Crop yield and soil fertility with integrated nutrient management in rice-potato system in coastal Odisha

A field experiment was conducted during kharif and rabi seasons of 2007–08 and 2008–09 in the Central Research Station of Odisha University of Agriculture and Technology, Bhubaneshwar on rice-potato system in irrigated condition. The soil was medium in organic carbon (0.54%) and available phosphorus (18 kg ha⁻¹) and low In available nitrogen (228 kg ha⁻¹) and potassium (122 kg ha⁻¹). The experiment was laid out in randomized block design with 8 treatments replicated thrice. Application of 50% nitrogen (N) each through chemical fertilizer and dhaincha to rice registered the highest grain yield. Whereas, in potato application of 50% recommended dose of nitrogen (RDN) as chemical fertilizer + 50% N as farmyard manure (FYM) or vermicompost registered the highest average tuber yield. The highest amount of available N was found in the treatment receiving 50% chemical N along with 50% N as Azolla to rice and 50% chemical N + 50% RDN as neem cake to potato. The available soil phosphorus (P) was highest with 25% inorganic N substitution by Azolla in rice and neem cake in potato. The highest net gain of available N was observed with application of 75% RDN through chemical fertilizer + 25% RDN was through FYM to both rice and potato. Build up of P was observed with the supplementation of 25% RDN from Azolla in rice and neem cake in potato. The treatments receiving 100% chemical fertilizer and 75% RDN as chemical fertilizer + 25% N through FYM to both rice and potato exhibited maximum net loss of K at the end of two years of cropping sequence. The study revealed that substitution of chemical nitrogen to the tune of 25 to 50% not only enhanced the crop yield but also increased the available nitrogen and phosphorous status of the soil. However, the available potassium content of the soil was heavily depleted irrespective of various treatment combinations.