Abstract
In the rice growing area of Kenya’s highlands, the development of a water-saving rice cultivation system is a key strategy because the shortage of irrigation water is a frequently occurring problem. The purpose of this study was to investigate the effect of alternate wetting and drying (AWD) on the growth and yield of rice under the unique cultivation environment of tropical highlands. Field experiments were performed over a period of four years (2014–2017) in a paddy field. Dry matter production of a lowland variety, Basmati 370, was greater under continuous flooding (CF) than under AWD. In years with low minimum temperature (less than 15 °C) during the reproductive and ripening stages, filled grain ratios were significantly higher under AWD than under CF. Accordingly, higher dry matter production under CF did not contribute to grain yield. In the years when rice was not exposed to low minimum temperature during the reproductive and ripening stages, filled grain ratio did not decrease even under CF. Therefore, there was no difference between filled grain ratio under AWD and CF. Our results indicated that AWD could mitigate the decline in grain filling, induced by low minimum temperature during the reproductive and ripening stages in Basmati 370, under the cultivation conditions in tropical highlands. Although AWD may reduce the above-ground biomass, its mitigation effect on grain filling could outweigh this drawback and can still be beneficial to rice farmers in the tropical highlands.
Highlights
We investigated the effects of AWD on rice growth and yield over four cropping seasons under the unique cultivation environment in the tropical highlands and analyzed the reasons behind the differential effects of AWD
The results of our trials revealed that AWD had negative effects on the above-ground biomass (Table 4)
The ripening process may have been affected, because there was a positive and significant correlation between filled grain ratio and average minimum temperature for the period from heading to 14 days after heading under continuous flooding (CF). These results suggested that the inhibition of translocation under CF in 2014 and 2016 was due to sterility at both flowering and ripening stages after heading
Summary
Rice is a staple food for over half the world’s population and rice consumption is increasing with population growth [1]. A key strategy for sustainable rice production would be developing water-saving rice cultivation systems. Alternate wetting and drying (AWD) is an irrigation practice that can reduce water consumption in rice fields without sacrificing yield. Its use has been proposed and tested in many regions [4,5,6,7,8,9]; the effect of AWD on rice yield has produced inconsistent results. The conflicting results of these reports suggest that yield responses under AWD may depend on the cultivation environment and rice variety. For successful local implementations of AWD, reliable validation and adaptation trials are needed
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