Soil quality and yield sustainability of maize-onion cropping system under organic farming

Attempts were made to evaluate the changes in soil quality under continuous organic farming for seven years. Field experiments were initiated in 2003 at College of Agriculture, Rajendranagar to evaluate the impact of organic farming practices in comparison to chemical farming on soil quality and yield of crops in maize-onion crop sequence. The experiment had six treatments viz., a pure organic treatment wherein the entire RDF was supplied through vermicompost (33%), FYM (33%) and neem cake (33%) on N equivalent basis and organics along with biofertilizers Azatobacter and PSB, an integrated treatment 50% FYM+50 chemical fertilizers and a pure inorganic treatment where the entire recommended dose of nutrients was supplied through mineral fertilizers. After seven years, there was an improvement in soil bulk density with organic treatments when compared to inorganic treatments. The organic treatments registered higher organic carbon content when compared to inorganic treatment and INM treatment. Build-up of available N was not prominent but, a very significant build-up of soil available phosphorus, potassium and micronutrients was noticed, with organic nutrition. Activity of enzymes viz., dehydrogenase, alkaline phosphates and acid phosphates also enhanced with organic treatments. Dehydrogenase activity was highest in organics+biofertilizers treatment followed by pure organic treatments. Alkaline phosphates activity was highest in INM treatment followed by organic and mineral fertilizer treatments, while activity of acid of phosphates was highest in organics+biofertilizers treatment. This prominent change in soil quality also resulted in improved yield of maize-onion cropping system under organic farming over years.