No abstract

Nitrogen supply and plant population are basic parameters for cereal-legume intercropping. In order to study plant population and nitrogen fertilizer effects on yield and yield efficiency of maize-bean intercropping, a field experiment was established. Three bean plant populations and three nitrogen levels were used. Maize dry matter accumulation decreased with increases in bean plant population. Competitive effect of intercrop beans on maize yields was high at higher plant populations, being decreased by nitrogen fertilizer; application of 50 kg ha-1 N was very efficient in increasing maize cob yield. Intercropping significantly decreased harvest index of beans in all plant population and nitrogen fertilizer situations. The efficiency of intercropping, compared to sole cropping, was evidenced by the values obtained for Land Equivalent Ratio (LER) for biomass, cob and pod yields that increased with increases in bean plant populations and nitrogen fertilizer levels.

Establishment of the ideal number of plant is a crucial point for obtaining maximum profits while cropping different species together. The main objective of the study was to investigate the effect of different plant populations of maize and beans, at two nitrogen levels, on the performance of the component crops. Two maize (20,000 and 40,000 plants ha -1 ) and three bean (30,000; 60,000 and 90,000 plants ha -1 ) populations were tested in a randomized complete block design with tree replicates. Grain yields of maize and beans were affected by intercropping and the effect was more detrimental to the legume mainly at the highest maize plant population. The application of nitrogen fertilizer to maize rows mitigated intercropping effect on maize at higher population (40,000 plants ha -1 ) and, at lower maize plant population (20,000 plants ha -1 ), benefited the associated beans by increasing grain yields. Land Equivalent Ratio values for grain yields of maize and beans showed that intercropping compared to sole cropping is advantageous and best indices were obtained at a bean plant population of 60,000 plants ha -1 . Key words: Zea mays, Phaseolus vulgaris, cropping system, plant density POPULAÇÃO ÓTIMA DE PLANTAS NO CONSÓRCIO MILHO-FEIJÃO NO SEMI-ÁRIDO BRASILEIRORESUMO: A definição do número de plantas por área é fundamental para a obtenção de ganhos quando diferentes espécies são plantadas juntas. O principal objetivo do estudo foi investigar o efeito de diferentes populações de plantas, sob dois níveis de nitrogênio, no desempenho do milho e do feijão em plantio consorciado Duas populações de milho (20.000 e 40.000 plantas ha -1 ) e três de feijão (30.000; 60.000 e 90.000 plantas ha -1 ) foram testadas em um delineamento de blocos ao acaso com três repetições. As produções de grãos de milho e feijão foram afetadas pelo consórcio, sendo o efeito mais prejudicial para a leguminosa. A aplicação de fertilizante nitrogenado diminuiu o efeito competitivo do consórcio para o milho na maior população (40.000 plantas ha -1 ), e, na menor população (20.000 plantas ha -1 ), favoreceu o feijão com o aumento de sua produção de grãos. Os índices para Uso Eficiente da Terra para produção de grãos de milho e feijão revelaram que o consórcio é mais vantajoso que o plantio isolado das culturas, com os melhores valores com a população de plantas de feijão correspondente a 60.000 plantas ha -1 . Palavras-chave: Zea mays, Phaseolus vulgaris, sistema de plantio, densidade de plantas

Na região do Vale do São Francisco, onde a exploração da agricultura irrigada é a principal responsável pela alta produção de frutas para exportação, a banana é uma das culturas que mais tem se expandido em área cultivada. Com o objetivo de registrar os fungos micorrízicos arbusculares associados a essa cultura, foram coletadas, sob a parte aérea da bananeira, amostras de solo da rizosfera, em quatro áreas com diferentes características de solo, sendo identificadas as espécies: Acaulospora longula Spain & Schenck, A. morrowiae Spain & Schenck, A. rehmii Sieverding & Toro, A. scrobiculata Trappe, A. spinosa Walker & Trappe, A. tuberculata Janos & Trappe, Entrophospora infrequens (Hall) Ames & Schneider, Gigaspora ramisporophora Spain, Sieverding & Schenck, Glomus diaphanum Morton & Walker, G. etunicatum Becker & Gerd., G. intraradices Schenck & Smith, G. macrocarpum Tui. & Tui., G. mosseae (Nicol. & Gerd.) Gerd. & Trappe, G. occultum Walker e Scutellospora sp. A percentagem de colonização das raízes de bananeiras nas diferentes áreas foi em média 55%.

Cowpea (Vigna unguiculata L Walp) is a legume of great social and economic importance in tropical regions. The plant is tolerant to soil and climatic adversity, while it has high nutritional value with high protein, minerals and vitamins contents. The cowpea legume has a very high ability to fix N 2 which is important because it can reduce the costs of soluble mineral fertilizers and may contribute to sustainable agriculture, preserving the environment and natural resources. In order to observe the influence of Rhizobia the agronomic effectiveness of cowpea strains was tested in two consecutive years compared with the mineral N fertilization. The experiments were carried out in different soils of the Brazilian Northeast (semiarid and rain forest region) which measured the effectiveness of rhizobia on grain yield. The results revealed the effectiveness of strain BR 3299 in the experiment that significantly increased the grain yield (3 times when 50 kg ha -1 of N, and 2 times when 80 kg ha -1 N were used). The Rhizobia treatment promoted the grain yield (up to 1,600 kg ha -1 ), compared to application of 80 kg ha -1 of N. In general, all applied strains promoted the Brazilian Northeast average cowpea yield (300-400 kg ha -1 ).