Tillage, Rice Straw Mulch and Nitrogen Fertilization Effects on Upland Rice Yield in Northern Benin

Abstract

In Benin, upland rice is typically grown under intensive tillage in slash-and-burn systems. Some of the major constraints associated with upland rice production are water deficit, declining soil fertility and rice yield. To explore effective ways to improve rice yield, field experiments were conducted on two upland rice soils (Lixisol and Gleyic Luvisol) in northern Benin, West Africa for two consecutive years. The treatments comprised two tillage systems (no-tillage, and manual tillage), two rice straw managements (no rice straw, and rice straw mulch at 3 Mg ha^-1) and three nitrogen fertilizer levels (no nitrogen, moderate level of nitrogen: 60 kg ha^-1, and high level of nitrogen: 120 kg ha^-1). Phosphorus and potassium fertilizers were applied to be non-limiting at 40 kg P₂O₅ ha^-1 and 40 kg K₂O ha^-1. Four replications of the twelve treatment combinations were arranged in a randomized complete block design. Soil moisture and soil temperature were measured at 5 cm depth in 6 to 10 days intervals during the growing seasons. At maturity, crop parameters measured included rice grain yield, aboveground biomass, and root biomass. No-tillage with rice straw mulch increased soil moisture and decreased soil temperature. Root biomass, shoot biomass and rice yield significantly increased with rice straw mulch and nitrogen fertilizer application. The highest response of rice yield to nitrogen fertilizer addition was obtained for 60 kg N ha^-1 in combination with 3 Mg ha^-1 of rice straw for the two tillage systems. No-tillage combined with rice straw mulch and 60 kg N ha^-1 could be used by smallholder farmers to improve soil water availability and upland rice yield in northern Benin.

Keywords: management practices, soil moisture, soil temperature, upland rice, yield.