Impacts of Different Fertilizer Application Approaches on Selected Soil Properties and Rice Yield in the Dry Zone of Sri Lanka

Abstract

Abstract

There is a growing concern to apply sustainable agricultural practices to optimize crop productivity. Hence, this study examined the effects of various fertilization strategies on soil fertility and rice yield. The study was consisted with three different treatments: T1-conventional fertilizer input management system (IMS); Department of Agriculture inorganic fertilizer recommendation (DOA), 2013, T2- reduced IMS; 50% DOA+ organic manure, and T3- organic IMS; organic manure only. The study was conducted during the 2020/2021 Maha season, which marked the fifth season of the long-term cropping system research project at the farm premises of the Faculty of Agriculture, Rajarata University of Sri Lanka. A randomized complete block design was used with three replicates for the field experiment. Statistical analysis was carried out using the mixed procedure in SAS version 9.0. Mean comparisons were performed using Tukey's method, with a significance level at p≤0.05.  Soil samples were collected from the surface (0-15cm) and subsurface (15-30 cm) soil depths during three growth stages of paddy: just after land preparation (initial stage), at the 50% flowering stage, and just after harvesting.  Soil Total Nitrogen (STN), Soil Organic Matter content (SOM) and Soil Microbial Biomass Carbon (SMBC) were analyzed and paddy yield was measured. STN levels did not significantly differ among the three IMSs (p≥0.05). SOM content in the organic IMS showed stability across all growth stages. The three-way interaction of the IMS, plant growth stage, and soil depth showed a significant effect on SMBC content (p≤0.05). Rice grain yields under organic IMS were notably similar compared to yields obtained with conventional IMS. The highest grain yield was significantly higher with reduced IMS (p<0.05). This indicates the potential to increase yields and sustain soil fertility by replacing 50% of synthetic inorganic fertilizers (SIF) with organic manure. Further inquiry is required for definitive results.

Keywords: Input management systems, Rice Yield, Soil Carbon, Soil microbial biomass, Soil Nitrogen