A study was conducted at Ibadan (Derived savanna), Ife (Rainforest), and Kishi (southern Guinea savanna-northern fringe) to ascertain the agronomic potentials and variation in early interference traits for weed suppression in pigeon pea in southern agro-ecologies of Nigeria. The experimental site was marked out into 4 x 4 m plots and twenty (20) genotypes were randomly assigned with three replicates. Results showed that across genotypes in all locations, NSWCC-29B-1 had the tallest plants. However, NSWCC-46 had the shortest plants. Genotypes sown at Ife were the tallest across locations. This might have resulted from superior growth factors in Ife. Tall crop plants compete and suppress weeds more than short crop plants. NSWCC-19 had the largest leaf area across genotypes and locations at 20 WAP. Genotypes sown at Ife had the broadest leaves across the locations. Large leaf area enhances canopy formation, weed suppression, and light interception for improved grain yield. NSWCC-7D had the broadest canopy width; though, similar to NSWCC-24, NSWCC-29B-1, NSWCC-27A, and AO/TB 79-9. Broad canopy width is loftier for weed suppression and crop yield. NSWCC-24 had the highest grain yield across genotypes in all locations. Plants sown in Ibadan and Ife had better and similar grain yields than Kishi, which was about 50% lower than other locations. NSWCC-7D, NSWCC-29A, NSWCC-35, NSWCC-46B, NSWCC-35A, NSWCC-34, NSWCC-29B-1, NSWCC-27A, NSWCC-24, CITA 3, AO/TB 79-9 and NSWCC/8B showed promising potentials for weed suppression and grain yield in all the agro-ecologies.

Field studies were conducted in the early and late season of 2010 in the tropical rainforest zone of Nigeria to investigate the effects of NPK fertilizer as an inorganic soil amendment at 75 kg/ha and 150 kg/ha in four replications on population densities of Pratylenchus brachyurus and on crop yield of maize. Seeds of maize variety, DMR LSR-Y were collected from Institute of Agricultural Research and Training, Ibadan. The experimental field was naturally infested with Pratylenchus spp. due to subsequent continuous cultivation of susceptible crop on the field. Seeds were planted and NPK was applied around the roots of maize plants 3 weeks after seedling emergence. Soil samples were taken on treatment plots at planting and harvest to determine the percentage change in nematode population. At the end of experiment, NPK application resulted in the increase in the nematode population. However, the grain yield of maize was not reduced by the increased nematode densities. The results of this study suggests that the usage of NPK caused a surge in the nematode reproduction on the field due to the availability of more feeding sites on the actively growing root system of the crop.