Determinação da umidade do solo no ponto de murcha permanente para hortaliças em diferentes tipos de solos

Abstract

The permanent wilting point (PWP) is defined as a minimum percentage of soil moisture at which plants are reduced to a wilted condition, at a soil tension of -1,500 kPa, below which they tend to wilt and are no longer able to grow. recover, even under accepted conditions. The authors Briggs & Shantz (1912) and Richards (1943) developed methods that determine the soil moisture in the PMP being the direct or physiological method where indicator plants are used and the indirect or laboratory method, in this work using the Richards chamber. Some factors such as soil types (texture, structure, number of pores), root density and depth can influence the PMP. Thus, the general objective of this work was to determine the moisture at the permanent wilting point (PWP) of the four different types of soils used, comparing the results obtained by the physiological method and by the Richards chamber, in addition to a modification of the moisture with the texture of soils. The chosen design was completely randomized (DIC), with a 4×2 bifactorial scheme with five replications. The treaties comprise the four types of soils used, with the classification Hapludalf mapping unit Santa Maria, two Hapludox mapping units comprising Cruz Alta and Santo Ângelo and Quartzipsamment with mapping unit Areais. The crops chosen to serve as physiological PMP indicators were Lettuce (Lactuca sativa L.) at the phenological stage of pre-head closure (12 leaves) and Cabbage (Brassica oleracea var. capitata L.) at phenological stage IV (9-10 sheets ). With the PMP detected, the collection of Soil Reception was carried out and the gravimetric and volumetric moisture of the soils was determined by the physiological method and by the Richards chamber. The results were transferred to the SAS software, where it was possible to observe that, when compared to two crops, cabbage had higher humidity in all treatments compared to lettuce. On the other hand, in comparing the methods, the Richards chamber - 1500 kPa where it obtained lower results compared to the physiological method at both temperatures experienced. In addition to comparing the methods, a change was made in the moisture retained in the soils with their texture, thus proving that clayey soils have greater water retention than sandy soils.