YIELD OF MAIZE AND WINTER-WHEAT AS AFFECT ED BY AVAILABLE WATER CAPACITY AND N-FERTILIZATION IN DRY YEARS

In two dry years yield formation of maize and winter wheat was determi ned as affected by N-fertilization on soils of an available water capa city (awe) ranging between 30 mm and 240 mm in order to develop site s pecific N-fertilization strategies. On soils with low awe maize reache d highest yields (220 dt/ha up to 123 dt/ha) if the first N-applicatio n was applied at a plant height of 15 cm. A lower plant density stimul ated yields on soils with low awe also. A starter fertilization > 60 k g N/ha, however, gave highest yield increases (> 0.44 dt/hamm nFK) wi th increasing awc. Wheat reached highest yield (69 dt/ha) on soils wit h low awe and the highest yield increase with increasing awe (18.6 dt/ haln mm nFK) if moderate N-fertilization in early spring (30 kg N/ha) together with 60 kg N/ha in EC 30 were applied. A total amount of 160 kg N/ha was necessary over the whole range of the examined awe to ach ieve highest yields. Starter fertilization > 30 kg N/ha lowered yields .