Means of Weed Control and Application of Nitrogen Fertilizer under the Canopies of Apple Trees

摘要

The initial aim of the trial was to find the best agronomic practices to maintain strips around trees free of weeds. In this paper the availability of nitrogen for fruit trees was emphasized. From 1976-1983 in Pure, Latvia, an orthogonal factorial experiment with apple cultivar 'Celminu Dzeltenais' on seedling rootstocks was established, where the effects of three methods for controlling weeds along with a nitrogen fertilizer applied in the strips was investigated as to the effects on growth and cropping of trees. The means of controlling weeds were: simazine (0.75 g m~(-2)), 2.4D (0.4 ml m~(-2)) and hand weeding. The nitrogen (N 120 kg ha~(-1)) was applied as ammonium nitrate. All factors were applied to circles areas around tree trunks (diameter 5.06 m). In the remaining area during the first four years the soil was cultivated, but during the next four-year period a sod mulch system was established. Weeds were almost completely controlled by simazine, but less efficiently mechanically by hoeing.The effect of 2,4D on the total amount of weeds was negligible, as only the dicotyledons were killed. During the first four years none of the four factors significantly influenced the growth or cropping of the trees. During the second four-year period ofthe trial, when perennial grasses were grown in the rows of trees, the largest on the yield of apples was exerted by the nitrogen fertilizer. The positive effect of simazine was less significant. Minimal, although present, was the effect of hoeing. 2,4Dhad no significant influence on the yield. The growth of the trees was significantly enhanced both by nitrogen and simazine, but the effect of hand weeding was minimal. The possible specific role of simazine in nitrogen availability for fruit trees in connection with soil microbiological activity is discussed.