Fertilizers come from natural resources, most of which are both limited in quantity and becoming more expensive. Efficiency in their use is increasingly important. Soil Tests, Timing, Placement Proper use of soil tests is the most feasible way for farmers to determine the amounts of fertilizer and lime needed for their particular combination of soils and Crops. Application timing also is important. In general, the greatest efficiency results when fertilizer is applied at or near planting time.
Proper timing is most important with nitrogen fertilizer.
In some locations, a large part of it may be lost if it is applied too long before the crop is planted. In some cases, applying nitrogen during growing season is more efficient than applying it at planting. Phosphorus application also is most efficient when made at or near planting time, especially with soils low in phosphorus. If the soils are relatively high in phosphorus, timing is not so important. Time of application is less critical with potassium than with nitrogen or phosphorus.