Phosphorus Level Affects Brown Blotch Disease, Development and Yield of Cowpea
Application of Phosphorus in adequate concentrations could directly or indirectly reduce disease incidence and severity of cowpea brown blotch and improve the forage and grain yield. A field experiment was conducted to investigate the effects of level of phosphorus application on Brown Blotch disease of cowpea (Vigna unguiculata (L.) Walp), caused by Colletotrichum capsici during 2003, 2004 and 2005 planting seasons. Application of phosphorus was at 30, 60, 90 and 120 kg ha of P O. As P level increased numbers of petioles, 1 25 pods, nodules, seed/pod, leaf area and yield significantly increased. Disease incidence and severity of Brown Blotch were significantly reduced at 90 and 120 kg ha of P O was not affected irrespective of the method of 1 25 application. Application method did not affect yield. Reduction in brown blotch disease at higher levels of P was recorded.
Effects of Phosphorus and Rhizobium Inoculation on Yield Components and Grain Yield of Some Selected Cowpea Genotypes
The effects of phosphorus (0, 20, 40kg P 2 O 5 ha -1 ) and rhizobium inoculation (inoculated and un-inoculated) on the yield components and grain yield of three cowpea genotypes (IT93K-452-1, IT97K-573-1-1 and IT98K-499-35) were investigated under field conditions at Bayero University, Kano, Teaching and Research Farm (11 0 59 N; 8 0 25 E; 466m above sea level) and Agricultural Research Station Farm, Minjibir (12 0 10’ N,  8 0 39’ E; 402m  above sea level) in 2014 rainy season. Cowpea genotypes were assigned to the main plot, while phosphorus levels were assigned to the sub-plots. The inoculation was assigned to the sub-sub plot. These were laid out in Split-split plot design and replicated three times. Results of the study indicated significant effect of genotype in all the characters measured except shelling percent. Significantly (p˂ 0.05) higher number of pods per plant, pod weight, fodder and grain yield was observed from IT99K-573-1-1 than all other genotypes evaluated. Similarly, the number of pods per plant, pod weight, fodder and grain yield were significantly influenced by application of phosphorus with better results recorded from 40 kg P 2 O 5 treated plants. Inoculation of cowpea with rhizobium MC92 strain, also recorded significant effect on the measured characters and grain yield. Inoculation of cowpea with rhizobium MC92 along with 40kgP 2 O 5 ha -1 could enhance performance of cowpea particularly with an adaptable genotype like IT99K-573-1-1. Keywords: Cowpea, grain yield, inoculation, yield components
Misconceptions and practical problems in the use of 15N soil enrichment techniques for estimating N2 fixation
The 15N methods are potentially accurate for measuring N2 fixation in plants. The only problem with those methods is, how to ensure that the 15N/14N ratio in the plant accurately reflects the integrated 15N/14N ratio (R) in soil which is variable in time and with soil depth. However, the consequences of using an inappropriate reference plant vary with the level of N2 fixation and the conditions under which the study was made. For example, the errors introduced into the values of N2 fixation are higher at low levels of fixation, and decrease with increasing rates of fixation. At very high N2 fixation rates, the errors are often insignificant. Also, the magnitude of error is proportional to the rate of decline of the 15N/14N ratio with time. Since N2 fixation in most plants would be expected to below 60%, the question of how to select a good reference plant is still pertinent. In this paper, we have discussed some of the criteria to adopt in selecting reference plants, e.g. how to ensure that the reference plant is not fixing N2, is absorbing most of its N from the same zone as the fixing plant, and in the same pattern with time, etc. In addition, we have discussed 15N labelling materials and methods that are likely to minimize any errors even when the fixing and reference plants don't match well in certain important criteria. The use of slow release 15N fertilizer or 15N labelled plant materials results in slow changes in the 15N/14N ratio of soil, and is strongly recommended. Where 15N inorganic fertilizers are used, the application of the fertilizer in small splits at various intervals is recommended over a one-time application. The problem with the reference crop, which has sometimes discouraged potential users of the 15N methods, is surmountable, as discussed in this paper.