Decomposition rate of pigs’ manures and nutrient release pattern in wetland condition

Recent studies reported the important contribution of animal dejections as organic manure for crop production but, little is known on the decomposition rate and nutrient release pattern in wetland of the manure of pigs nourished with diet enriched with Azolla filiculoides. A litter bag study was carried out under full control during 6 weeks in pots containing 25 liters of tap water and 15g of pigs’ dejection in each decomposition bag. The experimental design was a completely randomized block design with three replications. The treatments consisted of dejections of pigs nourished with : T1 (recommended diet composition) consisted of 15% Azolla + 55% provender + 5% coconut copra + 5% oil palm + 5% soybean bran + 10% rice bran + 5% kitchen waste ; T2 (partially improved diet with Azolla) consisted of 30% Azolla + 65% rice bran + 5% oil palm ; T3 (improved diet with Azolla) consisted of 47.5% Azolla + 47.5% rice bran + 5% oil palm; and T4 (improved diet with cereal bran) consisted of 15% Azolla + 40% rice bran + 40% wheat bran + 5% oil palm). Four pigs per diet were considered leading to 16 white landrace pigs of six months age. Decomposition rates in water were significantly (P < 0.05) fast during the first week and became very slow during the following weeks. After the six weeks of experiment, 58.2 % of manure from treatments T1 and T4 were decomposed against 47.2 % for T2 and T3. However, 40.1, 53.3, 67.4 and 57.1% of total N content in treatments T1, T2, T3 and T4 respectively were released. As consequence, manure from improved diet with Azolla (T3 and T2) are suggested for integrated rice and fish production system. Nevertheless, decomposition and nutrients (P, K, Ca and Mg) release patterns had significantly (P < 0.05) increased in water in treatments T1 and T4 compared with the two treatments containing more Azolla in the diet (T2 and T3).