Comparison of the effect of different ratios of chemical and biological fertilizers on the chlorophyll content of RGS rapeseed cultivar at different seed densities
Abstract
The pursuit of sustainable agricultural practices necessitates a reduction in synthetic fertilizer reliance. Integrating bio-fertilizers presents a promising alternative, but their efficacy can be influenced by crop management strategies, such as planting density. Understanding these interactions is crucial for optimizing crop physiology and yield in oilseed crops like rapeseed. This study aimed to investigate the individual and interactive effects of different fertilizer regimens and seeding densities on the chlorophyll content of the RGS cultivar of rapeseed (Brassica napus L.). A field experiment was conducted in a factorial arrangement based on a completely randomized design with three replications in Tashkent Province, Uzbekistan. The experimental factors consisted of three fertilizer ratios (100% chemical, 50% chemical + 50% biological, and 100% biological) and three seeding densities (30, 45, and 60 seeds per m2). The relative chlorophyll content of the leaves was measured at the full flowering stage using a SPAD-502 meter. Analysis of variance revealed that the main effects of both seeding density and fertilizer treatment, as well as their interaction, significantly influenced chlorophyll content at the 1% probability level. The highest chlorophyll content (65.5 SPAD units) was recorded in plants treated with the combined 50% chemical + 50% biological fertilizer at the lowest seeding density of 30 seeds per m2. Conversely, the lowest value (40.5 SPAD units) was observed in the 100% biological fertilizer treatment under the highest density of 60 seeds per m2. A general trend indicated that chlorophyll content increased notably as plant density decreased. The findings demonstrate that the integrated application of chemical and bio-fertilizers, particularly at lower planting densities, can significantly enhance the photosynthetic health of rapeseed by potentially improving nutrient uptake efficiency. For farmers in the region, adopting this combined fertilizer strategy at moderate densities is recommended as a viable approach for achieving optimal yield while aligning with the principles of sustainable agriculture.