Nitrogen fertilizer management effects on maize grain quality in the West African moist savanna

Until recently, breeding programs in Africa placed little emphasis on grain quality improvement. Consequently, some farmers have not adopted improved high yielding varieties because they lacked desired quality characteristics for processing and other end uses. We conducted this study to determine the effects of N application on some maize (Zea mays L.) grain quality parameters. In 1993 and 1994, five maize cultivars under four N levels (0, 30, 60, and 120 kg ha- ') were evaluated at Zaria (11° U' N), northern Nigeria, on a Plinthustalf (fiue-Ioamy isohyperthermic). Increasing N levels increased ~rain yield, kernel weight, and grain protein quadratically for all the cultivars. The hybrid 8644-27 had the highest grain yield and kernel weight of 5,3 Mg ha- ' and 26.62 mg kernel-I, respectively. Average grain protein yield per unit area was not significantly different among cultivars in both years. At 30 to 60 kg N ha- ', the cultivars 8644-27 and TZPB-SR had a greater percentage of floaters, than the other cultivars in both years, reflecting a greater proportion of floury endosperm, indicating that they would be best for traditional dry milling, where the whole grain is ground to produce nour. Also, at 30 to 60 kg N ha- I , SPL and TZ8-SR had a relatively low percentage of floaters and high test weights of over 811 kg m' in 1993 and 778 kg m' in 1994, and should give high yields of grits when processed. Thus, both cultivars have high value for industrial dry milling. Results showed that the choice of cultivar and N level may affect grain quality and they should be considered in producing maize for dry milling purposes

Combined effects of Stylosanthesguianensisfallow and tillage management on upland rice yield, weeds and soils in southern Benin

Intensifying upland rice cultivation has resulted in increased weed pressure and declining soil fertility and rice yield in West Africa. Integrated crop management technologies are needed for enhancing rice productivity. A field experiment was conducted from 2006 to 2008 in a TypicHaplustult soil in southern Benin to identify the optimal seeding date of stylo relay-cropped into upland rice, and to evaluate the effects of fallow treatment and tillage management on rice yield, weed biomass and soil properties. Stylosanthesguianensis(stylo), a legume species, was used as a short-term fallow crop. Rice was grown once each year and stylo was seeded during the wet season and grown until the next rice-growing season. The effects of fallow treatment and tillage management (no-tillage vs. manual-tillage) on weed biomass during the rice-growing season were evaluated in 2007 and 2008, whereas the effects on rice yield were examined in 2007 alone. Results indicated that stylo can be established as a relay crop withupland rice about 10 days after rice seeding. Stylo fallow reduced weed biomass by 71% and 95% and increased total biomass (weed + stylo + litter) by 594% and 107% at the end of the dry seasons in 2007 and 2008, respectively. No-tillage without stylo fallow increased weed biomass by 62–202% over manual-tillage during the rice-growing seasons, whereas stylo fallow reduced weed biomass by 45–83% and 11–36%, respectively, under no-tillage and manual-tillage management. There were no significant effects of fallow treatment and tillagemanagement on soil organic C, total N, inorganic N and extractable P. Rice yields following stylofallowwere 0.7 Mg ha_1 higher than after the natural fallow. Manual-tillage increased rice yield by 0.6 Mg ha_1 over no-tillage. Manual-tillage combined with stylo fallow can be recommended to smallholder farmers for improving upland rice productivity

Yield and Nuse efficiency of five tropical maize genotypes under different N levels in the moist savanna of Nigeria

Two field experiments were conducted during the 1993 and 1994 growing seasons at Samaru (7° 38' E; 11° 11' N), northern Nigeria, to evaluate N-use efficiency (kg grain per kg available soil N) and yield of 5 maize genotypes planted early in the season under five levels of N. The hybrid (8644-27) gave the highest grain yield and was the most N-use efficient genotype. It had a longer grain filling period, a higher harvest index, and a greater 1000-kerneI weight than other genotypes. The most widely grown open pollinated variety (TZB-SR) was the least efficient in utilizing available soil N for grain production, although it had the highest number of kernels per ear and total above-ground dry matter. The semiprolific (SPL) and EV8728-SR genotypes appeared to have a higher potential to adapt to nitrogen stress than other genotypes. They had higher grain yields under zero-N in both years, but the differences were not significant. They also showed greater synchronization of anthesis and silking, which indicates better ability to tolerate nitrogen stress. Traits such as extended grain filling and 1000-kernel weight should be further investigated for inclusion in a breeding scheme to increase maize yield. Early planting to capture the N flush, and application of a suboptimal amount of N (60 kg/ha at 2 WAP) was adequate for production of all the genotypes under the loamy soil conditions of the chosen site. A combination of legume rotation, 60 kg N/ha, and an N-use efficient genotype (8644-27) gave a yield advantage of 1.3 t/ha over a monocrop maize supplied with 60 kg N/ha on farmers' fields in the moist savanna of Nigeria

Effect of weed competition on upland rice production in north-eastern Nigeria

Rice production by smallholder farmers in the savannas of Nigeria is constrained by weed competition. A field study was conducted to assess the effect of weed competition on the performance of upland rice varieties in 2005 and 2006 in the northern Guinea and Sudan savannas of Nigeria. The experiment was set up as a split plot in randomized complete block design. One hoe weeding at 3 weeks and two hoe-weeding regimes at 3 and 6 weeks after planting and a weedy plot were the main plot treatments. Five rice varieties CG14 (Oryza glaberima), WAB56-104 (O. sativa, tropical japonica, type), NERICA1, NERICA2 and NERICA4 (New Rice for Africa) constituted the subplot treatments. In the weedy plot, grain yield did not differ significantly between varieties. Grain yield in all varieties was significantly depressed by over 86% in the weedy plot compared with plots that were hoe-weeded once or twice. Grain yield, number of spikelets plant-1 and days to flowering, differed substantially in plots that were hoe-weeded once or twice. Across locations and varieties, grain yield were 4.8 and 6.7 times higher in plots weeded once or twice, respectively than in the weedy plots. Weed biomass was negatively correlated with grain yield (r=-0.70; P=<.0001), number of spikelets plant-1 (r=-0.40;; P=0.0060) and plant height (r=-0.41; P=0.0049). Averaged over locations, NERICA 4 produced grain yield that was significantly higher than other varieties. Our result suggests that two hoe-weedings are needed for optimum grain yield of the rice varieties

Genotypic differences in concentration and bioavailability of kerneliron in tropical maize varieties grown under field conditions

Iron deficiency is estimated to affect over one-half the world population. Improving the nutritional quality of staple food crops through breeding for high bioavailable iron represents a sustainable and cost effective approach to alleviating iron malnutrition. Forty-nine late maturing tropical elite maize varieties were grown in a lattice design with two replications i

Assessment of concentrations of iron and zinc and bioavailable iron in grains of earlymaturing tropical maize varieties

Twenty elite early-maturing (75−90 days) tropical maize varieties grown in three diverse agroecologies in West Africa were evaluated to identify varieties with high kernel-Fe and -Zn and bioavailable Fe levels. Bioavailable iron was assessed using an in vitro digestion/Caco-2 cell model. Significant (P < 0.001) varietal differences were observed in mean kernel-Fe and -Zn levels. The ranges were 15.5−19.1 mg kg-1 for Fe and 16.5−20.5 mg kg-1 for Zn. Genetic component accounted for 34% of the total variation in kernel-Zn and for 11% of the variation in kernel-Fe levels. Mean bioavailable Fe in varieties ranged between 4% below and 49% above the reference control variety. A significant negative relationship was detected between kernel-P concentration and bioavailable Fe (R = −0.36; P < 0.004; n = 60). Two varieties, ACR90POOL16-DT and ACR86TZESR-W, were identified as the most promising for further evaluation to determine their efficacy as improved sources of iron in target populations

Assessment of iron bioavailability from twenty elite latematuring tropical maize varieties using an in vitro digestion/Caco2 cell model

An in vitro digestion/Caco-2 cell model was used to assess iron bioavailability of twenty elite late-maturing tropical maize varieties grown in three diverse agroecologies in West and Central Africa (WCA). Kernel-iron concentration of the varieties, averaged across locations, varied from 19.2 to 24.4 mg kg−1, while mean kernel-zinc concentration ranged between 19.4 and 24.6 mg kg−1. Significant differences in iron bioavailability were observed among varieties, but the environment had no significant effect. Mean bioavailable iron ranged between 14% below and 43% above the reference control variety, TZB-SR. Variety DMR-LSR-Y with the highest concentrations of kernel-iron and -zinc of 24–25 mg kg−1 across the three locations had a similar quantity of bioavailable iron as the reference control, TZB-SR. In the long run this variety could be potentially effective in reducing iron deficiency because of its high kernel-iron. The most promising varieties were Mid-altitude STR synthetic and ACR91SUWAN-1-SRC1. They had kernel-iron and -zinc levels of 22–24 mg kg−1 and bioavailable iron 24–36% higher than the reference control, TZB-SR. Additional research is necessary to determine if the increases in kernel-iron concentration and bioavailable iron observed in this study can significantly improve the iron status of individuals in WCA at risk for iron deficiency