Water availability and forage production in arable crops areas

A comparison trial between various feed strategies (crop rotation versus ley) was established in 2009 in the western part of Switzerland, at an altitude of 390 m. From 2010, two water regimes were tested, corresponding to the average annual amounts of 900 mm (local rainfall) and 1200 mm (additional water supply by drop irrigation). During periods of drought in 2010 and 2011, water supplies were the most effective on grass-clover mixtures. A quantity of ten liters of water per square meter has increased performance of 120 kg DM/ha, while the increase was only 50 kg DM/ha for maize. In contrast, a sharp deterioration in the botanical composition of leys was observed from the third year. It was accompanied by a steady decline in production. The effect of additional water supply results in a small decrease in N contents for all crops and an increase in K content of grass-legume mixtures (luxury consumption). The contents of the other elements analyzed (P, Ca and Mg) have been little affected. This study highlights the weaknesses of grassland during drought and the benefits of maize and alfalfa.