Interactions of water, nutrient, and mulch on sorghum water use in a Sahelian agroecosystem

Vita.In the Sahel region o f Africa, grain sorghum (.Sorghum bicolor (L.) Moench) is a major human food source. Due to scarce water resources and soil infertility efficient crop water use is a key challenge for sustainable crop production. The objectives o f this study were to use supplemental irrigation, nutrient, and mulch to manipulate the system energy and soil water balance in order to improve crop water use efficiency and to integrate the soil-plant-atmosphcre continuum water relationships into a mechanistic model capable o f predicting soil evaporation and crop transpiration. The experiment site was located in Maradi, Niger. Soil physical, chemical, and hydrological properties were characterized, and water balance components (rainfall, soil evaporation, deep drainage, and changes o f soil water storage), crop growth parameters (height, leaf area index, biomass production and root distribution), and relevant climatic parameters (temperatures, humidity, wind speed, and solar radiation) measured. Mulch reduced sensible flux between soil and air 3 to 5 times and soil long wave radiation emission 100 to 200 W m '^. Soil net radiation balance was reduced 220 to 350 W m '^, crop net radiation increased 60 to IOO W m '-, and soil evaporation reduced 22%. Mulch caused significant (P = 0 .0 ^ WUE(ET) increase (18%). and W UE(T) 6%. Nutrient significantly increased biomass production, crop transpiration 12%, increased WUE(ET) 11%, and W UE(T) 9%. Irrigation increased soil evaporation 24%, crop transpiration 5%. WUEfET) 22% and WUE(T) 34%. It reduced the effect o f mulch and nutrient on WUE(ET) and the effect of mulch on WUE(T) but improved the effect of nutrient on WUE(T). Interactions indicated that either irrigation or mulch significantly improved WUE(T) only w ith the other inputs. Grain water use efficiency was significantly improved by ail factors. Results indicate that nutrient and sotl evaporation control are required in water balance manipulation schemes for efficient crop water use in the Sahelian agroecosystem. Die EN W ATBAL model predicted soil evaporation of eight production systems with 5 to 15% error. This indicates that it can be a valuable tool for water balance studies in this region