EFFECT OF COMBINED SLURRY AND MINERAL FERTILIZATION ON YIELD FORMATION, YIELD COMPONENTS AND NITROGEN EFFICIENCY OF WINTER-WHEAT

From 1984/85 to 1987/88 field trials were conducted on the experimental farm Roggenstein in order to examine the efficiency of pig slurry applied at different developmental stages of winter wheat combined with different dosage and distributions of mineral N-fertilizer. On the average over 4 years maximum grain yield by applying exclusively mineral N-fertilizer has been achieved with 120 kg N/ha, with the optimal amount of N-fertilizer at the 3 developmental stages being 40 kg N/ha, respectively. Decreased yields induced by a reduced mineral N-fertilization could be compensated by application of 20 m(3)/ha or 40 m(3)/ha slurry either at the beginning of the growing period. EC 30-31 or EC 33-35 developmental stages. However, mineral fertilizer equivalents calculated on the oasis of the NH4-N-content of slurries for each year ranged from 25 to 79 in dependence of application date and prevailing, weather conditions. Regarding the effect on yield components, no difference between slurry and mineral N-fertilizer were observed. The mediocre and very variable efficiency of slurry-N leads to the conclusion, that the use of slurry in cereal production may be of limited value for agronomic as well as for ecological reasons, as long as no efficient and cost-effective application techniques are available.