The use of mepiquat chloride (MC) in cotton (Gossypium hirsutum L.) cultivation has increased significantly in recent years. The use of MC, a growth regulator, results in higher precocity and lower height and consequently increases yield and reduces crop costs. The objective of this study was to evaluate the effects of nitrogen (N) and MC doses on fiber quality and cotton yield. This study was conducted during the 2012/13 and 2013/14 harvests in the experimental area of the Fundação de Apoio à Pesquisa Agropecuária de Chapadão, located in the municipality of Chapadão do Sul, MS, Brazil, at 18° 48’ 45.9” S, 52° 36’ 3” W, having an altitude of 820 m. The experimental design was a randomized blocks in a 5 × 4 factorial scheme comprised of five N doses (0, 40, 80, 120, 160 kg ha-1) and four MC doses (0, 50, 100, 150 mL ha-1) with four repetitions. Analyses of fiber quality included: length, uniformity, elongation, strength, micronaire index, reflectance, yellowing degrees and short fiber content. Regarding cotton yield, green color index (GCI), plant height at harvest time, and cotton seed yield were determined. The best results for fiber quality and productivity occurr with the application of 76.8 mL ha-1 of MC to the cotton crops when the N dose is greater than 80 kg ha-1. Increasing N doses causes an increase in cotton yield and micronaire index, but there is a decrease in fiber uniformity.

A B S T R A C TThe objective of this work was to evaluate leaf gas exchanges of sweet corn as a function of defoliation when submitted to different irrigation depths. The experimental design was randomized blocks in split-plot scheme, with four irrigation depths in the plots [50, 75, 100 and 125% of crop evapotranspiration (ETc)], and three levels of defoliation in the subplots (0%, control; 35%, removal of four fully expanded leaves; 100%, total removal of the leaves -section of the aerial part) with three replicates. Defoliation was manually performed when the plant had four fully expanded leaves. It was verified that the dephs of irrigation and defoliation levels affect leaf gas exchanges in sweet corn plants, allowing the conclusion that the plant tends to activate a mechanism of photosynthetic compensation, when subjected to leaf stress, which can vary according to the degree of severity and water availability to which it is submitted. The most expressive values of gas exchanges in sweet corn plants that did not have defoliation were generally observed at irrigation depths estimated between 87 and 99% ETc and, in the treatments with defoliation, regardless of the level, at irrigation depth of 125% ETc. Desfolha em plantas de milho doce sob diferentes lâminas de irrigação e seu impacto nas trocas gasosas R E S U M O Objetivou-se neste trabalho avaliar as trocas gasosas foliares de plantas de milho doce em função da desfolha, quando submetidas a diferentes lâminas de irrigação. O delineamento experimental foi em blocos casualizados em esquema de parcelas subdivididas, tendo nas parcelas quatro lâminas de irrigação 50, 75, 100 e 125% da evapotranspiração da cultura (ETc) e nas subparcelas três níveis de desfolha (0%, testemunha; 35%, remoção de quatro folhas completamente expandidas; 100% remoção total das folhas -secção da parte aérea) com três repetições, sendo a desfolha realizada manualmente quando a planta apresentava quatro folhas completamente expandidas. Verificou-se que os níveis de irrigação e desfolha afetam as trocas gasosas foliares em plantas de milho doce, permitindo a conclusão de que a planta quando submetida a estresses foliares, tende a ativar um mecanismo de compensação fotossintética, podendo variar em função do grau de severidade e da disponibilidade hídrica a qual está submetida. Os valores mais expressivos de trocas gasosas em folhas de milho doce que não tiveram desfolha foram, de forma geral, observados nas lâminas de irrigação estimadas entre 87 e 99% da ETc e nos tratamentos com desfolha, independente do nível ocorrido, na lâmina de 125% da ETc.

The largest corn yeld in Brazil is currently in the second harvest, which is the most susceptible period to climatic adversities occurring during the cycle. Thus, introducing beneficial elements for maintaining the adequate development of the plant can help producers in obtaining greater kernel yields. Among studied elements, nicotinamide has potential use since it is associated with accumulating secondary metabolites and manifesting defence metabolism in plants. The objective of this work was to evaluate the influence of nicotinamide applied in different doses (only once or in instalments) on the biometric and productive characteristics of corn. The treatments were composed by the number of nicotinamide applications (one or two) and five doses (0, 50, 100, 150 and 200 mg L-1). Plant diameter, plant height, ear insertion height, leaf area and dry matter, yield and 100-kernel mass were evaluated. It was found that doses close to 100 mg L-1 resulted in increases in vegetative and reproductive development, regardless of the number of applications. In this way, foliar nicotinamide application positively influences the biometric and productive characteristics of second crop corn. Highlights The use of nicotinamide in corn plants improves its growth, yield components and grain yield. A single application of nicotinamide during vegetative stage V3 at a dose of 100 mg L-1 is sufficient to increase the leaf area of corn plants. Corn grain yield can be increased by 12.6% with a single application of nicotinamide. There was no need for two applications of nicotinamide in corn crop.

Reduction of leaf area significantly affects maize productivity, due to its low plasticity. Thus, appropriate water application can minimize this problem, considering that under favorable water conditions the plant would express its maximum production potential. The aim of this study was to evaluate the influence of irrigation on the productive performance of sweet corn submitted to different defoliation levels at the beginning of crop cycle. The experimental design was a randomized block design, arranged in split plot scheme; plots consisting of four water depths [50, 75, 100 and 125% of crop evapotranspiration (ETc)] and the subplots consisted of three defoliation levels [0% (control); 35% (removal of four fully expanded leaves), 100% (total removal of leaves, shoot section)], with three replicates. The use of irrigation has a positive influence on recovery of damages caused by defoliation at the initial development stages of sweet corn, and the success of irrigation management, as a strategy to mitigate damages caused by defoliation, depends on the level of the lost leaf area and the amount of water used.

A cevada constitui uma importante cultura no Brasil devido, principalmente, a utilização de seu grão na produção de cervejas. O objetivo deste trabalho foi avaliar os efeitos da adubação nitrogenada e da inoculação com Azospirillum brasilense em cevada. O experimento foi instalado em campo, utilizando o delineamento em blocos casualizados em esquema fatorial, sendo quatro doses de nitrogênio (0, 40, 80 e 120 kg ha-1) na presença ou ausência de inoculação de sementes com A. brasilense e três repetições. Foram avaliadas características de crescimento e massa seca de planta, componentes de produção, teor de N e produtividade de grãos. A maior produtividade de grãos foi alcançada com 66 kg ha-1 de N, sem a aplicação da bactéria. Concluiu-se que o uso de A. brasilense aumenta a produtividade de grãos de cevada na ausência da adubação nitrogenada, mas não suplanta o ganho de produtividade apenas com o uso do N em doses superiores. A severidade de B. sorokidiana foi favorecida com a aplicação de A. brasilense nas maiores doses de N. A inoculação com A. brasilense é uma alternativa viável para aumentar a produtividade de grãos de cevada, caso se opte pelo cultivo sem fertilização mineral nitrogenada.Palavra-chave: Hordeum vulgare, bactérias diazotróficas, malte. NITROGEN FERTILIZATION AND INOCULATION WITH AZOSPIRILLUM BRASILENSE IN BARLEY ABSTRACT:The barley is an important crop in Brazil, mainly due to the use of its grain in the production of beers. The objective of this work was to evaluate the effects of nitrogen fertilization and inoculation with Azospirillum brasilense on barley. The experiment was carried out in the field, using a randomized block design in a factorial scheme, with four nitrogen doses (0, 40, 80 and 120 kg ha-1) in the presence or absence of seed inoculation with A. brasilense and three replications. Growth characteristics and dry mass of the plant, production components, N content and grain yield were evaluated. The highest grain yield was achieved with 66 kg ha-1 of N, without application of the bacteria. It was concluded that the use of A. brasilense increases the yield of barley grains in the absence of nitrogen fertilization, but does not supplant the productivity gain only with the use of N in higher doses. The B. sorokidiana severity was favored by the application of A. brasilense in the highest N doses. The inoculation with A. brasilense is a viable alternative to increase the yield of barley grains, in case of cultivation without nitrogen fertilization.Keywords: Hordeum vulgare, diazotrophic bacteria, malt. DOI: