SPAD Chlorophyll Meter-Based Real-Time Nitrogen Management in Manure-Amended Lowland Rice

Ghosh, Mainak; Roychowdhury, Arnab; Dutta, Swaraj Kumar; Hazra, Kali Krishna; Singh, Garima; Kohli, Anshuman; Kumar, Sanjay; Acharya, Shivashankar; Mandal, Jajati; Singh, Yanendra Kumar; Pathak, Sushil Kumar; Gupta, Sanjeev Kumar

Abstract

Precise adjustment of timing and dosage of fertilizer nitrogen (N) under real-time nitrogen management (RTNM) is crucial to maximize benefits. The study aimed to assess and recommend the best combination of threshold SPAD-502 chlorophyll meter reading (SCMR) and top dressing N rate for lowland flooded rice, amended with farmyard manure 5 t ha−1, to maximize yield, N use efficiency, and economic gains. In optimization trial, four SCMR-based N scheduling (SCMR34, SCMR36, SCMR38, SCMR40), each with three top dressing N rates (15, 20, 25 kg N ha−1) as RTNM treatments, were evaluated for crop growth and yield, nutrient use efficiency, simulated N2O emission, and economics, comparing with fixed-time N management (FTNM) (100 kg N ha−1, 4 splits). Subsequently, the best-fit SCMR treatment was validated across seven rice cultivars. Top dressing of 20 kg N ha−1 at ≤ SCMR 38 (SCMR38N20) led to a higher yield (+ 8%), N use efficiency (+ 43%), net return (+ 11%), and reduced N input (− 18%) compared to FTNM. The yield advantage with SCMR38N20 was attributed to higher internal N use efficiency and optimal source–sink balance (higher harvest index). In validation trial, the best-fit RTNM treatment (SCMR38N20) showed yield advantage (+ 7%), but significant for four out of seven cultivars. In lowland rice production, the RTNM with top dressing of 20 kg N ha−1 at ≤ SCMR38 can increase yield of medium duration cultivar (Rajendra Swata) and N use efficiency. However, cultivar-specific adjustments to the SCMR threshold and N rate are equally important for significant yield advantage.

Citation

Ghosh, M., Roychowdhury, A., Dutta, S. K., Hazra, K. K., Singh, G., Kohli, A., …Gupta, S. K. (in press). SPAD Chlorophyll Meter-Based Real-Time Nitrogen Management in Manure-Amended Lowland Rice. Journal of Soil Science and Plant Nutrition, https://doi.org/10.1007/s42729-023-01457-3

• Journal Article Type: Article
• Acceptance Date: Aug 25, 2023
• Online Publication Date: Sep 5, 2023
• Deposit Date: Sep 16, 2023
• Publicly Available Date: Sep 6, 2024
• Journal: Journal of Soil Science and Plant Nutrition
• Print ISSN: 0718-9508
• Electronic ISSN: 0718-9516
• Publisher: Springer
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1007/s42729-023-01457-3
• Keywords: Plant Science; Soil Science; Agronomy and Crop Science