Optimizing nitrogen (N) inputs is crucial for maximizing wheat yield and ensuring environmental sustainability. Wheat’s economic significance in India calls for a comprehensive evaluation of its ecological implications to develop a resilient production system. This study aimed to identify and evaluate ten wheat cultivars for their yield and N-use efficiency under varying nitrogen inputs (control (N₀), half of the recommended nitrogen (N₇₅), and the recommended nitrogen (N₁₅₀)) using the surface application of neem-oil-coated urea. All N inputs were applied in three splits, basal, crown root initiation, and tillering stages, and an experiment was conducted in a split-plot design. The application of N₁₅₀ gave the highest dry matter accumulation (DMA) at harvesting stage (AHS) (871 g m⁻²), seed/spike (60), grain yield (GY = 7.4 t ha⁻¹), straw yield (SY = 8.9 t ha⁻¹), harvest index (HI = 45.2%), protein (12.5%), and total uptake of N (TUN) (223 kg ha⁻¹) by the cultivar ‘HD 3249’, being closely followed by the cultivar ‘HD3117’. Six cultivars (‘HD 3298’, ‘HD 3117’, ‘HD 3249’, ‘PBW 550’, ‘HD 3086’, ‘HD 2967’) out of the ten cultivars evaluated responded well to different input treatments with respect to the grain yield efficiency index (GYEI ≥ 1). Regarding N input, N₇₅ and N₁₅₀ recorded the highest increases in plant height, AHS (16.5%; 21.2%), dry matter accumulation (DMA) at 30 days after sowing (DAS) (37.5%; 64%), DMA-60 DAS (42%; 53%), DMA-90 DAS (39.5%; 52.5%), TILL-30 DAS (19.8%; 26.4%), TILL-60 DAS (33.3%; 44%), TILL-90 DAS (37.2%; 47.2%), seed/spike (8%; 10%), 1000-grain weight (7.8%; 12.2%), and protein content (23.3%; and 33%) when compared with N₀. Furthermore, the application of N₇₅ and N₁₅₀ improved GY (72.1%; 142.6%), SY (61.1%; 110.6%), BY (65.5%; 123%), and HI by 4.4% and 9%, respectively, over N₀. Nitrogen addition (N₇₅ and N₁₅₀) also significantly increased total nitrogen uptake (104.7%; 205.6%), respectively, compared to N₀. The correlation analysis revealed a positive association among most of the crop parameters. Overall, our research results suggest that the cultivars ‘HD 3249’ and ‘HD 3117’ have the potential to be effective options for improving N utilization efficiency, grain yield, and GYEI in North-West India.

Nitrogen (N) losses from conventional N fertilizers contribute to environmental degradation and low N use efficiency. Highlighting the need for slow-release fertilizers (SRFs) to mitigate these problems, this study aims to develop slow-release N fertilizers using starch-grafted-poly[(acrylic acid)-co-acrylamide] based nanoclay polymer composites (NCPCs) and investigate their efficacy for slow N delivery in soil. Three types of NCPCs, NCPC(A) (poly [(acrylic acid)-co-acrylamide]), NCPC(W) (wheat starch-grafted-poly[(acrylic acid)-co-acrylamide), and NCPC(M) (maize starch-grafted-poly[(acrylic acid)-co-acrylamide) were prepared and characterized using FTIR spectroscopy and X-ray diffraction techniques. N-release behaviour of the products was assessed under two distinct soils, i.e., Assam (Typic Hapludults, pH 4.2) and Delhi (Typic Haplustepts, pH 7.9) soils. Additionally, the effects of varying soil moisture and temperature levels on N release were studied in the Assam soil. The N-release kinetics of the synthesized fertilizers were assessed using zero-order, first-order, Higuchi, and Korsmeyer−Peppas models. Degradability of the NCPCs was evaluated by measuring evolved CO₂–C under various soil conditions as an indicator of microbial degradation. The results indicated that NCPC fertilizers significantly slowed down the release of N compared to urea. According to the R² values obtained, it was evident that the first-order kinetic model most accurately describes the N release from both urea and NCPC-based N fertilizers in the studied soils. Among the formulations, NCPC(A) exhibited the lowest N release (42.94–53.76%), followed by NCPC(M) (51.05–61.70%), NCPC(W) (54.86–67.75%), and urea (74.33–84.27%) after 21 days of incubation. The rate of N release was lower in the Assam soil compared to the Delhi soil, with higher soil moisture and temperature levels accelerating the release. Starch addition improved the biodegradability of the NCPCs, with NCPC(W) showing the highest cumulative CO₂-C evolution (18.18–22.62 mg g⁻¹), followed by NCPC(M) (15.54–20.97 mg g⁻¹) and NCPC(A) (10.89–19.53 mg g⁻¹). In conclusion, NCPC-based slow-release fertilizers demonstrated a more gradual N release compared to conventional urea and the inclusion of starch enhanced their degradability in the soil, which confirms their potential for sustainable agricultural applications. However, soil properties and environmental factors influenced the N release and degradation rates of NCPCs.

Imbalanced use (form, quantity, and ratio) of nitrogen fertilization can result in decreased grain yields and increased nitrogen loss, leading to adverse effects on overall environmental quality. Globally, limited empirical research has been conducted on the comprehensive effects of different levels of N that can significantly influence wheat agronomic and genotypic traits. Therefore, this study aimed to evaluate wheat genotypes for two consecutive years (2020–2021 and 2021–2022) under different N fertilization treatments: N0 (native N, without external application of N), N75 (½ of the recommended dose of N), and N150 (recommended dose of N). The study findings revealed that ‘HD 3249’ and ‘HD 3117’ were the top-performing genotypes in terms of grain yield (5.3 t ha⁻¹; 5.0 t ha⁻¹), straw yield (6.9 t ha⁻¹; 6.7 t ha⁻¹), biological yield (12.2 t ha⁻¹; 11.8 t ha⁻¹), and harvest index (42.9%; 42.4%). In particular, the application of N75 and N150 increased grain yields by 142.6% and 61.3%, respectively; straw yields by 72.3%; and by 110.6% over N0. Furthermore, N levels (N75 and 150) significantly increased the higher concentration of N in grain (23.1% and 33%) and straw (21.1% and 29.8%); N uptake in grain (70.2 and 104.2) and straw (64.8 and 41.5); and total N uptake (68.8% and 101.4%) than N0, respectively. Additionally, correlation analysis revealed that there were positive correlations between yields, harvest index as well as N concentration and uptake. This study identified the two elite genotypes, ‘HD 3249’ and ‘HD 3117’, with N150 splits giving a better response, which can be used as selection criteria for developing wheat varieties that are more efficient in using nitrogen, leading to high yields and N uptake.

Low nitrogen use efficiency of prilled urea contributes to substantial economic loss and environmental pollution through leaching, denitrification, and ammonia volatilization. This study evaluated urea-loaded nanoclay biopolymer composites (NCBPCs), synthesized from clay-acrylic acid + aczrylamide-based polymer composite grafted with maize flour (NCBPC-M) and mango kernel flour (NCBPC-MK), integrated with phosphorus- and zinc-solubilizing bacteria (Lactococcus lactis and Pseudomonas aeruginosa), as a sustainable alternative nitrogen source in a maize–wheat cropping system. FTIR, XRD, and SEM analyses confirmed successful polymerization and clay exfoliation. Both the composites showed high water absorption capacity (NCBPC-M: ~68 g/g; NCBPC-MK: ~62 g/g after 24 h). A field experiment (randomized complete block design) compared ten treatments, including 75% recommended nitrogen delivered via NCBPCs with or without microbial inoculants, against 100% recommended dose through conventional urea. Treatments combining NCBPCs with both phosphorus- and zinc-solubilizing cultures (T9, T10) sustained higher and more synchronized soil ammoniacal and nitrate nitrogen levels, and significantly increased grain and stover phosphorus and zinc content in both crops compared with conventional urea. These treatments also reduced cumulative N₂O emissions by 17–29% in wheat and 21–24% in maize relative to full-dose urea, with the maize flour-based composite showing the greatest mitigation potential. These findings demonstrate that microbe-integrated, urea-loaded nanoclay biopolymer composites can simultaneously improve nutrient synchronization, enhance micronutrient biofortification, and mitigate greenhouse gas emissions, offering a promising climate-smart strategy for sustainable nitrogen management in cereal cropping systems.