Avaliação do desempenho da cultura da alface (Lactuca sativa) cultivada em sistema orgânico de produção, sob diferentes lâminas de irrigação e coberturas do solo

Abstract

The present work had like objective study the effect of different levels of irrigation handled on the basis of the evaporation of the tank Class TO in the growth and performance of the lettuce (Lactuca sativa) cultivated in different epochs of the year in soil with and without utilization of dead cover. They were driven two series of experiments evaluating the effect of different levels of water in the first phase they determined itself the growth rates of the culture and in the second one evaluated the performance of the lettuce cultivated in a soil with and without utilization of dead cover. Both the series were carried out in the experimental area of the SIPA (System Integrated of output Agroecológica), located in the town of Seropédica-Rio de Janeiro. The experimental delineation adopted in the first essay was in randomized blocks, with 5 handlings (25, 50, 80, 100 and 115% of the evapotranspiração of the culture - ETc) and four repetitions, totalling up 20 experimental units containing 44 plants by installment. They were carried out collections of the plants during the cycle of the culture to the 10, 16, 22, 28 and 32 days after transplant (DAT), with an aim to determine the growth rates of them plants by the functional approach, being analyzed the variables area foliar and batter drought of the plants. To the 32 DAT was characterized the productivity of the culture by the analysis of the variables area foliar, fresh batter, number of sheets and diameter of the head. The culture presented a slow growth to the cultivation day 22o, being observed, from this date, a bigger accumulation of biomassa and increase of area foliar. The handling that replaced a sheet of 80% ETc provided a better performance of the culture regarding the productivity in all the variables analyzed, but was not possible observe significant differences between the handlings, due to humidity of soil to remain homogeneous during the conduction of the experiment. In the second phase, were driven two simultaneous experiments, being applied 5 levels of irrigation (25, 50, 80, 100 and 115% ETc), in two conditions of cover of him soil: soil nú and soil covered with straw of leguminous plant gliricídia (Gliricidia sepium). The delineation adopted was in randomized blocks, with 5 handlings (sheets of irrigation) and 4 repetitions. After it attend all the of the statistical viewpoint, was carried out a joint analysis of the facts, with regression for the irrigation level variable, and test F for the variable dead cover. For the variables analyzed, in the system of plantation with dead cover had an increase in the area foliar, fresh batter and number of sheets to the level of 100% ETc and for the level of 115%, had a decrescimento of the same, due to the excess of humidity. Utilizing the equations adjusted, the maximum values of the variables studied were observed in the break of the sheets of irrigation 80 and 100% of the ETc. In the system of plantation without dead cover, the levels of irrigation analyzed were not sufficient for manifest the maximum performance of the culture. In the joint analysis for the variable fresh batter, the system of cultivation with utilization of dead cover was over the without cover differentiating estatisticamente level with 5% probability by the test F. Only not they were observed statistical differences between the corresponding sheets to 25 and 115% ETc, showing that only the utilization of dead cover is not sufficient for obtaining of better productivity.