GROWTH AND NUTRIENT-UPTAKE OF SPRING BARLEY UNDER DIFFERENT WATER AND NUTRIENT REGIMES

To study the effects of irrigation on spring barley in the field, the crop growth was monitored weekly in each of three treatments. The irrigated (I) treatment was irrigated using a drip-tube system. The control (C) and the drought treatment (D) were identical, except that transparent screens (2 x 3 m) were used to divert rainwater. In addition, a fourth treatment (IF) was established, were the drip-irrigation system was used to distribute a liquid fertilizer. The aim of the IF treatment was to give the plant access to non-limiting amounts of water and nutrients during the entire growing season. Biomass, phenological development, plant density and canopy height were recorded. The N content of the crop and the green areas of Various assimilating plant parts were determined. Net above-ground primary production and nitrogen uptake were both estimated as the annual peak in organic matter and nitrogen, respectively. More stems were produced in IF than in D, C and I, and the canopy was higher in IF. However, phenological development until anthesis did not differ between any of the treatments. The above-ground net production of dry matter in D, C, I and IF was 930, 987, 1 129 and 1 247 g m(-2) respectively. The corresponding annual nitrogen uptake was 12.4, 15.6, 15.1 and 25.8. The total uptake of K, Mg and Ca reflected the differences in dry matter yields between treatments; i.e. differences in uptake between D, I and C were much smaller than differences between any of them and IF, in which uptake was highest. However, drought decreased the uptake of P substantially. The effect of drought on crop growth could have been due at least partly to inadequate phosphate uptake. The harvest index was lower in IF than in the other treatments. Mean grain yields, expressed at 15% water content ranged between 530 and 620 g m(-2) and were highest in I and IF. Corresponding nitrogen yields ranged between 9.0 and 12.9. Both dry mass and nitrogen inputs to the soil from harvest residues were highest in IF. The supply of water and nitrogen affected the green area of all plant parts. The green area index was lowest in D (2.2) and highest in TF (6.8). Crop growth is discussed in relation to soil mineral N dynamics and leaching risks.