Moisture availability is a fundamental challenge to rice productivity in the rainfed environment. Most of the rice varieties released for cultivation under rainfed ecosystem in Tanzania are missing out on information about their moisture requirement under different soil moisture regimes. A pot experiment was conducted at Ifakara in a split-plot design. The main plots was assigned to water regimes of 100, 75, 50 and 25% based on saturated soil conditions, and the sub-plots were assigned to six rice varieties NERICA 1, NERICA 2, NERICA 4, TXD 306, Tai and Komboka. The results revealed that TXD 306 produced the highest grain yields after utilizing 36.91 kg water followed by Tai 30.24 kg water, Komboka 30.20 kg water and NERICA 4 27.47 kg water at 100% moisture saturation. NERICA 1 and NERICA 2 produced the highest grain yields at 75% moisture saturation transpiring 25.28 and 19.05 kg water, respectively. It was concluded that 100% moisture saturation in soils was the optimum moisture for TXD 306, Tai, Komboka and NERICA4 rice varieties since they produced the highest grain yields with highest productivity value than other moisture regimes investigated, and 75% moisture in soils was the optimum moisture requirement for NERICA1 and NERICA2 rice varieties at which they produced the highest grain yield and water productivity value. In the lower soil moisture contents of 50 and 25%, NERICA 2 and NERICA 4 rice varieties had higher grain yield and productivity value than the other varieties and are therefore recommended for cultivation in areas with moisture limited conditions.
Key words: NERICA, productivity, rainfed rice, soil moisture levels, water use.
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