Most methods are based on measuring the soil nutrient level and on calculating the planned yield. From the yield, the farmer estimates the removal of nutrients, that is, how much nutrients plants will take from the soil. Knowing this, you can calculate the dose of fertilizers that will provide the needed level for this desired yield.
Usually, the logic is as follows:
- If the level of phosphorus and potassium is below the optimum one, it is necessary to apply more fertilizers than the predicted removal.
- If the level of phosphorus and potassium is above the optimum one, then it is necessary to apply fewer fertilizers than the predicted removal.
It sounds simple, but the problem is that the nutrient level and productivity greatly differ from zone to zone.
The level of phosphorus and potassium can be estimated only by conducting an agrochemical soil analysis. This is an expensive method, and the selection of soil samples requires time and special equipment. Many commercial companies offer such a service. But it is still tricky: there is a clear methodology for carrying out the analysis itself, but there are different views on how to properly select soil samples.