Effect of variety, soil type and fertiliser on the establishment, growth, forage yield, quality and voluntary intake by cattle of oats and vetches cultivated in pure stands and mixtures

In this study oats and vetch were evaluated under two experimental settings in the central highlands of Ethiopia. In the first experiment compatibility of mixtures, forage yield, and quality of three varieties of oats (Avena sativa L.) and two species of vetch (Vicia villosa and Vicia dasycarpa) sown in pure stands and mixtures were investigated with and without application of fertiliser on red nitosols and black vertisols. Experiment 2 assessed the voluntary intake of hays made of mixtures and pure stands of the oats and vetch by cattle. Soil, fertiliser, and variety were found to be factors, which determined the compatibility, yield and quality of the forage produced. Higher average dry matter (DM) forage yields of mixtures, pure oats and pure vetch were obtained on the red soil (9.7, 9.4 and 4.5 t ha(-1), respectively) than on the black soil (5.6, 5.5 and 2.8 t ha(-1), respectively). Fertiliser increased the total biomass yield by 15% but affected compatibility and decreased the proportion of DM vetch in the biomass by 24%. The crude protein (CP) content of pure oats (7.0%) was increased by growing in mixtures with vetch (8.5%), and so was the in vitro organic matter digestibilty (IVOMD). The oats variety 2806 produced the highest biomass yield and the shorter and late maturing variety 2291 was compatible with vigorous and intermediate maturing hairy vetch (K villosa). DM intake of pure vetch (25.8 g kg(-1) live weight) was significantly greater than all the other experimental feeds. The mixture with oats had also significantly higher CP and digestible organic matter (DOM) intakes compared to pure oats. The IVOMD and CP content showed a positive relationship to DM, CP and DOM intake, while neutral detergent fibre (NDF) content was inversely related. Growing compatible oats-vetch mixtures can thus be a practically relevant intervention in increasing forage productivity per unit area, CP content, IVOMD and intake by cattle. (C) 2001 Elsevier Science B.V. All rights reserved.