A produtividade de diversas culturas agrícolas é intensamente dependente da oferta pluvial, bem como de sua frequência e intensidade, por isso, objetivou-se avaliar o comportamento espacial da precipitação e da produtividade do milho no semiárido brasileiro. Para isso foram utilizadas as técnicas da análise dos componentes principais (ACP) e a análise de correlação de Pearson das variáveis para o período de 1990 a 2014. Através dessas técnicas constatou-se a alta variabilidade dos dados em escala interanual, revelando as áreas mais propícias ao cultivo do milho, como também, as áreas com as menores produtividades e assim, mais afetadas pelo estresse hídrico. Na maior parte do território a produtividade do milho é inferior a 1000 kg ha-1. A variabilidade do rendimento do milho, nas últimas décadas, está intimamente relacionada com a variabilidade climática, haja vista que se trata de uma agricultura de subsistência e em sistema sequeiro. O efeito das chuvas sobre a produtividade do milho foi estatisticamente positivo, ou seja, na maior parte da região semiárida brasileira, a eficiência da produção do grão é dependente das precipitações pluviais locais.Palavras-chave: ACP, rendimento agrícola, Zea mays L. VARIABILITY OF RAINFALL AND YIELD OF MAIZE AT THE BRAZILIAN SEMIARID THROUGH MULTIVARIATE ANALYSIS ABSTRACT: The productivity of several agricultural crops is highly dependent on the rainfall supply, as well as their frequency and intensity. Therefore, the objective was to evaluate the spatial behavior of maize precipitation and yield in the Brazilian semi-arid region. The main components analysis (PCA) and Pearson's correlation analysis of the variables for the period from 1990 to 2014 were used. Through these techniques, the high variability of the data on a year-to-year scale was verified, revealing the most important areas. Propitious to maize cultivation, as well as areas with the lowest yields and thus, more affected by water stress. In most of the territory corn yield is less than 1000 kg ha-1. The variability of maize yield in the last decades is closely related to climatic variability, since it is subsistence agriculture and a dry land system. The effect of rainfall on maize productivity was statistically positive, that is, in most of the Brazilian semi-arid region, grain production efficiency is dependent on local rainfall.Keywords: PCA, crop yield, Zea mays L.
A produtividade de diversas culturas agrícolas é intensamente dependente da oferta pluviométrica, bem como de sua frequência e intensidade. O objetivo deste trabalho foi classificar a região semiárida brasileira em regiões homogêneas através da análise de agrupamento, levando-se em consideração a precipitação e a produtividade do milho, além de analisar a tendência temporal da precipitação por meio do teste de Mann-Kendall. Desse modo, pôde-se dividir a área de estudo em quatro grupos, evidenciando que o semiárido brasileiro é afetado pela alta variabilidade intrasazonal e interanual da precipitação que influencia diretamente no rendimento do milho. Os grupos 2 e 4 apresentaram uma tendência de aumento nos totais médios de produtividade do milho e tendência negativa na precipitação, isso pode ser explicado pela possível adoção da prática de irrigação, como também pelo o uso de variedades mais resistentes à seca, mecanização e manejo de solo. O milho é uma das culturas de maior importância econômica no semiárido, no entanto, os agricultores não conseguem explorar a potencialidade produtiva da cultura em virtude da alta variabilidade climática da chuva o que condiciona baixos rendimentos do grão.Palavras-chave: tendências de chuva, produtividade, caatinga.
Cowpea is a legume crop cultivated in diversified production systems, under different conditions of climate, soil, cultivars and technological level. Although the crop is resistant to water stress, lack of moisture in the soil profile during its reproductive stage causes significant losses in its yield. The objective of this study was to calibrate and evaluate the AquaCrop model in the simulation of cowpea yield under water stress in two cropping seasons (rainy and dry) under no-tillage system condition. Experiments were carried out in two cropping seasons (rainy and dry) with five forms of water stress (without water stress, water suspension for 5, 10 and 15 days and rainfed cultivation), under no-tillage system. Regardless of the cowpea cropping season, water stress reduced grain yield and biomass yield, which was more pronounced in the dry season. The Aquacrop model simulated cowpea yield well for the rainy and dry seasons, with root mean square error of 16 and 9.1%, respectively. Aquacrop model showed poor performance for simulation of dry biomass production in both cropping seasons, overestimating the values obtained in the field.
Objetivou-se com o presente trabalho utilizar o software IntecPerímetro® na avaliação do manejo da irrigação na cultura do feijão. O software foi alimentado por dados de clima, cultura, solo e os referentes ao equipamento de irrigação. A avaliação do manejo da irrigação procedeu-se pela comparação entre os valores médios de lâmina aplicada e tempo de funcionamento do equipamento de irrigação praticados pelo irrigante e calculados por meio do uso do software IntecPerímetro® em todas as fases de desenvolvimento da cultura, por meio do teste “t” de Student ao nível de 5% de probabilidade. A lâmina média de irrigação proposta pelo software foi 28,3% menor que a praticada pelo irrigante. Os valores de umidades obtidas em campo pelo método do forno micro-ondas não diferiram estatisticamente da umidade referente à lâmina de irrigação executada pelo irrigante utilizando o software.
Cowpea is considered a subsistence crop, so it is generally cultivated by family farming in the rainy season and, outside this season, with the aid of irrigation. Its yield is reduced if there is water stress due to the lack of rainfall or irrigation water. Objective of this study was to evaluate the influence of water stress in the rainy and dry seasons on grain yield, biomass, harvest index and water use efficiency in the ‘Costela de Vaca’ cowpea variety cultivated in no-tillage system using crop residues present in the experimental area. Experimental design used was randomized blocks, in a 2 x 5 factorial scheme (cropping season x water stress), with four replicates. Treatments consisted of two cropping seasons (rainy and dry) and five forms of water stress (without water stress, water suspension for 5, 10 and 15 days, and rainfed cultivation). Biomass was the only parameter influenced by the cropping season versus water stress interaction. Regardless of the cowpea cropping season, water stress reduced grain yield and biomass. Harvest index showed no sensitivity to water stress and cropping season. Water use efficiency was influenced by the cropping season. Soil cover promoted maintenance of soil moisture during cowpea cultivation in both periods.
Water demand and agronomic and economic efficiency of cowpea are strongly related to agricultural practices and climatic conditions. This study aimed to determine in which cropping season cowpea has the highest water demand and maximum agronomic and economic efficiency as a function of water stress under the edaphoclimatic conditions of the semi-arid region of northeastern Brazil. Cowpea was cultivated in two cropping seasons (rainy and dry) and subjected to five forms of water stress (without water stress, water suspension for 5, 10 and 15 days and rainfed cultivation) and four replicates, started in the flowering and grain filling stages, under no-tillage system. Agronomic (yield, biomass, harvest index and water use efficiency) and economic (gross revenue, net revenue, rate of return and profit margin) parameters were evaluated. The water demand of cowpea in the dry season was 20.2% higher than in the rainy season; consequently, the Kc values obtained were also higher in this period. The climatic conditions that occurred during the cropping seasons and water stress negatively influenced the agronomic performance and financial profitability of cowpea, being more evident in the rainfed cultivation. For the edaphoclimatic conditions of the study, cowpea can be grown without significant losses of yield and profitability in both cropping seasons, provided that the water stress does not last more than 10 days during its reproductive stage.
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