Sylvester O. Oikeh

Responses of upland NERICA® rice varieties to nitrogen and plant density

Improved varieties, nitrogen fertilizer, and plant spacing have been identified for increasing upland rice productivity. However, these factors have not been adequately investigated on interspecific rice, New Rice for Africa (NERICA®). Different levels of nitrogen (0, 30, 60 and 120 kg ha−1) and plant spacing (dibbling: 30 × 30 cm, 20 × 20 cm, and drilling: 25 × 5 cm) on the growth and yield of three interspecific rice varieties and a check variety were evaluated on Terre de barre soils. Rainfall in both years was unevenly distribution which caused drought in both years. Across both years, rice yield was significantly depressed with 60N and 120N by 53–81%, compared with other N levels. NERICA4 with 30N gave the highest panicles density and harvest index, and the best yield (1.2 Mg ha−1). Wide spacing of 20 × 20 cm or 30 × 30 cm with four plants stand−1 was optimum for the NERICA. Drilling rice at 25 × 5 cm with one plant stand−1 depressed yield. Results showed that in smallholder upland ecosystems prone to unpredictable drought, wide spacing and low N can be recommended for production of NERICA.

Cultivar and Weeding Effects on Weeds and Rice Yields in a Degraded Upland Environment of the Coastal Savanna

Abstract Weeds are a major constraint to rice production in labor-limited, upland rice-based systems in West Africa. The effects of weeding regimes and rice cultivars on weed growth and rice yield were investigated at two upland locations (Abomey-Calavi and Niaouli) in the degraded coastal savanna zone of Benin in 2005 and 2006 with below-average rainfall. Four weeding regimes (hoe weeding at 21 d after sowing [DAS], delayed hoe weeding at 31 DAS, hoe weeding at 21 and 42 DAS, and a no weeding control) were the main plot treatments. Cultivars comprising three interspecific upland rice cultivars (NERICA 1, NERICA 2, and NERICA 7) and the parents (Oryza sativa WAB56-104 and O. glaberrima CG14) were tested in subplots. The most dominant weed species identified were Jamaican crabgrass, Mariscus, and silver spinach. Rice yield was generally low because of drought stress; none of the experiments had a higher mean yield than 1,400 kg ha−1 across cultivars. Across cultivars, the best weeding regimes in terms of weed control and rice yields were single weeding at 31 DAS (W31) and double weeding at 21 and 42 DAS (W21+42). Under these weeding regimes, WAB56-104 out-yielded the three NERICA cultivars. CG14 showed the strongest weed suppressive ability (WSA) in Abomey-Calavi but did not have strong WSA in Niaouli because of lower biomass accumulation. WSA of WAB56-104 was similar to that of the three NERICA cultivars. Single weeding at 31 DAS, together with the use of cultivars with good adaptation to unfavorable rice growing conditions, would increase land and labor productivity of upland rice-based systems in West Africa. Nomenclature: Jamaican crabgrass, Digitaria horizontalis Willd.; Mariscus, Mariscus alternifolius Vahl.; silver spinach, Celosia trigyna L.; rice, Oryza glaberrima Steud ‘CG14’; rice, Oryza sativa Linn. ‘WAB56-104’; rice, O. sativa × O. glaberrima, NERICA 1 ‘WAB450-IBP-38-HB’; rice, O. sativa × O. glaberrima, NERICA 2 ‘WAB450-11-1-P-31-1’; rice, O. sativa × O. glaberrima, NERICA 7 ‘WAB450-IBP-20-HB’.

Integrated soil fertility management involving promiscuous dual-purpose soybean and upland NERICA enhanced rice productivity in the savannas

Integrated soil fertility management (ISFM) involving a nitrogen-fixing grain legume, limited chemical fertilizer, and a resilient rice variety may reduce the rate of soil fertility loss and enhance rice productivity in fragile upland rice ecosystems. A 2-year, on-farm study was carried out at Eglimé in the southern Guinea savanna (SGS) and Ouake in the northern Guinea savanna (NGS) of the Republic of Benin to evaluate the contribution of dual-purpose soybean cultivars (Glycine max) to grain yield of upland NERICA® rice receiving low fertilizer N. In 2005, four dual-purpose, promiscuous soybean varieties (cv. TGX 1440-IE, TGX 1448-2E, TGX 1019-2EB, and TGX 1844-18E), a popular soybean variety (cv. Jupiter), and a popular rice (control) were sown in ten farmers’ fields. In 2006, resilient upland interspecific rice (NERICA1) and popular rice (IRAT-136) were sown in all plots with only 15 kg N ha−1. Soybean cv. TGX 1440-1E (late-maturing) ranked highest in nodulation, dry matter, shoot- and grain-N accumulation, and N-balance (21 kg ha−1) in NGS, while TGX 1448-2E (medium-maturing) surpassed other varieties in the SGS. Nitrogen fertilizer replacement value for growing cv. TGX 1440-1E in NGS prior to rice ranged from 17 to 45 kg N ha−1 depending on the reference rice. Grain yield of NERICA1 following 1-year rotation with soybean cv. TGX 1440-1E or TGX 1019-2EB was 1.5 Mg ha−1 greater than the yield obtained from farmers’ control of 2-year continuous IRAT 136 rice cropping. Results indicate that integrating appropriate dual-purpose soybean in an ISFM package can enhance rice productivity in resource-limited smallholder production systems.

The Water Efficient Maize for Africa Project as an Example of a Public–Private Partnership

The Water Efficient Maize for Africa (WEMA) project was started in 2008 with the main objective of developing drought tolerant white hybrid maize for smallholder farmers of sub-Saharan Africa (SSA) that yields at least 20 % more under drought conditions compared to commercial check hybrids. To achieve this, a combination of breeding and biotech approaches are followed to introduce drought tolerance in African maize varieties. To protect the yield benefit, the insect protection trait (Bt) was added in the year 2011. This work is conducted through a public–private partnership led by the African Agricultural Technology Foundation based in Kenya with collaborating partners that include the International Maize and Wheat Improvement Center, Monsanto Company, and five National Agricultural Research Systems for Tanzania, Kenya, Mozambique, Uganda, and the Republic of South Africa. Among the key achievements for the first 5 years of the project (Phase 1) include the successful running of confined field trials for transgenic maize varieties in Kenya, Uganda, and South Africa and the submission of conventional drought tolerant maize hybrids into the national performance trials in Kenya. The next Phase 2 of the program (2013–2017) involves the deployment of the WEMA products. The first WEMA conventional drought tolerant maize hybrids are scheduled to be released to farmers in the year 2013. These are WEMA hybrids that outperformed some of the best local check hybrids on the market. Next for release in 2016/2017, subject to receiving appropriate regulatory approvals, will be the transgenic products of WEMA which will carry two biotech traits, Bt insect protection trait and the drought tolerance trait from the cold shock protein B (cspB). The overall impact of WEMA project will be the availability of both transgenic and non-transgenic drought tolerant maize hybrids for use by smallholder farmers in SSA.

Rice Yields Enhanced through Integrated Management of Cover Crops and Phosphate Rock in Phosphorus‐deficient Ultisols in West Africa

The relatively low solubility and availability of phosphorus (P) from indigenous phosphate rock could be enhanced by legumes in the acid soils of humid forest agroecosystems. Crotalaria micans L. was grown in a screenhouse without P or with P from triple superphosphate (TSP) and Malian Tilemsi Rock P. The P response of 20 cover crops was field‐evaluated using TSP and Rock P. In both experiments, the fertilized cover crops were followed by upland rice without mineral N or P application. Mean rice grain yield and agronomic residual P‐use efficiency were similar for both P sources. In the field, 1‐year fallow treatment of Canavalia ensiformis (velvet bean) supplied with Mali Rock P gave the highest rice grain yield of 3.1 Mg ha−1, more than 180% that of 2‐year continuous unfertilized rice (cv. ‘WAB 56‐50’). Among continuous rice plots, ‘NERICA 2’ (interspecific rice) supplied with Rock P produced the highest yield (2.0 Mg ha−1), suggesting that ‘NERICA 2’ might have greater potential to solubilize rock P. Results indicate that when combined with an appropriate legume, indigenous rock‐P can release sufficient P to meet the P requirement of the legume and a following upland rice crop in rotation. WARDA Manuscript No. 020607.

Resistance of Bt-maize (MON810) against the stem borers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) and its yield performance in Kenya

A study was conducted to assess the performance of maize hybrids with Bt event MON810 (Bt-hybrids) against the maize stem borer Busseola fusca (Fuller) in a biosafety greenhouse (BGH) and against the spotted stem borer Chilo partellus (Swinhoe) under confined field trials (CFT) in Kenya for three seasons during 2013–2014. The study comprised 14 non-commercialized hybrids (seven pairs of near-isogenic Bt and non-Bt hybrids) and four non-Bt commercial hybrids. Each plant was artificially infested twice with 10 first instar larvae. In CFT, plants were infested with C. partellus 14 and 24 days after planting; in BGH, plants were infested with B. fusca 21 and 31 days after planting. In CFT, the seven Bt hybrids significantly differed from their non-Bt counterparts for leaf damage, number of exit holes, percent tunnel length, and grain yield. When averaged over three seasons, Bt-hybrids gave the highest grain yield (9.7 t ha−1), followed by non-Bt hybrids (6.9 t ha−1) and commercial checks (6 t ha−1). Bt-hybrids had the least number of exit holes and percent tunnel length in all the seasons as compared to the non-Bt hybrids and commercial checks. In BGH trials, Bt-hybrids consistently suffered less leaf damage than their non-Bt near isolines. The study demonstrated that MON810 was effective in controlling B. fusca and C. partellus. Bt-maize, therefore, has great potential to reduce the risk of maize grain losses in Africa due to stem borers, and will enable the smallholder farmers to produce high-quality grain with increased yield, reduced insecticide inputs, and improved food security.

Combining ability and testcross performance of drought-tolerant maize inbred lines under stress and non-stress environments in Kenya

Abstract Drought and poor soil fertility are among the major abiotic stresses affecting maize productivity in sub‐Saharan Africa. Maize breeding efforts at the International Maize and Wheat Improvement Center (CIMMYT) have focused on incorporating drought stress tolerance and nitrogen‐use efficiency (NUE) into tropical maize germplasm. The objectives of this study were to estimate the general combining ability (GCA) and specific combining ability (SCA) of selected maize inbred lines under drought stress (DS), low‐nitrogen (LN) and optimum moisture and nitrogen (optimum) conditions, and to assess the yield potential and stability of experimental hybrids under these management conditions. Forty‐nine experimental three‐way cross hybrids, generated from a 7 × 7 line by tester crosses, and six commercial checks were evaluated across 11 optimum, DS and LN sites in Kenya in 2014 using an alpha lattice design with two replicates per entry at each site. DS reduced both grain yield (GY) and plant height (PH), while anthesis–silking interval (ASI) increased under both DS and LN. Hybrids ‘L4/T2’ and ‘L4/T1’ were found to be superior and stable, while inbreds ‘L4’ and ‘L6’ were good combiners for GY and other secondary traits across sites. Additive variance played a greater role for most traits under the three management conditions, suggesting that further progress in the improvement of these traits should be possible. GY under optimum conditions was positively correlated with GY under both DS and LN conditions, but GY under DS and LN was not correlated. Our results suggest the feasibility for simultaneous improvement in grain yield performance of genotypes under optimum, DS and LN conditions.

Water Efficient Maize for Africa: A Public-Private Partnership in Technology Transfer to Smallholder Farmers in Sub-Saharan Africa

Water Efficient Maize for Africa (WEMA) is a public-private partnership working to improve food security and rural livelihoods among smallholder farmers and their families in sub-Saharan Africa by developing and deploying new drought-tolerant and insect-pest-protected hybrid maize (corn) varieties. Maize is the most widely grown staple crop in Africa, where more than 300 million people depend on it as their main food source. Droughts, foliar diseases, and insect pests are intensifying food production problems in Africa, which makes for a vulnerable food security situation. Smallholder farmers in Africa, like farmers everywhere, want the choice to use the best tools and technologies available to minimize their risks and improve their lives.

Correction to: Genotype by environment interactions and agronomic performance of doubled haploids testcross maize (Zea mays L.) hybrids

The original version of this article was revised because it should have been published with open access which it is at present.

Grain-yield stability among tropical maize hybrids derived from doubled-haploid inbred lines under random drought stress and optimum moisture conditions

Abstract. Drought is a devastating environmental stress in agriculture and hence a common target of plant breeding. A review of breeding progress on drought tolerance shows that, to a certain extent, selection for high yield in stress-free conditions indirectly improves yield in water-limiting conditions. The objectives of this study were to (i) assess the genotype × environment (GE) interaction for grain yield (GY) and other agronomic traits for maize (Zea mays L.) across East African agro-ecologies; and (ii) evaluate agronomic performance and stability in Uganda and Tanzania under optimum and random drought conditions. Data were recorded for major agronomic traits. Genotype main effect plus GE (GGE) biplot analysis was used to assess the stability of varieties within various environments and across environments. Combined analysis of variance across optimum moisture and random drought environments indicated that locations, mean-squares for genotypes and GE were significant for most measured traits. The best hybrids, CKDHH1097 and CKDHH1090, gave GY advantages of 23% and 43%, respectively, over the commercial hybrid varieties under both optimum-moisture and random-drought conditions. Across environments, genotypic variance was less than the GE variance for GY. The hybrids derived from doubled-haploid inbred lines produced higher GY and possessed acceptable agronomic traits compared with the commercial hybrids. Hybrid CKDHH1098 ranked second-best under optimum-moisture and drought-stress environments and was the most stable with broad adaptation to both environments. Use of the best doubled-haploids lines in testcross hybrids make-up, well targeted to the production environments, could boost maize production among farmers in East Africa.