Proposed method for the determination of rational nitrogen fertilization of pastures

摘要

The nitrogen fertilization of pastures has been rather less investigated in France than that of annual crops. The method described here serves for the determination of rational fertilizer dressings for pastures, but it has to be adapted to regionalcircumstances (cf. following paper). Following a reminder of the specific features of nitrogen flows under pastures, an explanation of the method's principle is given. The equation of utilization efficiency of a fertilizer and its adaptation to pasturesis detailed term by term, each term of the equation being illustrated by references taken from Western France. The determination of nitrogen removal and of nitrogen supply by the soft, the contributions of recyclings by grazing and of symbiotic fixation,the direct effect of farmyard fertilizers, and the values of the apparent utilization co-efficient of a fertilizer are given in a wide development. The reasoning process is summed up in an application to an exclusively grazed pasture in Western France,followed by a discussion on its merits and its limits.