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Six lowland experiments were conducted over three years in southern Benin to assess yield differences in 28 rice (Oryza spp.) genotypes grown under nonfertilized and fertilized conditions. These included the interspecific hybrids, the lowland New Rice for Africa (NERICA) genotypes developed from crossing O. sativa and O. glaberrima. Fertilizer rates were 70-86N: 30-37P 2 O 5 : 30-37K 2 O kg ha -1 . Fertilizer application increased average grain yield across all genotypes and experiments by 39% (154 g m- 2 increase). Considerable genotypic differences existed in grain yields under both nonfertilized and fertilized conditions, and in yield response to fertilizer application. Two lowland NERICA genotypes ('NERICA-L-6' and '-54') outyielded 'IR 72' and 'WITA4' (standard checks) across nonfertilized and fertilized conditions in four experiments with favorable water availability in wet seasons (651 vs. 575 g m- 2 ). The high grain yields resulted from large spikelet number m- 2 and biomass accumulation. In contrast, three indica genotypes from Asia ('B 6144F-MR-6-0-0', 'IR 70181-32-PMI-1-1-5-1', and 'PSBRc 80') outperformed the checks in two experiments, one straddling wet and dry seasons and the other with no standing water during most of the usual wet rice-growing season. These results indicate that while specific adaptations are likely to provide significant yield advantage in particular environments, interspecific breeding still offers an effective approach to improving lowland rice productivity. |
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