Combined effects of foliar nano-N and soil-applied N on growth, yield, and nutrient status in high-density apple orchards

Nano-N, a sustainable agricultural innovation, is an efficient alternative to conventional nitrogen sources, enhancing nutrient use efficiency and reducing environmental impact. A two-year field study (2021–2022) evaluated the effects of nano-nitrogen combined with graded levels of conventional nitrogen on tree growth, yield, fruit quality, and soil nutrient attributes in high-density apple cv. ‘Jeromine’ orchards. The experiment used a Randomized Block Design (RBD) with five treatments—T1: Recommended Dose of Nitrogen (RDN), T2: 70% RDN + 2 sprays of nano-N, T3: 60% RDN + 2 sprays of nano-N, T4: 50% RDN + 3 sprays of nano-N, and T5: 40% RDN + 3 sprays of nano-N—replicated four times. Foliar nano-N sprays were applied at pink bud, petal fall, and walnut stages, while soil-applied urea was given in two splits, 15 days before and after flowering. Tree height, annual shoot growth, and leaf area were 2.79 and 0.84, 4.34 and 1.89, and 11.85 and 7.60% higher in T2 and T3 than the control. Yield increased by 8.11% and 9.45% in T2 and T3. Leaf N, P, and K ranged from 2.10–2.46%, 0.23–0.28%, and 1.75–1.90%, correlating positively with yield. Soil N, P, K, exchangeable Ca, Mg, and micronutrients (Fe, Mn, Cu, Zn) were 1.23–6.93% higher in T1–T3. PCA identified five components, with the first two explaining 51.8% and 11.7% of variance. Foliar nano-N with 60–70% RDN significantly improved growth, yield, and nutrient status, demonstrating its effectiveness and sustainability for high-density apple orchards.