ISSN 2320-5407 International Journal of Advanced Research (2014), Volume 2, Issue 12, 43-52 43 Journal homepage: http://www.journalijar.com INTERNATIONAL JOURNAL OF ADVANCED RESEARCH REVIEW ARTICLE INFLUENCE OF CONSERVATION AGRICULTURE PRACTICES ON PHYSICAL AND CHEMICAL PROPERTIES OF SOIL S. Marahatta 1 , S. K. Sah 2 , A. MacDonald 3 , J. Timilnisa 4 and K. P. Devkota 5 1. Department of Agronomy, Institute of Agriculture and Animal Science, Tribhuvan University (TU), Nepal 2. Faculty of Agriculture, Agriculture and Forestry University (AFU), Chitwan, Nepal 3. CIMMYT-Nepal, Kathmandu, Nepal 4. Former Senior Scientist at International Rice Research Institute (IRRI), Philippines 5. International Rice Research Institute (IRRI), Philippines Manuscript Info Abstract Manuscript History: Received: 25 October 2014 Final Accepted: 22 November 2014 Published Online: December 2014 Key words: *Corresponding Author S. Marahatta Tillage has various negative impact on soil. Minimum soil disturbance, residue retention and appropriate crop rotation are basic principles of conservation agriculture (CA) that significantly improve the soil physical and chemical properties. CA practices improve soil aggregation, bulk density and infiltration in long run due to the presence of carbon pool. The higher amount of SOC in surface soil layer in CA is due to higher accumulation of crop residue which also increase nutrient availability. Copy Right, IJAR, 2014, All rights reserved Introduction Tillage is the mechanical disturbance of the soil (through plowing, cultivation or digging) and has been used by farmers since the ancient time (Wells et al., 2000). There are a number of reasons of tillage as it incorporates weed seeds and biomass in deeper layer of soil; incorporates fertilizers, manure and residues to the soil; preparation of a seedbed to facilitate sowing or planting of crops; optimized the bulk density; helps to maintain soil aeration; release nutrients from organic matter in available forms; controls several soil and residue borne diseases and pests through residue incorporation and provides compaction that reduce water infiltration and percolation (Hobbs, 2007). However, it is also well-established that there are various negative impacts of excessive or inappropriate til lage practices (Figure 1). Conservation agriculture (CA) can be defined as “resource-conserving agricultural crop production system to achieve acceptable profits together with high and sustained production levels while at the same time conserving natural resources and environment” (FAO, 2007).The primary rationale is to protect the natural resources for agriculture (e.g. preventing soil erosion) thereby sustaining and maintenance of agricultural productivity in long run. CA has also a range of secondary benefits to farmers (e.g. cost-savings from mechanization), and environment (e.g. reduced emissions of greenhouse gas, reduction in irrigation water use). CA has been regarded as management of soil, water and agricultural resources to achieve economic, ecological and socially sustainable agricultural production (Jat et al., 2012). CA is more sustainable agriculture production practice than narrowly-defined 'conservation tillage' (Wall, 2007). Conservation tillage is a widely-used terminology to denote only soil management systems in which at least 30% of the soil surface being covered with crop residues after seeding (Jarecki and Lal, 2003). CA combines the following basic principles (Verhulst et al., 2010 and Jat et al., 2012):