Phosphorus is important for cowpea production and is inherently low in many tropical soils. Selection of cowpea genotypes that produce good yield under low soil P or those with high P response efficiency can be a low input approach in solving this problem. Therefore, the effect of root architecture and P application on the yield of cowpea and its P uptake were investigated. A screen house experiment was conducted at the International Institute of Tropical Agriculture (IITA) Ibadan, Nigeria. Three hundred cowpea genotypes obtained from the germplasm collection Unit of IITA were screened for number of root whorls and total number of roots using a completely randomized design with 12 replicates. Ten cowpea genotypes were further selected from the initial screening to determine the effect of three levels of P (0, 20 and 40 mg P kg^-1 soil) application on their growth and nutrient uptake. The experiment was replicated three times. Phosphorus application significantly (p<0.05) enhanced shoot and root dry weight, total biomass, number of nodules, nodules dry weight, N and P uptake of the cowpea genotypes investigated. Six cowpea genotypes exhibited increases in nodules dry weight with P application. There was no significant relationship between root architecture and P uptake (r = -0.13). The N and P uptake were enhanced by the application of P in the cowpea genotypes studied. In low P soil, IT97K-414-5 was efficient in P uptake and IT92KD-267-2 was efficient in N uptake. The two genotypes may produce cowpea lines suitable in low P soils when used as breeder lines.

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Turmeric production is greatly hampered by dearth of knowledge of its agronomic requirements in Nigeria, particularly nitrogen requirement and possible enhancement of nutrient uptake by mycorrhiza. Hence, investigations aimed at examining the effect of nitrogen and the contribution of arbuscular mycorrhizal fungi on the yield and nutrient uptake of turmeric were conducted. It was a potted experiment with 5 levels of nitrogen (0, 45, 90, 135 and 180 kg N ha-1), and two levels of mycorrhiza (with and without). The experiment was arranged in a 5 × 2 factorial fitted into a completely randomized design with three replications. Data were obtained on the dry biomass yield, rhizome yield, curcumin content of the rhizome, nitrogen, phosphorus, calcium, magnesium and potassium uptake in the shoot. A repeat experiment was conducted using the best two treatments and the control in a 3 × 2 factorial experiment replicated thrice. All data were subjected to analysis of variance using SAS PROC. GLM and significant treatment means separated using LSD values. Applications of nitrogen and mycorrhiza independently and in combinations significantly enhanced the yield and curcumin content of turmeric. The rhizome yield in the mycorrhiza infested soil was not significantly different with the non application of mycorrhiza but there was an increase of approximately 15 % in the rhizome yield in the mycorrhiza infested soil. Application of 180 kg N ha-1 with mycorrhiza gave the highest biomass and rhizome yield and as such is the most suitable for turmeric production.