Effect of integrated nitrogen management through organic and inorganic sources on the yield of rice (Oryza sativa L.) and status of soil fertility at harvest

The present investigation was conducted with the objective of utilizing locally available organic resources for substituting chemical fertilizer nitrogen partly and augmenting soil health.  The experiment was carried out for the crop kharif rice (Oryza sativa L.) in coastal Karnataka with eleven treatments laid out in randomized block design with three replications. Vermicompost (VC), Poultry manure (PM) and Fish manure (FM) were used as organic nitrogen sources integrated with mineral nitrogen source of fertilizer urea at substitution ratios of  25, 50 and 100 percent. These treatments were compared with control and recommended dose of nitrogen. The results revealed that the substitution of 50 per cent of nitrogen through VC  recorded significantly (P<0.05) higher plant height  (92.27 cm), higher number of productive tillers (16.85 hill-1), higher grain yield (5434 kg ha-1) and straw yield ( 6817 kg ha-1) compared to control. The results of the soil sample analysis for soil fertility parameters indicated that the major nutrients were significantly (P<0.05) influenced by integrated nitrogen management.  The available nitrogen (382.36 kg ha-1) and available potassium (143.7 kg ha-1) were significantly (P<0.05) higher in the treatment T4 where a recommended dose of nitrogen was substituted by 50 percent VC compared to control (294.05 kg ha-1 and 92.31 kg ha-1 respectively). However, the available soil phosphorus was significantly higher with treatment 50 per cent  RDN substituted by PM  (78.83 kg ha-1) as compared to control (43.93 kg  ha-1).  Thus, integrated resource management improved crop yield and post-harvest soil fertility.