PONTO DE MURCHA PERMANENTE PARA TRIGO E CEVADA EM SOLOS DOS CAMPOS GERAIS DO PARANÁ

Abstract

Determining the levels of water stored in the soil using indicator cultures allows gather information that can optimizing the natural use of resources in regions prone to drier periods. The objective of this work was to determine the permanent wilt point (PMP) for wheat and barley in sedimentar Latosols with different textural classes. The study was conducted in pots under greenhouse conditions. The design was in randomized blocks, in factorial arrangement (3x2x2). The treatments consisted in a combination of soils with three distinct texture classes (clayey, sandy loam, sandy loam), two cultures (wheat and barley) and four cultivars: wheat (NOBLE and MESTRE) and barley (BRS BRAU and ANAG 01). The soils were kept close to 90% of field capacity, up to 45 days, for the beginning water stress, when they didn’t receive water. At the first sign of wilt in cultures, the pots were transferred to a dark chamber, with relative air humidity close to 100%, to verify the definitive non-return of the turgidity. In PMP soil samples were collected without roots to determine the water content on gravimetric basis. By the laboratory method the determination of water content occurred in 1500 kPa tension. Volumetric rings were removed from plots and submitted to tension table at: -0,1, -10, -20, -40, -60, -80, -100, -300, -500, -700 kPa. Soil water content for PMP was obtained by physiological method and Richards chamber. The data were submitted to descriptive statistical analysis to observe the homogeneity. When, according to assumptions, F-test of significance was performed for 5%. The moisture variables obtained by two methods were correlated, presenting equivalence for the cultures. By regression, the potential in which the plants were wilted was estimated. Statistical analyzes were performed using software R (R CORE TEAM, 2013). The results showed that the structural soil variables present correlation with the higher water contents and the textural ones, assumed correlation with the water contents in higher values of tension. The physiological PMP could be used to indicate crops with greater tolerance to water deficit.