Browsing by Author "Diels J."

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    On-farm evaluation of biological nitrogen fixation potential and grain yield of Lablab and two soybean varieties in the northern Guinea savanna of Nigeria
    (Springer, 2005) Okogun J.A.; Sanginga N.; Abaidoo R. C; Dashiell K.E.; Diels J.; 0000-0002-1235-2252
    Several legumes with high biological nitrogen fixation (BNF) potentials have been studied in on-station trials. The processes involved in BNF and the benefits of these species to crop production need to be evaluated using farmers’ management practices in farmers’ fields. An on-farm trial with 20 farmers was conducted in the northern Guinea savanna (NGS) of Nigeria. The aims were to evaluate the BNF potentials of an improved soybean variety (TGx 1448-2E) and a local variety (Samsoy-2) when inoculated with Bradyrhizobium strains, and of Lablab in farmer-managed and researcher-managed soybean-maize and Lablab-maize crop rotation systems. The level of soil P was generally low with more than 50% of the fields having less than the critical P level. The plant available P content was statistically significantly (P = 0.05) correlated with P in grain (r = 0.60), P in the shoot (r = 0.68), grain yield (r = 0.40) and nodule weight (r = 0.35). Variations in plant parameters (nodulation, shoot dry matter, percentage nitrogen derived from the air [%Ndfa], grain yield, and nutrient uptake) among and within farmers’ fields were attributed to differences in soil fertility and crop management. About 60% of the fields were mod erately fertile, sufficient to support legume establishment, while about 30% of the farmers’ fields had a low fertility level. For farmers in the study area to benefit from the BNF potentials of the legumes, an external P fertilizer input was necessary as well as suitable crop management practices because all parameters mea sured in the researcher-managed plots were higher than in the farmer-managed plots.
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    Phosphate rock utilization by soybean genotypes on a low-P savanna soil and the status of soil P fractions after a subsequent maize crop
    (Ajol, 2009) Nwoke O. C.; Okogun J. A.; Sanginga N.; Diels J.; Abaidoo R. C; Osonubi O.; 0000-0002-1235-2252
    Information on the inter- and intra-specific variability in the acquisition and utilization of phosphorus (P) by promiscuous soybean genotypes under low-P conditions can be helpful in the short-term management of soil P availability. Thirteen promiscuous soybean genotypes were evaluated in a low-P soil at Fashola in the derived savanna of Nigeria to compare their ability to acquire and utilize P from phosphate rock (PR) and single superphosphate (SSP). Changes in soil P fractions after a subsequent maize crop were also assessed. The treatments were 90 kg P/ha added as PR (90-PR), 30 kg P/ha as SSP (30-SSP), and 0 kg P/ha as a control (0-P). Large differences occurred in growth, nodulation, and mycorrhizal infection rates among the soybean genotypes and were related to the P sources. Three genotypes (Tgm 1511, Tgm 1419, and Tgm 1360) increased their shoot dry matter yield significantly with PR application. The efficiency of the genotypes to acquire and utilize fertilizer or soil P differed significantly, and their ranking depended on how efficiency is defined. Shortly after application, 90-PR and 30-SSP resulted in similar increases in available P but the effects of 90-PR on the Ca-bound pool were significantly higher than those of 30-SSP. The difference in Ca-bound P between 90-PR and 0-P decreased from 44 to 26 mg/kg after the second cropping, leading to significantly higher levels of resin P (p = 0.006) and HCO3-Pi (p = 0.038) in the PR treatment than in the control. The results of this study indicate that exploiting genotypic differences in P use efficiency may lead to the selection of soybean genotypes that can potentially enhance productivity in the low-P savanna soils.