Abstract:
A field trial was conducted to study the effect of different nitrogen sources on soil organic carbon (0C) content and growth of okra grown in sandy regosol under integrated nutrient management (INM). Initially nitrogen sources such as farmyard manure (FYM), poultry manure (PM), AmuthaKaraisai (AK) and urea were analyzed for their nitrogen content and applied on equal N basis at 135 kg Nitrogen / ha by each nitrogen sources. There were eight treatments replicated thrice. They are 100% N by each nitrogen sources, 50% N from each organic nitrogen source + 50% N from Urea and unfertilized one, But P205 and K20 were applied at the rate of 90 kg / ha by chemical sources. All the cultural practices were adopted according to the recommendation. Variety Haritha was planted in pots containing 14 kg of soil.
The results revealed that in all INM combinations, except Amuthakaraisal and urea combination, the soil OC content was higher than sole inorganic fertilizer treatment. There was no significant difference in soil OC content between PM and AmuthaKaraisal treatments. The soil OC content was significantly higher in treatment received nitrogen from FYM alone. It may be due to the mass of FYM added with regards to low N content of FYM.
The results showed higher OC content in soils treated with organic or inorganic fertilizers than control. In treatments except sole AmuthaKaraisal and control there was an increment in soil OC content, from planting to harvest. This may be due to higher nutrient availability and crop growth. Crop growth was significantly higher in treatments received nitrogen from FYM and urea integration and sole PM application than others. This may be due to higher retention and availability of nutrient. But sole N by FYM ranked third and was on par with others.
Key words: AmuthaKaraisal, Farmyard manure, Growth of okra, Integrated nutrient management, Organic carbon, Poultry manure, and Sandy regosols.
