Mineralization and Decomposition of Four Types of Compost Based on Biomass of Sida cordifolia L. in a Sandy Soil in the Semi-arid Zone of Niger

The low nutrient availability rainfall patterns regimes are the main constraints to agricultural production in Niger. This was a study of the decomposition and mineralization of nutrients of four types of composts (M1P, M2P, M1H and M2H) in a sandy soil. It was carried out at the experimental N'Dounga station (CERRA Kollo) located about 15 km from Niamey. A randomized blocks design with five repetitions was used. For the evaluation of yield, two doses (1 t ha-1 and 1.5 t ha-1) were applied per millet. Decomposition and mineralization were assessed after burial at 10 cm depth between of a small bag containing 100 g (five small bags / compost). The characterization of the physico-chemical elements of composts samples after incubation has shown that composts are rich in nutrients. Nitrogen ranged from 0.8% to 1.1%, phosphorus from 9.99 mg.kg-1 to 12.76 mg.kg-1 and potassium from 19.94 cmolc dm-3 to 26.26 cmolc dm-3. All four composts are basic (pH> 7). Compost M2H lost more than 80% of its weight during the 10 weeks of the experiment compared to 48% for the M1P. the mineralization of N, P and K is greater at compost M1P (83.6% N, 72.72% P and 89.5% K). This compost also gave the highest yield (1272.5 kg ha-1). The decomposition and mineralization of the main elements (N, P and K) allow the synchronization between the release of nutrients from these composts and the nutrient requirements of millet in a sandy soil.