Sensor-based precision nutrient and irrigation management enhances the physiological performance, water productivity, and yield of soybean under system of crop intensification

Abstract

Sensor-based decision tools provide a quick assessment of nutritional and physiological health status of crop, thereby enhancing the crop productivity. Therefore, a 2-year field study was undertaken with precision nutrient and irrigation management under system of crop intensification (SCI) to understand the applicability of sensor-based decision tools in improving the physiological performance, water productivity, and seed yield of soybean crop. The experiment consisted of three irrigation regimes [I₁: standard flood irrigation at 50% depletion of available soil moisture (DASM) (FI), I₂: sprinkler irrigation at 80% ET_C (crop evapo-transpiration) (Spr 80% ET_C), and I₃: sprinkler irrigation at 60% ET_C (Spr 60% ET_C)] assigned in main plots, with five precision nutrient management (PNM) practices{PNM₁-[SCI protocol], PNM₂-[RDF, recommended dose of fertilizer: basal dose incorporated (50% N, full dose of P and K)], PNM₃-[RDF: basal dose point placement (BDP) (50% N, full dose of P and K)], PNM₄-[75% RDF: BDP (50% N, full dose of P and K)] and PNM₅-[50% RDF: BDP (50% N, full P and K)]} assigned in sub-plots using a split-plot design with three replications. The remaining 50% N was top-dressed through SPAD assistance for all the PNM practices. Results showed that the adoption of Spr 80% ET_C resulted in an increment of 25.6%, 17.6%, 35.4%, and 17.5% in net-photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), and intercellular CO₂ concentration (C_i), respectively, over FI. Among PNM plots, adoption of PNM₃ resulted in a significant (<i>p</i>=0.05) improvement in photosynthetic characters like P_n (15.69 µ mol CO₂ m^-2 s^-1), T_r (7.03 m mol H₂O m^-2 s-¹), G_s (0.175 µmol CO₂ mol^-1 year^-1), and C_i (271.7 mol H₂O m² s^-1). Enhancement in SPAD (27% and 30%) and normalized difference vegetation index (NDVI) (42% and 52%) values were observed with nitrogen (N) top dressing through SPAD-guided nutrient management, helped enhance crop growth indices, coupled with better dry matter partitioning and interception of sunlight. Canopy temperature depression (CTD) in soybean reduced by 3.09-4.66°C due to adoption of sprinkler irrigation. Likewise, Spr 60% ETc recorded highest irrigation water productivity (1.08 kg ha^-1 m^-3). However, economic water productivity (27.5 INR ha^-1 m^-3) and water-use efficiency (7.6 kg ha^-1 mm^-1 day^-1) of soybean got enhanced under Spr 80% ETc over conventional cultivation. Multiple correlation and PCA showed a positive correlation between physiological, growth, and yield parameters of soybean. Concurrently, the adoption of Spr 80% ET_C with PNM₃ recorded significantly higher grain yield (2.63 t ha^-1) and biological yield (8.37 t ha^-1) over other combinations. Thus, the performance of SCI protocols under sprinkler irrigation was found to be superior over conventional practices. Hence, integrating SCI with sensor-based precision nutrient and irrigation management could be a viable option for enhancing the crop productivity and enhance the resource-use efficiency in soybean under similar agro-ecological regions.