アグロテクノロジー

概要

Evaluation of Organic and Conventional Rice Production Systems for their Productivity, Profitability, Grain Quality and Soil Health

K. Surekha, K.V. Rao, N. Shobha Rani, P.C. Latha and R.M. Kumar

Considering the importance of organic farming and growing demand for organically produced foods, field studies were conducted for 5 years (2004-05 to 2009-10) on a black clayey vertisol soil at the Directorate of Rice Research, Hyderabad, to study the influence of organic and conventional farming systems on productivity, grain quality, soil health and economic returns of super fine rice varieties. Two main plot treatments, with and without plant protection, and four sub plot treatments viz., Control; 100% inorganics; 100% organics; and 50% inorganics+50% organics (integrated nutrient management, INM) were imposed. During wet season, grain yields under 100% inorganics and INM were near stable (4.7-5.5 t/ha) and superior to organics by 15-20% during the first two years, which improved with organics (4.8-5.2 t/ha) in the later years to comparable levels with inorganics, while it had taken five years during dry season. Moderate improvement in nutritional quality was recorded with organics, especially in brown rice. There was a significant improvement in soil physical, fertility and biological properties with organics, which resulted in further improvement in soil quality indices. The sustainability index of the soil was maximum with organics (1.63) compared to inorganics (1.33), after five years of study. The soil organic carbon (SOC) stocks were higher with organics by 44 and 35%, compared to conventional system during wet and dry seasons, respectively, after five years of study. The carbon sequestration rate was also positive with organics (0.97 and 0.57 t/ha/yr during wet and dry seasons, respectively), compared to conventional system that recorded negative SOC sequestration rate (-0.21 and -0.33 t/ha/yr during wet and dry seasons, respectively). Benefit cost ratio was less with organics in the initial years and improved later over inorganics by fifth year.