Produtividade de cebola (Allium cepa L.) em cultivo agroecológico sob lâminas de irrigação e cobertura do solo

Abstract

The technique of irrigation and use of soil mulch can cause changes in the variables of crop production. Thus aimed to evaluate the effects of different blades irrigation applied through drip method and use of straw elephant grass (Pennisetum purpureum Schum. cv. Cameron) as mulch on the soil variables of production of onion bulbs (Allium cepa L.) and its water use efficiency under agroecological farming. The experiment was conducted from May to September 2012 in the Integrated system Agroecological Production, located between the coordinates 22 º 45 'S and 43 º 41' W, in the municipality of Seropédica-RJ. The experimental design was a randomized complete blocks with split plots, with 10 treatments and 7 replications, characterized by the presence (CC) and absence straw how mulch soil (SC) and five blades irrigation caracterized for percentages of the crop evapotranspiration (ETc) 22, 45, 75 and 100%, termed blades L1, L2, L3 and L4, respectively, and the blade L0, characterized by the absence of irrigation. The variables evaluated were the total productivity of bulbs (PTB), Average fresh bulb weight (MMFB), dry matter content of the bulbs (TMSB), diameter bulbs (DMB), which are divided into 7 classes in diameter, total soluble solids content (TSST) and the efficiency of water use (EUA). Data were tabulated and subjected to analysis of variance and means were assessed with the regression technique to the blade factor for irrigation, and of the f test for comparison of means with regard to the coverage factor of the soil. The blades irrigation factor significantly affected the variables PTB, MMFB and DMB ranging, respectively, from 11.4 to 52.1 t ha-1, 28.6 to 130.3 g and 3 to 5 mm, and in average 98.6% of their variations were explained by the polynomial regression second-order. The blade also influenced significantly in the polynomial regression second-order (condition SC) the EUA, which ranged from 107.08 to 140.67 kg ha-1 mm-1 and in the linear regression with values ranging from 148.35 to 218.10 kg ha-1 mm-1 (CC condition). Unlike, the applied blade did not significantly affect the levels of total soluble solids, ranging from 9.9 to 12.2 ° Brix, and the dry weight of the bulbs, which presented variation of 6.4 7.5%. The presence of mulch provided savings of 5.7% in water depth at L4 and influenced significantly the production variables. Despite having reduced TMSB, has provided to culture the increase in USA, PTB, MMFB and DMB, and influenced the distribution of the percentage of bulbs in diameter classes, with 35% reduction in the percentage of bulbs classified as class 1 (<35mm with no or very low commercial value) and increased by 31 and 30.8%, respectively, the percentage of bulbs classified in class 3 and 3 full (50 to 70 mm, of best commercial value). This the distribution was significantly influenced by different levels of irrigation and, in general, the percentage of bulbs classified in classes of larger diameter (best commercial value) decreased the percentage of bulbs grouped in classes of reduced diameter increased with the reduction of blade water applied. It was concluded, based on the results, that the technique of irrigation promotes improvements in the yield components of onion and the use of mulch on the soil favors better yields and quality of bulbs, with increased EUA.