Patent Publication Number: US-10765074-B2

Title: Cultivation system

Description:
CULTIVATION SYSTEM 
     This is a national stage application filed under 35 U.S.C. 371 of international application PCT/BE2016/000030, filed Jun. 28, 2016, which claims priority to Belgian patent application BE 2015/5409, filed Jun. 30, 2015, the entirety of which applications are incorporated by reference herein. 
     The present invention relates to a system for cultivating a crop. The invention relates particularly to a system for cultivating a crop by means of hydroponics. 
     Hydroponics is the growing of plants in water to which the necessary nutrients have been added. It is a cultivation method which is applied increasingly often, not only for house plants but also for cultivation of vegetables, such as tomato, chicory, lettuce and other crops, in a protected space (glasshouse or building) or outside. An important advantage of hydroponics relative to soil cultivation is that water and nutrients can be dosed in simple and precise manner. Soil-bound diseases usually do not occur, and there is thereby much less need for treatment with agents against disease. 
     Cultivating a crop in hydroponics typically comprises multiple stages. A first stage is the sowing and germination stage. Different units of medium (substrate) are first placed, optionally packaged (soil block (root ball), potting compost, pot, net, . . . ), in a receptacle or tray. One or more seeds are then placed in or on the medium. The number calculated per m 2  varies from 200 to more than 1000, depending on the dimensions of the medium and the type of seed. The germination stage takes place in a germination chamber (germination cell). Temperature and moisture are mainly controlled here in order to bring about optimal germination of de seed. After germination, the receptacles/trays are displaced from the germination space to the glasshouse, where the plants can grow to a determined size. This is the raising stage. After the raising stage, the plants are usually carried from the plant grower to the market gardener. At the market gardener with a hydroponics system in gutters the plants will be transplanted to a tray. One density of 100 per m 2  is usually applied. This stage is referred to as the extended raising stage. Water, optionally with fertilizers, is supplied onto the tray via overhead irrigation. The extended raising stage is followed by the cultivation stage. In the cultivation stage the plants are typically placed in gutters which are provided to slide apart as the crop grows, such that the crop has space to reach full growth while the surface area is utilized optimally. 
     WO 94/07354 describes a system of movable gutters for cultivating a crop. This system is typically used in the cultivation stage. WO 94/07354 describes a system for cultivating a crop with a guide for guiding a plurality of gutters in a predetermined area, wherein each gutter is provided to contain a plurality of crop units of a crop and wherein the guide is provided to guide the gutters in a first direction extending from a first edge to a second edge of the area, wherein the guide is further provided to gradually increase the distance between adjacent gutters in said direction, such that the number of crop units per m 2  in the area substantially decreases from the first edge to the second edge. A surface area in a glasshouse can in this way be utilized optimally when hydroponics is applied, wherein the advantages of hydroponics relative to soil cultivation are described above. 
     It is an object of the present invention to further optimize the process of cultivating a crop. 
     The invention has for this purpose the feature that the area comprises a first zone adjacent to the first edge and a second zone adjacent to a second edge, and wherein each gutter in the first zone is provided to contain crop units with a first intermediate distance and wherein each gutter in the second zone is provided to contain crop units with a second intermediate distance, wherein the first intermediate distance is considerably smaller than the second intermediate distance and wherein the distance between adjacent gutters in the first zone at the position of a transition from the first zone to the second zone is considerably greater than the distance between adjacent gutters in the second zone at the position of the transition. 
     Because the area with gutters now comprises two zones and the crop units in the first zone are positioned considerably closer together in the gutters, it is possible in this first zone to optimally fill the available surface area with plants which are considerably smaller than in a prior art gutter system. The gutters in the first zone move apart as the small plant grows, until the transition location between the first zone and the second zone is reached. The plants or crop units are then at least partially transplanted to the second zone, where the intermediate distance in the longitudinal direction of the gutter between the crop units is considerably greater than in the first zone. The plants are hereby given considerably more space in the longitudinal direction of the gutter, and the distance between adjacent gutters can therefore be considerably reduced. It is noted here that the plants of the mutually adjacent gutters are preferably positioned in a triangular pattern. The gutters can then be moved apart in the second zone as the crop grows, such that the crop can be harvested when the gutters reach the second edge and the crop has then also reached full growth. 
     Tests have shown that constructing the system for cultivating a crop in this way enables considerable optimization of the extended raising stage as well as the cultivation stage. The plants are traditionally placed on trays (in receptacles) in the extended raising stage, typically at the market gardener. Crop units in such receptacles or trays are considerably more difficult to provide with water and nutrients than crop units in gutters. Because the trays or receptacles are irrigated from above, the distribution of water and nutrients is further not homogeneous. This often causes crop units located at the edge of a zone to dry out, which results in losses. Watering the crop by means of irrigation is further considerably less efficient than watering in a gutter. It has also been found that the roots of the crops grow considerably less well on the sides of tray or receptacle zones than in the gutter, this because they are often subjected to drying out and to light in the receptacle or tray. The root of a tray plant is not the same root as a root which is continuously wet owing to the nutrient solution (water with fertilizers) flowing intermittently through the gutter. The intermittent watering is fully computer-controlled, and once the start time and end time have been set (a combination of time-based starts and light-based starts (until a threshold value of the light is reached)) the times at which the plants must receive nutrient water need not be given any more thought. In the tray (receptacle) zone this is completely different and cannot be automated, and the area surrounding the root constantly varies between wet and dry area. 
     Because the system according to the invention allows relatively small plants to be placed in gutters in an optimal manner, plants coming from the raising stage can be placed directly in gutters. When these plants are placed in the gutters, watering can take place in optimal manner, roots of the plants can develop properly because they are subjected much less to drying air (and also light), and no losses will occur due to uneven or irregular watering. Along the transition from the first to the second zone at least part of the plants are transplanted, wherein the intermediate distance of adjacent plants in a gutter is considerably greater. 
     An unexpected and surprising advantage has surfaced in the transplanting or transferring of the plants from gutters in the first zone to gutters in the second zone. It has been ascertained in this transplanting or transferring of the plants to gutters in the second zone that the plants experience no appreciable stress because the roots have already developed in a gutter with an intermittent throughflow of a nutrient solution. This is the same in the second zone, and the plant thereby continues to grow optimally. This is in contrast to the transplanting of plants from a tray or receptacle to a gutter. When plants from a receptacle or tray are planted in a gutter, the plant experiences stress because the manner of watering and fertilizing is different. A plant in a tray field is in practice watered a maximum of twice per day in summer, and is in winter even watered only a few times per week. This discontinuous watering results in a different type of root (an aerial root) being formed. The tray plant which is transplanted into a gutter has to adapt to this change from discontinuous (from several times per week to a maximum of twice per day) to intermittent watering (from six times per day in winter to more than double that in summer), which causes stress (production of new roots), whereby the rate of growth of the plant suffers a setback. Because transferring takes place from one gutter to another gutter in the system according to the invention, the area surrounding the plant and root remains substantially the same and the plant will experience no appreciable stress. In the case of tray plants a lag in growth of a few days can easily occur. 
     The stepwise increase in intermediate distance between adjacent plants in a gutter is at least partially compensated in that the distance between adjacent gutters in the second zone is considerably smaller at the position of the transition than the distance between adjacent gutters in the first zone at the position of the transition. The surface area remains optimally utilized hereby. 
     The ratio of the first intermediate distance and the second intermediate distance and the ratio of the distance between adjacent gutters in the second zone and the first zone at the position of the transition is preferably such that the number of crop units per m 2  remains substantially constant along the transition. Crop units per m 2  remaining substantially constant is defined here as the difference in the number of crop units per m 2  being smaller than 25%, preferably smaller than 20%, more preferably smaller than 15%. Because the number of crop units per m 2  remains substantially constant, the surface area can remain optimally utilized along the transition from the first zone to the second zone. It is noted in this respect that the system with movable gutters has for its object to substantially continuously increase the available surface area per crop unit. The substantially continuous increase can also take place in small steps here, and along the transition from the first zone to the second zone such a step can be performed such that the transition does indeed display an absolute jump in number of plants per m 2 . Such a jump is however still considered substantially constant because this jump is considerably smaller than the difference in number of plants per m 2  at the position of the first edge and the second edge. 
     The guide preferably comprises a drive for moving the gutters in the first direction, wherein the drive is provided to change the distance between adjacent gutters in said direction. Such a drive can be formed in different ways, for instance by a robot, or by a drive rod or pull rod or drive chain with catches which are placed at a mutual distance corresponding to the distance between the gutters. One or more of such drives can be provided here, wherein a plurality of drives is for instance each time provided to drive one segment of the area. 
     A device is preferably further provided for transplanting at least part of the crop units along said transition from the first zone to the second zone. This device can be fully automated or can require intervention by a worker, wherein the device is for instance provided to position a full gutter of the first zone adjacently of one or more gutters of the second zone, such that a worker can manually transfer the plants from the gutter of the first zone to the gutter or gutters of the second zone. A device can alternatively be provided for automatically lifting at least part of the crop units from the first zone and placing these lifted crop units in gutters of the second zone. 
     The device is preferably provided to transplant all crop units from gutters in the first zone to gutters in the second zone. When all crop units are transferred from gutters of the first zone to gutters in the second zone, the gutters of the first zone can be optimized for relatively small plants while the gutters of the second zone are optimized for relatively larger plants. 
     Each gutter preferably comprises a plurality of means for containing a crop unit, this plurality of means having predetermined intermediate distances in the longitudinal direction of the gutter. The gutters are here preferably substantially tubular or U-shaped in cross-section with a cover (lid), wherein the plurality of means are formed as openings in the tube or cover, wherein each opening is formed to contain one or more crop units such that the medium and roots of the crop unit are situated substantially under the cover while leaves of the crop unit are situated substantially above the cover. This gutter construction is found to have a number of advantages, the intermediate distance between adjacent crop units is on the one hand predetermined and can thus be optimized. The cover will on the other hand ensure that less light reaches the roots of the crop units, so that these roots can grow. The cover further ensures that water in the gutter does not evaporate directly from the gutter. 
     The gutters are preferably placed in draining manner and the system comprises at the position of an end of the gutters a water dosing system and at the position of the other end of the gutters a water collecting system, such that the nutrient water flows through the gutters in controlled manner through the use of the system. The water collecting system is more preferably operatively connected to the water dosing system (for instance by a collecting tank), such that substantially all nutrient water can be recuperated. A closed circuit in which the water with the nutrients flows is obtained in this way. This allows for water and fertilizers to be handled highly efficiently and for water to leave only through evaporation, and fertilizers through uptake by the plant. 
     A plurality of water dosing systems and a plurality of water collecting systems are preferably provided such that a different quantity of water and/or water with different properties can be supplied to various gutters. This plurality of nutrient water dosing systems and collecting systems can then be placed in predetermined segments of the area so that the nutrient water (water with fertilizers) can be optimized depending on the growth stage which the crop is in. It will be apparent here that small plants have different needs than large plants. 
     The system preferably further comprises a raising zone with a further guide for guiding a plurality of raising gutters in a further area adjacent to the first edge, wherein each raising gutter is provided to contain a plurality of the crop units with a further intermediate distance which is considerably smaller than the first intermediate distance, wherein the guide is provided to gradually increase the distance between adjacent raising gutters in said direction and wherein the distance between adjacent raising gutters at the position of a further transition from the raising zone to a first zone is considerably smaller than the distance between adjacent gutters at the position of the further transition, such that the number of crop units per square metre remains substantially constant along the further transition. Just as in the transition from the first zone to the second zone, it is the intention that there is no sharp transition here from for instance 200 to 100, but that the drop in the number of units/m 2  follows a continuously declining trend. This raising zone is thus optimized by making use of gutters. The intermediate distance between plants in a raising zone is considerably smaller here than the intermediate distance between plants in the first zone. This allows the surface area to be optimally utilized. This also makes it possible to give the plants more space in the raising stage by moving raising gutters apart as the plant grows in the raising stage. This allows the whole system to be optimized further, wherein the raising stage is for instance longer, wherein the plant can become bigger than in a raising stage carried out in the traditional manner. The transition location between the extended raising stage and the cultivation stage can in the system according to the invention also be chosen so as to further optimize the growth of the crop, the production process and the surface area utilization. This is not possible in traditional systems, even if the cultivation stage is carried out in movable gutters. 
     The invention further relates to a method for cultivating a crop, wherein the method comprises the following steps of: 
     planting units of a crop in a plurality of gutters at the position of a first edge of a predetermined area; 
     guiding a plurality of gutters in a first direction which extends from the first edge to the second edge of the area, wherein the distance between the adjacent gutters gradually increases during the guiding such that the number of crop units per m 2  decreases from the first edge to the second edge; 
     harvesting the crop units at the position of the second edge; characterized in that the method further comprises of: 
     transplanting at least part of the crop units along a transition from the first zone of the area adjacent to the first edge to a second zone of the area adjacent to the second edge, such that each gutter in the first zone is provided to contain crop units with a first intermediate distance and each gutter in the second zone is provided to contain crop units with a second intermediate distance, wherein the first intermediate distance is considerably smaller than the second intermediate distance and wherein the distance between adjacent gutters in the first zone at the position of the transition is considerably greater than the distance between adjacent gutters in the second zone at the position of the transition. This method describes the use of the system described above. The effects and advantages described above therefore also apply for the method according to the invention. 
     The method preferably further comprises of advancing at least part of the plurality of gutters in said first direction by means of a drive. 
     The invention will now be further described on the basis of an exemplary embodiment shown in the drawing. 
    
    
     
       IN THE DRAWING 
         FIG. 1  shows a schematic top view of a cultivation system according to an embodiment of the invention; 
         FIG. 2  shows a side view of a zone of a cultivation system of  FIG. 1 ; 
         FIG. 3  shows a perspective view of a gutter for application in the cultivation system according to the invention; 
         FIG. 4  shows a cross-section of a gutter with crop unit; 
         FIG. 5  shows a schematic illustration of a greenhouse with a plurality of systems according to the invention; 
         FIG. 6  shows different gutters from different zones of a preferred system according to the invention; 
         FIG. 7  shows a preferred drive system for application in the cultivation system according to the invention; and 
         FIG. 8  shows a graph which illustrates the effect of the cultivation system according to the invention. 
     
    
    
     The same or similar elements are designated in the drawing with the same reference numerals. 
       FIG. 1  shows a top view of a system for cultivating a crop according to an embodiment of the invention which is placed in a predetermined area  1 . This predetermined area  1  is in practice preferably formed by a greenhouse or glasshouse or an outdoor installation. A section of a greenhouse or glasshouse can here also form the predetermined area, wherein another section of the greenhouse or glasshouse is used for other purposes. It is also possible for a plurality of systems for cultivating a crop according to the invention to be placed in one greenhouse or glasshouse, which is illustrated in  FIG. 5 . A first edge  2  and a second edge  3  can be defined in predetermined area  1 . First edge  2  and second edge  3  are situated opposite each other and define a first direction extending from first edge  2  to second edge  3 . This first direction is the direction in which the crop will move during cultivation. The predetermined area  1  further comprises lateral sides  4  which demarcate area  1 . It is noted in this respect that gutters from another zone can likewise be transplanted to zone  2 . 
     At the position of first edge  2  crop units of a crop are introduced into the system for cultivating the crop, this being designated schematically in the figure with arrow  5 , and at the position of second edge  3  fully grown crop units are harvested and thereby removed from the system for cultivating a crop, this being designated schematically with arrow  6 . The system for cultivating a crop comprises two zones, a first zone  7  adjacent to the first edge  2  of predetermined area  1  and a second zone  8  adjacent to the second edge  3  of predetermined area  1 . First zone  7  and second zone  8  are further mutually adjacent at the position of a substantially centrally located section  12  of predetermined area  1 . Substantially centrally located section is defined here as the location located at least a first distance removed from both first edge  2  and second edge  3 , wherein the first distance is preferably at least 5% of the distance between first edge  2  and second edge  3 , more preferably at least 10%. Substantially centrally thus does not imply that it must lie at the mathematical midpoint between the first edge and the second edge. 
     A plurality of gutters, designated respectively with reference numerals  9  and  10 , are placed in both first zone  7  and second zone  8 . Each gutter extends here substantially parallel to first edge  2  and second edge  3 , and a guide  11  is provided for guiding gutters  9 ,  10  in the first direction. The first direction is substantially perpendicular to gutters  9 ,  10 . In the embodiment of  FIG. 1  guide  11  lies on a plurality of support profiles which are placed substantially horizontally (in the longitudinal direction from edge  2  to  3 ). In the transverse direction (direction of the gutters) the support profiles lie at an incline corresponding to the drainage of the gutters. The number of support profiles (from edge  2  to  3 ) can be adjusted here on the basis of the support requirements of the gutters. The support profiles are preferably interrupted in their longitudinal direction at the position of transition  12  from first zone  7  to second zone  8  such that gutters of first zone  7  can also remain in this first zone and can be carried back to first edge  2 , while the gutters of second zone  8  can remain in this second zone and are carried back to transition  12  after harvesting at the position of second edge  3 . The support profiles comprising guide  11  preferably have a flat upper side such that gutters  9 ,  10  can slide on the flat upper side of the support profiles. It is usually the case in practice that zone  2  is divided in two in respect of the guide system. The support profiles and therefore also the guide system change at the point of division. 
     The technical difference between first zone  7  and second zone  8  lies in the intermediate distance between adjacent crop units in the gutters. The intermediate distance  13  between crop units in gutters  9  of first zone  7  is particularly considerably smaller than the intermediate distance  14  between crop units in gutters  10  of second zone  8 . Apart from this difference between intermediate distances  13  and  14 , the technical construction and the operation of the system will be substantially the same in first zone  7  as in the second zone. Zone  7  now has only one driven pull rod system (due to the limited length). 
     Characteristic of this system with two zones  7  and  8  is that a transition  12  can be designated where at least part of the crop units are transplanted or transferred from one gutter to another gutter. In the exemplary embodiment as shown in  FIG. 1 , all crop units are transferred from gutter  9  at the position of transition  12  to one or more gutters  10  of second zone  8  at the position of the transition. This can take place automatically, mechanically or with intervention by a worker. In the embodiment of  FIG. 1  gutters  9  remain in first zone  7  and are carried back to first edge  2 . Gutters  10  of second zone  8  also remain in this zone, and when they reach the position of second edge  3  they are carried back to transition  12  and there filled once again. In an alternative embodiment the gutters continue from first zone  7  to second zone  8 , and gutters are added at the position of transition  12  so that part of the crop units can be transferred or transplanted from the gutters in the first zone to the additional gutters in order to thus increase the intermediate distance between adjacent crop units in the gutters. For the sake of clarity the space between two crop units is in this description referred to with the term intermediate distance, while the space between two gutters is referred to with the term distance. 
     In each zone  7 ,  8  gutters  9 ,  10  move in the first direction such that a start and an end can be defined for each zone  7 ,  8 , wherein the end of the zone is the section where the gutters arrive when they move in the first direction. At the position of the start of each zone  7 ,  8  gutters  9 ,  10  are positioned with a first distance between adjacent gutters  9 ,  10 , which first distance is designated respectively with reference numerals  15  and  17 . The first distance is minimal and, depending on the configuration of the system, can differ for first zone  7  and second zone  8 . Distance between gutters is defined as the distance between the central axes of the gutters. The first distance  17  of gutters  10  in second zone  8  at the position of transition  12  is preferably greater than the width of the gutter +0 mm, preferably greater than the width of the gutter +5 mm (+1 mm), more preferably greater than the width of the gutter +10 mm, such that gutters  10  do not come into contact with each other at the position of transition  12 . When gutters  10  in second zone  8  at the position of transition  12  are not pressed against each other, leaves of the crop are not pressed between adjacent gutters  10  either, such that the crop is not damaged. Advancing of gutters  10  during filling of the gutters or filling of at least part of the gutters along transition  12  is however considerably more difficult when gutters  10  may not be pressed against each other. This is further explained hereinbelow with reference to  FIG. 7 . At the position of the end of each zone  7 ,  8  gutters  9 ,  10  display a second distance between adjacent gutters, designated respectively with reference numerals  16  and  18 , which is considerably greater than first distance  15 ,  17 . The second distance is a predefined maximum distance and, depending on the configuration of the system, can differ for first zone  7  and second zone  8 . 
     The distance between adjacent gutters is increased from the first distance  15 ,  17  to the second distance  16 ,  18  in stepwise manner or continuously between start and end of the zone, over the length of each zone  7 ,  8 . The effect hereof is that the number of crop units per square metre decreases from the start of each zone toward the end of each zone. This has the result that the surface area per crop unit increases in each zone from the start toward the end, which allows each crop unit to grow and also to be given the surface area necessary for this purpose. The surface area at the start of each zone is optimally utilized here because the distance between the gutters is small when the crop units are also small and require less surface area per crop unit, and each crop unit is given sufficient space to grow in each zone because the distance between gutters increases from the start toward the end of each zone. 
     At the position of transition  12  the end of first zone  7  is adjacent to the start of second zone  8 . The gutters of the first zone at the position of transition  12  will hereby display a considerably greater distance between adjacent gutters than gutters  10  of second zone  8  at the position of transition  12 . Because of the combination of the considerable increase in the intermediate distance of crop units in one gutter in transition  12  from first zone  7  to second zone  8  and the considerable decrease in the distance between adjacent gutters along transition  12  from the first zone to second zone  8 , the number of crop units per m 2  can remain substantially constant along the transition from first zone  7  to second zone  8 . Substantially constant in this context is here defined above. Tests have shown that this way of working with two zones  7  and  8  allows a crop to be cultivated in considerably more efficient manner. The number of crop units per m 2  in predetermined area  1  can hereby decrease continuously and/or in stepwise manner from first edge  2  toward second edge  3 . The crop units can be planted here at the position of first edge  2  at a number of crop units per m 2  which is optimized as a function of the size of the crop units which are planted. At the position of second edge  3  the crop units are harvested and each crop unit has reached full growth, and the number of crop units per m 2  is optimized as a function of the size of the fully grown crop units. This allows cultivation of a crop in a manner which optimizes surface area. 
       FIG. 2  shows a side view of a first zone  7  of the system of  FIG. 1  and shows how gutters can be carried back to the start of the zone under guides  11 , as indicated with arrow  19 . The gutters are first emptied for this purpose, wherein crop units are first transplanted from gutters  9  of the first zone to gutters  10  of the second zone, which is indicated with arrow  20 . Gutters  9  can then be carried via a transport system under guides  11  to the start of the first zone. At the position of the start of the first zone gutters  9  are placed onto the start of the first guide and filled with crop units. This is illustrated in the figure with arrow  21 . The return of gutters  10  takes place under the guides. 
       FIG. 3  shows a perspective view of a gutter  10  of the second zone. Each gutter  10  is preferably tubular or U-shaped in cross-section, with a substantially slightly curved underside  25  on the inner side (the nutrient solution thus runs centrally through the gutter), and wherein the gutter is preferably provided with downward protruding legs  23  extending in the longitudinal direction of gutter  10 . Protruding legs  23  allow gutters  10  to be advanced in simple manner by means of a drive which is illustrated in  FIG. 7 . The tubular gutter requires no separate cover at the position where the U-shaped gutter is preferably provided on an upper side with a cover  24 . A plurality of openings  22  are formed in the upper side or in these covers, wherein each opening is provided to receive one crop unit. Openings  22  can take on any dimensions and shape (round, oval, square, rectangular . . . ) and have an intermediate distance  14 , as discussed at length above. Gutters  9  of first zone  7  are constructed in similar manner as the gutter shown in  FIG. 3 , however with an intermediate distance between openings  22  which is considerably smaller than the intermediate distance  14  shown in  FIG. 3 , which difference is illustrated in  FIG. 6 . 
       FIG. 4  shows a cross-section of a gutter  10  at the position of an opening  22  and shows a crop unit placed therein. The crop unit grows in a substrate (medium)  26 . The roots of the crop grow in the medium but also outside the medium, on the bottom of the gutter. The crop has leaves and/or fruits  27 . Leaves and/or fruits  27  typically extend above cover  24  here, while the medium with roots  26  extends substantially under cover  24 . The advantage hereof is that the roots are shielded from the light. The water mixes with air and thereby takes up oxygen. The oxygen is very important for the growth of roots and plant. This manner of cultivating crops in gutters is generally known as NFT (Nutrient Film Technique), i.e. a thin film of nutrient solution flows through the gutter, in which the roots of the plant then develop, which is a form of hydroponics. 
       FIG. 5  shows a predetermined area  1  in which a plurality of systems according to the invention are placed and wherein a further area  28  is provided which is adjacent to the first edge of predetermined area  1 . This further area  28  is provided with a system which is similar to the system of each of the zones  7 ,  8 , whereby a third zone is created, also referred to as raising zone, which is provided just as the first zone and the second zone with a guide and with a plurality of raising gutters, wherein each raising gutter is provided to contain a plurality of crop units with an intermediate distance smaller than first intermediate distance  13  and wherein the further guide is provided to move the raising gutters in the direction of the first edge of predetermined area  1 , while the distance between adjacent raising gutters increases. The same effect as described above in respect of transition  12  will hereby occur in a further transition from raising zone  28  to first zone  7 . This means that the number of crop units per m 2  along the transition from the raising zone to the first zone can remain substantially constant. The surface area of further area  28  can also be optimally utilized. 
       FIG. 6  shows three gutters of three different zones  7 ,  8  and  28 . The figure shows here a gutter  10  of second zone  8 , a gutter  9  of first zone  7  and a gutter  29  of raising zone  28 . The figure makes clear here that the intermediate distance between adjacent crop units in raising gutter  29  is considerably smaller than the intermediate distance between adjacent crop units in gutter  9  of the first zone (extended raising zone), and that this intermediate distance between the adjacent crop units in first zone  7  is considerably smaller than the intermediate distance between adjacent crop units in gutters  10  of second zone  8 . In combination with the reduction in the distance between adjacent gutters  9 ,  10  and  29 , this allows the number of crop units per m 2  to be kept substantially constant at each transition between zones. 
       FIG. 7  shows a preferred drive for application of the system according to the invention. It will be apparent here that different sorts and types of drive, including manual driving of the gutters wherein gutters are displaced manually, can be applied in order to execute the principle of the invention. A robotic system can also be used to advance the gutters. The preferred drive system of  FIG. 7  comprises a drive rod, for instance a pull rod,  30  with a plurality of catches  31 . Drive rod  30  is provided to move forward and backward as indicated in the figure with arrow  33 . A plurality of such drive rods, each time controlling a segment of the length of the system, are provided over the length of the system for cultivating a crop which extends from first edge  2  to second edge  3 . A physical division of zone  2  and the resistance of materials usually determine the length of a pull rod or guide system. 
     Each of the catches  31  can be tilted between a lying position in which the catch extends substantially parallel to drive rod  30  and an at least partially upward position in which catch  31  extends at least partially above drive rod  30  so as to be able to hook behind a leg of a gutter and thus pull the gutter along in first direction  34 . Catches  31  are here spring-loaded in upward direction such that they always tend to extend upward. When a downward force however engages on catches  31 , catch  31  will tilt counter to the spring force and extend substantially lying. Such a disposition allows gutters  10  to be driven when drive rod  30  moves in first direction  34 , while catches  31  extend upward and pull the gutters along. When the drive rod moves in the opposite direction, catches  31  will be pressed downward by gutters  10 , counter to the spring force of catch  31 , such that the gutters are not moved back. A one-way system for driving gutters is thus obtained hereby, wherein the distance between gutters can be changed in simple manner. 
       FIG. 7  shows on the right of the figure a further option wherein a part of drive rod  30  is covered at the top by a covering  35  which ensures that gutters  10   a  which are situated above the covering cannot be co-displaced in first direction  34  by catches. This allows a predetermined segment to be advanced in a zone, while another segment is intentionally not advanced due to covering  35 . This option becomes particularly relevant when the harvesting at second edge  3  of predetermined area  1  and the planting and/or transplanting in respectively first edge  2  and transition  12  do not take place simultaneously. 
     Harvesting and not simultaneously transplanting (along transition  12 ) creates a gap in zone  8 , which is filled once again during planting and/or transplanting. Closing of this gap then typically takes place by means of a drive rod connected to a drive chain in combination with a drive rod which starts at transplanting zone  12  and ends N gutters past cover plate  35 . The drive rod connected to a chain is typically situated in a starting position under the gutters at the position of covering  35 . During harvesting the gutters will be co-displaced by the drive rods ending at the second edge and starting at covering  35 . A gap, which has to be filled during transplanting, will result behind cover plate  35 . In order to fill the gap the pull rod on the chain will first move forward N positions so that the catches are pulled past cover plate  35  and extend upward. The drive rod which starts at transplanting zone  12  will then push N gutters past the cover plate. This process is repeated until the chain has moved the gutters over the whole gap. A gap in a field with gutters can thus be filled without gutters having to be pushed against each other. 
     The drive as shown in  FIG. 7  provides many options for designing and controlling the gutters in their movement in the first direction. This drive of  FIG. 7  particularly allows gutters to be added at the start of a zone, without these gutters having to be pushed against each other. The drive allows these gutters to be pulled along with a distance between adjacent gutters, wherein no leaves can be pressed between adjacent gutters, as already stated above. 
       FIG. 8  shows a graph which displays the effect of the use of a system as shown in  FIG. 1 . The graph shows the number of days a crop has been growing on the horizontal axis, while the number of crop units per m 2  is shown on the vertical axis. The values included in the graph are only an example, and it will be apparent that these values can differ considerably depending on the type of crop. The principles shown by this graph are however characteristic of the system according to the invention and are therefore generally applicable. The figure shows three stages, wherein first stage  37  indicates the raising stage. In the example of  FIG. 8  crop units are planted in the raising gutter at a rate of 216 crop units per m 2 . 
     After raising stage  37  the crop units are transplanted from gutters  29  to gutters  9  (extended raising stage zone  7 ) at the position of first edge  2 , where gutters  9  are then situated close together such that  108  crop units per m 2  are situated in gutters  9  at the position of first edge  2 . By increasing the distance between adjacent gutters in first zone  7 , in the example of  FIG. 8  in steps, the number of crop units per m 2  systematically decreases to 49 crop units per m 2  when gutters  9  are at the position of transition  12 . The crop units are then transferred or transplanted to gutters  10  in second zone  8  at, in the example of  FIG. 8 , a rate of 38 crop units per m 2 . This number of crop units of 38 per m 2  is obtained while the gutters in second zone  8  are situated close together, this by considerably increasing the intermediate distance between adjacent crop units in gutter  10  relative to first zone  7 . By increasing the distance between the gutters in second zone  8  while the gutters are moving from transition  12  to second edge  3 , the number of crop units per m 2  decreases systematically in order to give the crop space to reach full growth. At the position of second edge  3  the crop units have a density of about 15 crop units per m 2 , crop units have reached full growth, and can be harvested. The surface area of predetermined area  1  is in this way optimally utilized. 
     It will be apparent on the basis of the above description that, when the claim defines that the guide (pull rod) is provided for guiding the gutters in a first direction extending from a first edge to a second edge of the area, this does not mean that one guide covers the whole route from the first edge to the second edge. The guides will indeed all move in the first direction. This first direction extends from the first to the second edge. The plurality of guides together will ensure that the crop units move from the first edge to the second edge. 
     The skilled person will be able to understand the operation and advantages of the invention, as well as the different embodiments thereof, on the basis of the figures and the description. It will be apparent here that the description and the figures are intended solely for the purpose of understanding the invention and not to limit the invention to a few embodiments or examples used therein. It is therefore stressed that the scope of protection will be defined solely in the claims.