Impact of long-term application of fertilizer, manure and lime under intensive cropping on physical properties and organic carbon content of an Alfisol

Intensive cropping with conventional tillage results in a decline of soil organic carbon (SOC) with consequent deterioration of soil physical properties. Some studies indicate that this decline in SOC can be arrested by way of organic manure application and improved nutrient management practices. This study was conducted to find out the long-term effects of inorganic fertilizer, manure and lime application on organic carbon content and physical properties of an acidic Alfisol (Typic Haplustalf) under an annual soybean–wheat crop rotation. Six treatments namely, control (CON), nitrogen fertilization (NIT), nitrogen and phosphorus (NP), nitrogen, phosphorus and potassium (NPK), NPK plus manure (NPKM) and NPK plus lime (NPKL) from a long-term fertilizer experiment continuing at Ranchi, India, were chosen for this study. Soil samples were collected from the selected treatments after 29 crop cycles and analyzed for physical and chemical properties. The results indicated that SOC content in all the treatments decreased from initial levels, but the decrease was considerably less in NPKM (8.7%) and NPKL (10.9%) treatments than that in NIT (28.3%) treatment. The SOC at 0–15 and 15–30 cm depth was lowest in NIT and CON. The NPKM, NPKL and NPK treatments up to 30 cm soil depth recorded significantly higher SOC than NIT and CON. Application of balanced fertilizer along with manure (NPKM) or lime (NPKL) improved soil aggregation, soil water retention, microporosity and available water capacity and reduced bulk density of the soil in 0–30 cm depth over CON. In contrast, soil aggregate stability, microporosity and available water capacity were significantly lower in the NIT plots than that in CON. The study thus suggests that soil management practices in acidic Alfisols should include integrated use of mineral fertilizer and organic manure or lime to maintain the organic carbon status and physical environment of soil.