Alterações químicas no solo, aspectos nutricionais, fisiológicos e de produção da cultura do milho irrigado com água salina / Chemical changes in the soil and nutritional and physiologic, nutritional and productive aspects in maize cropping irrigated with saline water

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

An experiment was carried out in drainage lysimeters under greenhouse conditions in order to evaluate the effects of the soil solution salinity on the mineral nutrition, growth, development, relative yield and physiologic characteristics as well as the effects of the saline water irrigation upon the chemical properties of an Eutrophic Red Argisol cropped with the maize variety UFVM 100. The experiment was set up on an entirely randomized design with seven treatments consisting of one irrigated with fresh water (without leaching) and six irrigated with saline water of 1.2 dS m-1 and leaching fractions of 40, 30, 20, 15, 10 and 5% of the leaching depths applied and three replicates. In the variety under evaluation, the increase in the soil salinity due to irrigation with saline water rather raised the contents of chlorine, sodium and the relationships Cl/N, Cl/P, Cl/S, Na+/Ca+2, Na+/Mg+2 and Na+/K+, besides reducing the leaf contents of the cationic and anionic macronutrients. The following were reduced: the dry matter yield of the aerial part and roots, the rates of the net assimilation, the absolute and relative growths, both total and useful leaf areas, photosynthesis, stomatic conductance, perspiration, water use efficiency in the productivity, the grain weight by lysimeter, average weight of either strawless maize ear and the leaf water potential on predawn, following the increase of the dead leaf area and leaf area ratio. The application of saline water compared to fresh water rather increased the availability of Na+, Ca2, the values of SB and effective CTC, total CTC, PST, RAS and MO followed by decrease in either the average values of the pH and Mg2+ availability. With the increased leaching fractions, however, there occurred a decrease in the Na+ availability, whereas the values of PST, P-rem, RAS and total CTC also decreased from the leaching fraction of 20%.. The three classification methods for crop tolerances to the salinity that were based on the electric conductivity in the paste extract of the saturated soil, relative evapotranspiration deficit and water stress daily index (WSDI), respectively, showed different results. The maize variety UFVM 100 exhibited a sensibility coefficient of 0.99 to the salinity and the relative yield decreased down to 6.85% with the unit increment of WSDI as well as 15.68% with the unit increment from the salinity threshold of 1.20 dS m-1. The values of WSDI were significantly affected by the increased salinity levels in the soil, therefore showing to be really a sensitive methodology to characterize the decrease in the relative yield as a function of the soil salinity.

ASSUNTO(S)

solos soil salinity salinidade engenharia de agua e solo Índice de estresse hídrico diário (wsd) water stress daily index (wsdi) zea mays irrigation zea mays irrigação

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