Sulfur nanoparticle-coated urea improves growth and nitrogen use efficiency in wheat (Triticum aestivum L.) and rice (Oryza sativa L.)

Nitrogen (N) is an essential macronutrient required for plant productivity. Urea is a major source of N in global agriculture systems that is lost due to leaching, runoff, and volatilization, inflicting serious productivity, economic, and environmental issues. In contrast, coated urea minimizes N losses by decreasing urease activity and enhances its efficiency by maintaining a continuous N supply for plant uptake and productivity. The present study describes the impact of sulfur nanoparticle (S NP )-coated urea (S NP CU) on the morpho-physiological, biochemical, and yield traits of rice and wheat. Chemically synthesized S NP coated onto urea revealed a fine layer of S NP on urea under a scanning electron microscope. Two varieties each of rice and wheat grown in pots were fertilized as follows: control N/recommended non-coated urea U 100 , three doses of S NP CU (50%, 70%, and 90% of recommended N) in split doses (40% at transplanting, 30% at tillering, and 30% at the panicle stage). Analysis revealed that S NP CU at all doses increased the growth and yield parameters of both crops. The maximum increase was observed in S NP CU 90 , that is, chlorophyll (up to 39%), carotenoids and proteins (up to 20%), sugars and amino acids (up to 60%), along with an increase of at least 5% or more in agronomic efficiency, 10% or more in grain weight, 6% or more in harvest index, and 70% or more in N uptake in both cultivars of wheat and rice. S NP CU 90 increased the nitrogen recovery efficiency by 34% and 26% in wheat varieties Galaxy and FSD-2008, while 36% and 30% in Green Super Rice and 1121 Basmati rice, respectively. S NP CU 90 decreased urease activity up to 37%, 52% on day 2, and 16% and 25% on day 15 in wheat and rice, respectively. This delay increased the duration of N availability in soil for wheat and rice plants, resulting in increased nitrogen use efficiency (NUE) till 15 days. This study has demonstrated that S NP CU minimizes N loss, revealing that even a lower application of S NP CU fulfills the crop N demand. It is concluded that S NP CU at lower rates can be used for large-scale testing in fields for reducing N losses and improving yields.