EFFECT OF NITROGEN FERTILISATION AND SOIL MANAGEMENT ON SOIL MINERAL NITROGEN IN THE APPLE ORCHARD

摘要

In autumn 1993, 'sampion' apple trees were planted 3 x l m apart in humus-rich, silty alluvial loam in Warsaw-Wilanow. Herbicide was applied in a l m wide strip between rows. Starting in the spring of 1994, nitrogen was applied as ammonium nitrate according to five different treatments: N-0 (no nitrogen); N-50 (50 kg N ha~(-1) over the whole growing area in early spring); N-100 (100 kg N ha~(-1) over the whole growing area in early spring); N-5+5 (split dose: 50 kg N ha~(-1) over the whole growing area in early spring, repeated about five weeks later); and N-50-Herb (50 kg N ha~(-1) only in herbicide strips). In 1996 and 1997, mineral nitrogen (NH_4+ N0_3) in the upper 20 cm of the soil column was measured on three dates: before fertilisation (beginning of April); four weeks later (May) and nine weeks later (June). Separate soil samples were taken from the herbicide strips and from the swards. Soil treated with higher doses of fertilizer contained more mineral nitrogen (N-min), though this effect was not significant in the swards. As a rule, N-min was higher in the herbicide strips than in the swards; this difference was more pronounced in plots which were fertilised than in plots which were not fertilised. Soil N-min increased over time, peakingin June. N-min in unfertilised soil was similar at different sampling dates in 1996; in 1997 it was higher in June than in April or May. In 1996, N-min in unfertilised soil did not depend on where the sample was taken; in 1997, it was slightly higher under the herbicide strips.