The increased productivity or yield advantage provided by intercropping is attributed to a better use of resources by crops grown in mixtures, as compared to the same species grown in sole stands. In an intercropping system with upland rice and cowpea, the intra and inter-competition was quantified, as affected by plant population density and rate of nitrogen. Reductions in number of panicles per rice plant and number of grains per panicle were obtained with high density in both sole and mixture rice populations. Increasing nitrogen rate did not affect yield and yield components in both populations, but number and weight of pods per plant of cowpea in sole stands increased. Land equivalent ratios exceeding unity were obtained, indicating an improved resource use by the crop mixture. Relative crowding coefficient and aggressivity indices showed cowpea to be the dominant crop, with rice being dominated. Nitrogen utilization efficiency was high with intercrops, but was generally poor in stands of high population density. Key words: aggressivity index, land equivalent ratio, nitrogen utilization efficiency, relative crowding coefficient COMPETIÇÃO EM UMA CULTURA CONSORCIADA DE ARROZ-GUANDU EM FUNÇÃO DO FERTILIZANTE NITROGENADO E DA DENSIDADE POPULACIONAL DE PLANTASRESUMO: O aumento em produtividade devido a plantios consorciados é atribuído ao melhor uso dos recursos presentes pelas plantas em desenvolvimento conjunto, em comparação às mesmas espécies crescendo em dosséis separados. Em um sistema consorciado de arroz e guandu quantificou-se as inter-e intra competições em relação à densidade populacional e taxa de aplicação de nitrogênio. Reduções significativas do número de panículas por planta de arroz e número de grãos por panícula foram observados para alta densidade, tanto para culturas solteira de arroz como em populações mistas. O aumento das doses de nitrogênio não afetou a produção e os componentes de produção em ambos os sistemas, ao passo que o número e peso de vagens por planta do guandu aumentaram em culturas solteiras. Foram obtidas razões de área equivalente maiores que a unidade, mostrando melhoria no uso da terra nas culturas mistas. O coeficiente relativo de superpopulação e os índices de agressividade mostraram que o guandu é dominante e o arroz dominado. A eficiência do uso de nitrogênio foi alta nas culturas consorciadas, mas em geral baixa para populações de alta densidade. Palavras-chave: índice de agrssividade, razão de área equivalente, eficiência do fertilizante, coeficiente relativo de superpopulação

The study was aimed at evaluating the effects of four selected organic manures on the early seedling morphology of Irvingia wombolu. The experiment was undertaken in Asaba located in the tropical rainforest zone of Nigeria (60 0 12´ N and longitude 60 0 45´ E). The study consisted of four organic manure treatments, namely: Tithonia alone, Tithonia + pig manure, Tithonia + cow manure, Tithonia + poultry manure and control with no manure application. The five treatments were arranged in a randomized complete block design (RCBD) with three replicates. At 15 days after sowing (DAS) percentage of germinated seeds ranged from 95.45% (control) to 95.73 % (Tithonia + poultry manure). A mix of Tithonia + pig manure, Tithonia + cow manure and Tithonia + poultry manure increased seedling height by 3.9, 9.7 and 11.5 % respectively compared to Tithonia alone. The highest leaf number (9.03) and LAI (2.90) were observed in Tithonia + poultry manure. Stem volume of seedlings increased significantly (P<0.05) over the control with application of organic manures. Stem volume was found to be significantly (P<0.01) correlated with plant height (r = 0.988), stem diameter (r = 0.980) and leaf area (r = 0.976). The study recommends the use of Tithonia + poultry manure mixture for better performance of Irvingia seedlings.

Abstract.Maize is an agronomic cereal species that is sensitive to nutrient applications, especially nitrogen. Field experiments were conducted in 2011 and 2012 to evaluate the effect of nitrogen and mulching using dried weeds on maize growth and nutrient accumulation. The study was located in the Research Farm of the Agricultural Science Education Unit of the Delta State University, Abraka, Nigeria ((latitude 5 0 46'N and longitude 6 0 5'E). The experiment consist of eight (8) recorded the highest in all the treatments. It can be concluded based on the results in this study, that legume based weeds as mulch can be supplemented with nitrogen to improve maize growth.

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Maize is an agronomic cereal species that is sensitive to nutrient applications, especially nitrogen. Field experiments were conducted in 2011 and 2012 to evaluate the effect of nitrogen and mulching using dried weeds on maize growth and nutrient accumulation. The study was located in the Research Farm of the Agricultural Science Education Unit of the Delta State University, Abraka, Nigeria ((latitude 50 46’N and longitude 60 5’E). The experiment consist of eight (8) treatments (i) control (ii) 40kgNha-1 (iii) 80kgNha-1 (iv) 120kgNha-1 (v) 4.5t ha-1Panicum maximum + 40kgNha-1 (vi) 4.5t ha-1Pueraria phaseoloides + 40kgNha-1 (vii) 4.5t ha-1Eleusine indica + 40kgNha-1 (viii) 4.5t ha-1Stylosanthesgracilis + 40kgNha-1. The treatments were replicated three times. From research results, the combination of Pueraria phaseoloides with 40kgNha-1 showed higher maize plant height, foliage development attributes, shoot dry matter, crop growth indices and nutrient uptake compared to other combinations, while only nitrogen application of 120kgNha-1 recorded the highest in all the treatments. It can be concluded based on the results in this study, that legume based weeds as mulch can be supplemented with nitrogen to improve maize growth.