CHANGES IN LEAST LIMITING WATER RANGE UNDER DIFFERENT TILLAGE SYSTEMS AND TRAFFIC INTENSITIES IN A SUBHUMID PAMPEAN REGION

Resumen

Soil management practices can disrupt soil structure, affecting productivity through changes in water and oxygen availability, and mechanical impedance. These variables can be affected by
machinery traffic depending on the management practice used. This research aimed to quantify changes in the least limiting water range (LLWR) in the surface soil layer under varying traffic intensities in both no-till (NT) and conventional tillage (CT) systems. The treatments applied to
each system were: control without any traffic (0P), one tractor pass (1P), and five tractor passes (5P). To determine the LLWR and available water (AW), the following variables were measured: soil bulk density (BD), soil water retention curve (SWRC) and soil penetration resistance (SRP). Transit treatments gave different LLWR results depending on tillage system. The changes in AW were less sensitive than the LLWR values. The only treatment that did not reach the critical bulk density (BDc), where the LLWR is zero, was the 0P treatment. Both the NT and CT 1P treatments reached the same BDc of 1.39 m³ m-³. However, in the 5P treatment, the BDc was 1.33 m³ m-³ for CT and 1.41 m³ m-³ for NT, respectively. The LLWR showed a different response of its structural condition to the tillage system and traffic intensity in both tillage systems. These results provide evidence of a greater risk of soil degradation under CT than under NT management. Regardless of soil management and machinery
traffic treatments, soil penetration resistance was the attribute that had more influence on the LLWR.