The impact of foliar applied zinc fertilizer on zinc and phytate accumulation in dorsal and ventral grain sections of four thai rice varieties with different grain zinc

Zinc oxide nanoparticles enhanced rice yield, quality, and zinc content of edible grain fraction synergistically

Zinc oxide nanoparticles (ZnO NPs) have been widely used in agriculture as a new type of Zn fertilizer, and many studies were conducted to evaluate the effect of ZnO NPs on plant growth. However, there are relatively few studies on the effects of application methods and appropriate dosages of ZnO NPs on rice yield, quality, grain Zn content, and distribution. Therefore, in the 2019 and 2020, field trials were conducted with six ZnO NPs basal application dosages of no ZnO NPs, 3.75 kg hm-2, 7.5 kg hm-2, 15 kg hm-2, 30 kg hm-2, and 60 kg hm-2, and the effects of ZnO NPs application on rice yield, quality, grain Zn content, and distribution were investigated. The results demonstrated that applying ZnO NPs in Zn-deficient soils (available Zn < 1.0 mg kg-1) increased rice grain yield by 3.24%-4.86% and 3.51%-5.12% in 2019 and 2020, respectively. In addition, ZnO NPs improved the quality of rice by increasing the head milling rate, reducing chalky grain percentage, and increasing the taste value and breakdown of rice. In terms of Zn accumulation in rice, ZnO NPs application significantly increased the Zn content in both milled rice and brown rice, compared with no Zn treatment, in 2019 and 2020, Zn content in milled rice significantly increased by 20.46%-41.09% and 18.11%-38.84%, respectively, and in brown rice significantly increased by 25.78%-48.30% and 20.86%-42.00%, respectively. However, the Zn fertilizer utilization gradually decreased with increasing ZnO NPs application dosage. From the perspective of yield, rice quality, Zn fertilizer utilization, and Zn accumulation, basal application of 7.5 kg-30 kg hm-2 ZnO NPs is beneficial for rice yield and quality improvement and rice Zn accumulation. This study effectively demonstrated that ZnO NPs could be a potential high-performed fertilizer for enhancing rice yield, quality, and zinc content of edible grain fraction synergistically.

Grain Zinc and Yield Responses of Two Rice Varieties to Zinc Biofortification and Water Management

Zinc (Zn) biofortification can improve grain yield and nutritional quality in rice, but its effectiveness is subject to agronomic practices and other factors. In a previous study, the application of Zn to soil enhanced grain Zn in lowland rice in well-drained and waterlogged soil, whereas grain Zn in upland rice increased only in well-drained soil. This new study explores the hypothesis that the application of foliar Zn can enhance grain Zn in upland and lowland rice grown under waterlogged and well-drained conditions. Two rice varieties, CNT1 (wetland rice) and KH CMU (upland rice) were grown in containers in waterlogged or well-drained soil with three Zn treatments (no Zn, soil Zn and foliar Zn). For the soil Zn treatment, 50 kg ZnSO4 ha−1 was applied to the soil before transplanting. For the foliar treatment, 0.5% ZnSO4 (equivalent to 900 L ha−1) was applied at booting and repeated at flowering and milky growth stages. Grain yield in CNT1 was 15.9% higher in the waterlogged than in the well-drained plants, but the water regime had no effect on grain yield in KH CMU. Grain Zn concentration in CNT1 increased from 19.5% to 32.6% above the no Zn control when plants were applied with soil or foliar Zn. In KH CMU, there was an interaction between the water regime and Zn treatment. Application of foliar Zn increased grain Zn by 44.6% in well-drained and 14.7% in waterlogged soil. The results indicate strong interaction effects between variety, water regime and Zn fertilizer application on Zn biofortification in rice. Thus, the selection of rice varieties and growing conditions should be considered in order for producers to achieve desirable outcomes from high grain Zn concentrations.

Zinc Nutrition Responses to Agronomic and Yield Traits, Kernel Quality, and Pollen Viability in Rice (Oryza sativa L.)

Rice (Oryza sativa L.) is one of the major cereal crops worldwide with wheat and maize. A total of two field experiments were performed to evaluate the response of some rice cultivars to various foliar zinc (Zn) concentrations based on different measurements, such as agronomic, yield, yield compounds, and grain technological parameters. The experimental layout was a split plot in three replicates; the five rice cultivars (Skaha 101, Giza178, Yasmeen, Fourate, and Amber 33) were distributed in the main plots while the four foliar applications of Zn (1,500, 2,000, 2,500 mg/L besides spray water) were occupied the sub-plots. The findings showed significant differences among the five rice cultivars regarding plant height, grain yield, straw yield, biological yield, harvest index, 1,000-grain weight, panicle length, protein percentage, and grain Zn content. There is a significant effect of Zn on all plant attributes. A significant interaction between rice cultivars and foliar application of Zn was observed, whereas fertilizing Giza 178 with foliar application of Zn at the rate of 2,500 mg/L achieved the highest mean values of grain yield and straw yield, biological yield, harvest index, 1,000-grain weight, panicle length, protein %, and Zn content followed by Sakha 101 with Zn application at the rate of 2,000 mg/L, respectively, in both seasons. The rice cultivars significantly differed in hulling (%), broken (%), hardness, grain length, shape, amylose (%), gel consistency, and gelatinization temperature. Unfortunately, the commercial Zn product used was genotoxic to pollen grains with a higher rate of Zn. Aberrations were observed such as stickiness, ultrastructural changes in the exterior and interior walls, partially or fully degenerated grains, and shrunken and unfilled grains. This study concluded that using Zn application at the rate of 2,000 mg/L to protect human and environmental health, the side effects and toxicity of the local commercial Zn product market should be investigated before making recommendations to farmers.

Green Synthesis of Zinc Oxide Nanoparticles: Fortification for Rice Grain Yield and Nutrients Uptake Enhancement

Applications of metal oxide nanoparticles in the agriculture sector are being extensively included as the materials are considered superior. In the present work, zinc oxide nanoparticle (ZnO NPs), with a developing fertilizer, is applied in the fortification of rice grain yield and nutrient uptake enhancement. To evaluate the role of ZnO NP, two field experiments were conducted during the 2018 and 2019 seasons. ZnO NPs were small, nearly spherical, and their sizes equal to 31.4 nm, as proved via the dynamic light scattering technique. ZnO NPs were applied as a fertilizer in different concentrations, varying between 20 and 60 mg/L as a foliar spray. The mixture of ZnSO₄ and ZnO NP₄₀ ameliorated yield component and nutrients (N, K, and Zn) uptake was enhanced compared to traditional ZnSO₄ treatment. Nevertheless, the uptake of the phosphorous element (P) was adversely affected by the treatment of ZnO NPs. Thus, treatment via utilizing ZnO NPs as a foliar with a very small amount (40 ppm) with of basal ZnSO₄ led to a good improvement in agronomic and physiological features; eventually, higher yield and nutrient-enriched rice grain were obtained.

Nano-micronutrients [γ-Fe2O3 (iron) and ZnO (zinc)]: green preparation, characterization, agro-morphological characteristics and crop productivity studies in two crops (rice and maize)

Nanotechnology based fertilizer production possessing the desired chemical composition, can improve plant nutrition and may reduce the environmental impact and enhance the plant productivity.

Effect of zinc-biofortified seeds on grain yield of wheat, rice, and common bean grown in six countries

Seeds enriched with zinc (Zn) are ususally associated with better germination, more vigorous seedlings and higher yields. However, agronomic benefits of high-Zn seeds were not studied under diverse agro-climatic field conditions. This study investigated effects of low-Zn and high- Zn seeds (biofortified by foliar Zn fertilization of maternal plants under field conditions) of wheat (Tritcum aestivum L.), rice (Oryza sativa L.), and common bean (Phaseolus vulgaris L.) on seedling density, grain yield and grain Zn concentration in 31 field locations over two years in six countries. Experimental treatments were: (1) low-Zn seeds and no soil Zn fertilization (control treatment), (2) low-Zn seeds + soil Zn fertilization, and (3) Zn-biofortified seeds and no soil Zn fertilization. The wheat experiments were established in China, India, Pakistan, and Zambia, the rice experiments in China, India and Thailand, and the common bean experiment in Brazil. When compared to the control treatment, soil Zn fertilization increased wheat grain yield in all six locations in India, two locations in Pakistan and one location in China. Zinc-biofortified seeds also increased wheat grain yield in all four locations in Pakistan and four locations in India compared to the control treatment. Across all countries over 2 years, Zn-biofortified wheat seeds increased plant population by 26.8% and grain yield by 5.37%. In rice, soil Zn fertilization increased paddy yield in all four locations in India and one location in Thailand. Across all countries, paddy yield increase was 8.2% by soil Zn fertilization and 5.3% by Zn-biofortified seeds when compared to the control treatment. In common bean, soil Zn application as well as Znbiofortified seed increased grain yield in one location in Brazil. Effects of soil Zn fertilization and high-Zn seed on grain Zn density were generally low. This study, at 31 field locations in six countries over two years, revealed that the seeds biofortfied with Zn enhanced crop productivity at many locations with different soil and environmental conditions. As high-Zn grains are a by-product of Zn biofortification, use of Zn-enriched grains as seed in the next cropping season can contribute to enhance crop productivity in a cost-effective manner.

Absorption of foliar-applied Zn fertilizers by trichomes in soybean and tomato

The present study investigated the role of trichomes in absorption of foliar-applied zinc fertilizers in soybean and tomato. Using synchrotron-based X-ray fluorescence microscopy for in situ analyses of hydrated leaves, we found that upon foliar application of ZnSO4, Zn accumulated within 15 min in some non-glandular trichomes in soybean, but not in tomato. However, analyses of cross-sections of soybean leaves did not show any marked accumulation of Zn in tissues surrounding trichomes. Furthermore, when near-isogenic lines of soybean differing 10-fold in trichome density were used to compare Zn absorption, it was found that foliar Zn absorption was not related to trichome density. Therefore, it is suggested that trichomes are not part of the primary pathway through which foliar-applied Zn moves across the leaf surface in soybean and tomato. However, this does not preclude trichomes being important in other plant species, as they are known to be highly diverse. We also compared the absorption of Zn when supplied as either ZnSO4, nano-ZnO, or bulk-ZnO, and found that absorption from ZnSO4 was about 10-fold higher than from nano- and bulk-ZnO, suggesting that it was mainly absorbed as soluble Zn. This study improves our understanding of the absorption of foliar-applied nutrients.