Investigations on the nitrogen dynamic as a basis for the N fertilizer recommendations in vegetable production

摘要

The results of investigations carried out over the last 10-15 years are discussed with regard to N fertilizer recommendations for vegetable production. Measurement of the soil N content at planting or before top dressing results in precise determination of fertilizer needs. When mineralization increases as a result of the addition of organic materials, this must be taken into account, as must leaching losses of nitrate due to extreme summer rainfall. When deriving mathematical estimates of N fertilizer requirements, the Nmin content of the soil, and N release from humus and fresh organic materials must be considered on the supply side, and N uptake by plants, the necessary mineral N content of the soil and N immobilization must be considered on the demand side.