This paper examined actual farmers’ cultivation practices of NERICA (New Rice for Africa) and the determinants of its yield, based on data obtained from a field survey conducted in central Uganda. NERICA’s high yielding potential was realized in farmers’ fields. On average, farmers attained yield as high as 3 t ha^-1. A high seeding rate, high fertilizer/chemical applications and high laborintensity characterized the upland NERICA cultivation in the study area. The estimation of yield function revealed that the response of rice yield to nitrogen was as high as 46 kg ha^-1 of paddy per 1 kg ha^-1 of nitrogen applied, and that the continuous planting reduced the yield significantly. The large difference in the unit yield between large and small farmers was explained by small farmers’ higher input intensities than large farmers’, and it is the high labor requirement of NERICA that makes it a pro-smallholder technology.

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The effects of plant density on yield and yield components in upland rice cultivation were examined by conducting a series of field experiments in Central Uganda, using three African and one Japanese improved upland rice varieties. The estimation of plant-density response functions with respect to yield components and yield revealed that an increase in plant density significantly decreased the number of panicles per hill, number of spikelets per panicle, and 1000-grain weight, and significantly increased the number of panicles per square meter. The percentage of filled grain was not affected by plant density. Compared to the Japanese variety, the three African varieties were characterized by more numbers of panicles/hill, less numbers of spikelets/panicle, higher grain-filling ratio and lighter 1000-grain weight, but differences in the degrees of response to plant density were less distinct between them. Rice yield increased in the range of plant density tested, though the marginal increase in yield due to an increase in plant density by 1 hill/m 2 diminished from 100 kg/ha at the plant density of 11 hills/m 2 to 30 kg/ha at 33 hills/m 2 . No significant differences were found among the four varieties for the level of yield as well as for its degree of positive response to plant density. The yield components that determined the increase in yield were the number of panicles per square meter and the number of spikelets per panicle, or combined together, the number of spikelets per square meter, which was estimated to reach the maximum at the plant density of 35 hills/m 2 . When the differences among the treatments in the costs of seeds and weed-control were considered, the optimum plant density was found to be 22 hills/m 2 (plantspacing of 30 cm × 15 cm), lower than the plant density that gives the maximum yield.

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In East Africa where a drastic improvement in food security is an urgent need, rice, a non-traditional crop in most of countries in the region, has emerged as an important food crop that could extend the Green Revolution to the region following the introduction of New Rice for Africa (NERICA) in the early 2000s. Using data collected through a nationwide survey, this paper examines the possibility of rice green revolution by estimating the technical efficiency (TE) of rainfed rice farmers in Uganda and simulates how unfavorable climate changes affect it. The estimated stochastic frontier yield function showed that the mean TE was 65% for lowland and 60% for upland, and that the potential yield of rainfed rice cultivation was as high as 3 t•ha −1. However, the stochastic simulation of rainfall and rice yield revealed that unfavorable climate changes could erase the high potential in crop yield. Rainfed rice cultivation could be a leading sector for realizing Green Revolution in East Africa. It plays a critical role in this process to improve rice farmers' TE, which is lower in the region than in Asia. Worsening climatic conditions, if occur, make this need even more imperative.