Split application of nano urea and conventional urea for optimizing nitrogen management in chrysanthemum under polyhouse conditions

Abstract

<title>Abstract</title> Synthetic fertilizers have played a pivotal role in enhancing crop productivity and quality; however, excessive dependence on conventional fertilizers, particularly urea, has led to low nutrient-use efficiency, environmental contamination, soil fertility depletion and associated ecological risks. These challenges have intensified the need for sustainable and climate-resilient nutrient management strategies, especially under protected cultivation systems. Chrysanthemum is a high-value floricultural crop, is a heavy nitrogen feeder and its growth, flowering and yield are strongly influenced by nitrogen availability. Nano urea, owing to its higher foliar absorption efficiency (80%) and controlled nutrient release, has emerged as a promising alternative to conventional urea for improving nitrogen-use efficiency while minimizing nutrient losses. A factorial randomized block design experiment was conducted during 2022–2023 under polyhouse conditions to evaluate the effect of split applications of urea and nano urea on growth, flowering, yield and soil nutrient status of chrysanthemum. Treatments comprised different doses of nano urea and urea applied at weekly, biweekly and fortnightly intervals, starting after pinching and continued up to twelve weeks. Results indicated that nano urea applied at 100 ppm once in a fortnight significantly enhanced plant height (170.49 cm), plant spread (58.90 cm), flowering earliness (138.5 days), flower size (16.23 cm), cut flower yield/plant (6.37) and postharvest longevity (27 days), with improvements of 15–30% over conventional urea treatments. This treatment also resulted in lower residual soil nitrogen, phosphorus and potassium levels, reflecting improved nutrient uptake efficiency and reduced nutrient accumulation. The study highlights nano urea as a sustainable, high-efficiency nitrogen management strategy capable of improving productivity, profitability and resource-use efficiency in chrysanthemum cultivation.