Elucidating the Impact of Long-Term Fertilization on kharif Rice (Oryza sativa L.) Productivity and Soil Microbial Activities in Acidic Inceptisols

Abstract

An appraisal was made in an ongoing long-term field experiment with a rice-rice cropping system followed for the last 17 years with 12 treatments and four replications having various combinations of inorganic fertilizers and organic manure. The 12 treatments were control, 100% N, 100% NP, 100% PK, 100% NPK, 150% NPK, 100% NPK + FYM@10 t ha-1,100% NPK + lime@1 t ha-1, 100% NPK + lime@1 t ha-1 + FYM@10 t ha-1, 100% NPK + Zn, 100% NPK + B +Zn, 100% NPK + S + Zn. The present investigation was conducted during the year 2021-2022. After the harvest of kharif rice, the grain (42.4 q ha-1) and straw (53.8 q ha-1) yield were recorded as highest in plots receiving an integrated package of practices of both organic (FYM) and inorganic fertilizers along with ameliorant (100% NPK+FYM @ 10 t ha-1 +lime @1 t ha-1). The relative agronomic efficiency (RAE) was calculated as the highest (209%) in the same treatment followed by an optimal dose of NPK with organics. Various soil enzyme activities like dehydrogenase (DHA), urease, phosphatase, and â-glucosidase were also estimated the highest (72.62 μg TPF g soil-1day-1, 106.40 μg NH4 +-N g-1 soil 2 hr-1, 432 μg p-nitrophenol g-1soil hr-1 and 97.98 μg p-nitrophenol g-1soil hr-1 respectively) in treatment where 100% NPK + FYM @ 10 t ha-1 + lime @1 t ha-1 was applied. A similar response was also noticed for microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorous (MBP) (182.86 μg C g soil-1, 139.40 μg N g soil-1, 19.78 μg P g soil-1 respectively) in the same treatment followed by an optimal dose of NPK with organics. Interestingly SOC had a significant correlation with DHA (0.928**), urease (0.925**), phosphatase (0.950**), â-glucosidase (0.853**), MBC (0.789**), MBN (0.732**) and MBP (0.790**). The soil enzymatic activities (DHA, urease, phosphatase, and â-glucosidase) were also positively correlated (R2=0.86, 0.93, 0.86, 0.77, respectively) with the total yield of rice and microbial biomass (C, N, P) was also positively correlated with SOC (R2=0.81, 0.83, 0.89, respectively).