Untersuchungen zur Optimierung der N-Aufnahme von Winterweizenbeständen durch ergänzende Düngungmaßnahmen

Investigations on supplemental N-fertilizer application for the optimum course of N-uptake into winter wheat stands
During a period of 5 years 14 N-fertilization field trials with winter wheat have been carried out in which N-uptake and biomass production in 6 growth stages were analysed. By comparison with non-optimal variants of N-supply a critical range for N-uptake has been recognized which centered around an optimum value of 86 kg biomass N/ha at growth stage EC32. In connection with intensified N-uptake during later growth stages, this has allowed full exploitation of the wheat yield potential without substantial decrease of the N-harvest index.
Field trials on two different soil types (Parabraunerde and humose Auenrendzina), different dates of sowing and long year stands in wheat monoculture as well as applications of N-fertilizers containing dicyandiamid for delay of nitrification showed differences in efficiency as related to the fertilizer dosages but no systematic deviation from the optimum course of N-uptake for full exploitation of yield potential.
Provided that excessive fertilizer dosages before EC32 had been avoided, it seems possible to adjust the reuptake of winter wheat stands close to its optimum within an error of not more than 30 kg fertilizer N/ha by growth stage oriented splittings of fertilizer application and adequate account of soil-N supply and weather conditions during early growth stages.
Full exploitation of the wheat yield potential has been possible in all trials without significant losses in N-use efficiency if optimal splittings and dosages of supplemental N-fertilizers were provided.