Umidade no ponto de murcha permanente de culturas agrícolas em diferentes tipos de solo

Abstract

The soil is responsible for storing and providing water to plants, and its texture directly influences its water retention capacity. Therefore, the objective of this study was to determine the moisture retained in each soil at the physiological permanent wilting point (PWP) in wheat and corn crops. The design used was completely randomized with 4 treatments and 5 replications. The treatments were composed of 4 types of soil in 5-liter pots. The soils used were a Hapludox from the Santo Ângelo mapping unit, a Hapludox from the Cruz Alta mapping unit, a Abaqualf from the Vacacaí mapping unit, and a Quartzipsament from the Areais mapping unit, collected during a study trip. A 500g sample was sent to the UFSM laboratory. After correction, 5 seeds were sown for each crop sequentially, and only 3 plants per pot were kept after germination. During the vegetative stage, irrigation was suspended for corn, and for wheat, irrigation was suspended during the reproductive phase. Aluminum foil was used to cover the soil surface, and the plants lost water only through transpiration until they reached the permanent wilting point. Then, a sample was collected to determine the gravimetric and volumetric moisture content at the PWP of each crop, along with the rings mounted for determination on the tension table and Richards chamber. After data collection, the Shapiro-Wilk test was used to verify the data distribution, and then the mean comparison test was performed using Tukey at a 5% significance level. The soil with the highest moisture content at the physiological permanent wilting point was the typical dystroferric Red Latosol from the Santo Ângelo mapping unit in both crops for all methods, with a physiological gravimetric moisture content of 0.148 cm³cm-³ and a physiological volumetric moisture content of 0.157 cm³.cm-³ for corn and a physiological gravimetric moisture content of 0.154 cm³.cm-³ and a physiological volumetric moisture content of 0.140 cm³.cm--³ for wheat. These values are considerably lower than those found by the laboratory method at -1500 kPa.