Soil Fertility and Quality Assessment under Tree-, Crop-, and Pasture-Based Land-Use Systems in a Rainfed Environment

A study was conducted to assess the long-term impact of land-use systems on soil physicochemical properties and chemical properties (exchangeable and total nutrients) and overall chemical soil quality in a rainfed Alfisol (Typic Haplustalf) representing the semi-arid tropical region at Hayathnagar Research Farm of the Central Research Institute for Dryland Agriculture, Hyderabad, India, situated at 17° 18' N latitude, 78° 36' E longitude with an elevation of 515 m above mean sea level. Four, 10-year-old land-use systems were adopted for this study. Soil samples were collected from 12 soil profiles (4 systems x 3 replications) from depths of 0-0.05, 0.05-0.15, 0.15-0.30, and 0.30-0.60 m. Study revealed that physicochemical properties such as pH, electrical conductivity (EC), cation exchange capacity (CEC), and organic carbon (OC) were significantly influenced by the land-use systems. Among the land-use systems, agroforestry system resulted in the highest pH (7.5), CEC (13.6 cmol kg-1), and organic carbon (C) content (9.6 g kg-1). Exchangeable nutrient cations [calcium (Ca), magnesium (Mg), and sodium (Na)] and total nutrients [nitrogen (N), phosphorus (P), potassium (K), Ca, Mg, copper (Cu), manganese (Mn), zinc (Zn), and iron (Fe)] were also significantly influenced by land-use systems. The greatest Ca content was found (7.4 c mol kg-1) in arable land system, whereas greatest Mg content (4.7 c mol kg-1) was found in the agroforestry system. Total N content was greatest (607.5 mg kg-1) in the pastoral system and decreased with soil depth. Total P content varied from 473.5 mg kg-1 in arable land to 880.0 mg kg-1 in the pastoral system and decreased with depth. The effect of land-use systems on total hydrolyzable-N pool was significant only up to the 0- to 0.15-m soil depth. Despite being statistically nonsignificant, the agroforestry system recorded greater humic acid (12.8%) and fulvic acid (7.9%) contents than the agrihorticultural system. Chemical soil quality index (CSQI) varied from 0.76 in arable land to 0.92 in the agroforestry system. From the viewpoint of aggradation of soil chemical quality, the agroforestry system (CSQI: 0.92) was most superior, followed by the agrihorticultural system (CSQI: 0.86) and pastoral system (CSQI: 0.80).