Long-term organic nutrient management in high value rice (Oryza sativa)–potato (Solanum tuberosum)/onion (Allium cepa) cropping system in Chhattisgarh

A field experiment was conducted at Raipur, Chhattisgarh, in Inceptisols for 10 years to compare organic, integrated and chemical fertilizer nutrient inputs packages in scented rice (Oryza sativa L.)–potato (Solanum tuberossum L.) from 2003–04 to 2008–09 and from 2009–10 to 2012–13 in scented rice (Oryza sativa L.)–onion (Allium cepa L.) sequence on same field. Of the 7 nutrient treatments, 5 used organic inputs and one each having integrated (50% through chemical fertilizer and 50% through organic nutrient and 100% through chemical fertilizers) were studied in randomized block design with 3 replications. Organic transition effect in which decline in yield during the first year and again increase in yield was noticeable in rice as well as in onion under organic nutrient inputs packages. These treatments followed a steady increase and registered 33% more rice yield after 10 years over the first year, i.e. 2003–04, 40% potato yield at the end of sixth year, i.e. 2008–09 and 9% more onion bulb yield at the end of study, i.e. 2012–13 than yield obtained during 2009–10. However, bulb yield of onion achieved from organic input treatments was still lower than inorganic and integrated treatment. Rice–potato cropping system showed the maximum total productivity (13.81 t/ha) in terms of rice-equivalent yield under 100% recommended dose of fertilizer (RDF) at the end of the sixth cropping cycle during 2008–09. However when the system was changed into rice–onion, it was found the highest (13.62 t/ha) under 50% RDF + 50% N one-third each from cowdung manure + neem cake + composted crop residues closely followed by 100% chemical fertilizer dose (13.09 t/ha). The 100% N (one-third each from cowdung manure, neem cake and composed crop residue) + green manuring in rice appreciably sustained the organic carbon (5.6 g/ha) and available N (266 kg/ha) over initial value (169) and the generated the maximum total net return (126.7×103/ha) owing to premium price given to the produce. Organic as well as integrated nutrient approaches did not to enhance or maintain the K content of soil even after 10 years.