Impact des pratiques de fertilisation sur la productivité des prairies et mélanges céréales - protéagineux et la qualité du fourrage

Effects of fertilisation practices on the productivity of pastures and of mixtures of cereals and high-protein crops and on the quality of the forage

The optimization of the forage production on lowland livestock-rearing systems implies an adequate control of the nitrogen fertilisation of the pastures, ensuring the best utilization of the mineral and the organic nitrogen fertilisers. The use of innovating forages (cereals - legumes) can also bring about an economy of inputs.
Trials made in 2008 on mown grasses confirmed the advantage of an early first dressing of nitrogen at the end of winter, determined the necessary amount of nitrogen according to the harvesting method (silage or hay) and estimated the effects of late or split dressings on the yield and the quality of the herbage. The apparent coefficient of utilization of the organic nitrogen from different sources depends on the proportion of mineral nitrogen in these sources (low for farmyard manure and composts, up to 40% for slurries) ; the contribution of the applications of organic nitrogen to the mineral nutrition of the plants is very slight after the growth cycle following the dressing. Besides, the productivity (bio-mass and Crude Protein) of many mixtures of cereals with legumes is shown in a series of trials ; the share of each species is decisive, but very largely dependent on the availability of nitrogen.