Crop Canopy Mapping
A map showing crop veg index changes and so changes in Kg of nitrogen within the field. The ideal base for variable rate nitrogen.
Leaves contain valuable nitrogen, overwintered crops store nitrogen taken from the soil in their leaves. As the plants cope with winter and gather all the nitrogen that they are able to from the soil natural variation occurs. As the varying canopies contain different amounts of nitrogen, and it is possible to measure these differences, it makes little sense to apply an even rate. HGCA research such as the "wheat growth guide" have created crop growth models based on canopy size and the optimum size at each growth stage. This information along with a map of crop canopy gives a scientifically valid method of managing nitrogen application. The biggest variable in this technique is the efficiency with which the soil can deliver the nitrogen to the plant. A variable rate nitrogen system will work best when there are no other major limiting factors and where canopy maps are delivered on time.
