Effect of Long-Term Integrated Nutrient Management on Rice (Oryza sativa L.) - Wheat (Triticum aestivum L.) Productivity and Soil Properties in North-Western Himalaya

The effect of nitrogen substitution (25 to 50%) through different organics, viz., FYM (farmyard manure), GM (green manure) and WS (wheat straw) on crop yield and soil physicochemical and microbiological properties in a rice-wheat system was studied after 20th cropping cycle at Padhiarkhar farm of CSK Himachal Pradesh Agricultural University, Palampur, India. Among different sources of organics, application of FYM and GM proved better than WS. Grain and straw yields of rice and wheat were recorded after 20th and 21st cropping cycles (2010–11 and 2011–12). Pooled data of two years revealed that continuous substitution of 50% N through green manure in rice produced maximum rice grain (7.37 t ha−1) and straw (6.21 t ha−1) yield which was 16.8 and 14.8 per cent higher over 100% NPK added through chemical fertilizers. However, 50% N substitution through FYM in rice was not only statistically at par with 50% N substitution through GM in respect of crop yields but also recorded the highest improvement in soil properties. The analysis of soil samples collected at harvest of wheat 2010–11 showed that organic carbon content increased from its initial value of 6.0 to 8.66 g kg−1, CEC from 11.5 to 14.6 cmol (p+)kg−1 and available phosphorus from 21.9 to 75.2 kg ha−1 through integrated use of organic and fertilizers for the last twenty years while the status of available N and K declined over the years in all the treatments. No addition of fertilizer or manure (control) also led to the significant reduction in available sulphur in comparison to fertilizer-treated plots.