Monday, 14 January 2019

Inter-Cropping Insight

Inter-cropping Sprayed Off
Back when we planted the oilseed rape crops in August we also planted their companion crops. This year we used 10Kg of vetch and 2kg of  Berseem clover/per hectare. These companions have grown very successfully through the autumn and into the winter. During the winter we sprayed a weed killer on most of the crop to remove the companion crops as well as weeds like sow thistle, mayweed, brome and black-grass. This herbicide does not affect the oilseed rape crop. Both of these legume crops are able to host soil bacteria to make plant available nitrogen from the atmosphere, something that the oilseed rape crop in unable to do. We hope that as much as 30-50Kg/ha of nitrogen will be available free of charge from these companion crops, easily covering the initial cost of the seed. This could be worth between £25-£41/Ha.
Canopy of Sprayed Off Inter-cropping
The picture above shows the crop where the companion crop has been sprayed off. We can measure the GAi (Green Area Index) or amount of green plant material with an app on a mobile phone. This picture shows a GAi of 1.34. There is about 50Kg/Ha of nitrogen in every GAi of an oilseed rape crop. Therefore this crop has captured 67Kg of Nitrogen. The picture below, where the companion hasn't been sprayed off, has a GAi of 3.05 indicating a potential level of 152Kg/ha of nitrogen in this whole canopy. Whether all of this canopy will relate to available nutrients for the oilseed crop to capture is something we don't know but its very interesting to see these levels of free nitrogen, even accounting for the 25Kg of fertiliser applied at planting.
Canopy Of Inter-cropping
We are planning to leave this area of the field until harvest to see what effect it has on the overall yield of the combined species. We should be able to reduce the amount of nitrogen this part of the field receives in order to keep the crop standing but also to rely on the nitrogen being created by the vetches and passed over to the oilseed rape. Time will tell what the outcome will be!