Foliar Nano‐Nitrogen Fertilizer Application for Enhancing Growth and Rice ( Oryza sativa L.) Yield in Vertic Epiaquepts and Typic Epiaquepts

Nanoenabled nitrogen (N) fertilizers are being explored to improve nitrogen use efficiency and reduce conventional N inputs in rice production. Their nanoscale size enables a steady nitrate supply during critical reproductive stages, supporting sustained N assimilation via nitrate reductase and glutamine synthetase rather than short‐term N surges typical of bulk urea. Most studies to date remain confined to a single soil type. This first field trial in Indonesia showed that nano‐N performance and the optimal application rate vary across soil types while maintaining rice yield and N uptake. The study aimed to evaluate the agronomic effectiveness of nano‐N applied in combination with urea doses in two contrasting paddy soil types, Vertic Epiaquepts and Typic Epiaquepts, arranged in a randomized complete block design. Treatments consisted of urea applied at 100%, 75%, and 50% of the recommended rate (225 kg ha −1 ), combined with nano‐N doses of 0–4 mL L −1 . The results showed that rice chlorophyll responses to foliar nano‐N were driven mainly by soil type rather than fertilizer form. Higher chlorophyll contents in Vertic Epiaquepts reflected greater N availability compared with Typic Epiaquepts. Rice growth and yield were controlled by N availability rather than nano‐N rate. Supplementation with 1 mL L −1 nano‐N maintained yield (6.18–6.54 t ha −1 ) while reducing urea inputs by 25%–50%, particularly in Vertic Epiaquepts. Rice yield showed a quadratic relationship with leaf chlorophyll content, indicating that nano‐N improved the effectiveness of fertilizer N applied while maintaining comparable yield. The effectiveness of nano‐N was strongly soil‐dependent. Nano‐N improved relative agronomic effectiveness (113%–124%), maintained yield and N uptake in Vertic Epiaquepts, even with 25%–50% reduced urea rates, but provided little benefit in Typic Epiaquepts. These results highlight the need for soil‐specific nano‐N strategies to maintain rice productivity and enhance the agronomic efficiency of N.