Pasture and grain crop intercropping is considered an alternative for increasing biomass production during the winter periods in Brazil for the establishment of no-tillage systems. We studied nitrogen (N) fertilization rates in a corn-palisadegrass intercropping system that would allow both corn and biomass production without a reduction in corn yield. A field trial was carried out in São Desidério, Bahia -Brazil using a complete block experimental design with a 5 x 2 factorial layout with two factors: N rate (control, 50, 100, 150, and 200 kg ha -1 N) and two cropping systems (corn with or without palisadegrass). Both corn and palisadegrass were sown simultaneously with N fertilizer applied at sowing. The measurements included corn biomass, grain yield and N uptake. In addition, palisadegrass biomass was assessed at corn harvest and at three consecutive times during the winter. There was an interaction between N rates and the intercropping system. Grain yield was affected by intercropping when N fertilizer rates were lower than 100 kg ha -1 , but above that rate, corn grain yield reached 10,000 kg ha -1 and was similar with or without palisadegrass. Nitrogen fertilizers also positively affected corn N uptake. There was no residual effect of N fertilization on palisadegrass biomass production during the sampling periods. However, the biomass of the palisadegrass increased during the winter period and reached 5,000 kg ha -1 of dry matter by the following season. There was no corn yield reduction when corn was intercropped with palisadegrass using nitrogen rates above 100 kg ha -1 . In addition, it is possible to increase biomass production for the establishment of no-tillage systems in Brazil.

The corn biomass and nutrient dynamics may be altered when it is intercropped with Brachiaria (syn. Urochloa spp.). The present study aimed to investigate the dynamics of biomass, nitrogen (N), phosphorus (P) and potassium (K) for farming systems that produce corn intercropped with Brachiaria species. Field experiments were performed during the season and off-season, in a split-plot design. The main plots were composed of Brachiaria species (B. brizantha,B. ruziziensis and B. Convert) intercropped with corn, in addition to corn monocropping. The subplots consisted of three forage sampling periods, ranging from 0 to 60 days after the corn harvest. The intercropping arrangements did not affect the corn grain yield, nutrient accumulation and partitioning, relatively to the corn monocropping. After the grain harvest, B. brizantha achieved the greater biomass accumulation rate in both the season (69 kg ha-1 day-1) and off-season (17 kg ha-1 day-1). The nutrient accumulation ranged widely between the Brachiaria species and planting seasons: 0.2-1.2 kg ha-1 day-1 for N; 0.01-0.07 kg ha-1 day-1 for P; and 0.13-0.8 kg ha-1 day-1 for K. However, the greatest nutrient accumulation was found for B. brizantha, followed by B. ruziziensis and then B. Convert. In the short-term, corn intercropped with Brachiaria in the season showed the largest effect on the nutrient cycling and biomass yield. The intercropping between corn and B. brizantha in the season was the best way to enhance the biomass yield and the N, P and K cycling.

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Corn grain yield, nitrogen (N) fertilizer efficiency and distribution to corn alone and three forms of corn and palisadegrass (Urochloa spp.) intercropping implantation was investigated. A field experiment with 15 N labeling fertilizer was performed in randomized block design. No form of palisadegrass intercropping implantation affected corn grain yield, total N accumulation and N use efficiency (NUE), which were 8.7 t ha -1 , 205 kg ha -1 and 37% respectively. The palisadegrass produced on average 1.9 t of dry mass, absorbing a maximum of 6 kg ha -1 or 5.5% of N fertilizer during corn growing. Furthermore, the palisadegrass did not affect N fertilizer distribution in soil-plant system, in which 28.2% was recovered in the soil and 40.4% in the plants (corn + palisadegrass). The results show that for the three intercropping implantation methods the palisadegrass did not compete with corn for N fertilizer.

-The objective of this work was to evaluate methods of intercropping corn and Panicum spp. forages and their effects on corn yield and forage development. Two experiments with Panicum spp. were conducted, one with 'Tanzania' and other with 'Massai' in the municipality of Piracicaba, in the state of São Paulo, Brazil, in the 2012/2013 growing season. In both experiments, the treatments were: broadcast seeding of Panicum spp. at the same time of corn sowing; corn with Panicum spp. between rows; Panicum spp. sown with fertilizer; Panicum spp. sown between corn rows after corn establishment; broadcast seeding of Panicum spp. after corn establishment; and sole corn sowing. For corn, leaf nitrogen content, ear height, and grain yield were evaluated. For Panicum spp. cultivars, height, dry mass, tiller density, and leaf:stem ratio were evaluated. The intercropping establishment methods used do not affect corn growth, grain yield, and N leaf content. The seeding of both cultivars of Panicum spp. when corn plants had four expanded leaves reduces forage dry mass production and increases the leaf:stem ratio. The Panicum spp. broadcast method, performed after corn was established, does not allow appropriate establishment, with few plants in the area.Index terms: Zea mays, guinea grass, interspecific competition, tropical perennial grass. Produtividade de milho, produção e qualidade de forragem afetadas pelos métodos de consórcio do milho com Panicum maximumResumo -O objetivo deste trabalho foi avaliar métodos de implantação do consórcio milho e espécies forrageiras de Panicum spp. e os efeitos na produtividade do milho e no desenvolvimento das forragens. Dois experimentos com Panicum spp. foram conduzidos, um com 'Tanzania' e outro com 'Massai' em Piracicaba, SP, na safra 2012/2013. Em ambos os experimentos, os tratamentos foram: Panicum spp. semeado a lanço no momento da semeadura do milho; milho com Panicum spp. nas entrelinhas; Panicum spp. semeado com fertilizante; Panicum spp. semeado nas entrelinhas depois do estabelecimento do milho; Panicum spp. semeado a lanço depois do estabelecimento do milho; e milho solteiro. Para o milho, avaliaram-se a concentração de nitrogênio foliar, a altura de espigas e a produtividade de grãos. Para as cultivares de Panicum spp., avaliaram-se altura, massa seca, número de perfilhos e relação folha:colmo. Os métodos de implantação do consórcio avaliados não afetam o crescimento, a produtividade de grãos e a concentração foliar de N do milho. A implantação das cultivares de Panicum spp., quando o milho apresenta quatro folhas expandidas, reduz a massa seca e aumenta a relação folha:colmo das plantas forrageiras. A semeadura a lanço de Panicum spp., depois do estabelecimento do milho, não permite o estabelecimento adequado, com poucas plantas na área.

Early fertilizer nitrogen (N) application on cover crops or their residues during the off-season is a practice adopted in Brazil subtropical conditions under no-tillage corn (Zea mays L.) systems. However, the effect of early N application on yield, plant N content, and N recovery efficiency (NRE) for corn is not yet well documented. Five fertilizer N timings in an oat-corn system were evaluated in two studies utilizing an isotopic-labeled N determination, 15N isotope. The N fertilization timings were: (i) oat tillering, (ii) 15 days before corn planting time, over the oat residues, (iii) at corn planting time, (iv) in-season at the three-leaf growth stage (V3), and (v) in-season split application at V3 and six-leaf (V6) growth stages. Based on the statistical analysis, the N fertilization timings were separated into three groups: 1) N-OATS, designated to N applied at oat; 2) N-PLANT, referred to pre-plant and planting N applications; and 3) N-CORN, designated to in-season corn N applications. Corn yield was not affected by the N fertilization timing. However, the N-CORN N fertilization timings enhanced NRE by 17% and 35% and final N recovery system (plant plus soil) by 16% and 24% all relative to N-OATS and N-PLANT groups, respectively. Overall, N-OATS resulted in the largest N derived from fertilizer (NDFF) amount in the deeper soil layer, in overall a delta of 10 kg N ha-1 relative to the rest of the groups. Notwithstanding corn yield was not affected, early N fertilization under subtropical conditions is not a viable option since NRE was diminished and the non-recovery N increased relative to the in-season N applications.

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