Spatial distribution of N, P and K in major yam soils of southeastern Nigeria

Pedometrics, the application of numerical techniques to describe soil attributes and enhance objectivity in soil-related decision making, was applied to soil samples from 149 geo-referenced locations in yamgrowing area of southeastern Nigeria. Geostatistical technique was applied using Krigin to estimate soil parameters from unsampled sites. Results revealed multi-nutrient deficiencies of N, P, and K in the area. The magnitude of deficiency is N > K > P. Pragmatically, 4.19, 2.59 and 1.76 m ha are deficient in total N, exchangeable K and available P, respectively. This could guide soil nutrient management decision for sustainable yam production in the area

Nitrogen derived from promiscous soyabean in maize-based cropping system in the moist savanna of Nigeria

Promiscuously nodulating soybeans were developed by IITA, Ibadan, and introduced in the moist savanna region of Nigeria to encourage smallholder farmers to cultivate the crop since it has no requirement for artificial rhizobial inoculation. The anticipated benefits include increased income and quality of livelihoods to farmers and improved soil fertility management strategy. Studies conducted by collaborating scientists within the moist savanna of Nigeria have shown promiscuous soybeans to respond to rhizobial inoculation, which is often accompanied by increases in arbuscular mycorrhizal fungal (AMF) infection of plant roots and P uptake. The actual amount of N2 fixed by the promiscuous soybean cultivars in this environment ranges from 30 – 130 kg N ha-1, representing 25 – 60% of N2 derived from fixation. Cultivation of these soybean cultivars either as an intercrop or in rotation with maize often results in significant increases in the maize crop. However, results have shown that these increases cannot be due solely to the carry-over of N from soybean residue. Nigerian Journal of Soil Science Vol. 15 2005: 109-11

Productivity of a maize-promiscuous soybean intercrop as affected by fertilizer in the Southern Guinea Savanna Zone of Nigeria

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Nitrogen rhizodeposition from soybean (Glycine max) and its impact on nutrient budgets in two contrasting environments of the Guinean savannah zone of Nigeria

Nitrogen (N) rhizodeposition by grain legumes such as soybean is potentially a large but neglected source of N in cropping systems of Sub-Saharan Africa. Field studies were conducted to measure soybean N rhizodeposition in two environments of the Guinean savannah of Nigeria using 15N leaf labelling techniques. The first site was located in Ibadan in the humid derived savannah. The second site was in Zaria in the drier Northern Guinean savannah. Soybean N rhizodeposition in the top 0.30 m of soil varied from 7.5 kg ha-1 on a diseased crop in Ibadan to 33 kg ha-1 in Zaria. More than two-thirds of soybean belowground N was contained in the rhizodeposits at crop physiological maturity, while the rest was found in the recoverable roots. Belowground plant-derived N was found to constitute 16–23% of the total soybean N. Taking rhizodeposited pools into account led to N budgets close to zero when all residues were removed. If residues were left in the field or recycled as manure after being fed to steers, soybean cultivation led to positive N budgets of up to +95 kg N ha-1. The role and potential of grain legumes as N purveyors have been underestimated in the past by neglecting the N contained in their rhizodeposits