Abstract

The growth of 20 rice varieties, including both lowland and upland varieties, was evaluated in Kenya under well-watered and water-deficit conditions in four different soil types (black cotton, red clay, volcanic ash, and sandy clay) to compare the adaptability of these varieties to the two water regimes. Under water-deficit condition, after terminating irrigation, the reduction in soil water potential differed markedly according to soil type. The rice varieties tested were classified into four groups, which were largely consistent with differences in rice variety ecotype. We confirmed that lowland varieties such as Basmati 370 should not be considered as a candidate for cultivation under rain-fed upland conditions in Kenya. Furthermore, the results revealed that even potentially high-yielding varieties may not attain their yield potential if the cultivation environment is unsuitable. Although we found that five upland varieties (Dular, IRAT109, NERICA 1, NERICA 4, and Yumenohatamochi) presented relatively higher grain yield under water-deficit conditions in all soil types, individual variety’s grain yield depended on the soil type. Their higher yield is attributable to certain root traits and their yield variations to an interactive effect between root development and soil type. Our results indicated that the varieties Dular, IRAT109, NERICA 1, NERICA 4, and Yumenohatamochi are suitable for cultivation under rain-fed upland conditions across the major rice-growing areas in Kenya and that soil type should be considered when selecting varieties for an area’s maximum productivity.

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