EFFECTS OF SHEEP BROWSE DIET ON FECAL MATTER DECOMPOSITION AND N AND P CYCLING IN THE HUMID LOWLANDS OF WEST AFRICA

Abstract

A greenhouse study utilizing two experiments was used to evaluate the effects of applying browse leaves, or feces derived from these feeds, at equal organic-N application rates (120 kg ha⁻¹), alone or with fertilizer N (30 kg ha⁻¹), on feces and leaf decomposition in soil, on maize (Zea mays L.) dry matter (DM) yield, nitrogen (N), and phosphorus (P) uptake, and on soil chemical properties. Decomposition rates of amendments varied considerably due to amendment type, browse species, and fertilizer N. Maize DM and cumulative N uptake were most affected by browse species, followed by browse species & amendement interaction, browse & N effect, amendment type, and, to a lesser extent, by fertilizer N. Although more N and P were recycled in feces than in leaves, browse leaves decomposed faster, and some had greater positive effect on maize yield than feces. Fertilizer N increased maize DM by 10%, N uptake by 31%, and P Uptake by 6% and enhanced N mineralization from most organic amendments. The relatively high cell wall content of feces may have been an effective sink for fertilizer N, which when remineralized provided more N to maize than soils amended with leaves. Whereas most of the P contained in feces mineralized and was taken up by maize, P was slightly less available in some soils amended with leaves. The results are discussed in relation to the importance of ruminants in enhancing the soil fertility of the humid forest lowlands of West Africa.