Nano-fertilizers are new generation of the synthetic fertilizers which contain readily available nutrients in nano scale range. Nano fertilizers are preferred largely due to their efficiency and environment friendly nature compared to conventional chemical fertilizers. To evaluate the effects of foliar spray of micronutrient nano-fertilizer (iron and zinc) and nano-titanium dioxide (nTiO2) solution on grain yield and its components in barley under supplemental irrigation conditions, a field experiment was carried out in the semi-arid highland region of Maragheh, Iran. Barley plants were separately treated with of chelated nano-scale zinc oxide (ZnO) and ferric oxide (Fe2O3) suspensions during tillering stage, booting and milky stages. Results revealed that days to anthesis and maturity significantly increased after application of both nano-fertilizers. Furthermore, a considerable improvement was observed in grain mass, spike length, number of the grains per spike, chlorophyll content, grain yield and harvest index by application of nano-fertilizer. However the impact of nano zinc fertilizer was more prominent than iron. Foliar application of nTiO2 positively affected some morphophysiological characteristics like as days to anthesis, chlorophyll content and straw yield. The results suggest that the delivery of Zn into barley seedling through spray of nano-fertilizer can be an efficient nutrient management strategy in semi-arid regions. Overall, our result indicated that the integration of nanotechnology in fertilizer products can improve fertilizer use efficiency and significantly increase of barley yield. However, plant response to nanoparticles significantly depend on concentration and time of application as well as size, shape, and surface functionalization of the particles.

Silicon nanoparticles have distinctive physicochemical characteristics and are able to enter into plants and impact the metabolism of plants as well as improve plant growth and yield under unfavourable environmental conditions. Besides, low soil organic matter content, imbalanced nutrient and inadequate water supply may adversely affect crop productivity in semiarid areas. To understand the effects of foliar spray of silicon dioxide nanoparticles (nSiO₂) with application of farmyard manure (FYM) or inorganic fertilizer on morpho-physiological traits and yield of safflower, a field experiment was carried out in a highland semiarid region of Maragheh, northwest Iran. The experiment consisted of two levels of nSiO₂ (0 and 20 mM) and four fertilizer regimes (control, 15 t ha⁻¹ FYM, 30 t ha⁻¹ FYM, 90 kg ha⁻¹ N-P-K chemical fertilizer). Safflower plants were treated with nSiO₂ suspension at leaf development, branching and capitulum emergence stages. Although the nSiO₂ significantly improved some growth parameters such as canopy spread, stem diameter, plant height, ground cover and the number of achenes in capitulum, it did not affect achene yield and harvest index. However, fertilizer treatments considerably affected most of morpho-physiological traits, achene yield and yield components. The result showed that the best growth and the highest achene yield were achieved by application of 30 t ha⁻¹ FYM before sowing. Application of high FYM increased the achene yield by 48% compared to the control, however, application of N-P-K chemical fertilizer or of 15 t ha⁻¹ FYM improved achene yield only up to 17% over the no fertilizer condition. Moreover, this work revealed some positive effects of exogenous application of nSiO₂ on safflower growth. This finding suggests that application of organic fertilizers with foliar spray of nSiO₂ can improve safflower production and is an advisable agronomic option.

Sustainable crop production is required for the semi-arid areas, and it will be achieved by the wise use of several production inputs which must be tailored to the unique conditions of each district. Effective nutrient management and irrigation are just two parts of the crop production puzzle. It seems that nano-fertilizers may have high potential for achieving sustainable crop production. A field experiment was carried out to investigate the effect of adding different fertilizers on maize (S.C 704 Hybrid) growth under various irrigation regimes in Moghan, northwest of Iran. The experiment included three irrigation levels (up to ~100, ~50, and ~25% field capacity) which were applied from the beginning of the reproductive period. During the vegetative period, all plants were fully irrigated. Fertilizer treatments included control (no-fertilizer application), N biofertilizer, P biofertilizer, nano-chelated B, nano-chelated Zn, complete nanofertilizer, and bulk NPK fertilizer. Investigation of morphophysiological traits such as leaf area, ear length, ear diameter, relative water content, and chlorophyll content revealed that application of complete micronutrients, bulk NPK, and nano-chelated Zn significantly improved these traits over the control. A similar status was recorded for grain yield and yield components. Results indicated that although irrigation up to ~25% of field capacity (FC) reduced the grain yield compared to the control, there was not observed any significant difference between normal irrigation and ~50% FC. The best plant performance was recorded for plants grown by complete nanofertilizer under optimum or ~50% FC. Deficient irrigation up to ~50% FC could be assigned as an appropriate water management strategy in semi-arid regions to minimize water losses through evaporation and achieve higher water use efficiency. In conclusion, a combination of precision deficient irrigation and application of nanofertilizers play a critical role for enhancing the efficient use of water and improving the productivity of maize production systems in Mediterranean semi-arid regions.

Contamination of soils by lead (Pb) is of widespread occurrence as result of human, agricultural and industrial activities. A pot study was carried out to evaluate physio-biochemical responses (chlorophyll content, soluble protein, proline content and activities of enzymatic antioxidants) of 10 bread wheat genotypes to inoculation of plant growth promoting rhizobacteria (combination of Azospirillum brasilense and Azotobacter chroococcum) under Pb stress (0 and 65 mg kg^-1). Result revealed that lead stress averagely decreased grain yield of wheat cultivars by 41.4 %. Lead stress increased lipid peroxidation and induced a significant accumulation of proline in leaves. Protein content decreased from 8-25.4% in different cultivars in Pbcontaminated soils. Activities of antioxidant enzymes, such as, ascorbate peroxidase, superoxide dismutase and catalase were significantly increased in the presence of lead. An increase in total hydrogen peroxide (H₂O₂) content was noticed under lead stress in all cultivars, which was similar to production of malondialdehyde (MDA). However, promotion of growth was evident in most cultivars as a consequence of rhizobacterial inoculation, since plant growth promoting rhizobacteria could improve grain yield, proline content and membrane integrity, while significantly reduced the production of MDA and H₂O₂. Total chlorophyll content considerably declined with Pb stress. Between cultivars the best performance under lead stress was observed in Sardari, Shahriyar and Gaspard which had the highest yield and antioxidants activity. Obtained results showed that inoculation with Azotobacter and Azospirillium possibly through bioremediation strategy can stimulate plant growth under adverse environmental conditions, such as heavy metal contamination.