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

Abstract

Phaseolus vulgaris is an essential legume crop for Bwanje people, because of its protein content for low-income population and good market availability. However, its yield is very low below pontential (2-3 t ha-1). In terms of irrigation scheme utilisation, Bwanje irrigation scheme is heavily under-utilised in winter as only 145 ha is cultivated out of 800 ha. The Major factors contributing to all these problems are; inadequate nutrition, use of uncertified seed, poor water management and poor agronomic practices. The research was carried out to find the best way to use water and nutrients in order to improve the bean yields, and increase the irrigated area planted after flooded rice through use of residual soil water. The pontential yield could be achieved with appropriate balance of nutrients, water, good agronomic practices and timely use of residual soil water. The study looked at four different treatments replicated three times; Farmer Practice (FP), Farmer Irrigation and Luxury Nutrients (FILN), Optimum Irrigation and Luxury Nutrients (OILN), and Strategic Irrigation and Luxury Nutrients (SILN). Climatic database, Climwat and Cropwat were used to test the possibility of expanding irrigated area through better use of residual soil water by timely planting. FP received water as the farmer desired, OILN received water based on Chameleon sensors colours and SILN received water only when the crop showed stress signs. FP received 387 mm, FILN received 391 mm, OILN received 226 mm and SILN received 213 mm. OILN produced highest yield (2.75 t ha-1), and FP produced lowest yield (2.1 t ha-1). Farmer Irrigation leached most of the nutrients unlike in OILN and SILN where leaching was minimal. Through a desktop analysis the model indicated that in winter, an irrigated area could be increased by 78 ha. Therefore, Wetting Front Detectors and Chameleon Sensors could be used to minimise the loss of nutrients and improve water management through continuous monitoring thereby improve bean yield.

Key Words: Phaseolus vulgaris, water management, nutrients, Chameleon sensors, Wetting Front Detectors, residual soil water.