Impact of management practices on weed infestation, water productivity, rice yield and grain quality in irrigated systems in Côte d'Ivoire

Abstract

• AWD reduced weed biomass due to reduction of lowland and broad-leaved weeds. • AWD increased water productivity without yield penalty compared to CF. • Soil pH and N fertilization affected rice yield and water productivity in AWD fields. • Choice of rice variety largely determined grain quality. Management practices that simultaneously enhance rice yield, water productivity, labor productivity, and grain quality are needed for improving crop production and mitigating the negative impact of water scarcity on food security. The objectives of this on-farm study were to evaluate the effects of water management practices including the safe alternate wetting and drying (AWD) method of irrigation on rice yield, water productivity, weed biomass, and grain quality, and identify the factors associated with their variabilities in the fields with AWD. On-farm trials were conducted over two years in 30 fields within two irrigation schemes in the region of Bouake, central Côte d’Ivoire. Before rice cultivation, in each field, three plots consisting of water management practices were established: continuous flooding (CF), safe AWD, and farmers’ practice (FP). Lowland weeds were dominant in rice fields in this study area. Large variations in weed biomass, rice yield, and water productivity were found across fields for each water management practice. Weed biomass and irrigation water input were lower under safe AWD than CF due to higher soil drying while there was no significant difference in rice yield between safe AWD and CF. Water productivity was higher under safe AWD than CF and FP. Rice milling recovery, head yield, and chalkiness were not significantly different among water management practices. Higher rice yield and water productivity in the safe AWD fields were associated with higher soil pH and nitrogen (N) fertilizer rate and better congruence between nitrogen fertilizer application and crop N demand. Milling recovery, head yield, and chalkiness in the safe AWD fields were strongly affected by the choice of rice variety. Combination of safe AWD with varieties having good grain quality characteristics and improved nutrient management practices could be recommended to the smallholder rice farmers to improve rice yield, water productivity, and grain quality and reduce labour requirement for irrigation and weeding particularly in schemes where lowland weeds are dominant.