Soil physical quality in an orange orchard in northwestern Paranaas affected by groundcover management

The traffic of agricultural machinery and soil compaction occur near the canopy of citrus trees, which increases soil physical restrictions to root growth. Soil management strategies include the use of permanent groundcover in the interrows of orange tree plantations, although the effects of these practices on the soil physical quality are largely unknown. The objective of this study was to assess the impact of groundcover management systems on some indicators of soil physical quality for orange tree orchards. The study was performed in a long-term experiment with Pera' orange grafted onto 'Rangpur' lime combined with groundcover systems, established in 1993, in the Alto Parana county, northwestern Parana state, Brazil, in a Typic Paleudult with a sandy surface horizon. Bahiagrass (Paspalum notatum) or perennial peanut (Arachis pintoi) groundcover treatments were compared with the usual management in which weeds are controlled by post-emergence herbicide. The experimental design consisted of randomized blocks with three replications. In May 2003, soil samples were collected from under and between the wheel tracks. The following indicators were assessed in undisturbed soil samples from the mid 0-15 cm layer: water content at field capacity, total porosity and bulk density. The data were used to estimate soil aeration and water storage capacity indicators. Disturbed soil samples were collected in the 0-5 cm and 10-15 cm depths to measure the organic carbon content and calculate the soil organic carbon stratification ratio. The soil aeration capacity, water storage capacity and organic carbon stratification ratio were efficient indicators to evaluate groundcover management systems in citrus. Bahiagrass maintained better soil physical conditions both under and between wheel tracks. The soil physical quality was negatively affected under the wheel tracks on perennial peanut groundcover and under the wheel tracks and between tracks on the usual control of spontaneous vegetation with postemergence herbicide.