Crescimento e produção de alface sob saturação temporal do solo.

Abstract

Extensive agricultural áreas, cultivated in the horticultura! crops in northeast Brazil, are exposed constantly to flooding, in the rainy period, because of location in low lands soils or of slopes. Considering the inexistence of research on the theme in the area, this study was undertaken with the objective of studying the growth and the production of the cultivars of lettuce ' Elba' and ' Irene', submitted to saturation temporal of soil. During July and October of 2007. two experiments were conducted. in the experimental area of the Academic Unit of Agricultural Engineering of UFCG. The cultivars were grown in plastic vases (4 plants/vase) of 40 L capacity. containing material of sandy-clay-loam soil; the basal dose of fertilizer consisted of 22.79g of P?Os. 0.72g of K?0 and 2050 g of earth worm. for vase. The plants were irrigated. daily. with a volume of water that provided drainage (approximately 10%). In Experiment I. the beginning of waterlogging occurred 17 days after transplant (DAT) and it consisted of 7 times of duration (0. 6. 12. 18. 24. 30 and 36 hours of waterlogging). evaluating the effects at 22. 28 and 38 DAT. this last one of the occasion of harvest of the plants: combined factoriais in the two cultivars. resulted in 14 (7 x 2) treatments. Experiment II. two waterlogging intervals imposed at 12 and 22 DAT. resulting in two statistical procedures: in the first. the effects of the anoxia caused with waterlogging at 12 DAT were analyzed. with tive duration of time (0. 12. 24. 36 and 48 hours of waterlogging). in 2 cultivars. resulting in 5 x 2 factorial, with the evaluations at the Sth and lOth day after the application of the treatment (DATr): in the second procedure. evaluation was proceeded to the 20 DATr and the plants were submitted to the single (12 DAT) and double O 2 and 22 DAT) waterlogging. resulting in a factorial 4 x 2 x 2 . consisting of 4 duration times of waterlogging (12. 24. 36 and 48 hours). applied to 2 cultivars and 2 waterlogging leveis (one and two times), being added to the factorial 2 more treatments (control). one for each genoíype (resulting in 18 treatments). The experiments were installed in randomized blocks. with three repetitions. The duration and the duple waterlogging reduced the growth and the lettuce production. being the fresh dry matter of the aerial part the variable of larger sensibility to the anoxitic stress: both the cultivars were sensitive to the anoxia, but they tended to recover part of the growth with the time after stress. The cv. Elba was superior the to ' Irene' in terms of number of leaves, diameter and stem height, dry matter of the aerial part and root, rate of absolute and relative growth, root/shoot relationship and rate of liquid assimilation; the ' Irene' stood out in fresh phytomass of the aerial part.