convert the farmland FL to the upland TF (S20) again after the rice cultivation (S60) and to carry out the upland cultivation (S40).
Further, FIG. 8 is a flow chart of a method S20 (hereinafter, referred to as a first conversion method S20) for converting a paddy field PF to a field TF, which is a part of the conversion method of the present embodiment. That is, the flow chart of FIG. 8 shows the specific contents of S20 in the flow chart of FIG. 7. On the other hand, FIG. 9 is a flow chart of a method S30 (hereinafter referred to as a second conversion method S30) for converting from a field TF to a paddy field PF, which is another part of the conversion method of the present embodiment. That is, the flow chart of FIG. 9 shows the specific contents of S30 in the flow chart of FIG. 7.

Hereinafter, the characteristics of the soil of the paddy field PF (paddy soil) and the soil of the upland TF (field soil) will be described with reference to FIG. 10, and then, based on the characteristics of the soil of the paddy field PF and the soil of the upland TF, The conversion method of the present embodiment will be described separately for the first conversion method S20 and the second conversion method S30.

Here, the first conversion method S20 of the present embodiment is a farmland conversion method for converting farmland FL from paddy field PF to upland TF as a basic configuration, and is arranged under the farmland FL and has a plurality of outer circumferences. Using a water level adjusting system 10 (or a water level adjusting device 20) including an underdrain pipe 26A in which a through hole is formed and a paddy field 22 connected to the underdrain pipe 26A and adjusting the underground water level using the head pressure. , A step performed after the water level adjusting step S22 for adjusting the underground water level to a predetermined water level and the water level adjusting step S22, in which the soil SO of the paddy field PF contains rotaceous acid while plowing the soil SO of the paddy field PF. It includes an agglomeration step S23 in which the agglomerating material is mixed to agglomerate the soil SO of the paddy field PF (see FIGS. 1, 8 and the like).

Further, the second conversion method S30 of the present embodiment is a farmland conversion method for converting a farmland FL used as a field TF after being used as a paddy field PF into a paddy field PF again, and is arranged under the farmland FL. An underdrain pipe 26A having a plurality of through holes formed on the outer circumference, a water bar 22 that is connected to the underdrain pipe 26A and adjusts the water level underground by using the water head pressure, and a supply unit that supplies water W on the farmland FL. A water level raising step S31 for raising the underground water level and a step performed after the water level raising step S31 using the water level adjusting system 10 (or the water level adjusting device 20) including 24, in which the ground of the field TF is pressurized. A step to reduce the seepage water (water W) underground in the field TF and a step to be performed after the seepage water reduction step S32, using the water level adjusting system 10 (or the water level adjusting device 20) to ground the ground. It includes a water supply step S36 for supplying water W on the top (see FIGS. 1, 9, etc.).

Then, the conversion method S10 of the present embodiment includes the first conversion method S20 and the second conversion method S30, and performs the step S40 of utilizing the farmland FL which became the field TF after the first conversion method S20 for upland farming. Further, after the step S40, the second conversion method S30 is performed to perform the step S60 in which the farmland FL changed from the field TF to the paddy field PF is used for rice cultivation (see FIG. 7). In the conversion method S10 of the present embodiment, the first conversion method S20 can be performed again after the step S60.

<Characteristics of paddy soil and upland soil>
Hereinafter, the characteristics of paddy soil and upland soil will be described with reference to FIG. In addition, supplementing the meaning of "-" used in the numerical range in the following description, for example, "2 cm to 3 cm" means "2 cm or more and 3 cm or less". And, "~" used in the numerical range in this specification means "more than the description part before" ~ "and less than the description part after" ~ "".

[Characteristics of paddy soil]
As shown in FIG. 10, the paddy soil is laminated in the order of the soil layer, the plow bed, and the lower soil in the direction from the ground to the underground (from the upper side to the lower side in the vertical direction). It has a structure.

The paddy soil has the following characteristics.
-The thickness of the soil layer is about 15 cm as an example.
・ There is a plow bed just below the soil layer. The plow bed has a function as an impermeable layer.
The thickness of the plow bed is, for example, about 5 cm.
-The strength of the plow bed has been increasing in recent years due to the demand for bearing capacity to accommodate large machines.
-The water reduction depth is 2 cm to 3 cm as an example.
-Paddy soil is flooded for more than half of the cultivation period. That is, paddy soil is always in a state of oxygen deficiency. Therefore, the decomposition rate of organic matter is slow.
-In the case of paddy soil, the underdrain pipe 26A is mainly used as a drainage measure. That is, it is used as an oxygen supply to the soil due to falling water. Therefore, it is good for mid-drying, combine harvester strength, winter drainage and spring work.
-In paddy soil, the pH value drops significantly due to acidification of irrigation water, leaching by the underdrain pipe 26A, and reduction of material input.
・ In paddy soil, fertilizer-based cultivation and rooting deteriorate due to a decrease in the supply capacity of soil nitrogen (incubation nitrogen reduction). As a result, it becomes a factor of unstable rice cultivation.
The above is an explanation of the characteristics of paddy soil.

[Characteristics of upland soil]
As shown in FIG. 10, the upland soil is laminated in the order of the soil layer, the plow bed, and the lower soil in the direction from the ground to the underground (from the upper side to the lower side in the vertical direction). It has a structure.

The upland soil has the following characteristics.
-The thickness of the soil layer of the upland TF is thicker than the thickness of the soil layer of the paddy field PF. The thickness of the soil layer of the upland TF is preferably 30 cm or more as an example.
-There is a hard disk layer directly under the soil layer. Therefore, it has the bearing capacity to handle large machines.
・ Rapid surface drainage and vertical infiltration are observed in upland soil due to rainfall. Therefore, the roots of crops are deficient in oxygen due to flooding.
・ Upland soil is always dry. Therefore, sufficient oxygen is contained and microbial activity is observed. As a result, the decomposition of organic matter is fast.
-For upland soil, it is necessary to adjust the groundwater level according to the crops to be cultivated. For example, the water requirement during the flowering period is high, and the water requirement for the upland soil differs depending on the crop species. Therefore, a drainage and water supply system is required, which enables optimum moisture management of upland soil.
-Unlike paddy soil, upland soil has vertical ridges (vertical ridges). Therefore, leaching of nutrients occurs due to rainfall. As a result, for upland soil, supplementation of nutrients, etc. is an absolute requirement for the production of good products, and omissions (neglect of nutrient supplementation) are directly reflected in the harvest.
The above is an explanation of the characteristics of upland soil.

The above is an explanation of the characteristics of paddy soil and upland soil.

<First conversion method (method of converting farmland from paddy fields to upland fields)>
As shown in FIG. 8, the first conversion method S20 of the present embodiment includes the installation (process) S21 of the water level adjustment system, the water level adjustment process S22, the agglomeration process S23, the analysis process S24, the soil improvement process S25, and the recharge. Step S26 is included, and the steps are basically performed in the order described in these steps. Hereinafter, each step will be described.

[Installation of water level adjustment system (process) S21]
This step is a step of installing the water level adjusting system 10 (or the water level adjusting device 20) on the farmland FL used as the upland TF (see FIG. 1).
In this case, the underdrain pipe 26A is constructed at an arrangement interval of 5 m to 8 m as an example. This makes it possible to set the groundwater level in a field where there is a hard disk (plow bed) peculiar to the paddy field PF and the vertical penetration of water W is small.
Further, a bullet culvert (not shown) that fills rice husks so as to be orthogonal to the culvert pipe 26A may be constructed in combination.
Since the drainage device 28 is also installed along with the installation of the groundwater level adjustment system 10 (or the groundwater level adjustment device 20) of the present embodiment (see FIG. 1), the response when the farmland FL is changed from the field TF to the paddy field PF again. There is an advantage that it is also possible.
If it is expected that seepage water will infiltrate from the adjacent paddy field PF, for example, even if a water-impervious sheet (not shown) or a water-impervious culvert (not shown) is installed at the position adjacent to the ridge RD. Good. Further, when the water level adjusting system 10 (or the water level adjusting device 20) is installed in the farmland FL in advance and the field TF is converted into the paddy field PF, this step can be naturally omitted.

[Water level adjustment step S22]
In this process, the set water level of the water level 22 (see FIGS. 2A, 2H, etc.) installed in the installation (process) S21 of the water level adjustment system is adjusted, and as an example, the underground water level by the water level 22 is set from the ground of the farmland FL. Adjust so that it is below the position at a depth of 60 cm. As described above, when the farmland FL is changed from the field TF to the paddy field PF again, that is, when S30 and S60 are performed in the flow diagram of FIG. 7 and S20 is performed again, in this step, the underground by the water level 22 is used. The water level may be raised above the set water level at the time of field TF.

[Agglomeration step S23]
In this step, the soil SO of the paddy field PF is cultivated and the agglomerating material containing humic acid is mixed with the soil SO of the paddy field PF to aggregate the soil SO of the paddy field PF. This step is carried out for the purpose of promoting agglomeration of paddy soil and removing surface water of paddy soil.
In addition, in this process, in order to quickly improve the paddy soil with a single grain structure to the upland soil mainly composed of aggregates, the soil SO is cultivated by mixing the aggregated material, that is, the physics. Improvement. Pseudo-aggregation increases the amount of voids in the soil SO and significantly improves drainage. Here, as an example of the aggregated material in this step, there is Azumin (manufactured by Denka Co., Ltd., Azumin is a registered trademark of Denka Co., Ltd.). Azumin is a humic acid fertilizer containing humic acid as the main component. In this step, by mixing the agglomerate material into the soil SO, the bonding of soil particles can be promoted and the ratio of the three soil phases (solid phase, liquid phase and gas phase) can be adjusted. Therefore, the water permeability and fertilizer retention capacity of soil SO can be improved, the occurrence rate of so-called "wet damage" can be reduced, and the fertilizer retention capacity of soil SO can be improved. This effect is a characteristic effect of this step performed by installing the underdrain pipe 26A under the farmland FL and combining it with the groundwater level adjusting system 10 (groundwater level adjusting device 20) of the present embodiment. The agglomerating material used in this step may be a material other than azumin as long as it is a material exhibiting the above effects. For example, it may be a material in which a PVA-based material and a humic acid-derived material are combined, or a material in which an EVA (ethylene vinyl acetate copolymer resin) -based material and a humic acid-derived material are combined. May be good.

Further, in order to further exert the effect of this step, it is preferable to carry out deep plowing 30 cm or more as an example. Specifically, soil SO having a depth of at least 30 cm from the ground of the farmland FL is cultivated by a plow (not shown) or the like. In this case, the soil SO of the paddy field PF is further cultivated using an up-cut rotary (not shown), a down-cut rotary (not shown), a deep-cultivated rotary (not shown), a super-crushed soil rotary (not shown), or other rotary. Is preferable. As a result, a soil structure suitable for hard disk crushing and root elongation can be formed. In this case, for example, at least one or two or more of up-cut rotary, down-cut rotary, deep-cultivated rotary and super-crushed soil rotary may be used.
It should be noted that the use of the up-cut rotary when cultivating the soil SO of the paddy field PF is more effective than the case of using other rotary in that an artificial soil structure can be created in the field TF after conversion. is there. Then, when the soil SO of the paddy field PF is cultivated using the up-cut rotary, the soil SO on the surface of the soil becomes fine particles and the particle size of the soil SO can be increased from the surface to the lower layer side. As a result, the drainage property of the soil can be improved by further plowing the soil SO using an up-cut rotary in this step.

[Analysis step S24]
In this step, soil analysis of the soil SO aggregated in the agglomeration step S23 is performed to identify the nutrients required for using the aggregated soil SO for the upland field TF and the required amount of the nutrients. It is a process to do.
Specifically, in this step, soil analysis is performed for the purpose of confirming the amount of soil nutrients required for upland farming.
In the soil analysis of the present embodiment, as an example, quantitative analysis of K, Ca, Mg, phosphoric acid, humus and the like and analysis of pH value are performed. In order to cultivate field crops in paddy soil, it is indispensable to improve the chemical properties of the soil in addition to the above-mentioned improvement of the physical properties of the soil. Therefore, the soil is analyzed in this step, and based on the result, the chemical properties of the soil are improved in the next step (soil improvement step S25). Paddy soil generally has a low pH value and low saturation of bases (K, Ca, Mg). Therefore, in the analysis of this step, the chemical properties suitable for upland farming in the next step (soil improvement step S25) It is necessary to obtain basic data for improvement in soil SO. In general, there are cases where materials are applied without analysis, but improper application without analysis may result in a hindrance to productivity.
In addition, when paddy field PF is converted to upland TF, pH value is the most important factor of soil chemistry. Since the pH value of the paddy field PF is biased toward acidity, in the present embodiment, it is a guideline to raise the pH value to about 6 (5.8 to 6.2 as an example). In addition, it is necessary to balance each other with the amount of bases, and the soil CEC (cation exchange capacity), which is the basis for the integration, is an important analysis item.

[Soil improvement step S25]
This step is a step of mixing the soil SO aggregated in the agglomeration step S23 with the soil improvement material corresponding to the required nutrient in the required amount specified in the analysis step S24. Here, the soil conditioner used in this step is, for example, the above-mentioned azumin, bitter lime, potassium fertilizer lime and the like. However, the soil conditioner is not limited to this as long as it is a material corresponding to the nutrient specified in the analysis step S24.

In addition, soil improvement materials are applied in order to obtain soil chemistry suitable for upland farming, but it is preferable to pay attention to the pH value of the soil. For example, as a result of soil analysis in the analysis step S24, if a large amount of soil improvement material is applied in order to significantly change the pH, there may be a problem in growing upland crops. Therefore, regarding the adjustment of the pH value, as an example, it is preferable to gradually increase the pH value with a guideline of increasing the pH value to about 6 (5.8 to 6.2 as an example) after 3 years. The optimum pH value differs depending on the crop to be cultivated. Therefore, in this step, for example, an alkaline soil conditioner may be used to improve the pH of the soil.

Further, in this step, it is preferable to use azumin as an example of the soil improvement material for the following reasons. That is, azumin contains humic acid as a main component. Paddy soil has a low content of humic acid. Therefore, Azumin can sufficiently compensate for the deficiency of humus, which is significantly consumed by upland farming. In addition, compost, whose application has been decreasing in recent years, has a function of improving chemical properties, but azumin, which is an example of the soil improvement material of the present embodiment, has humic acid as described above. Therefore, azumin used as a soil improvement material in this step is effective in that it can improve the chemical properties of soil SO.

In addition, there are field crops that absorb a lot of silicic acid. Therefore, when cultivating such field crops after conversion to upland TF, a material having an alkaline main component of silicic acid may be used as the soil improvement material in this step. An example of such a material is BM Toretaro (made by Zen-Noh).

Further, base saturation for the cation exchange capacity of the soil, 40% to 70% in the calcium oxide (CaO), 12% to 25% in magnesium oxide (MgO), 1% in potassium oxide _(K 2 O) _~8 It is any value of%, and the total base saturation is preferably 60% to 80%. The total base saturation refers to the total base saturation of calcium oxide, magnesium oxide and potassium oxide. In this case, a value obtained by dividing the molar amount of CaO in a molar amount of MgO is 6 or less, it is preferable that the value obtained by dividing the molar amount of CaO in a molar amount of K _{2 O} in 2 or more. Further, in the soil SO mixed with the soil improvement material, the content of toluoglycic acid (effective phosphoric acid) in the dry soil per 100 g is preferably 20 mg to 50 mg. Further, it is preferable that the content of humus in the soil SO mixed with the soil improvement material is 3% by mass or more. However, since the base saturation differs depending on the CEC, in the case of a low CEC, it is necessary to set the base saturation higher than the above-mentioned preferable range of the total base saturation.

Although this step has been described above, in order to further exert the effect of soil improvement by this step, it is preferable to carry out deep plowing of 30 cm or more as an example. By deep plowing in this way, homogeneous soil chemistry can be obtained. In addition, when deep plowing is carried out in this step, the chemical properties of the subsoil may be inferior due to the old soil, so in the soil analysis in the analysis step S24, the soil SO is sampled stepwise to the planned deep plowing depth. It is preferable to analyze in the depth direction of the underground.

[Recharge process S26]
This step is a step of recharging organic nitrogen in the soil SO mixed with the soil improvement material in the soil improvement step S25.
In this step, for example, in paddy field PF, the purpose is to promote the ripening of rice straw left in the field (farmland FL) by paddy rice cultivation immediately before the first conversion method S20, and to recharge soil nitrogen (organic nitrogen). It is something to do. In this step, for example, after harvesting paddy rice, the farmland FL is cultivated in a state where 20 g / m ² of lime nitrogen is sprayed on the farmland FL where the rice straw remains. In other words, in this step, lime nitrogen is sprayed on the rice straw left in the paddy field PF (farmland FL used as), and the rice straw on which the lime nitrogen is sprayed is used as the soil improvement material in the soil improvement step S25. It is cultivated together with the mixed soil SO to recharge organic nitrogen. As a result, the ripening of rice straw is promoted, and the soil fertility is enhanced from the viewpoint of biological properties. In addition, recharge of rice straw as in this step (reduction of rice straw to soil) is effective in that the remaining rice straw can be used as a useful resource.

The above is the description of the first conversion method S20 (method of converting farmland from paddy field to upland) of the present embodiment.

<Second conversion method (method of converting farmland from farmland to paddy field)>
Next, the second conversion method S30 of the present embodiment will be described with reference to FIG. The second conversion method S30 of the present embodiment includes a water level raising step S31, a seepage water reducing step S32, an analysis step S33, a fertilizer mixing step S34, a replenishment step S35, a water supply step S36, and a water reduction depth adjusting step S37. These steps are performed in the order described in. Hereinafter, each step will be described.

[Water level rise step S31]
This step is a step of raising the underground water level by using the water level adjusting system 10 (or the water level adjusting device 20). Specifically, in the water level adjusting step S22 of the first conversion method S20 (see FIG. 8), the set water level of the water lock 22 (see FIGS. 2A, 2H, etc.) is adjusted, and as an example, the underground water level by the water lock 22 Is set to be 50 cm or less from the ground of the farmland FL to raise the underground water level.

[Penetration water reduction step S32]
This step is a step of pressurizing the ground of the field TF to reduce the seepage water under the field TF.
By using the farmland FL as a field TF, vertical infiltration of the field (water path (within a pair of broken lines drawn vertically in FIG. 10)) is formed, and the water retention is greatly deteriorated when the paddy field PF is used. It is possible that you are doing it.
Therefore, as a countermeasure, as an example, the floor is tightened with a heavy machine (not shown), and the ground of the farmland FL used as the field TF is pressurized by further scratching (preferably multiple times). Reduce underground seepage water. Further, regarding water leakage from the edge of the ridge RD, it is preferable to install a storm wave (not shown) and perform a black coating (shore coating) operation.

The groundwater level adjusted by the sluice 22 is lowered to the minimum water level during the time when excess nitrogen etc. flows out during puddling, during the mid-drying period, and at the time just before harvesting, but basically the maximum water level at other times. (Refer to the case of paddy rice cultivation in Fig. 2J).
In addition, the drainer 28, which helped to smoothly discharge the surface water of the field TF, changes the height of the second plate 334 of the shutter 330 according to the growth of paddy rice, and changes it at any time so as to always secure an appropriate water level. (See FIGS. 4A-4D).

[Analysis step S33]
In this step, soil analysis of the soil SO with reduced seepage water in the seepage water reduction step S32 is performed, and the nutrients required for use in the paddy field PF for the soil SO with reduced seepage water and the required amount of the nutrients. Is the process of identifying.
In this step, soil analysis (for example, analysis of the amount of silicic acid, humus, etc.) is performed for the purpose of confirming the amount of nutrients in the soil required for paddy rice cultivation.
Here, when the field TF is converted to the paddy field PF again, the expression level of soil nitrogen has the greatest effect on the growth of paddy rice. And, depending on the amount, lodging may occur even without fertilizer. Therefore, the amount of basal fertilizer can be adjusted by grasping the nitrogen expression level by incubation for about 3 years after returning to the field. After vegetable cultivation in the upland field TF, fertilizer nitrogen remains in the farmland FL. Therefore, in this step, it is preferable to remove the residual nitrogen content in the soil by performing puddling (preferably a plurality of times). That is, in this step, it is effective to perform soil analysis after removing residual nitrogen of soil SO in which permeation water has decreased.

[Fertilizer mixing step S34]
This step is a step of mixing a necessary amount of fertilizer corresponding to the nutrient specified in the analysis step S33 into the soil SO whose seepage water has been reduced in the seepage water reduction step S32. As an example of fertilizer in this case, there is Toretaro (Toretaro is a registered trademark of Denka Co., Ltd.) as an example of silicic acid fertilizer, and Azumin and the like as an example of humic acid fertilizer.

Here, it is assumed that silicic acid, which is extremely important for paddy rice, is reduced in large quantities from the soil due to an increase in vertical infiltration when using farmland FL in upland TF. In addition, silicic acid is also very effective in reducing lodging caused by excess nitrogen, and it can be expected that yield will be improved by improving the ripening rate. Therefore, the application of silicic acid in this step is an essential requirement.

It should be noted that this step is basically performed based on the result of soil analysis in the analysis step S33, but on the contrary, since it is assumed that it may be excessive, it may be not applied except for silicic acid and humus. .. In this case, it is preferable that the content of effective silicic acid in the dry soil per 100 g of the soil SO mixed with fertilizer is 20 mg or more. Further, it is preferable that the content of humus in the soil SO mixed with fertilizer is 3% by mass or more.

[Recharge process S35]
This step is a step of recharging the soil nitrogen (organic nitrogen) of the soil SO by utilizing the residue at the time of upland farming on the farmland FL after the fertilizer mixing step S34.
In this step, 20 g / m ² of lime nitrogen is sprayed as an example on the residue (for example, straw, bean husk, vegetable residue, etc.) at the time of upland cultivation left in the upland field TF (farmland FL used as). In the fertilizer mixing step S34, the residue sprayed with lime nitrogen is cultivated together with the soil SO mixed with fertilizer to recharge organic nitrogen. As a result, the ripening of the residue is promoted, and the soil fertility is enhanced from the viewpoint of biological properties. In addition, recharging as in this step (reduction of residue to soil) is effective in that the residue can be used as a useful resource.

[Water supply process S36]
This step is a step of supplying water W onto the ground by using the water level adjusting system 10 (or the water level adjusting device 20) on the farmland FL completed from the water level raising step S31 to the recharge step S35. The water level of the water W supplied on the ground is adjusted to the set water level by using the water lock 22 (see the case of paddy rice cultivation in FIG. 2J) (see FIG. 2H).

[Water reduction depth adjustment step S37]
This step is a step of scraping the ground so that the water reduction depth per day is 2 cm to 3 cm as an example. Water leakage is suppressed by this step.

The above is the description of the second conversion method S30 (method of converting farmland from farmland to paddy field) of the present embodiment.

As described above, if each conversion method (first conversion method S20 and second conversion method S30) included in the conversion method S10 of the present embodiment is used, the water level adjusting system 10 (water level adjusting device 20) is used, respectively. By converting the farmland FL according to the flow chart shown in FIG. 8 or 9, the "three elements of physicality, chemicality and biologicality" necessary for the activation of soil SO can be obtained. It is possible to realize agricultural production in consideration. In other words, by using this embodiment, it is possible to realize agricultural production with excellent cost performance in consideration of the "three elements of physicality, chemicality and biologicality" necessary for activation of soil SO.

The above is the description of the conversion method of the present embodiment.

As described above, the specific embodiment of the present invention has been described as an example, but the present invention is not limited to the above-described embodiment. For example, the water level adjusting system 10 used in each method of the present embodiment may use a water level (not shown) having a structure different from that of the components (water level 22 or the like) of the present embodiment.

10 Water level adjustment system (groundwater level adjustment system)
20 Water level adjustment device (groundwater level adjustment system)
22 Water lock 24 Supply mass (supply section)
26 Agricultural land inland waterway 26A Underdrain pipe 28 Drainer 29A Outflow waterway 29B Outflow waterway 30 Drainage pipe 200 Outer cylinder 202 Peripheral wall 204 Bottom wall 206A Through hole 206B Through hole 208 Inner wall 208A Inner peripheral surface 210 Inflow part 220 Outflow part 230 Slide cylinder 240 Lid 250 Extraction member 252 Middle cylinder 252A Telescopic cylinder (bellows)
252B Lower cap 252B1 Elastic member 252C Upper cap 252D Fixing screw 254 Shaft part 254A Hollow shaft 254B Slide shaft 254C Fastener 254D Fixing member 300 Bottom plate 310 Opposing wall 312 Recessed 314 Inclined surface 320 Connecting wall 322 Through hole 330 Shutter 332 1st Board 332A Depression 334 Second plate 340 Retaining plate 340A Depression 350 Outflow part 360 Main body FL Farmland FP1 Crop (rice)
FP2 crops (vegetables such as wheat)
IS Interior MS Main liquid supply pipe OD Meidori PF Paddy field RD Ridgeside SO Soil S10 Farmland conversion method S20 First conversion method (method of converting farmland from paddy field to field)
Installation of S21 water level adjustment system (process)
S22 Water level adjustment process S23 Aggregation process S24 Analysis process S25 Soil improvement process S26 Recharge process S30 Second conversion method (method of converting farmland from field to paddy)
S31 Water level rise process S32 Permeation water reduction process S33 Analysis process S34 Fertilizer mixing process S35 Recharge process S36 Water supply process S37 Water reduction depth adjustment process S40 Upland farming utilization process (process used for upland farming)
S60 Rice cultivation process (process used for rice cultivation)
TF field W water (example of liquid)

Claims (14)

It is a farmland conversion method that converts farmland used as upland into paddy fields.
An underdrain pipe that is placed underground in the farmland and has a plurality of through holes formed on the outer periphery, a sewage that is connected to the underdrain pipe and adjusts the water level in the underground by using the head pressure, and the farmland. A water level raising step of raising the underground water level using a water level adjusting system provided with a water supply unit,
A step of reducing the seepage water, which is a step performed after the step of raising the water level, in which the ground of the field is pressurized to reduce the seepage water under the field.
A step performed after the permeation water reduction step, which is a water supply step of supplying water onto the ground using the water level adjustment system.
Farmland conversion methods including. In the permeation water reduction step, the ground of the field is pressurized by tightening the floor with a heavy machine.
The farmland conversion method according to claim 1. In the permeation water reduction step, the field is further scratched.
The farmland conversion method according to claim 2. A step performed after the seepage water reduction step and before the water supply step, in which soil analysis of the soil in which the seepage water is reduced in the seepage water reduction step is performed, and the soil in which the seepage water is reduced is used for paddy fields. An analysis process that identifies the nutrients required to produce and the required amount of the nutrients,
The farmland conversion method according to any one of claims 1 to 3. In the analysis step, the soil analysis is performed after removing the residual nitrogen of the soil in which the permeated water has decreased.
The farmland conversion method according to claim 4. The removal of the residual nitrogen is carried out by scraping the soil with reduced seepage water.
The farmland conversion method according to claim 5. A fertilizer corresponding to the required amount of the required nutrient specified in the analysis step on the soil whose seepage water has been reduced in the permeation water reduction step, which is a step performed after the analysis step and before the water supply step. Fertilizer mixing process,
The farmland conversion method according to any one of claims 4 to 6, which comprises. The fertilizer contains silicic acid,
The farmland conversion method according to claim 7. In the soil mixed with the fertilizer, the content of effective silicic acid in the dry soil per 100 g is 20 mg or more.
The farmland conversion method according to claim 7 or 8. Increase the content of humus in the soil mixed with fertilizer to 3% by mass or more.
The farmland conversion method according to any one of claims 7 to 9. The fertilizer contains humic acid,
The farmland conversion method according to claim 7. A step performed after the fertilizer mixing step and before the water supply step, in which lime nitrogen is sprayed on the residue of the field, and the residue to which the lime nitrogen is sprayed is combined with the soil mixed with the fertilizer. A cultivation process that cultivates and recharges soil nitrogen,
The farmland conversion method according to any one of claims 7 to 11, which comprises. A step performed after the water supply step, which is a step of adjusting the water reduction depth by scraping the ground so that the water reduction depth per day is 2 cm to 3 cm.
The farmland conversion method according to any one of claims 1 to 12, which comprises. In the water level raising step, the underground water level due to the water bar is adjusted so as to be equal to or less than a position at a depth of 50 cm from the ground.
The farmland conversion method according to any one of claims 1 to 13.

Images