Integrated nutrient management and system of rice intensification to optimise black rice production for growth, chlorophyll, soil health, quality and yield

Abstract

The influence of integrated nutrient management (INM) on the growth characteristics, soil nutrient status, grain quality metrics and overall productivity of black rice cultivated under the system of rice intensification (SRI) was evaluated through a field experiment. This research was conducted during the 2024 kharif season on sandy loam soil at the Lovely Professional University's Agriculture Research Farm in Phagwara, Punjab within the Indian subtropical zone. The optimal treatment combination, encompassing the full recommended dose of fertilisers (RDF), 15 t ha-1 farmyard manure, 3.5 kg ha-1 Azospirillum culture and 40 kg ha-1 zinc sulphate mono-hydrate (ZnSO₄·H₂O), yielded the highest growth and yield parameters. Physiologically, this INM strategy demonstrated the best expression of crop growth rate (CGR) and absolute growth rate (AGR), also enhanced photosynthetic pigment content, including chlorophyll a, chlorophyll b and total chlorophyll. Concurrently, grain biochemical quality was maximised, notably the levels of protein and total soluble sugars and milling performance improved significantly across recovery rates. Furthermore, this balanced nutrient regimen resulted in the highest measurable grain, straw and total biological yields, simultaneously improving soil health indicators, such as organic carbon and available macronutrients. Consequently, this study validates the use of combined chemical and organic inputs (FYM, Azospirillum and ZnSO₄·H₂O) as a highly recommended and sustainable management strategy for enhancing black rice production under the SRI method in subtropical climates.