Strength and Stability of Aggregates as the Key Indicators for Evaluating Soil Physical Conditions

Effect of long-term fertilization and manuring on strength and water stability of soil aggregates, dispersibility of clay, and their relationship with soil organic C (SOC) was evaluated on three different Indian soils. Aggregate parameters showed significant variations under the recommended and 50% higher than the recommended NPK fertilizer and fertilizer-plus-manure applications. However, tensile strength and friability of aggregates were identified as the most sensitive to either particulate organic C (POC) or total organic C (TOC) content change in the soil. Fertilizers and manure had a distinct effect on POC, a reactive form of SOC with greater response to soil management. Results suggested that monitoring the micro-or aggregate scale soil response was critical to identify the best agricultural management practice for sustaining the soil quality. Role of fertilizer alone or in combination with manure in maintaining soil physical condition through the modification of soil aggregate properties and clay dispersibility was clearly evident.