Physical quality of a Luvisol under agroforestry systems in a semi-arid region, Brazil

摘要

Agroforestry systems provide many environmental benefits in semi-arid regions; however, trampling by cattle, and agricultural practices, can degrade physical quality of the soil. The aim of this study was to evaluate the degree of compaction and the compression behaviour of a Luvisol after 14 years under agro-silvopastoral (ASP) and silvopastoral systems (SILV), compared with a soil under natural vegetation (NV). We evaluated the degree of soil compactness, compaction index, pre-consolidation pressure, maximum bulk density, critical water content and the stocks of total organic carbon (C), organic matter (OM), C in light organic matter (LOM), and nitrogen (N) in LOM. The results indicated that agroforestry systems change the compressive behaviour of the soil, increasing maximum bulk density (P < 0.05) and reducing critical water content (P < 0.05). Despite the increases in maximum bulk density, changes induced by agroforestry system did not affect the pore space, as shown by similar values for degree of compactness (P > 0.05) under ASP, SILV and NV. This suggests a change in the quality of OM, as evidenced by the lower values for stocks of N in LOM (P < 0.10) and total organic C (P < 0.05) under ASP and SILV, whereas pre-consolidation pressure was unaffected (P > 0.05). After 14 years, the degree of compactness and load-bearing capacity of the soils under ASP and SILV had not increased, being suitable for plant growth.