PHOTO: ANTON DINGEMANSE
PHOTO: ANTON DINGEMANSE
VARIABLE TILLING ▶▶▶
Adapted spacing and fertilising yields better potato quality
BY LUUK MEIJERING F
or three years now, Johan van der Wekken at crop farm Thes Agro has been using prescription maps to plant chipping potatoes with variable spac-
ing. The prescription maps are produced by supplier Van Iperen. According to Anthon Slootweg, Specialist in Precision Agriculture, these maps are compiled on the basis of data that are publicly available free of charge, such as soil type maps, topographic maps, contour maps and satellite images.
Potential map Combining all the available data produces what is known as a potential map. It shows the areas of the plot that are most suitable for growing certain crops. Important factors in
Crop farm Thes Agro plants chipping potatoes with variable spacing, and this year Urean has also been applied at variable degrees. This yields a higher quality potato.
this regard include the heaviness of the soil and supply of moisture. In heavier soil, the de- gree of tuber formation is lower, making it nec- essary to plant closer together. However, if the supply of moisture is insufficient, this makes it necessary in turn to increase plant spacing, be- cause the plants then cannot grow all tubers to maturity. Thes Agro has these basic maps available for all plots. A prescription map is de- rived each time the land is cultivated, and this is done by Van Iperen.
Thes Agro
Johan van der Wekken (37), Burgh Haam- stede (Zeeland, Netherlands), is responsible for the application of precision agriculture techniques within Thes Agro. The heaviness of the clay and loam soil varies from 15 to 60% elutriable. The cropping plan consists of chipping potatoes, wheat, grass seed, sugar beet, seed onions, onion sets, alfalfa, and poppy seed.
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Calculating optimum site-spe- cific planting spacing The optimum number of potato stalks per square metre is determined, and that forms the basis for the number of tubers formed by a plant. As soon as the seed potatoes are in, Van Iperen carries out a germination test to deter- mine how many stalks one tuber can form, which is used to calculate the optimum plant- ing spacing at a specific site. This calculation therefore immediately indicates the necessary quantity of seed potatoes. During the three years of working in this way, Van der Wekken has found that the quantity of seed potatoes recommended as standard is often too little to achieve an optimum crop. This knowledge enables the available seed potatoes to be planted more effectively.
Sufficient variation In Van der Wekken’s view, the practical execu- tion of this type of precision agriculture poses no barrier whatsoever to trying out new tech- nologies. “Transferring from prescription maps to the on-board computer does require a great deal of time the first time you do it, but you become increasingly efficient at it. The potato planter then does exactly what you instruct it to do.”
▶ FUTURE FARMING | 1 November 2018
In the case of Agria potatoes, for example, Van der Wekken plants the tubers at intervals of between 25 and 33 centimetres. The grower believes, however, that the spacing needs to be varied sufficiently in order to achieve a good yield: “There is little point in varying plant spacing by 1 or 2 centimetres.”
Variable application of Urean In addition to varying planting spacing, this is the first season in which Van der Wekken has varied the nitrogen dose to the seed potatoes. To do this, he built an additional tank with a pump and coulters onto the potato planter in order to administer Urean into the soil close to the tuber. Prior to planting, all plots receive a basic dose of nitrogen according to the re- quirements of the variety and the plot. During planting, an additional 100 litres of Urean con- taining 30% nitrogen is applied per hectare. The variation in dose is around 50%. The same prescription map is used for the application of Urean as for the planting spacing. The high-po- tential parts of the plot receive larger doses, as this is where larger numbers of tubers need to be fed.
The potential maps Thes Agro starts out with. On the basis of these maps the planter deter- mines tuber spacing and dose of nitrogen.
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