Improving water and nutrient use efficiency of Maize after flooded rice in Bwanje irrigation scheme, Malawi

Abstract

Bwanje Valley Irrigation Scheme experiences low maize yields and shortage of water in the winter irrigation season. The scheme is also under-utilized in terms of irrigated area during winter as only 145 ha is cultivated out of a possible 800 ha. This research was carried out to find the best way to utilize water and nutrients in order to improve maize yields, and expand irrigated area planted after flooded rice through optimal use of residual soil water. The experiment had four treatments replicated three times; farmer irrigation and farmer nutrients (FIFN), farmer irrigation and luxury nutrients (FILN), optimum irrigation and luxury nutrients (OILN) and strategic irrigation and luxury nutrients (SILN). Climatic database (Climwat and Cropwat) was used to test the possibility of expanding irrigated area through better residual water utilization by early planting. FIFN received 140 mm after every 21 days (FI) and 104 kg N ha-1, 24 kg P ha-1, 0 kg K ha-1 and 17 kg S ha-1 (FN). FILN received FI and 180 kg N ha-1, 130 kg P ha-1, 71 kg K ha-1 and 5000 kg of Calcitic Lime ha-1(LN). OILN received water based on Chameleon Sensor colours (OI) and LN, while SILN received water only if crops showed signs of water stress (SI) and LN. Results show that FI received more water (488 mm) than OI (255 mm) and SI (235 mm). OILN produced highest yield (5.75 t ha-1) while FIFN produced lowest yield (3.4 t ha-1). FILN yielded 4.7 t ha-1 and SILN yielded 4.3 t ha-1. Through a desktop analysis, Cropwat and Climwat indicates that 354 ha would be cultivated utilizing residual soil water by early planting. Therefore; the best way to irrigate is to use Chameleon Sensors and Wetting Front Detectors to schedule irrigation and manage the nutrients respectively, and application of LN increases maize yield. Key Words: Nutrients, Water, Yields, Area, Chameleon Sensors, Wetting Front Detector