Disponibilidade de água para as plantas em três solos de diferentes texturas: comparação de métodos de determinação.

Abstract

The present work was conducted to study the water availability in the soil for the cotton, sunflower and cowpea, determining the field capacity by the field and laboratory methods and the permanent wilting point by the physiologic and laboratory methods. The soils used were a Distrophic Regossol ( sandy loam ) and two Red-Yellow Podzolic Equivalent Eutrophic ( clay loam and sandy clay). In order to identify the best methodology to determine the soil water availability for the plants, the results obtained when using different methods to determine the field capacity and the permanent wilting point were statistically compared. The results allowed to conclude that the laboratory methods ( Richards extractor ) loose efficiency as the clay content of the soil increases. It was also founded that in the need of high precision, the field and physiologic methods to determine, respectively , the field capacity and the permanent wilting point of the soil can not be replaced. Similar comparisons with the calculation of the irrigation depths showed the same trends , which confirm the conclusions.