Proposta de redução de volume de água a ser aplicado pela irrigação localizada na fase inicial da cultura do coqueiro anão.

Abstract

This research had as objective to study different possibilities of reduction of the water volume to be applied by localized irrigation in the dwarfish coconut crop in the Northeast semi-arid region, through a management of water, soil and of the crop. Thus, the following tasks were accomplished: a new calculation methodology was tested for the volume of water applied to the coconut crop, that considers only the effective area of higher concentration of the root system, seeking to the domestication of its development in a certain wetted bulb; the soil temperature was controlled by using plastic manta, purposing the reduction in the soil water evaporation and, consequently, decrease in the volume of water to be applied; and the initial development of the coconut crop was evaluated, through the variables plant height and diameter of the stem, for the water, soil and crop management procedures proposed in this research. The field experiment was installed in entirely randomized blocks, resulting from two factorial combinations between four wetted diameters (Di = 0,7 m, D2 = 0,8 m, D3 = 0,9 m, D4 = 1,0 m), delimited by zinc rings having a height of 35 cm, being 20 cm buried into the soil, and two conditions of soil covering (covered and nude), plus a control (4x2 + 1), resulting in nine treatments with three replications, totaling twenty-seven plots. For both conditions of soil covering, the different applied volumes of water in the several diameters of influence of the root system didn't present significant effect on the development of the coconut crop, regarding its height and stem diameter, during the first 120 days after sowing. The procedure of calculation of the applied volume of water promoted considerable economy of water, with maximum and minimum values, respectively, of 93.95 and 87.62%, in the soil condition without covering, and of 96.98 and 93.81%, in soil with covering. The isolation of the evaporation contributed to substantial reduction (50%) in the applied volume of water, being demonstrated the importance of controlling the soil temperature in semi-arid áreas and the efficiency of the two faces polyethylene film for this purpose.