Long-term application of fertilizer and manure on rice productivity and soil biological properties

The effect of continuous use of inorganic fertilizers and organic manure for 38 years on yield of rice (Oryza sativa) and soil biological properties was studied for two consecutive years during 2009 and 2010 in rotation of wheat at Pantnagar. The experimental soil was an Aquic hapludoll with silty clay loam texture. Application of 100% NPK along with 15 t FYM ha⁻¹ by recording highest mean grain and straw yields of rice of 5110 and 4448 kg ha⁻¹ was significantly better than all other treatments. It was followed by 100% NPK+Zn in mean grain and straw yields of rice. The treatment of 50% NPK, 100% NPK, 150% NPK and 100% N were at par and gave significantly more yields than control. The yield attributes also followed the similar trend that observed in grain and straw yields. The treatment of 100% NPK + 15 t FYM ha⁻¹ also recorded maximum and significantly more mean soil microbial biomass C of 24.1%, soil microbial biomass N of 53.2%, soil dehydrogenase activity of 18.2%, urease activity of 33.9% and respiration rate of 40.5% than 100% NPK alone. The treatments of 100% NPK, 100% NPK+ Zn and 100% NPK+hand weeding were at par and superior to the control in different soil biological properties.