Kinetic of pigs’ manures decomposition and nutrient release pattern in ferralitic soil of Benin (West Africa)

Abstract

Our study aims to assess the kinetic of the decomposition and nutrient mineralization process of organic manures from pigs’ dejection. A litter bag study was carried out during 12 weeks following decomposition and nutrient release process in ferralitic soil in southern Benin (West Africa). 200 g of pigs’ manures from four groups of pigs fed with four diets were considered as treatments: T1 (recommended diet composition, consisted of 15% Azolla pinnata + 55% provender + 5% coconut copra + 5% oil palm + 5% soybean bran + 10% rice bran + 5% kitchen waste), T2 (partially improved diet with Azolla pinnata, consisted of 30% Azolla pinnata + 65% rice bran + 5% oil palm), T3 (improved diet with Azolla pinnata, consisted of 47.5% Azolla pinnata + 47.5% rice bran + 5% oil palm), and T4 (improved diet with cereal bran, consisted of 15% Azolla pinnata + 40% rice bran + 40% wheat bran + 5% oil palm). Animals of six months age were fed during three months. A randomized complete block design with three replicates was set up for litter bag study. One component exponential decomposition model y = y0e-kt was found for all treatments. Nutrient mineralization was slow in the soil. Less than 50% of the pigs’ manures were decomposed after 12 weeks. In addition, manure from treatment T1 was richer in K, Ca and Mg than manures from treatment T3. High quantity (42.65%) of N was released in treatment T3. Pigs fed with diet enriched with Azolla produce manure which has released high N proportion in the soil. This is an opportunity to sustain food crop production.