Table 1 Impact of nitrogen and nano-nitrogen on crop plants

Oryza sativa L.

25–100% n-NF

Improved plant length, biomass, and number of tillers. The highest crop yield (2.8 t ha⁻¹) was found at 100% n-NF application. Based on the present findings, nano-N fertilizer can reduce negative effects of nitrogen to the environment by minimizing harmful nitrogen inputs

[77]

Zea mays L.

0.32% and 0.76% n-NF

Higher nutrient uptake, improved N-use efficiency, enhanced plant performance, and better fruit/grain quality for nanozeourea application than conventional urea

[35]

Borago officinalis L.

0.002% and 5% n-NF

Nano-urea (n-NF) improved essential oil production and growth responses in terms of plant biomass, both dry and fresh, and also plant length

[29]

Glycine max L. and Zea mays L.

25–75% n-NF

Significantly impacted agronomic characteristics, yield and quality. Increases in these traits due to partial replacement of conventional urea with nano-urea might be attributable to nano-fertilization enhancing availability of nutrients to the developing plant and reducing traditional N losses. The application of 25% nN recorded the highest values in both crops as compared to 50% and 75% of nN

[78]

Pennisetum glaucum L.

0.3–0.5% n-NF

The number of productive tillers plant⁻¹ was significantly influenced by the application of nano-N fertilizer. When nano-urea was applied twice to the leaves (foliar spray), it increased the nutrient uptake via the stomatal openings and nutrient translocation within the plant. It enhanced the nutrient uptake/accumulation, resulting in increased cell division, meristematic activity, and cell elongation stimulation, producing more productive tillers plant⁻¹. The crop productivity was influenced by the use of nano-urea

[79]

Glycine max L.

90 kg N/ha

Shoot, root, nodulation traits, seed yield, and protein were significantly affected. Specifically, seed yield and seed protein were maximum when treated with nN, and number of nodules, biomass of root, and nodule dry weight were enhanced. In addition, the NFs (nano-N) could be a better alternative to the standard N fertilizer (urea)

[80]

Saccharum officinarum L.

80–161 kg N/ha

Increased cane stem length and fresh weight with increasing concentration of fertilizer. The order of NUE for stems and sugar yield changed from high to low. Nano-nitrogen fertilizer had significant effects in reducing nitrate leaching and increasing sugar production. However, when nitrate leaching and its effects on human health and the environment were viewed, nano-fertilizers (nN) awee valuable to urea

[81]

Solanum tuberosum L.

25% n-NF and 46% N

Agronomic traits were significantly enhanced, such as photosynthetic pigments, biomass, soft tubers yield, and the biological yield—proteins and ascorbic acid. NFs had positive impacts on upgrading the quality of potato yield compared to conventional N-fertilizer (urea). Potato plants treated with nN resulted in more soft and dry vegetative yield, potato fresh tuber yield, higher nutrient content. Results were better than the comparison treatment in the presence of better water management and when using drip irrigation technique

[82]

Triticum aestivum L.

14–41 kg/ha (17% n-NF) and 37–110 kg/ha (46% N)

Improved agronomic and biochemical activities, i.e., biomass, spike weight and length, plant length, number of tillers, stem diameter, seed weight, biological yield, seed yield, harvest index, anthocyanin, flavonoid, proline, soluble carbohydrates, photosynthetic pigments, and carotenoid contents. According to analyzed activities, replacing urea by nano-chelated nitrogen can improve crop production in response to adverse environmental conditions and reduce the amount of required fertilizer

[83]

Zea mays L.

69–161 kg N/ha

Increased growing-season N₂O emissions and enhanced growth and yield traits. The biomass showed an incremental trend with increasing concentration of N application

[84]

Triticum aestivum L.

94–130 kg N/ha

Enhanced plant length, water use efficiency (WUE), dry matter accumulation, crop index, and grain yield. Slow-release N fertilizers had positive and increased effects on crop development and productivity subjected to arid environmental conditions. Various N concentrations showed significant effects on plant development, especially in terms of crop productivity

[61]

Triticum aestivum L., Pennisetum glaucum L., Brassica nigra L., Sesamum indicum L.

2.5 mL/L n-NF

Increased crop yield in wheat (5.35%), sesame (24.24%), pearl millet (4.2%), and mustard (8.4%) by applying n-NFs. The increased yield was observed in agronomic traits, such as wheat tillers, ear head length of pearl millet, capsule number per plant in sesame, and siliquae number per plant in mustard. The results suggested that the field demonstrations with applied organic manure, bio-fertilizer, and NFs in combination resulted in optimum yield and better plant performances when compared to synthetic fertilizer practice

[85]

Brassica napus L.

30–90 kg N/ha

Effectively improved the growth, and physiological and biochemical activities, such as photosynthetic pigments, SOD, CAT, and POD. Reduced MDA content during in vivo and in vitro conditions. The amendment of N-fertilizer could effectively minimize the loss of soil flooding. The application of 60 kg ha⁻¹ N after 6 days of stress or 90 kg ha⁻¹ N after 9 days of stress had significantly improved the photosynthetic and metabolic responses of rapeseed and contributed to the better recovery of rapeseed. The N-induced increase in soil flooding of rapeseed might be attributed to the strong antioxidant defense system, as well as maintenance of photosynthetic apparatus and nutrient balance

[86]

Punica granatum cv. ardestani

0.25 and 0.50 g nN/L

4.6 and 9.2 g N/L

Increased fruit yield (~ 17–44%) and number of fruits per plant (15–38%). The highest fruit yields and number of fruits per plant were obtained in nN treatment as compared to control plants. On the other hand, fruit diameter, fruit cracking, peel thickness, aril content, weight of 100 arils, juice pH, maturity index, antioxidant responses, and total phenolic compounds were unaffected by N application. Results indicated that the pomegranate fruit yield was improved by the use of nN and application of N (urea). However, quality of fruit was upgraded with the nN as compared to urea. In fact, the application of urea was less efficient than nN

[87]

Triticum aestivum L.

120–240 kg N/ha

Exhibited higher levels of total chlorophyll content, spike length, 100-grain weight, grain yield in kg/ha, and nitrogen and potassium. Foliar application of nN fertilizer (14 L/ha) combined with mineral fertilizer (240 kg/ha) significantly enhanced the photosynthetic pigments as compared to normal plants. Upregulating the availability of N is an important strategy for enhancing nutrient efficiency, boosting plant nutrition, improving yield traits, and reducing soil contamination

[88]

Lactuca sativa L.

75% nN (drip irrigation) and 25% nN (foliar spray)

Application of nN as a soil and foliar treatment was more efficient. Application of 75% nN via drip irrigation system and 25% of nN in foliar spray significantly affected the agronomic and biochemical activities, i.e., plant biomass, leaf area expansion, relative growth rate, photosynthetic leaf gas exchange, β-carotene, crude protein, and productivity. Similarly, N uptake, N use efficiency, and apparent N recovery were increased as compared to lower N rates. It could minimize the recommended N rate to reduce environmental contamination without any yield loss

[89]

Solanum tuberosum L.

¼, ½, ¾ and 100% of recommended fertilizer

Spraying with NFs showed superiority in plant development in the field, and increased yield and quality

[90]

Triticum aestivum L.

37–110 kg N/ha

14–41 kg nN/ha

Nitrogen (urea) and nano-chelated nitrogen (nN) had significant effects on RWC; ion leakage; protein, phosphorus and potassium content; remobilization; and photosynthetic responses. Application of nN (41 kg/ha), in comparison with urea, led to increased RWC (4%), ion leakage (3%), protein (52%), phosphorus (26%), potassium (6%), remobilization (6%), and photosynthetic rate (21%), as compared to control. Therefore, it was recommended to replace NFs with synthetic fertilizers, especially in sandy soils due to the possibility of more leaching of synthetic urea and groundwater contamination

[91]

Olea europaea L.

2.21 and 2.95 g N

6–8 g nN

Nano-N enhanced the fruit sets. Mineral elements, chlorophyll,and carbohydrate content of plant leaves were affected during summer season and fall by N-treatments. The maximum oil (%) was achieved by nN application. Normally, fertilizing the trees with urea was better than nN

[92]

Zea mays L.

300 kg N/ha

1 and 2 mL/L nN

The interaction between the nN fertilizer and synthetic fertilizer had significant effect on most of the agronomic traits for both seasons

[93]

Triticum aestivum L.

100–200 ppm

Optimum values of macro- and micro-nutrients concentrations in grains except N, Zn, and Mn

[94]

Solanum tuberosum L.

40 L/ha (25% N)

Enhanced the WUE, NUE, PUE, and KUE. It can be concluded that better crop yield can be achieved through the adoption of fertigation and good irrigation strategies, high WUE, AE, and EUE, as well as a consistent distribution of nutrients in the soil

[95]

Pennisetum americanum L.

80 ppm

The application of 80 ppm of nN on pearl millet plants (15 days) indicated an appreciable improvement in root morphology (539%), root length (159%), root perimeter (46%), number of tips (14%), average root diameter (76%), and total biomass (157%). The result clearly demonstrated the possibility of biosynthesized nN for efficient use as NF

[96]

Pleurotus ostreatus (Jacq. Ex Fr.) P. Kumm

3–5 g kg⁻¹ n-NF

Protein (0.64%), total carbohydrates (0.48–3.76%) and fiber contents (0.2%) enhanced as compared to control plants. Essential amino acids improved. Potassium, sodium, calcium, iron, and copper contents reduced with minor changes

[43]

Salvia officinalis L.

40–80 kg N/ fed and 250–500 ppm n-NF

Agronomic traits enhanced with increasing level of nano-N and N application. The highest nitrogen use efficiency (NUE) and nitrogen uptake efficiency (UPE) were achieved by the application of nN

[97]

Camellia sinensis L.

100 kg N acre⁻¹

The application of N increased the length of plant height, plant canopy, fresh tea leaves and productivity as compare to control plants

[98]

Camellia sinensis L.

¹⁵N-Urea

Foliar application of N significantly increased the N content of the mature leaves and improved the tea quality. The application of N increases the N content of the mature leaves, improved the quality and productivity of spring tea

[99]

Asparagus racemosus L.

100–300 kg N ha⁻¹

The number, length, diameter and biomass of tuberous roots were found higher with application of N and nN. The different concentrations of N noted significant effect on plant length, number of leaves, length, diameter and biomass of tuberous roots as compared to control. Root protein content was found higher at different levels of N, respectively

[100]