ABSTRACT
Summary Stability and continuity of forage production are primarily dependent upon the actual water supply and the level and distribution of nitrogen applications. Under the soil and climatic conditions in the GDR, in almost every year there are certain periods when the natural water supply does not satisfy the water needs of forage plants, leading to severe yield loss unless sprinkle irrigation is practiced. As sprinkle irrigation is very costly and water resources are limited, we must make full use of all potential for achieving high yields while keeping the water input at a minimum — i.e., maximizing overall efficiency of the supplemental water applied. The effect of nitrogen fertilization and sprinkling on yield, continuity of production, and quality of multicut forage plants of different sites was examined. At all sites studied, sprinkle irrigation gave significant increases in forage yield, with yield increments decreasing with rising soil quality, from sand to loess. With regard to field grasses (Lolium multiflorum, Dactylis glomerata), the yield differences from irrigation between diluvial and loess sites were similar. Italian ryegrass (L. multiflorum) proved to be the most efficient field forage plant (17 t dry matter [DM]/ha) under sprinkling, and mixtures of red clover and grasses ranked second. Water utilization by forage plants improved as the need for sprinkling due to soil or climatic conditions increased. Yield increment was 30% to 40% (productive values > 20 kg DM/mm sprinkling water) on the diluvial sites (sandy and loamy soils) and 18% to 21% on loess. Energy, dry-matter, and crude-protein content, as parameters of forage quality, declined under sprinkling, and crude-fiber content increased slightly. The variation differed among forage plant species and among sites. The significant results obtained were immediately made available to cooperative farms and State farms for crop production. The experimental results now serve as the basis for selecting forage plants that would give maximum and most reliable crop yields under sprinkle irrigation.
