WO2016091878A1

WO2016091878A1 - Method for growing crops on ridges

Info

Publication number: WO2016091878A1
Application number: PCT/EP2015/078984
Authority: WO
Inventors: Erik Frans Renilde DE MAEYER
Original assignee: A.I.R.T. Bvba
Priority date: 2014-12-08
Filing date: 2015-12-08
Publication date: 2016-06-16
Also published as: BE1022306B1

Abstract

The invention provides a method for the cultivation of a terrain for the growing of crops (122) comprising the dividing of the soil of the terrain along parallel ridges (100, 101). The ridges are formed in such a way so as to have an east-west longitudinal direction. The ridges comprise a first (115) and a second surface (116) of the ridges, whereby the angle of the surface which during the period of growth of the crop at 12h solar time is not directed toward the sun and a horizontal plane is defined in relation to the solar elevation angle at 12h solar time.

Description

METHOD FOR GROWING CROPS ON RIDGES TECHNICAL FIELD The invention in question concerns the growing of crops in natural soil and more specifically the cultivation of the natural soil for the planting of the crops in such a way so as to obtain increased yields. This natural soil includes both soil in open air and in greenhouses. BACKGROUND

The expansion of the world population creates a continuous increase in the demand for food and consequently for cultivated crops such as potatoes, lettuce, zucchini,... Since the available amount of arable land is limited, an important part of the research for crops and their cultivation centres on increasing the yield for a same surface of available land.

For example, increased yields have already been obtained through the development of new cultivars that produce more fruits per plant and therefore per surface unit. This development can be carried out naturally through crossbreeding, or artificially through genetic manipulation, or through a combination of both.

Another way to obtain increased yields is by optimizing the growing conditions of the crop. This can be done by artificially controlling the growing conditions, as is the case in hydroculture and in greenhouses where crops are grown under glass.

Many of the aforementioned solutions are expensive, however, and in addition have a possible negative impact on man or the environment. It is therefore an objective of the invention in question to obtain increased yields in a way that is both widely applicable and financially interesting.

Furthermore, land that is not suitably located for growing certain crops is increasingly being cultivated. In some geographic areas, for example, there is an excess of thermal radiation which will often lead to excessive leaf temperatures, which in turn reduce photosynthetic activity and necessitate the plant's evaporation of large quantities of water. An additional result of excessive thermal radiation is the extensive evaporation of water on ground surface. In addition to an excess of thermal radiation, excessive energy can also take the form of photosynthetically active radiation (PAR). Once a certain quantity of PAR is exceeded, a crop's production will decrease or the crop will even be destroyed. As a result of these aforementioned phenomena, the yield of much arable land is mediocre to low. As a consequence, there is a need for systems that can neutralize the negative effects of energy surpluses, be it in the form of thermal radiation or PAR, or, better still, use these surpluses. Another objective of the invention in question is therefore to put these energy surpluses to use.

SUMMARY OF THE INVENTION

The objectives mentioned above are achieved by means of a first aspect of the invention, by means of a method for the cultivation of a terrain for the growing of crops comprising the step of dividing soil of the terrain along parallel ridges (100, 101, 400); whereby said ridges (100, 101, 400) are provided with a longitudinal direction (104, 105, 404, 405) substantially parallel to an east-west direction; and whereby said ridges (100, 101, 400) comprise a first (111) and a second (112) top plane defining respectively a first (115, 415) and a second surface (116, 416) of said ridge; whereby an angle (120, 420, 421) between (i) a horizontal plane (130, 430) and (ii) a first and/or second shadow surface is not larger than an angle of elevation at 12h solar time during the period of growth of the crop. Said shadow surface is defined as said first and/or second surface which during the period of growth of the crop at 12h solar time is at times not directed toward the sun (140, 201, 440, 441).

More specifically, said method comprises the steps of dividing of the soil of the land along parallel ridges The ridges are formed in such a way that they have an east-west longitudinal direction. Preferably, the ridges are formed in such a way that they have a triangular cross section with a first and a second upstanding side defining respectively the first and the second surface of the ridge. Preferably, said angle between the first and/or second shadow surface and a horizontal plane is not larger than a smallest angle of elevation minus 5 degrees. This smallest angle of elevation corresponds to a smallest angle of elevation of the sun at 12h solar time during the period of growth of the crop when the sun is not directed toward the first and/or second surface, respectively. In this way, the natural soil and the terrain by consequence are divided into alternatingly oriented surfaces at an angle with the terrain before it was cultivated. Because of the east-west longitudinal direction of the ridges, the sun will light the surfaces at an approximately identical angle during the sunniest period of the day. For a terrain situated above and therefore north of the Tropic of Cancer, one same surface will always be directed toward the sun during the sunniest period of the day, i.e. the surface facing south. The other surface will then always be directed away from the sun during the sunniest period of the day, i.e. the surface facing north. For a terrain situated under and therefore south of the Tropic of Capricorn, one same surface will also always be directed toward the sun during the sunniest period of the day, but this time the surface facing north. The other surface, facing south, will then always be directed away from the sun during the sunniest period of the day. Between the tropics the sun is in the north at 12h solar time during certain periods of the year, but it is in the south at 12h solar time during other periods of the year. Therefore, depending on the period of growth of the crop, it might happen that each surface is at times not directed toward the sun during the sunniest period of the day, i.e. the surface facing north as well as the surface facing south. Throughout the following description, a surface of the ridges that during the period of growth of the crop is at times not directed toward the sun at 12h solar time will be referred to as a shadow surface, and a surface of the ridges that during the period of growth of the crop is always directed toward the sun will be referred to as a solar surface. According to this definition, there will always be a solar surface and a shadow surface outside of the tropics, and within the tropics there will be either a solar surface and a shadow surface or two shadow surfaces.

Said ridges can be provided as soil from a terrain on which said ridges are provided to form at least a first plane and a second plane which second plane has a cross line with said first plane; said cross line being directed substantially in the east-west direction.

In a further or alternative embodiment, said ridges can be provided as frames or frameworks or supporting structures, preferably aluminium structures, which structures define at least a first plane and a second plane which second plane has a cross line with said first plane; said cross line being directed substantially in the east-west direction; and on which first and/or second plane soil can be provided. Additionally or alternatively, said supporting structures may be comprised of a light-weight material such as plastic, wood composite, wood, MDF, HDF, cardboard, etc. or of steel, such as stainless steel . Preferably, said first and/or second plane are provided with reinforcements to facilitate the support of soil on the inclined plane(s). Such reinforcement can be comprised of one or more shelflike structures perpendicular on said first and/or second plane. Also preferably, said soil, when provided on said first and/or second plane, can be reinforced by providing i.e. a net structure in or on top of the soil on said first and/or second plane.

In a further or alternative embodiment, said first and/or second plane are provided with one or more conduits in which soil can be provided for providing a crop growing soil. This is advantageous since such conduits easily allow for artificial soil or substrates, aeroponic growing and/or hydroculture of crops on said first and/or second plane. Said conduits can further be connected to a water channel for providing water and optionally nutrients to said crops. In a first embodiment, said conduits can be provided in the longitudinal direction of said ridges. In a second embodiment, said conduits can be provided in a direction perpendicular to the direction of said ridges.

Solar time is the time scale in which the sun is due south, i.e. at 180° azimuth, at 12.00h for the Northern Hemisphere and due north, i.e. at 0° azimuth, at 12.00 for the Southern Hemisphere.

A horizontal plane is a fictional surface perpendicular to the direction of gravity and which intersects the first or the second surface.

This arrangement of the land in ridges creates arable surfaces formed by the first and the second surfaces which are larger than the underlying surface formed by the terrain, i.e. than the surface formed by the base of the triangular cross section. In this way, an increase in arable surface area is obtained.

Because of the specific angle of the shadow surface and the east-west longitudinal direction, the shadow surface nevertheless receives sufficient direct sunlight during almost the entire day, so that the crop can still be grown on this surface. The obtained increase in arable surface area therefore also produces an increased yield. On an overcast day, on the other hand, diffuse sunlight will fall virtually vertically on both surfaces. It is an additional advantage that the crops on the shadow surfaces have less photosynthetically active radiation and thermal radiation to process. This makes it possible to grow crops on the shadow surface which under normal conditions, i.e. when grown on a horizontal plane, would not be able to grow due to an excess of photosynthetically active radiation or excessive thermal radiation.

Because of the geographical east-west longitudinal direction of the surfaces, the shadow surface still receives direct incidence of solar rays during the sunniest period of the day. This is essential for avoiding any negative impact on the yield of the crop. The deviation from the geographic east-west axis should therefore not exceed 10 degrees, and preferably not exceed 5 degrees and more preferably not even exceed 1 degree. The geographic east-west axis is defined in reference to the geographic north or the geographic south, the points of intersection of the earth's axis of rotation with the earth's surface. The geographic north differs from the magnetic north, with a difference of several degrees, i.e. the magnetic declination.

Preferably, the angle between the first and/or the second surface that during the period of growth of the crop at 12h solar time is at times not directed toward the sun and a horizontal plane is larger than 15 degrees. In other words, the angle between the shadow surface and a horizontal plane is preferable larger than 15 degrees. In the case of smaller angles, the increase in yield becomes negligible.

Additionally, the angle between the surface that during the period of growth of the crop at 12h solar time is always directed toward the sun and a horizontal plane should be made to be as large as possible, as the solar surface is always directed toward the sun during the sunniest period of the day. By making the angle between the solar surface and a horizontal plane as large as possible, an optimal increase in arable surface area is obtained. Preferably, this angle is as large as possible, for example between 30 and 90 degrees. According to practical feasibility, the largest possible angle will be selected from this interval. In most cases, this angle will not exceed 70 degrees. However, in case frameworks or supporting structures are used, said angle may be comprised between 45 and 90 degrees, and more preferably between 60 and 90 degrees, and even more preferably be equal to 65 degrees, 70 degrees, 75 degrees, 80 degrees, 85 degrees or 90 degrees, or any angle there in between. When the surfaces have been formed, these can be planted or sown with the crops. This can be done on both surfaces or only on the first or the second surface. Optionally, the solar surface can be used for other purposes. Solar panels can be placed on the solar surface, for example. This can be done in case of an excess of solar radiation on the solar surface, precluding the growth of desired crops on it.

In accordance with a second aspect, the invention in question is connected to) an agricultural tool or agricultural machinery adapted for the practical implementation of the method following the first aspect of the invention in question.

DESCRIPTION OF FIGURES

Figure 1 illustrates cultivated land divided in parallel ridges following an implementation of the invention; and

Figure 2 illustrates a side view of the plane of the cross section of a constructed ridge in accordance with the implementation of Figure 1 in which several positions of the sun during the period of growth of the crop are shown; and

Figure 3 illustrates cultivated land on a sloping terrain, divided in parallel ridges following an implementation of the invention; and

Figure 4 illustrates the installation of ridges on land situated between the tropics; and

Figure 5 illustrates the photosynthetically active radiation (PAR) incident on a crop located on the Equator during the day; and Figure 6 illustrates the relative assimilation of C0₂ in a crop in function of the photosynthetically active radiation that is incident on the crop.

DETAILED DESCRIPTION OF THE INVENTION The invention in question concerns the cultivation of land for the planting or sowing of crops with the objective of obtaining an increased yield. In Figure 1 this is illustrated for a horizontal terrain according to a practical implementation of the invention. The terrain in question is situated in the Northern Hemisphere above the Tropic of Cancer where the sun 140, 141 is in the south 112. The natural soil of the terrain is to be divided over parallel ridges 100, 101 with triangular cross section 102, i.e. the cross section perpendicular to the direction of the ridge 100, 101.

The ridges are to be arranged so that their longitudinal direction corresponds to the geographic east-west axis, i.e. from the east 104 to the west 105 or vice versa. As a reference, the base 110 of the cross section 102 is defined as parallel to the terrain before cultivation, i.e. horizontal in this case. Since it is the cultivation of natural soil that is concerned here, the base 110 is not a tangible surface and serves only as a reference point. The upstanding sides 111 and 112 of the triangular cross section further determine the form of the constructed ridges 100, 101. The first side 111 determines the surface area 115 of the ridges 100, 101 and the second side 112 determines the surface area of 116 of the ridges 100, 101. Since, given a terrain situated in the Northern Hemisphere, the surface 115 is always directed toward the sun at 12h solar time, this surface 115 is a solar surface. The surface 116, however, is always directed away from the sun at 12h solar time and is therefore a shadow surface. For an identical implementation in the Southern Hemisphere under the Tropic of Capricorn, this would be inversed and surface 116 would therefore be the solar surface and surface 115 would be the shadow surface.

The form of ridges 100 and 101 is then further determined by the acute angles 121 and 120. The fist acute angle 121 corresponds to the acute angle between a horizontal plane 130, i.e. a plane perpendicular to the direction of gravity, and the solar surface 111. The second acute angle 120 corresponds to the acute angle between the horizontal plane 130 and the shadow surface 112. The selection of the second sharp angle 120 is especially of crucial importance, as the shadow surface 116 is directed north. If the selected second angle 120 is too large, it can occur that during the period of growth of a crop 123 the crop does not receive any more direct sunlight, as the angle of elevation 110, 119 of the sun 140, 141 at 12h solar time will vary during the period of growth.

In order to guarantee a sufficient quantity of direct sunlight on shadow surface 116, the second acute angle 120 is not to be larger than the smallest angle of incidence or angle of elevation 119 of the sun at 12h solar time during the period of growth of the crop 122 minus 5 degrees. The right selection of angle 120 and the east-west longitudinal direction guarantees the shadow surface's exposure to sunlight of approximately the same intensity during a minimum of four hours. The smallest angle of elevation should therefore be measured on the day that the sun, at 12h solar time, is at its lowest point in the sky during the period of growth of the crop. In the description that follows, the smallest angle of elevation is defined as the smallest angle of elevation of the sun during the period of growth of the crop 122 at 12h solar time. On the other hand, the second acute angle 120 should not be too small either, since that would render negligible the obtained increase in arable surface area. The increase in arable surface area is hereby defined as the relation between the sum of surfaces 115 and 116 and the surface area defined by the base 110 of the cross section 102. Therefore, the second acute angle 120 is preferably larger than or equal to 15 degrees.

The side 111 and therefore the solar surface 115 is always directed towards the sun at 12h solar time . To maximize the increase in surface area, the first acute angle 121 is to be as large as possible, so preferably 90 degrees. Since the ridges 110, 101 are constructed in natural soil, it is possible that in practice the upper limit for the first acute angle is at 70 degrees. To maximize the increase in surface area, the first acute angle is nevertheless preferably larger than 30 degrees.

If the minimal angle is selected for the second acute angle 120, i.e. 15 degrees, but the first acute angle 121 is 90 degrees, then the theoretical increase in surface area is still 30%. If the angle 121 is reduced to 70 degrees, however, the theoretical increase in surface area will only amount to 20%. This illustrates the importance of selecting the angle 121 so as to be as large as possible.

Having determined the direction of the ridges 100 and 101 and having determined the first and the second acute angles 121 and 120, only the size of the cross section 102 still needs to be determined. The size is reasonably open for determination and is only limited by practical considerations. For the minimal size, it should be possible to plant or sow minimally one row of the crop 122 on the first and the second surface 115, 116. For the maximal size, limits are only set by practical feasibility. In a preferred form of implementation, the base 110 of the cross section is selected so as to correspond to the track width of the agricultural vehicle used to construct the ridges 100, 101. In an alternative form of implementation, the track width can also correspond to a multiple of the base 110. When the direction of the ridges 100, 101, the first and the second acute angles 121, 120 and the size of the cross section have been determined, the ridges 100, 101 can be actually constructed. This can be done with an agricultural tool or agricultural machinery adapted for the construction of the predetermined form of the ridges. Subsequently, the first or the second surface 115, 116, or both, can be planted or sown with the crop 122.

The east-west longitudinal direction is essential to the invention in question. This is illustrated in Figure 2, where a view of the ridge 101 is shown, perpendicular to the longitudinal direction of the ridge. During the day and during the period of growth of the crop 122 the position of the sun 201, 202, 211, 212 will change continuously. Positions of the sun 201, 202 illustrate the position of the sun early or late in the growing season, for example on a day in spring or fall. Because of the east-west longitudinal direction, during the sunniest period of the day, the sun will move approximately along the direction 203. The course of the sun in the depicted plane thus follows the direction of the incident solar rays 231. Because of this, the solar surface will always be in the sun during the sunniest period of the day. A second example in Figure 2 shows the course of the sun along direction 213 on a day in the middle of the growth season, for example during the summer months when the sun reaches higher positions in the sky. Position of the sun 212 corresponds to the position of the sun in the course of the morning and the afternoon, while position of the sun 211 corresponds to the highest position of the sun during the day, i.e. at 12h solar time. To achieve this effect it is important that the longitudinal direction of the ridges be kept exactly the same. Simulations have demonstrated that for this reason the longitudinal direction must not deviate more than 5 to 10 degrees from the geographic east-west axis, depending on the location of the terrain and the shadow surface. Preferably, the longitudinal direction of the ridges does not deviate more than 1 degree. The more acute the angle 120, the less deviation from the longitudinal direction can be tolerated.

The implementation illustrated in Figure 1 can also be applied to slightly sloping terrains. This is illustrated in Figure 3 for a south sloping terrain. This figure differs from Figure 1 in that the base 110 of the cross section 102 no longer corresponds to the horizontal plane 130. Because of this, the same first and second acute angles 121 and 120 will be obtained for one same crop in one same location. Because of the slope, the solar surface 115 will nevertheless be larger if a same shadow surface area 116 is maintained. The method as illustrated in the preceding examples can also, mutatis mutandis, be applied to terrains situated under the Tropic Capricorn. In this case, however, the solar surface 115 will be facing north and the shadow surface 116 will be facing south.

In the case of a terrain situated between the tropics, different situations are possible. Within the tropics, the sun will be in the north during one period of the year and in the south for the remaining period. Therefore, it needs to be determined first if during the period of growth of the crop the sun is in the north, in the south or possibly in both the north and the south.

If during the period of growth of the crop the sun is always in the south at 12h solar time, the terrain is to be divided into ridges according to the preceding implementations illustrated in Figures 1, 2 and 3, as in this case the shadow surface faces north and the solar surface faces south.

If during the period of growth of the crop the sun is always in the north at 12h solar time, the terrain is also to be divided into ridges according to the preceding implementations illustrated in Figures 1, 2 and 3, i.e. by means of a solar surface and a shadow surface 115, 116. However, the direction of both surfaces is in this case reversed, i.e. the solar surface faces north and the shadow surface faces south. The third situation within the tropics occurs when during the period of growth of the crop the sun is at times in the north as well as in the south. In this situation, as illustrated in Figure 4, there are two shadow surfaces 415 and 416 and there is no solar surface. Here the ridges 400 are also constructed along the east-west geographic axis, i.e. from the east 404 to the west 405 or vice versa. Analogous to Figure 1, the ridges 400 have a triangular cross section 402 and in this way two arable surfaces 415 and 416 are obtained.

The surface 415 forms an acute angle with the fictional horizontal plane 430. To determine the maximum size of the angle 420, first the lowest angle of elevation 419 of the sun 441 at 12h solar time during the period of growth of the crop is determined when the surface 415 is not directed toward the sun. The maximum size of the angle 420 is then this angle of elevation minus 5 degrees. Since in this case there are two shadow sides and therefore there is no sun side whereby the angle can be chosen to be as large as possible, the angle 420 is preferably larger than 30 degrees so as to still obtain a substantial increase of the yield.

In the same way surface 416 forms an acute angle 421 with the fictional horizontal plane 430. To determine the maximum size of the angle 421, first the lowest angle of elevation 417 of the sun 440 at 12h solar time during the period of growth of the crop is determined when the surface 416 is not directed toward the sun. The maximum size of the angle 421 is then again this angle of elevation minus 5 degrees. Here also this angle 421 is again preferably larger than 30 degrees so as to obtain the substantial increase of the yield. In the case where both angles 420 and 421 are 30 degrees, the theoretical increase in surface area is 15,5%. The larger the size of the angles, the larger the increase in surface area.

The aforementioned method is used for the growing of crops on the shadow surface and/or the solar surface. The selection of the crops will then depend on various factors, such as the sufficient incidence of photosynthetically active radiation and/or thermal radiation on the cultivated surfaces, i.e. the shadow surface and/or the solar surface. The fact that the cultivated surface is at an angle does not mean however that there will be a decrease in crop yield.

Not all incident sunlight that reaches the earth's surface can be used by crops for photosynthesis. Only a portion of visible light qualifies for this. This portion is known as "photosynthetically active radiation", or "PAR" for short. Mostly PAR is expressed in μηηοΙ/(ηη².5), whereby μιτιοΙ represents the number of photons. To be able to define PAR, the position of the surface of reference needs to be specified. Obviously, the PAR varies, moreover, according to the latitude, the day of the year, the hour of the day and weather conditions. To determine PAR-values, it is possible to work with theoretical models, but often experimentally produced charts are used.

Figure 5 shows a chart illustrating how the amount of available PAR (Y-axis) (expressed in μηηοΙ/(ηη².5), for a horizontal plane) on the Equator (0°) on 21 March, 21 June, 21 September and 21 December varies during the day, expressed in hours of solar time (X-axis), and this during a day with few or no clouds.

Figure 6 shows a chart illustrating how photosynthesis, expressed in relative C0₂- assimilation (Y-axis), in most crops used in agriculture and horticulture changes in function of the amount of available PAR (X-axis) (expressed in μηηοΙ/(ηη².5)). One can gather from Figure 6 that:

- at very low radiation intensities there is a production of C0₂ instead of assimilation;

- after this, the photosynthesis increases very quickly.

- above a certain limit, often around 500 PAR, the photosynthesis hardly increases at all, not even under the most favourable conditions in terms of fertilizer, water, soil and leaf temperature, air humidity, etc. The plant must protect itself more and more against an excess of energy.

- finally the radiation intensity becomes so high that photosynthesis declines and irreversible damage to the plant can occur. Beyond a certain PAR value, usually around 1500 PAR, even the relative C0₂ assimilation decreases.

It should be pointed out that these PAR graphs in practice are determined by experiment. The yardstick for photosynthesis here is the relative C0₂ assimilation, since the absolute values are heavily dependent on a whole series of growth conditions, such as ambient temperature, fertilizer, soil moisture, air humidity, C0₂ concentration, etc. Furthermore, the relative values can vary within a particular plant species (several cultivars) .

One can clearly deduce from Figures 5 and 6 that the solar energy available for photosynthesis quite often exceeds the quantity of energy which can be used by the plant. This phenomenon increases as one approaches the Equator. This is not only inefficient, but can even lead to damage or destruction of certain crops.

This clearly shows that the growing of crops on the shadow surface does not necessarily entail any negative effects. It can even be advantageous for certain crops, since the damage or destruction caused by an excess of PAR can thus be avoided.

Apart from using the curves in Figures 5 and 6 to determine whether a crop will thrive on the shadow surface or the solar surface, this can also easily be done by planting the crop on the ridges following the aforementioned implementations and verifying experimentally whether or not the crop thrives. This has the additional advantage that in this way the influence of other factors can also be estimated. This includes for example the condition of the soil and more specifically the water management, which can also influence the crop. If, for example, the ridges are made too high, negative influence on the water table can occur, causing the soil on the upper sides of the ridges to become too dry and/or the soil at the bottom of the ridges to become too humid. Additionally, the plants' geotropism can also be a factor, i.e. the tendency of the plant to assume a certain position in relation to gravity. Especially in higher crops it can occur that the increase in surface area is cancelled out by geotropism. In such cases, the obtained angles can be selected to be smaller to cancel out the negative effects.

Crops that specifically qualify are cultivars of lettuce and many leafy vegetables in general, grasses, strawberries, potatoes, clover, alfalfa, lentils, bush beans, gherkins and succulent plants. With the exception of some grasses, these are mostly annual plants.

Below several specific examples are given for the determination of the size of the ridges in function of the cultivated crop.

EXAMPLES

Example 1 Lettuce - Lactuca sativa Lettuce, more specifically a cultivar of Lactuca sativa, is a crop of low height - 25 cm at most - that is hardly subject to geotropism. In this example it is planted at 50 degrees north latitude with a period of growth from 15 April to 15 September, i.e. the first plants are planted on 15 April and the last plants are harvested on 15 September. In this case the sun is always in the south at 12h solar time and therefore the implementation from Figure 1 is applicable. The lowest position of the sun is on 15 September, when it is at 43 degrees; in other words, the angle 119 is 43 degrees. From this can be deduced that the angle 120 of the shadow surface has a maximum size of 43 degrees minus 5 degrees, i.e. 38 degrees at most. In this example an angle of 35 degrees is chosen. The angle 121 at the sun side is chosen so as to be as large as possible, in this case 60 degrees. For the width of the base 110 2.3 meter is chosen, from which can then be deduced that the side 111 of the solar surface 115 is 1.3 meters and the side 112 of the shadow surface is 2 meters. The theoretical gain in surface area is then approximately 1.43. The practical losses - there is always some loss at the edges of the surfaces - are estimated at 5%, so that the total increase in yield equals 1.36 or 36% in case lettuce is planted on both the shadow and the solar surface. Example 2 Strawberries - Fragaria ananassa

Strawberries, more specifically a cultivar of Fragaria ananassa, is also a crop of low height - 30 centimetres at most - in which the effects of geotropism are negligible. In this example it is planted at 40 degrees south latitude, with a period of growth from 1 October to 20 March. In this case the sun is always in the north at 12h solar time and an implementation analogous to the one depicted in Figure 1 is therefore applicable, with an inversion of north 118 and south 112. The lowest position of the sun at 12h solar time is on 20 March, when it is at 51 degrees; in other words, the angle 119 is 51 degrees. From this can be deduced that the angle 120 of the shadow surface has a maximum size of 51 degrees m inus 5 degrees, i.e. 46 degrees at most. In this example an angle of 36 degrees is chosen. The angle 121 at the sun side is chosen so as to be as large as possible, in this case 55 degrees. For the width of the base 110 2,8 meters is chosen, from which can then be deduced that the side 111 of the solar surface 115 is 1.6 meters and the side 112 of the shadow surface 116 is 2,3 meters. The theoretical gain in surface area is then approximately 1.39. The practical losses - there is always some loss at the edges of the surfaces - are estimated at 10%, so that the total increase in yield equals 1.25 or 25% in case strawberries are planted on both the shadow and the solar surface.

Example 3 Grass - Brachiaria decumbens

In this example, grass, more specifically a cultivar of Brachiaria decumbens, is sown at 23.5 degrees north latitude, i.e. on the Tropic of Cancer, with a period of growth extending over the entire year. In this case, the sun is always in the north at 12h solar time and the implementation depicted in Figure 1 is therefore applicable. The lowest position of the sun at 12h solar time is on 21 December, when it is at 43 degrees; in other words, the angle 119 is 43 degrees. From this can be deduced that the angle 120 of the shadow surface has a maximum size of 43 degrees minus 5 degrees, i.e. 38 degrees. In this example, an angle of 38 degrees is indeed chosen. The angle 121 at the sun side is chosen so as to be as large as possible, in this case 45 degrees. The base 110 is in this case chosen to be wider so that the shadow surface and the solar surface can be cultivated with an agricultural machine. For the base 110 a width of 5.6 meters is chosen, from which can be deduced that the side 111 of the solar surface 115 is 3.5 meters and the side 112 of the shadow surface (111) is 4 meter. The theoretical gain in surface area is then approximately 1.34. The practical losses are estimated at 5%, so that the total increase in yield equals 1.27 or 27% in case grass is sown both the shadow and the solar surface.

Example 4 Clover - Trifolium rueppellianum

In this example, clover, more specifically a cultivar of Trifolium rueppellianum, is sown on the Equator, with a period of growth extending over the entire year. In this case, the sun is at times in the north and at times in the south at 12h solar time and both surfaces of the ridges are therefore shadow surfaces. Figure 4 is therefore applicable. On 21 December, the sun is in its lowest position in the north at 12h solar time, with the angle 419 at 67 degrees. On 21 June, the sun is in its lowest position in the south at 12 solar time, with the angle 417 at 67 degrees as well. The maximum size of angles 420 and 421 of both shadow surfaces is 5 degrees smaller and therefore 62 degrees. Due to the condition of the soil, an angle of 50 degrees is chosen in this case. For the base of the cross section 2.6 meters is chosen, which means that both sides are 2 meters in length. The theoretical gain in surface area is then 1.54 and after subtraction of an estimated practical loss of 8%, the estimated obtained increase in yield equals 1.4 or 40%.

Claims

Method for growing crops (122) on a terrain, comprising the steps of:

- dividing soil of the terrain along parallel ridges (100, 101, 400); characterized, in that

- said ridges (100, 101, 400) are provided with a longitudinal direction (104, 105, 404, 405) substantially parallel to an east-west direction; and

- said ridges (100, 101, 400) comprise a first (111) and a second (112) top plane defining respectively a first (115, 415) and a second surface (116, 416) of said ridge; whereby an angle (120, 420, 421) between (i) a horizontal plane (130, 430) and (ii) a first and/or second shadow surface is not larger than an angle of elevation at 12h solar time during the period of growth of the crop; whereby said shadow surface is defined as said first and/or second surface which during the period of growth of the crop at 12h solar time is at times not directed toward the sun (140, 201, 440, 441).

Method according to claim 1, wherein said angle (120, 420, 421) is at least 5 degrees smaller than an angle of elevation at 12h solar time during the period of growth of the crop.

Method according to claim 1 or 2, wherein said angle of elevation corresponds to a smallest angle of elevation (119, 419, 417) of the sun at 12h solar time during the period of growth of the crop when the sun is at times not directed toward the first and/or second surface, respectively.

Method according to any of the preceding claims 1 to 3, wherein said ridges (100, 101, 400) are formed to have a triangular cross section (102, 402).

Method according to any of the preceding claims 1 to 4, wherein said ridges (100, 101, 400) are provided as frames, preferably aluminium frames.

Method according to any of the preceding claims 1 to 5, wherein said soil is divided in one or more conduits provided along said ridges (100, 101, 400).

7. Method according to any of the preceding claims 1 to 6, wherein an angle (121) between (i) a horizontal plane ( 130) and (ii) said first and/or second surface which during the period of growth of the crop is always directed toward the sun at 12h solar time is at least 30 degrees.

8. Method according to any of the preceding claims 1 to 7, wherein an angle (121) between (i) a horizontal plane ( 130) and (ii) said first and/or second surface which during the period of growth of the crop is always directed toward the sun at 12h solar time is at most 70 degrees.

9. Method according to any of the preceding claims 1 to 8, wherein an angle (120, 420, 421) between (i) a horizontal plane (130, 430) and (ii) said first and/or the second surface which during the period of growth of the crop is at times not directed toward the sun at 12h solar time is at least 15 degrees.

10. Method according to claim 9, wherein said first and/or the second surface which during the period of growth of the crop is at times not directed toward the sun at 12h solar time is provided with reinforcements.

11. Method according to any of the preceding claims 1 to 10, comprising further the planting of crops (122) on one and/or both surfaces.

12. Method according to any of the preceding claims 1 to 11, comprising further the installation of solar panels on a surface which during the growth of the crop is always directed toward the sun at 12h solar time.

13. Agricultural machine adapted for the execution of the method according to one of the preceding claims.