Contribuição por ascensão capilar em diferentes níveis do lençol freático ao desenvolvimento da cultura da alface

Abstract

The research had as premise that the rate of capillary rise from the groundwater table would be able to supply the water needs of the culture and had as general objective to obtain, using the American lettuce cultivars Lucy Brow and Gloriosa, information that identifies the relations of response to capillary rise rates and depth levels of the groundwater. Specifically, the research sought to evaluate, from production variables, the response of the cultivars to depth levels of the water table; to calculate the SEW30 values for the groundwater depths established in a given interval and to establish crop productivity ratios at these water stress levels, as well as to provide information on the capillary rise rates from six depths of the groundwater table and based on the water needs of the crop. The experiment was installed in a physical model of drainage lysimeters, which allow, through piezometers, the control of the water table level from a water inlet system fed by a water box and output through drains For the treatments, seven lysimeters were used, and in six of them the only hydric supply to the crop occurred through capillary rise from the groundwater to the depths of 0.10 m; 0.15 m; 0.20 m; 0.25 m; 0.30 m and 0.35 m and only a lysimeter with irrigation and absence of water table. Daily, in addition to the monitoring of groundwater levels, water tension information was collected in the soil through tensiometers, and the necessary cultural treatments were carried out for the development of the crop. The results showed that the level of groundwater kept at 0.20 m from the soil surface was able to supply the water demand of the lettuce crop in sandy soil. The levels of the water table were significant at 1% level when analyzing data on productivity, photosynthesis, transpiration, stomatal conductance and efficiency of water use by the crop. The crop productivity data related to the SEW30 excess water stress index showed that water deficit stress was more limiting than water excess stress. These results allowed the following conclusions: - The physical factor-product relationship signals to a water table at 0,20 m as the most viable option in terms of crop response; - In the cultivation of American lettuce for conditions of excess water in the soil should be given preference to the establishment of the cultivar Gloriosa to the detriment of the cultivar Lucy Brow; - The high values of flow density allowed to corroborate with the premise of the thesis, that is, they were able to supply the water needs of the crop during its cycle.