Abstract
ABSTRACT Cropping calendar optimization contributes to an increase in rice yield. Information on the seasonal variation in grain yield and climate conditions is necessary to determine an appropriate cropping calendar. We sought to find the optimal cropping calendar in Mwea, Kenya, in a tropical highland in equatorial East Africa. We conducted a series of 58 experiments using a local popular rice variety, Basmati 370, between 2013 and 2016, using a secured water supply and adequate blast control, sowing every 15 days. The grain yield was 0–2 t ha−1 when the variety was sown between March and June. This poor grain yield was attributable to the low temperature and low solar radiation from May to September. In contrast, the grain yield was always more than 3 t ha−1 when the variety was sown between July and February. Sowing Basmati 370 between March and June is not recommended, because it may lead to a suboptimal yield due to cold stress. The current cropping calendar (July–December or August–January) is acceptable even under abundant year-round water supply, but sowing between October and February is a good alternative sowing period for single rice cropping. Rice production per year is expected to increase to >100% with the introduction of double cropping by adding cultivation from between January and February before the current cropping calendar. These findings serve as useful references for considering and determining the appropriate calendar options for single and double cropping of rice in tropical highlands in equatorial East Africa.
Highlights
Africa is far from self-sufficient in rice, and this situation is projected to worsen in the future (van Oort & Zwart, 2018)
We explored the grain yield of Basmati 370 under a secured water supply with adequate blast control throughout the year in Mwea, Kenya, as a representative of tropical highlands in equatorial East Africa
The grain yield of the variety sown during the long rains is very poor because of low temperature and solar radiation during this stage
Summary
Africa is far from self-sufficient in rice, and this situation is projected to worsen in the future (van Oort & Zwart, 2018). There are five options to close the gap between demand and production: (1) expansion of land under cultivation, (2) intensification in existing farmlands by growing two or three crops a year, (3) narrowing the yield gap in farmers’ fields by introducing new technologies, (4) raising yield ceiling by introducing highyielding cultivars, and (5) reducing postharvest losses (van Oort et al, 2015). Crop calendar optimization is well studied for rice cultivation in Sahel (Dingkuhn, 1995; van Oort et al, 2016), but studies in tropical highlands in central (equatorial) East Africa is limited (Sekiya et al, 2015). For preparing a globally complete and spatially explicit rice cropping calendar, which is a valuable global public good for food security (Laborte et al, 2017), more information is necessary to consider the appropriate crop calendar in each region of the world including tropical highlands in equatorial East Africa
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