GROWTH DYNAMICS OF WINTER-WHEAT IN THE FIELD WITH DAILY FERTILIZATION AND IRRIGATION

In a field experiment with fertilized and irrigated winter wheat the above-ground crop was sampled once a week. Phenological development, plant density and canopy height were recorded and the green surface areas of leaves, stems and ears were measured. Soil mineral nitrogen was sampled and the field climate monitored. There were four treatments. The daily irrigated/fertilized (IF) and daily irrigated (I) treatments were both irrigated by a drip-tube system. Liquid fertilizer was applied to IF following a logistic function according to calculated plant uptake. A total of 200 kg N ha(-1) was applied. Treatment I, control (C) and drought (D) were all fertilized once in spring with 200 kg N ha(-1). In treatment D transparent screens were used to divert rainwater. Dry matter production ranged between 1400 in D and 2352 g m(-2) in IF. The corresponding amount of nitrogen uptake ranged between 15.8 and 24.6 g m(-2). After harvest, soil mineral nitrogen was lowest in IF. An increase in the availability of nitrogen and water enhanced total biomass production as well as grain yield and leaf area. The daily supply of nitrogen according to crop demand delayed nitrogen uptake and increased total uptake. The results suggest that when the nitrogen is supplied in accordance with crop demand, the efficiency with which the applied fertilizer is utilized increases and the risk for nitrogen leaching decreases.