Irrigação por cápsula porosa: características e avaliação do método sob pressão hidrostática.

Abstract

The objectives of the present study were to evaluate the technical feasibility of the irrigation method by porous capsule and to determine the effects of different hydrostatic pressures and plant densities on production of corn (Zea mays L.) cultivar Centralmex using this method of irrigation. Different proportions of barbotinas A and B ( locally found clay), have been tested for the manufacture of porous capsule but the proportion of 401 and 60% was choosen, because capsule manufactured with this proportion presented the best technical characteristics with regard to discharge rate and firmness. A field experiment was carried out at the Bebedouro Experiment Station of EMBRAPA/CPATSA, Petrolina- PE, with three hydrostatic pressure treatments (0-35 : 0-50 and 0-75m) and five sub-treatments of plant populations (1,4,7,10 and 13 plants / capsule ) in a randomized block design. The experiment consisted of three replicates of 10 capsules each, installed along the contour lines at a depth of 0.25m with absolutely no slope. The different hydrostatic pressure heads significantly influenced the outflow of water from the capsule and total water consumption for the com was found to vary from 796 to 1.000 m /ha, thereby indicating the extent of water savings. However, pressure head treatments did not affect significantly production and average heights of plant and fruit buds but the differences in various subtreatments were found to be significant at 1% level of probability. A second degree quadratic equation described satisfactorily the yield curve and estimated that 9 plant per capsule would give the maxi mum yield. In the present study, density of 7 plants per capsule gave the best results with a total production of 861g, which converted to usual 50.000 plants/ hare presents a yield of 6.150 kg/ha. The average water use efficiency for this method of irrigation has been found to be 1.9 kg/m\ which compared to conventional methods of irrigation is rather high. The soil matric potential (^m) at a distance of 2cm from the capsule wall and at 25cm depth was found to be above -0.1 atm ( field capacity) and a vailable water in 20cm radius around the capsule and 15-45cm depth always remained in between 60-1001, indicating thereby the technical feasibility of this method of irrigation in small áreas with limited water supply.