RU2802955C1 - Method for determining the irrigation rate for drip irrigation of agricultural crops - Google Patents

Abstract

FIELD: drip irrigation of crops.

SUBSTANCE: method consists in the instrumental determination of the density of the moistened soil layer, the lowest moisture capacity of the soaked soil layer, the content of clay particles in the soil and the calculation of the irrigation rate, the issuance of which ensures the formation of a zone of soil moisture. Together with soil characteristics, the influence of water supply intensity (dropper consumption) and pre-irrigation soil moisture on the irrigation rate is taken into account, the calculation of which is made according to the dependence: N _drip = 4.78·y _vol ·h _mois ³ ·(P _p ·k _q ·k _β ) ² ·(ε _post -ε _pre ) · β _mm where N _drip is the irrigation rate per one drip water outlet, l/drop; y _vol is the density of soil composition averaged over the depth of the moistened layer, t/m³; h _mois is the thickness (depth) of the moistened soil layer, m; P _p is the parameter characterizing the influence of soil characteristics on the geometrical parameters of the moisture contour: P_p = 0.5·[0.66+0.009·W_c+0.034·W_mm] where W_c is the average content of clay particles in the moistened soil layer, % of the mass of dry soil (% MDS); W_mm is the average value of the minimal moisture for the moistened soil layer, % MDS; k _q is the coefficient characterizing the effect of water supply intensity on the geometrical parameters of the humidity circuit: k _q =(Q _drop /2) ^0.1Wc/Wmm , Q _drop is the consumption of drip water outlet, l/h; k _β is the coefficient characterizing the influence of pre-irrigation soil moisture on the geometric parameters of the moisture contour: k _β =(W _c /W _mm )0.4·(1-β_pre/β_mm) ^0.1Wc/Wmm ; β_pre is the average pre-irrigation soil moisture for the moistened soil layer, % MDS; β_mm is the soil moisture corresponding to the minimal moisture which is average in the moistened layer, % MDS, β_{mm =} W_mm; ε _post and ε _pre is the shares of β_mm indicating levels of post-irrigation and pre-irrigation soil moisture, respectively, measured in fractions of a unit.

EFFECT: dosed supply of irrigation water to the root-inhabited soil space.

1 cl, 1 tbl

Description

The invention relates to the field of drip irrigation of agricultural crops and is intended to determine the irrigation rate, ensuring the formation of drip moistening zones in the soil space with given geometric and moisture parameters.

There is a known method for determining irrigation rates for drip irrigation (Khrabrov, M. Yu. Calculation of the distribution of moisture in the soil during drip irrigation / M. Yu. Khrabrov // Melioration and water management. - 1999. - No. 4. - P. 34–35) , including obtaining and using experimental data to determine the volumetric mass of the calculated arable soil layer, layer moisture at the lowest moisture capacity, pre-irrigation moisture and moisture depth and calculation of irrigation norm:

- for medium and heavy soils according to the formula

Where $$m$$ – irrigation norm, m ³ /ha; $$V_{\text{w}\text{.With}\text{.}}=(2/3)\cdot \pi \cdot R_{\text{w}\text{.With}\text{.}}{}^2\cdot H$$ – volume of the humidification circuit formed under the dropper in the form of a spherical sector, m ³ ; $$R_{\text{w}\text{.With}\text{.}}$$ – radius of the spherical sector, m; $$H$$ – height of the spherical layer (height of the wetted contour), m; $$\gamma$$ – soil density, t/ ^m3 ; $${\beta }_{\text{n}\text{.V}\text{.}}$$ – soil moisture equal to the lowest moisture capacity, % of the mass of dry soil (% MSP); $${\beta }_{\text{P}\text{.V}\text{.}}$$ – average pre-irrigation moisture content over the wetted layer, % MSP;

- for light soils depending on:

Where $$H$$ – height of the humidification contour in the shape of a truncated cone, m;

$$R_{\text{at}\text{.To}\text{.}}$$ And $$r_{\text{at}\text{.To}\text{.}}$$ – radii of the bases of the truncated cone, m;

$$\pi \cdot H\cdot (R_{\text{at}\text{.To}\text{.}}{}^2+r_{\text{at}\text{.To}\text{.}}\cdot R_{\text{at}\text{.To}\text{.}}+r_{\text{at}\text{.To}\text{.}}{}^2)/3=V_{\text{at}\text{.To}\text{.}}$$ – volume of the humidification circuit in the shape of a truncated cone, ^m3 .

The disadvantages of the known method for determining irrigation norms for drip irrigation are: 1) lack of recommendations for determining the values $$R_{\text{w}\text{.With}\text{.}}$$ , $$R_{\text{at}\text{.To}\text{.}}$$ And $$r_{\text{at}\text{.To}\text{.}}$$ for a wide range of soil and technological irrigation conditions, which limits its use; 2) the volumes of the contour are determined by its conventionally accepted shape (its outline) in the form of a spherical sector (a ball truncated at the top and bottom) for heavy and medium soils and in the form of a truncated cone for light soils, which is not actually observed in all soil conditions. This circumstance does not allow us to determine the irrigation rate for various soil and technological irrigation conditions with the accuracy necessary for practice.

There is a known method for determining irrigation rates for drip irrigation of tomatoes (RU No. 2204241), including instrumental determination of the volumetric mass (density) of the soil, the moisture content of the moistened soil layer corresponding to the lowest moisture capacity, pre-irrigation moisture and the use of a calculated relationship for preliminary determination of the volume of water supply (irrigation rate) as:

Where $$V$$ – volume of water supply (irrigation norm), ^m3 ; $$a$$ – distance between droppers, m; $$b$$ – width of the moistening band, m; $$h$$ – depth of the soaked (moistened) layer, m; $$\alpha$$ – volumetric mass (density) of the soil, t/ ^m3 ; $$k_{\text{n}}$$ – coefficient that takes into account the degree of soil porosity and water permeability over the entire area of the irrigated area using the drip irrigation method; $$W_{\text{NV}}$$ – average moisture content of the active soil layer, corresponding to the lowest moisture capacity, % MSP; $$\lambda$$ – coefficient of pre-irrigation soil moisture corresponding to the permissible limit of soil drying, in fractions of unity.

In the given dependence the product $$a\cdot b\cdot h$$ corresponds to the volume of a single drip humidification circuit $$W_{\text{con}}$$ , which allows us to write it in the form $$V=W_{\text{con}}\cdot \alpha \cdot k_{\text{n}}\cdot (W_{\text{NV}}-\lambda \cdot W_{\text{NV}})$$ , i.e. in a form close to formula (1).

In the claimed method, the value of the irrigation rate pre-determined from dependence (3) is checked by setting up experimental measurements of the moisture contour formed in the subdrip soil space, which, if necessary, is clarified (corrected) by changing the value of the coefficient $$k_{\text{n}}$$ . When experimentally checking the compliance of the calculated and experimental parameters of the circuit, a calibrated or reference dripper with instrumentally determined characteristics is placed on an irrigated area of the established soil type and through it the required volume of water supply (pre-calculated irrigation rate) is determined (specified). By installing a reference dripper on the irrigated area in relation to the existing drip irrigation water distribution network system, a humidification zone and water supply are experimentally established until the irrigated areas are closed between adjacent (nearby) water outlets-drippers. Experimentally established parameters of the circuit (according to $$b$$ And $$h$$ ) when issuing a pre-calculated irrigation norm $$V$$ are compared with those accepted for calculation, and based on the results of the comparison, a decision is made to adjust the calculated dependence in terms of using the adjusted value $$k_{\text{n}}$$ .

The disadvantages of this known method include the following:

1. The conventionally accepted shape of the soil moisture contour is in the form of a parallelepiped (with dimensions $$a\times b\times h$$ ) does not correspond to its outlines observed in real conditions.

2. The discrepancy between the shape of a single contour of drip moistening of the soil adopted in the patent and the actually observed one, as well as the discrepancy between the linear dimensions of the contour and the real ones (both planned and vertical) leads to a discrepancy between the calculated values of the volumes of moistened soil space and the actual ones, which in turn leads to a discrepancy between the calculated irrigation standards to their required values.

3. When calculating the volume of water supply (irrigation rate), soil characteristics such as the content of clay particles in the soil and the rate of water absorption into the soil, which affect the processes of formation of drip moisture contours of soils, are not taken into account, which reduces the reliability of determining the irrigation rate that ensures the formation of a moisture contour with the required parameters and specified humidity.

4. To adjust the calculated values of the volume of water supply, the known method involves conducting experimental measurements of the depth of soil moisture during irrigation, which requires additional costs of money, labor and time.

There is a known method for determining the irrigation rate for drip irrigation of plants (RU No. 2683724), adopted as a prototype, including instrumental determination of the bulk density of the wetted soil layer, the lowest moisture capacity of the soaked soil layer, pre-irrigation soil moisture, the average content of clay particles over the wetted soil layer, the average absorption rate water into the soil during the first hour of irrigation and calculation of the irrigation rate per dropper, the dispensing of which ensures the formation of a single moisture circuit with a given depth of soil layer moisture and with the required level of post-irrigation moisture, which is produced according to the dependence:

Where $${(N_{\text{floor}})}_{\text{cap}}$$ – irrigation rate per dropper, m ³ /drop; $${\overline{\gamma }}_{\text{about}}$$ – average soil density over the depth of the moistened layer, t/ ^m3 ; $$h_{\text{con}}$$ – required depth of the soil drip moisture contour, m; $$W_{\text{g/h}}$$ – average content of clay particles over the moistened soil layer, % MSP; $$W_{\text{NV}}$$ – humidity of the moistened layer corresponding to the lowest moisture capacity of the soil, % MSP; $${({\overline{V}}_{\text{VP}})}_{\text{1}\text{hour}}$$ – average rate of water absorption into the soil during the 1st hour of watering, mm/min; $${\overline{\beta }}_{\text{p/p}}$$ – value of soil moisture averaged over the volume of the moisture contour during the post-irrigation period, % MSP; $${\overline{\beta }}_{\text{d/p}}$$ – average additional soil moisture within the moistened soil layer (profile), % MSP.

The disadvantages of the method adopted as a prototype include the following:

1. The method does not take into account the flow rate of the drip water outlet (water supply intensity), which has a significant impact on the geometric parameters of the moistening zone formed by the volume of water supplied by one drip water outlet per irrigation (irrigation rate).

2. When calculating the irrigation rate, the soil moisture at which watering begins and the formation of a drip soil moisture contour is not taken into account. The level of additional soil moisture also has a significant impact on the size of the soil drip moisture contour and on the amount of irrigation norm required to form a moisture zone with the required depth.

3. The known method involves using as one of the soil characteristics the average rate of water absorption into the soil during the 1st hour of irrigation, which is labor-intensive to determine instrumentally and, when taking into account the characteristics of volumetric mass, mechanical composition and the lowest moisture capacity of the soil, can be excluded from the calculation without reducing the accuracy of the obtained irrigation norm values.

The objective of the invention is to increase the accuracy of determining the irrigation rate per one drip water outlet, ensuring the formation of a zone of drip moistening of the soil with a given depth of moistening and humidity.

The technical result is to provide a dosed supply of irrigation water to the root-inhabited soil space in a volume that allows, under certain soil and technological conditions of drip irrigation, to form a drip moistening zone in the soil space with a given depth of soil layer moisture and with a certain level of post-irrigation moisture in the intra-circuit space.

The specified technical result is achieved by the proposed method for determining the irrigation rate for drip irrigation of agricultural crops, including instrumental determination of the bulk density of the wetted soil layer, the lowest moisture capacity of the soaked soil layer, the content of clay particles in the soil and the calculation of the irrigation rate, the issuance of which ensures the formation of a soil moisture zone with a given depth of soil layer moisture and with the required level of post-irrigation moisture, characterized in that, together with soil characteristics, the influence of water supply intensity (dropper flow rate) and pre-irrigation soil moisture on the value of the irrigation rate is taken into account, calculated according to the dependence:

$$N_{\text{cap}}$$ – irrigation norm for one drip water outlet, l/drop;

$${\gamma }_{\text{about}}$$ – average soil density over the depth of the moistened layer, t/ ^m3 ;

$$h_{\text{uvl}}$$ – thickness (depth) of the moistened soil layer, m;

$$P_{\text{P}}$$ – parameter characterizing the influence of soil characteristics on the geometric parameters of the moisture contour:

$$W_{\text{G}}$$ – average content of clay particles over the moistened soil layer, % of the mass of dry soil (% MSP);

$$W_{\text{NV}}$$ – average value of the lowest moisture capacity over the moistened soil layer, % MSP;

$$k_q$$ – coefficient characterizing the influence of water supply intensity on the geometric parameters of the humidity contour:

$$k_q={(q_{\text{cap}}/2)}^{{}^{0.1\cdot W_{\text{G}}/W_{\text{NV}}}}$$ ,

$$q_{\text{cap}}$$ – drip water discharge flow rate, l/hour;

$$k_{\beta }$$ – coefficient characterizing the influence of pre-irrigation soil moisture on the geometric parameters of the moisture contour;

$$k_{\beta }={(W_{\text{G}}/W_{\text{NV}})}^{0.4}\cdot {(1-{\beta }_{\text{d/p}}/{\beta }_{\text{NV}})}^{0.1\cdot W_{\text{G}}/W_{\text{NV}}}$$ ;

$${\beta }_{\text{d/p}}$$ – average additional soil moisture over the moistened soil layer, % MSP;

$${\beta }_{\text{NV}}$$ – soil moisture corresponding to the average moisture capacity of the wetted layer, % MSP, $${\beta }_{\text{NV}}$$ = $$W_{\text{NV}}$$ ;

$${\epsilon }_{\text{p/p}}$$ And $${\epsilon }_{\text{d/p}}$$ – shares from $${\beta }_{\text{NV}}$$ values of post-irrigation and pre-irrigation soil moisture levels, respectively, measured in fractions of a unit.

To confirm the adequacy of the proposed method for determining the irrigation rate, below are examples of calculating the irrigation rate for the conditions of three experimental plots based on the dependence from the prototype, the proposed method and their comparison with the indicators recorded during the drip irrigation process on the experimental plots.

Section No. 1. Initial data: $$W_{\text{G}}$$ = 66.0% SMEs; $$W_{\text{NV}}$$ = 27.4% of SMEs; $${({\overline{V}}_{\text{VP}})}_{\text{1}\text{hour}}$$ = 0.8 mm/min; $${\gamma }_{\text{about}}$$ = 1.32 t/ ^m3 ; $${\epsilon }_{\text{d/p}}$$ = 0.7; $${\epsilon }_{\text{p/p}}$$ = 1.0; $$q_{\text{cap}}$$ = 2.0 l/h.

When applying irrigation norm $$N_{\text{fact}}$$ = 60.0 l/drop. in the soil space at experimental plot No. 1, a zone of moistened soil with a depth of $$h_{\text{con}}$$ = 0.96 m.

Calculation of irrigation rates based on the dependence from the prototype:

Calculation of irrigation rates using the proposed method:

$$P_{\text{P}}=0.5\cdot \left[0.66+0.009\cdot W_{\text{G}}+0.034\cdot W_{\text{NV}}\right]=$$

$$=0.5\cdot \left[(0.66+0.009\cdot 66.0+0.14+0.034\cdot 27.4\right]=$$ 1.09;

$$k_q={(q_{\text{cap}}/2)}^{{}^{0.1\cdot W_{\text{G}}/W_{\text{NV}}}}={(2.0/2)}^{0.1\cdot 66.0/27.4}$$ = 1.0;

$$k_{\beta }={(W_{\text{G}}/W_{\text{NV}})}^{0.4}\cdot {(1-{\beta }_{\text{d/p}}/{\beta }_{\text{NV}})}^{0.1\cdot W_{\text{G}}/W_{\text{NV}}}$$ = $${(66.0/27.4)}^{0.4}\cdot {(1-(0.7\cdot 27.4)/27.4)}^{0.1\cdot 66.0/27.4}$$ = 1.06;

$$N_{\text{cap}}=4.78\cdot {\gamma }_{\text{about}}\cdot h_{\text{uvl}}^{}{}^3\cdot {(P_{\text{P}}\cdot k_q\cdot k_{\beta })}^2\cdot ({\epsilon }_{\text{p/p}}-{\epsilon }_{\text{d/p}})\cdot {\beta }_{\text{NV}}$$ =

= 4.78 · 1.32 · 0.96 ³ · (1.09 · 1.0 · 1.06) ² · (1.0 – 0.7) · 27.4 = 61.6 l/drop.

The deviation of the irrigation norm according to the prototype from the actual one will be:

$${\delta }_{\text{prot}}=(N_{\text{prot}}-N_{\text{fact}})/N_{\text{fact}}\cdot 100$$ = (54.0 – 60.0) / 60.0 · 100 = – 10%.

The deviation of the irrigation norm according to the proposed method from the actual one will be:

$${\delta }_{\text{prot}}=(N_{\text{calculation}}-N_{\text{fact}})/N_{\text{calculation}}\cdot 100$$ = (61.9 – 60.0) / 60.0 · 100 = 2.7%.

Section No. 2. Initial data: $$W_{\text{G}}$$ = 36.9% SMEs; $$W_{\text{NV}}$$ = 21.1% of SMEs; $${({\overline{V}}_{\text{VP}})}_{\text{1}\text{hour}}$$ = 0.9 mm/min; $${\gamma }_{\text{about}}$$ = 1.30 t/ ^m3 ; $${\epsilon }_{\text{d/p}}$$ = 0.58; $${\epsilon }_{\text{p/p}}$$ = 1.0; $$q_{\text{cap}}$$ = 2.4 l/h.

When applying irrigation norm $$N_{\text{fact}}$$ = 53.0 l/drop. in the soil space at experimental site No. 2, a zone of moistened soil with a depth of $$h_{\text{con}}$$ = 1.00 m.

The calculation results are shown in Table 1.

Section No. 3. Initial data: $$W_{\text{G}}$$ = 71.1% SMEs; $$W_{\text{NV}}$$ = 30.3% SMEs; $${({\overline{V}}_{\text{VP}})}_{\text{1}\text{hour}}$$ = 0.7 mm/min; $${\gamma }_{\text{about}}$$ = 1.29 t/ ^m3 ; $${\epsilon }_{\text{d/p}}$$ = 0.7; $${\epsilon }_{\text{p/p}}$$ = 1.0; $$q_{\text{cap}}$$ = 1.4 l/h.

When applying irrigation norm $$N_{\text{fact}}$$ = 66.0 l/drop. in the soil space at experimental plot No. 3, a zone of moistened soil with a depth of $$h_{\text{con}}$$ = 0.98 m.

The results of determining the irrigation rate using the prototype and the proposed method for areas No. 1, No. 2 and No. 3 are shown in the table:

No. of experimental plots Actual irrigation rate, l/drop. Estimated irrigation rate according to the prototype, l/drop. Deviation of the irrigation norm according to the prototype from the actual one, % Calculated irrigation rate according to the proposed method, l/drop. Deviation of irrigation norm according to the proposed method from the actual one, % 1 60.0 53.7 -10.4 61.6 2.7 2 53.0 40.4 -23.8 49.5 -6.6 3 66.0 72.6 10.0 68.1 3.2

Deviations of the calculated irrigation norm according to the proposed method from the actual one, necessary for the formation of a zone of drip moistening of the soil with the required depth and humidity, are significantly less than those determined for the irrigation norm calculated according to the prototype. Consequently, the proposed method for determining the irrigation rate for drip irrigation of agricultural crops will make it possible to more accurately calculate the volume of water that needs to be supplied to the soil space with one drip water outlet to form a soil moisture zone with the required geometric and moisture parameters.

The method for determining the irrigation rate for drip irrigation of agricultural crops gives results acceptable for practical use with an error of no more than 8% in the range of initial data: $$W_{\text{G}}$$ – from 20.0 to 72.0% of SMEs; $$W_{\text{NV}}$$ – from 16 to 33.0% of SMEs; $${\gamma }_{\text{about}}$$ – from 1.1 to 1.4 t/ ^m3 ; $${\beta }_{\text{d/p}}$$ – from 0.5 to 0.7 $${\beta }_{\text{NV}}$$ ; $${\beta }_{\text{p/p}}$$ – from 0.7 to 1.0 $${\beta }_{\text{NV}}$$ ; $$h_{\text{uvl}}$$ – from 0.5 to 1.4 m; $$q_{\text{cap}}$$ – from 0.8 to 4.0 l/drop.

Claims (17)

A method for determining the irrigation rate for drip irrigation of agricultural crops, including instrumental determination of the bulk density of the wetted soil layer, the lowest moisture capacity of the soaked soil layer, the content of clay particles in the soil and the calculation of the irrigation rate, the issuance of which ensures the formation of a soil moisture zone, characterized in that, together with Soil characteristics take into account the influence of water supply intensity (drip flow rate) and pre-irrigation soil moisture on the value of the irrigation rate, which is calculated according to the dependence: , - irrigation norm for one drip water outlet, l/drop; - average soil density over the depth of the moistened layer, t/m ³ ; - thickness (depth) of the moistened soil layer, m; - parameter characterizing the influence of soil characteristics on the geometric parameters of the moisture contour: , - average content of clay particles over the moistened soil layer, % of the mass of dry soil (% MSP); - average value of the lowest moisture capacity over the moistened soil layer, % MSP; - coefficient characterizing the influence of water supply intensity on the geometric parameters of the humidity contour: , - drip water discharge flow rate, l/hour; - coefficient characterizing the influence of pre-irrigation soil moisture on the geometric parameters of the moisture contour: ; - average additional soil moisture over the moistened soil layer, % MSP; - soil moisture corresponding to the average moisture capacity of the wetted layer, % MSP, = ; And - shares from values of post-irrigation and pre-irrigation soil moisture levels, respectively, measured in fractions of a unit.