Soil Health Improvement with Gliricidia Green Leaf Manuring in Rainfed Agriculture . On Farm Experiences

Abstract

S oils of drylands are highly degraded besides having low soil organic carbon. Organic carbon in soil plays crucial role in various soil processes, nutrient dynamics, water relations and in maintaining biological and physical health of soil. Thus, it determines the extent of soil productivity. Most of the dryland soils are low in organic carbon (Figure 1) due to rapid oxidation process in dry regions of the country (Srinivasarao et al. 2006, 2008, 2009a; Srinivasarao 2011 a, b, c). Besides, low biomass genera tion and erosion of top organic carbon rich soil under intensive rainfall are other important factors leading to low soil organic carbon status in tropical regions. Depleted levels of organic matter have significant negative impacts on water use efficiency due to poor porosity and infiltration, local and regional water cycles, plant productivity, the resilience of Agroecosystems and global carbon cycles (Wani et al. 2009). By controlling infiltration rates and water holding capacity, soil organic matter plays a vital function in buffering yields through climatic extremes and uncertainty that exist in drylands. Therefore management practices that augment soil organic matter and maintain it at a threshold level are urgently needed for assessing further degradation and rather have better soil health, carbon sequestration, mitigating greenhouse gases (GHGs) and food security of the country (Srinivasa Rao et al. 2011 b, c, d, e, Wani et al. 2009). Optimum levels of soil organic carbon can be managed through the adoption of appropriate crop rotation, fertility management, using chemical fertilizers and organic amendments and conservation tillage. Improved management as evident from long term experiment at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, India implies sustained productivity improvement as well as improved soil quality (physical chemical and biological parameters) along with increased carbon sequestration (Wani et al. 2003). Continuous application of organic matter as farm compost, farmyard manure, and plant residues is needed to maintain or increase soil organic matter content. However, shortage of organic manures and competing uses of farm residues as feed and fuel make it difficult to apply these to soil at desired levels