Rice Growth and Yield in Waste-Amended West African Lowland Soils

Abstract

The use of organic materials as an alternative to or in combination with inorganic fertilizer is being advocated for use by small-holder rice farmers in sub-Saharan Africa as way to reduce the cost of inputs and stabilize yields of modern varieties grown in the lowlands. In this study, the effects of humified sludge (HS), poultry manure (PM), cattle manure (CM), a mixture of humified sludge and poultry, and cattle manures (MM), and inorganic fertilizer (IF) were evaluated on growth and yield of rice during the dry and wet seasons. Three lowland soils, Eutric Vertisol (EV), Eutric Fluvisol (EF), and Haplic Gleysol (HG), were amended with 90 kg N/ha from the above nutrient sources. Organic materials incorporation was done four weeks before transplanting with 21-day-old rice seedling whereas IF was split-applied as basal and at panicle initiation. Soil was flooded until 10 d before harvest. Plant height, number of tillers and panicles, days to 50% flowering, 1000-grain weight, biomass, and grain yield as well as harvest index were recorded. Soil electrical conductivity (EC) and pH were measured before amendments and at maximum tillering, flowering, and maturity stages during the wet season. Soil amendments with manure or fertilizer improved the growth and yield of rice. Flowering was delayed more than 7 d in Vertisol without organic amendment. Humified sludge, PM, and IF significantly enhanced tillering and plant height more than did other nutrient amendments, especially in Vertisol. Mean grain yield in the wet season was 17.4% better than in the dry season. For the dry and wet seasons, nutrient amendment effect on grain yield was ranked HS > PM > MM > IF > CM > Control and HS > PM > IF > CM > MM > Control, respectively. The superiority of HS and PM to the chemical fertilizer may be attributed to balanced and gradual release of plant nutrients, which were synchronized with demand at various growth stages of the rice plant.

Keywords:

• organic materials
• humidified sludge
• lowland soils
• smallholder rice farmer