Extração de água pela cultura do limão "Tahiti" com porta enxerto citrumelo "Swingle" sob microaspersão nas condições semiáridas da Bahia.

Abstract

The present work had as objective to evaluate water distribution in the soil wetted volume generated by a sprayer for different irrigation frequencies. It emphasizes water uptake from root system of citrumelo 'Swingle' under 'Tahiti' lemon, and seeks to evaluate the potential area of uptake by roots in the soil profile. The work was accomplished in the Boa Vista farm in Iacu-Ba Brasil, where it has been tested three frequencies of irrigation: 1, 2 and 3 days. Soil water content was monitored using TDR wave guides, whose dispositions in the soil profile longitudinal to plant row were: 0,15; 0,25; 0,50; 0,75; 1,0; 1,5 and 2,0 m of horizontal distance from plant, and 0,15; 0,25; 0,50; 0,75; 1,0 and 1,2 m of depth in the soil profile. In ortogonal profile to plant row, the same positions were used adding the horizontal distance of 2,5 m from plant row. Root sampling work was done in the same positions where TDR waveguides were inserted. Results showed that: (i) citrumelo 'Swingle' rootstock under 'Tahiti' lemon extracts water of soil at low levels of water availability corresponding to soil water content of 0,10 to 0,11 m3 m"3; (ii) the larger the irrigation the larger the potential zones in the soil profile for water uptake; (Hi) root diameters among 0,5-2 ram, are the largest responsible for soil water extraction; (iv) the effective depth of water uptake by roots (PEe) and the effective distance from plant of water uptake (DEe) are more appropriate parameters to define soil sensor placement when compared to the traditional parameters: effective depth of roots (Pe) and effective distance of roots (De); (v) in the longitudinal direction to plant row, soil water sensors should be installed at depth of 0 - 0,5 m. In this direction, they should be installed at horizontal distances of 0,4 m from plant in case of irrigation frequencies less or equal than 2 days and at horizontal distances of 0,75 m for irrigation frequencies of of 3 days; (vi) It is recommended that in the ortogonal direction to plant row, sensors should be located at depths from soil surface to 0,75 m for irrigation frequencies of 2 and 3 days and at horizontal distances from plant equal or less than 0,5 m. Sensors should be located at horizontal distances from plant to 0,25 m and at depths from soil surface to 0,9 m for irrigation frequency of 1 day.