Produtividade do feijão-de-corda e acúmulo de sais no solo em função da fração de lixiviação e da salinidade da água de irrigação

Abstract

RESUMO:Neste trabalho, avaliaram-se o acúmulo de sais no solo e a produtividade do feijão-decorda, em função da fração de lixiviação (FL) e da salinidade da água de irrigação. Utilizou-se de delineamento em blocos ao acaso, com quatro tratamentos e cinco repetições. Foram estudados os seguintes tratamentos: 1 -água do poço com condutividade elétrica (CEa) de 0,8 dS m -1 (sem FL); 2 -água salina com CEa de 5,0 dS m -1 sem FL; 3 -água salina com CEa de 5,0 dS m -1 com FL de 0,14; 4 -água salina com CEa de 5,0 dS m -1 com FL de 0,28. Foram avaliadas as seguintes variáveis: acúmulo de sais no solo, crescimento vegetativo, produtividade, trocas gasosas e teores de Na + , Ca +2 , K + e Cl -nas folhas. A aplicação de água salina provocou acúmulo de sais no solo, porém esses efeitos foram parcialmente revertidos pelo aumento da FL; a salinidade reduziu a produtividade de grãos, porém não afetou sua qualidade; a redução na produtividade ocasionada pela salinidade deveu-se, em parte, à redução na assimilação líquida de carbono durante as fases de floração e frutificação, associada aos efeitos osmóticos e ao acúmulo de Na + e Cl -nas folhas; as frações de lixiviação não tiveram muita influência na superação dos danos provocados pela salinidade sobre o desenvolvimento das plantas. PALAVRAS-CHAVE:água salina, Vigna unguiculata L. Walp., estresse salino. COWPEA YIELD AND SOIL SALT ACCUMULATION AS A FUNCTION OF LEACHING FRACTION AND IRRIGATION WATER SALINITY ABSTRACT:The study had the objective to evaluate the effect of water salinity and the leaching fraction (LF) on soil salt accumulation and on the yield of grains of cowpea plants. A completely randomized block design, with four treatments and five repetitions, was adopted. The treatments studied were: 1 -well water with ECw of 0.8 dS m -1 (without LF); 2 -saline water with ECw of 5.0 dS m -1 (without LF); 3 -saline water with ECw of 5.0 dS m -1 with LF of 0.14, and 4 -saline water with ECw of 5.0 dS m -1 with LF of 0.28. The following parameters were evaluated: soil salt accumulation, vegetative plant growth, yield, gas exchange and leaf ion contents (Na + , Ca +2 , K + , and Cl -). The saline water application provoked salt accumulation in the soil profile, but this effect was partially reverted by the increase of the leaching fraction. Salinity reduced plant yield, but it did not affect its quality. The reduction in plant yield was related, at least in part, to decrease in net assimilation of carbon during flowering and fruit development due to osmotic effects and to accumulation of potentially toxic ions (Na + and Cl -). In general, the increase in leaching fraction did not reduce the effect of the salinity on plant development.

PRODUCTION COMPONENTS OF Vigna unguiculata (L. Walp) IRRIGATED WITH BRACKISH WATER UNDER DIFFERENT LEACHING FRACTIONS

“…The leaching fractions caused progressive reductions in the soil salinity levels throughout the experiment (Table 2), despite the increased salt concentrations in both soil layers caused by irrigation with saline water, indicating that it is an alternative to control the gradual increase of salts in the root zone (ASSIS JÚNIOR, 2007;SILVA et al, 2011), and contribute to the tolerance to problems caused by salinity in irrigated agriculture (RITZEMA et al, 2008;BEZERRA et al, 2010), especially in places where the precipitation and the availability of good quality water for irrigation is scarce. (SiBSC, 2006), with and without leaching fractions of 14% and 28%, found reductions in soil salts with the leaching fractions, and a more efficient salt leaching from the root zone with the leaching fraction of 28%.…”

“…This crop has a short cycle and relatively high water requirements, thus, irrigation is a viable alternative to improve this crop yield in the Brazilian semiarid, due to the precipitation irregularity in this region (ASSIS JÚNIOR et al, 2007).…”

“…The concentration of soluble salts is among the characteristics that determine the water quality for irrigation, since it is a limiting factor for the development of some crops (ASSIS JÚNIOR et al, 2007;SILVA et al, 2011), and can cause serious consequences to the soil, compromising even its use for crop productions.…”

“…Assis Júnior et al (2007) and Bezerra et al (2010) stated that the use of saline water for irrigation of Vigna unguiculata caused accumulation of salts in the soil and reduced vegetative growth and grain yield. Santana, Silveira and Vieira (2009) evaluated the effects of irrigation with saline water (0.1, 1.0, 2.5, 4.0 and 5.5 dS m -1 ) on common bean and found reductions in grain yield, number of grains per pod and number of pods per plant.…”

“…Assis Júnior et al (2007) evaluated the effects of irrigation with saline water under different leaching fractions on V. unguiculata yield and the accumulation of salts in a dystrophic Ultisol (SiBSC, 2006) and found that the water salinity of 5,0 dS m -1 increased the soil salinity and sodicity, however, these effects were partly reversed by the increase in the leaching fraction and completely by rainwater. Carvalho et al (2012) evaluated maize (Zea mays L.) irrigated with increasing salinity and leaching fractions and also found positive effects of leaching fractions on the crop performance.…”