Physical properties of a dystrophic Red Latosol (oxisol) under crop cultivation and native forest

The understanding and quantification of the impact caused by soil use and management on the physical soil quality are fundamental for the development of sustainable agricultural systems. The objective of this research was to quantify sonic physical soil properties to evaluate the physical quality of a dystrophic Red Latosol (Rhodic Ferralsol) in the northwest of the State of Parana, Brazil. Undisturbed soil samples were collected from two contiguous areas on an Experimental Farm of the State University of Maringa. One area was cultivated with annual crops under conventional tillage (disk plow and harrowing) and the other under native forest (semidecidual seasonal forest). The evaluated physical soil attributes were soil porosity and bulk density, soil water retention curve, soil resistance curve, and the least limiting water range. Results indicated significantly higher values of bulk density and lower values of soil porosity in the cultivated area. The soil water retention curve was not influenced by the soil use system, but was negatively influenced by bulk density. The soil resistance curve was influenced by the soil use system, evidenced by high values of soil resistance to root penetration under increasing drought in the cultivated soil. The least limiting water range was significantly smaller in the cultivated soil owing to the soil resistance to root penetration and air-filled porosity, which determined the lower and upper limits of soil water availability with bulk density increase. In. the soil under native forest, the least limiting water range was equal to the water availability determined by the field capacity and the permanent wilting point. Soil compaction in the cultivated soil induced changes in the soil porous system, which were described by lower values of the least limiting water range than in virgin soil.