Studies on Creation of Operational Range of Soil Fertility to Evolve Fertilizer Prescription Equations under Soil Test Crop Response Correlation Studies on Rainfed Bt Cotton

To derive fertilizer prescription equations for rainfed Bt cotton within the framework of Soil Test Crop Response (STCR) studies, a meticulously designed gradient experiment was executed at the esteemed Cotton Research Station located in Perambalur district, Tamil Nadu, India. Employing a targeted yield methodology, the investigation centered on the cultivation of fodder sorghum as the exhaustive crop during the kharif season. Adhering to an inductive-cum-yield target approach, the experimental plot was meticulously partitioned into three equitably-sized strips, each delineating a distinct fertility gradient. These gradients were meticulously established through the application of varying fertilizer regimes: N0P0K0, N1P1K1, and N2P2K2. Notably, the recommended fertilizer regimen (N1P1K1) encompassed precise quantities of essential nutrients, specifically 60 kg ha-1 of nitrogen (N), 345 kg ha-1 of phosphorus pentoxide (P2O5), and 96 kg ha-1 of potassium oxide (K2O). Fodder sorghum emerged as the strategic choice for the exhaustive crop, strategically cultivated to expedite the transformation of applied fertilizers within the soil matrix, leveraging both plant and microbial processes. The overarching objective of this methodological approach was to establish a discernible operational range of soil fertility across the designated fertility strips. This was meticulously evaluated through meticulous analyses of variations in fodder yield uptake and pertinent soil test values.