Determinação da umidade do solo no ponto de murcha permanente para cultura do trigo

Abstract

The soil is responsible for storing and making water available to plants and its texture directly influences its water retention capacity. In this regard, determining the permanent wilting point (PMP) is of paramount importance, as it refers to the point at which water in the soil is so strongly retained that plants can no longer absorb it, leading them to a permanent state of withering, even when subjected to favorable conditions. The work aimed to determine the moisture retained in six different soils at the permanent wilting point (PMP) for wheat crops, comparing the results obtained by the physiological method and the Richards chamber. The experimental design used was completely randomized (DIC), with six treatments and four replications, so the treatments encompass the six types of soils used, namely Hapludox collected in the municipality of Cerro-Largo (1), Hapludox collected in the municipality of Caibaté (2), Hapludox collected in the municipality of Cruz Alta (3), Quartzipsamment collected in the municipality of Quaraí, Hapludalf collected in the municipality of Santa Maria, and Gleysols collected in the municipality of Garruchos. The indicator crop chosen was wheat (Triticum spp.). The experiment was conducted in pots, and after the physiological PMP was detected, soil samples were collected and the gravimetric and volumetric soil moisture was determined. Soil samples were also subjected to tension of 1500 kPa using the Richards chamber method. The results were subjected to analysis of variance and the means compared using the Tukey test. The Oxisol (UM SA1) was the one with the highest humidity at the physiological permanent wilting point. Also, when comparing the methods, the Richards chamber obtained greater results compared to the physiological method in both humidity levels studied, showing that the wheat crop managed to extract water below the potential of – 1500 kPa. A correlation was also made between the moisture retained in the soil and its texture, finding that clayey soils have greater water retention when compared to sandy soils due to their structure and high surface area.