It has been found that the soil P & K status is more closely linked (inversly) to yield (crop offtake) than any other measurable factor. The yield map gives you a nutrient offtake map for replacement and naturally occuring management zones, to be used as the basis for a smart sampling solution and potentially much more. The smart sampling concept uses a combination of crop and soil sensors alongside farmer knowledge to predict natural variation and create zones of naturally similar soils and agronomic histories. This then allows great accuracy when measuring soil nutrient status without excessive costly sampling. Sensors used include weighcells in yieldmapping, canopy sensors such as CropCircle 4 and the EMI soil conductivity scanner 8. These sensors and maps can also be useful for variable rate seeding 8. All the maps can be managed in house using desktop software or through soilessentials office services.
Grid sampling for P & K is now more economic than ever. This gives a baseline of soil status that can be used as the starting point for a longer term system that encorporates measuring offtake. Traditionally low yielding areas may well have been overapplied with fertiliser for many years and so there is a saving to be made here. Ideally the grids should be aligned along the main fenceline.