Sachin KS, Dass A, Dhar S, Rajanna GA, Singh T, Sudhishri S, Sannagoudar MS, Choudhary AK, Kushwaha HL, Praveen BR, Prasad S, Sharma VK, Pooniya V, Krishnan P, Khanna M, Singh R, Varatharajan T, Kumari K, Nithinkumar K, San AA, and Devi AD
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 [I 1 : standard flood irrigation at 50% depletion of available soil moisture (DASM) (FI), I 2 : sprinkler irrigation at 80% ET C (crop evapo-transpiration) (Spr 80% ET C ), and I 3 : sprinkler irrigation at 60% ET C (Spr 60% ET C )] assigned in main plots, with five precision nutrient management (PNM) practices{PNM 1 -[SCI protocol], PNM 2 -[RDF, recommended dose of fertilizer: basal dose incorporated (50% N, full dose of P and K)], PNM 3 -[RDF: basal dose point placement (BDP) (50% N, full dose of P and K)], PNM 4 -[75% RDF: BDP (50% N, full dose of P and K)] and PNM 5 -[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 CO 2 concentration (C i ), respectively, over FI. Among PNM plots, adoption of PNM 3 resulted in a significant ( p =0.05) improvement in photosynthetic characters like P n (15.69 µ mol CO 2 m -2 s -1 ), T r (7.03 m mol H 2 O m -2 s- 1 ), G s (0.175 µmol CO 2 mol -1 year -1 ), and C i (271.7 mol H 2 O m 2 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 PNM 3 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., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Sachin, Dass, Dhar, Rajanna, Singh, Sudhishri, Sannagoudar, Choudhary, Kushwaha, Praveen, Prasad, Sharma, Pooniya, Krishnan, Khanna, Singh, Varatharajan, Kumari, Nithinkumar, San and Devi.)