Influence of Tillage Practices and Supplemental Irrigation Options on Growth , Yield and Soil Biological Properties of Rainfed Bt Cotton

Nature is comprised of biological diversity. A single gram of soil has been estimated to contain several thousand species of microbes. Traditional intensive agricultural practices deteriorate soil health [1]. Soil organisms are important elements for preserved ecosystem biodiversity and services thus assess functional and structural biodiversity in arable soils is interest. Main threats to soil biodiversity occurred by mechanical impacts (soil compaction, soil tillage) and chemical stress (plant protection measures) in agricultural management. A wide range of sustainable agricultural practices improve soil quality. For example reducing tillage, increasing organic content in the soil by adding local available organic wastes and crop residues and ensuring sufficient ground cover to protect soil from erosion during off season etc. Tillage systems influence physical, chemical and biological properties of soil and have a major impact on soil productivity and sustainability. It alters the organic matter content in soil, which ultimately affects the microbial population and their activity. Conventional tillage practices may adversely affect long–term soil productivity due to erosion and loss of organic matter in soil. Suitable soil management can be practiced through conservation tillage (including zero tillage), high crop residue return and crop rotation. Minimum-tillage (MT) is the most adapted conservation tillage system, which involves minimal disturbance of the surface residue. Soil quality can be described as the integration of the physical, chemical and biological properties of the soil for productivity and environmental quality [2]. Fertile and high quality soil will sustain long-term agricultural production by supporting the production capacity of the system [3]. However, conventional agricultural practices have diminished soil productivity at such a frightening pace [4], that many agricultural soils are depleted of nutrients and unable to naturally sustain crops [5]. Under current conditions, unproductive soils have to be actively rehabilitated into fertile and healthy soil in order to increase yields [6]. This conversion process gave rise to the three main principles applied in ecological-oriented conservation agriculture (CA): crop diversification, minimum soil Abstract A field experiment was conducted in two consecutive growing seasons at Agricultural Engineering College and Research Institute, Kumulur, Tamil Nadu to evaluate the tillage practices, crop residue and supplemental irrigation through drip irrigation in Bt cotton under rainfed condition. The experiment was laid out in strip plot design with three replications. The soil type of the experimental field was sandy loam in texture with pH 7.71. The fertility status of the soil was low, medium and high in the available N, P2O5, and K2O; the values are 212, 20 & 575 kg ha -1 respectively. The main plot treatments were conventional tillage, minimum tillage without crop residue, minimum tillage with crop residue @ 5 t ha -1 and minimum tillage with crop residue @ 10 t ha -1 . The sub plot treatments were control (without irrigation), supplemental drip irrigation 4, 6, 8 and 10 times during the cropping period. Tillage practices and crop residue with supplemental drip irrigation practices could potentially lead to significant difference in growth parameters, microbes populations, yield attributes and maximum yield 2947, 2923 kg ha -1 of Bt cotton in both the seasons by application of minimum tillage with crop residue 10 t ha -1 + supplemental drip irrigation ten times. Therefore, minimum tillage (one pass of mouldboard plough followed by two passes of disk harrow) with crop residue 10 t ha -1 + supplemental irrigation through drip irrigation ten times was found to be more appropriate and profitable to improving yield of Bt cotton under rainfed condition.