Abstract
The retention and availability of water in the soil vary according to the soil characteristics and determine plant growth. Thus, the aim of this study was to evaluate water retention and availability in the soils of the State of Santa Catarina, Brazil, according to the textural class, soil class and lithology. The surface and subsurface horizons of 44 profiles were sampled in different regions of the State and different cover crops to determine field capacity, permanent wilting point, available water content, particle size, and organic matter content. Water retention and availability between the horizons were compared in a mixed model, considering the textural classes, the soil classes and lithology as fixed factors and profiles as random factors. It may be concluded that water retention is greater in silty or clayey soils and that the organic matter content is higher, especially in Humic Cambisols, Nitisols and Ferralsol developed from igneous or sedimentary rocks. Water availability is greater in loam-textured soils, with high organic matter content, especially in soils of humic character. It is lower in the sandy texture class, especially in Arenosols formed from recent alluvial deposits or in gravelly soils derived from granite. The greater water availability in the surface horizons, with more organic matter than in the subsurface layers, illustrates the importance of organic matter for water retention and availability.
Highlights
Simulation models that evaluate water movement in the soil-plant-atmosphere system are an important tool in agriculture and in environmental management
The field capacity (FC) and permanent wilting point (PWP) were similar for most textural classes. This was the result of the large variability in FC and PWP observed within a single textural class, which raised the standard error of the estimate
The greater variability in water retention in the surface horizons occurred by the more intense weathering effect through the activity of microorganisms, of plants, of wetting and drying cycles, and of the anthropic effect through soil use and management. The combination of these effects resulted in a high standard error of the estimate of organic matter (OM) contents in surface horizons of soils of the same textural class
Summary
Simulation models that evaluate water movement in the soil-plant-atmosphere system are an important tool in agriculture and in environmental management. It is important to consider that there are confounding factors in the relation between texture and water retention in the soil This occurs because in more clayey soils, the chemical and physical protection of organic matter is generally greater (Oades, 1988; Dieckow et al, 2009), especially in soils of colder and wetter regions (Tate, 1992; Chen & Chiu, 2000; Dalmolin et al, 2006). This condition raises the organic matter content and, water retention, especially at low tensions (Rawls et al, 2003). In soils with predominance of 2:1 clay minerals water retention and availability are higher than in kaolinitic soils (Gaiser et al, 2000)
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