Application Of Zn Fertilizers Research Articles

Grain Phytic Acid Accumulation of Domestic and Exotic Rice Genotypes in Zinc-Deficient Soil

Micronutrient malnutrition in humans living in rice growing areas is increasing rapidly due to less absorption of mineral nutrients chelated by phytic acid (anti-nutrients) present in rice grains. A field study was conducted to evaluate the grain phytic acid and zinc (Zn) accumulation of 10 field grown rice (Oryza sativa L.) genotypes on a Zn deficient soil. Both the Zn- efficient (Shua-92, IR-9, Shandar, IR-36, and IR-6) and Zn-inefficient (Sarshar,. UPL-48, Khushboo-95 and RG-120) rice genotypes were included in the study. The two Zn treatments (0 and 15 kg ha-1) were arranged in a two factor randomized complete block design with three replications. Nitrogen (N) and phosphorus (P2O5) were applied at the rate of 120 and 80 kg ha-1. The rice genotypes IR-36, UPL-79, Shandar and Shua-92 were the most Zn accumulators whereas; Sarshar, IR-9 and Khushboo-95 the least accumulator in Zn deficiency. Zinc in-efficient genotype Sarshar was the highest Zn accumulator in response to Zn application. Phytic acid content of rice genotypes was significantly influenced (p < 0.05) by the application of Zn fertilizer. Phosphorus concentration in rice grains decreased with Zn application. Zinc in-efficient genotypes accumulated more phytic acid in their food reserves than Zn-efficient genotypes. Phytic acid: zinc ratio decreased significantly more in Zn-inefficient genotypes as compared to Zn efficient genotypes, with application of Zn fertilizer. Zinc efficient genotype Shua-92 accumulated low concentration of phytic acid. The rice genotypes Shua-92, IR-9, Shandar and IR-36 low accumulators of phytic acid performed successfully and contained higher concentrations of Zn than other genotypes.

ENRICHMENT OF BASMATI RICE GRAIN AND STRAW WITH ZINC AND NITROGEN THROUGH FERTI-FORTIFICATION AND SUMMER GREEN MANURING UNDER INDO-GANGETIC PLAINS OF INDIA

Zinc (Zn) deficiency is a well-identified problem in cereals, resulting in decreased crop yields and nutritional quality. Approximately half of the world's population suffers from Zn deficiency. Cereal crops play an important role in satisfying daily calorie intake in developing world, but they are inherently very low in grain-Zn concentrations, particularly when grown under Zn-deficient soils. Therefore, it is essential to increase the Zn concentration in cereal grains particularly in basmati rice. Application of Zn fertilizers or Zn-enriched [nitrogen (N)- phosphorus (P)- potassium (K)] fertilizers (ferti-fortification) offers a rapid solution for increasing Zn concentration in grain and straw. The present study was therefore undertaken to study nutrient concentrations in grain and straw, their uptake and use-efficiencies as influenced by summer green manuring (SGM) and Zn fertilization. Field experiments were conducted for two consecutive years during summer and rainy (Kharif) seasons (April–November) of 2008 and 2009; indicated that SGM and Zn fertilization had significant effects on concentrations and uptake of N, K, sulfur (S), Zn, manganese (Mn), copper (Cu), and iron (Fe) in basmati rice grain and straw. Amongst the SGM and Zn fertilization treatments, Sesbania aculeata green manuring (GM) and 2.0% Zn-enriched urea (ZEU) as zinc sulfate (ZnSO4.H2O) recorded the highest N, K, S, Mn, Cu, and Fe concentrations, and their uptake in grain and straw as well as total (grain + straw) of basmati rice compared to rest of the SGM crops and Zn fertilization treatments. In regards to Zn concentration, foliar spray of 0.2% (ZnSO4.H2O) recorded the highest values of Zn concentration in grain and straw viz. 24.1, 24.1 and 177.7, and 179.2 mg kg−1 DM during 2008 and 2009, respectively. Whereas, 2.0% ZEU as ZnSO4.H2O recorded the highest total Zn uptake viz. 3081.6 and 3089.0 g ha−1 in 2008 and 2009, respectively. The estimated values viz. partial factor productivity (PFP) and crop recovery efficiency (CRE) of applied N were the highest with Sesbania aculeata GM and 2.0% ZEU as ZnSO4.H2O treatments. But, the highest physiological efficiency (PE) of applied N was obtained after summer fallow and control (only N) viz. 25.7, 20.1 and 27.1, and 21.9 kg grain kg−1 of N absorbed in 2008 and 2009. All the Zn-use indices were also influenced significantly due to SGM crops and Zn fertilization treatments except ZnHI of basmati rice. Agronomic efficiency (AE) of applied Zn to rice crop was significantly higher with mungbean (Vigna radiata) GM and ZnO slurry Zn fertilization treatment, however, 0.2% foliar spray of ZnSO4.H2O recorded the highest Zn crop recovery efficiency (Zn CRE) viz. 57.6 and 61.6%, respectively. Overall, application of Zn fertilizer (ferti-fortification) to basmati rice through ZEU and foliar spray of 0.2% (ZnSO4.H2O) increased Zn concentration in grain and straw, resulting in greater bio-availability of grain Zn. Therefore, this would be a very important and useful strategy in solving the Zn deficiency related problems in Indo-Gangetic plains of India.

The effectiveness of foliar applications of synthesized zinc-amino acid chelates in comparison with zinc sulfate to increase yield and grain nutritional quality of wheat

The effectiveness of foliar spray of certain Zn-amino acid chelates (ZnAAC) including Zn-arginine [Zn(Arg)2], Zn-glycine [Zn(Gly)2] and Zn-histidine [Zn(His)2] on the yield and grain quality of two different Zn-deficiency tolerant wheat cultivars (Triticum aestivum cvs. ‘Back Cross’ and ‘Kavir’) was investigated under field conditions. Foliar application of Zn, regardless of the used source, significantly improved grain yield of both wheat cultivars with a mean increase of 15.2% for the first year and 19.2% for the second year. Grain Zn, iron (Fe) and protein concentrations were on average 14.3% higher in wheat plants sprayed with ZnAAC than those sprayed with ZnSO4. Very significant positive correlation between grain Zn, Fe, and protein concentrations indicates that the genes affecting the grain accumulations of Zn, Fe and protein are probably closely linked. Foliar application of Zn fertilizers resulted in significant decrease (on average 17.9%) of grain phytic acid (PA) and PA:Zn molar ratio (on average 16.3%) in comparison with the control treatment although the magnitude of this reduction was greater for ZnAAC than ZnSO4. According to the results obtained in this study, the ZnAAC should be considered as new Zn fertilizer sources for improving yield and total and bioavailable Zn concentrations of wheat grain.

Different increases in maize and wheat grain zinc concentrations caused by soil and foliar applications of zinc in Loess Plateau, China

Zinc (Zn) is an essential mineral nutrient for plant and human growth, and dietary Zn deficiency is a worldwide nutritional problem. Using different Zn fertilizer application methods, this study determines the potential of increasing the Zn concentrations of maize and wheat grain to improve the nutritional status of local residents. Field trials were conducted in the Loess Plateau for two growing seasons to investigate the effects of different Zn fertilizer application methods on the grain Zn concentrations of maize and wheat as well as the grain Zn recovery, yield, and iron (Fe) status of grains under rain-fed conditions. Soil and foliar Zn application did not significantly affect the biomass and grain yield of maize and wheat, suggesting that local soils are not Zn deficient. However, foliar Zn application significantly improved the grain Zn concentration of maize by 27% and 37% and of wheat by 28% and 89% during the first and second growing seasons, respectively. The maize grain Fe concentrations during both growing seasons were also enhanced by foliar Zn application. The foliar application of Zn realized higher grain Zn recoveries of 35.2‰ and 42.9‰ in maize as well as 26.4‰ and 32.3‰ in wheat during the first and second growing seasons, respectively, compared with the soil Zn application with a maximum grain Zn recovery of 1.7‰. Hence, in the Loess Plateau in China, foliar Zn application is an economical method of improving the grain Zn concentration in maize and wheat and increasing grain Fe concentration in maize.

Zinc nutrition in rice production systems: a review

Zinc (Zn) deficiency is one of the important abiotic factors limiting rice productivity worldwide and also a widespread nutritional disorder affecting human health. Given that rice is a staple for populations in many countries, studies of Zn dynamics and management in rice soils is of great importance. Changing climate is forcing the growers to switch from conventional rice transplanting in flooded soils to water-saving cultivation, including aerobic rice culture and alternate wetting and drying system. As soil properties are changed with altered soil and water management, which is likely to affect Zn solubility and plant availability and should be considered before Zn management in rice. In this review, we critically appraise the role of Zn in plant biology and its dynamics in soil and rice production systems. Strategies and options to improve Zn uptake and partitioning efficiency in rice by using agronomic, breeding and biotechnological tools are also discussed. Although soil application of inorganic Zn fertilizers is widely used, organic and chelated sources are better from economic and environmental perspectives. Use of other methods of Zn application (such as seed treatment, foliar application etc., in association with mycorrhizal fungi) may improve Zn-use efficiency in rice. Conventional breeding together with modern genomic and biotechnological tools may result in development of Zn-efficient rice genotypes that should be used in conjunction with judicious fertilization to optimize rice yield and grain Zn content.

Biofortification of rice grain with zinc through zinc fertilization in different countries

Increasing zinc (Zn) concentration of rice seed has potential benefits for human nutrition and health. Enhanced levels of Zn in grain also contributes greatly to crop production through better germination and seedling vigor of rice plants grown on soils with limited Zn supply. This study evaluated the effect of soil and/or foliar Zn fertilizer application on grain yield and grain Zn concentration of rice grown in 17 field trials conducted in 2008 to 2010 in China, India, Lao PDR, Thailand and Turkey on soils ranging in pH from 4.8 to 8.8 and DTPA- extractable Zn from 0.5 to 6.5 mg kg−1. Zinc fertilization had little effect on rice grain yield with the exception of increases of up to 10 % in some locations in China and India. As an average of all trials, Zn application increased grain yield by about 5 %. Grain Zn concentrations were, however, more effectively increased by Zn fertilization, especially with foliar Zn applications. On average, Zn concentration in brown rice (whole caryopsis with husk removed) was increased by 25 % and 32 % by foliar and foliar + soil Zn applications, respectively, and only 2.4 % by soil Zn application. The Zn concentration of un-husked rice (whole grain with husk), which was increased by 66 % by foliar Zn, showed a close association with the Zn in brown and white rice, indicating a possible penetration of Zn from the husk into the inner layers of the rice endosperm. Increase in grain Zn concentration by foliar Zn spray was significantly affected by the timing of the foliar application. More distinct increases in grain Zn by foliar Zn application were achieved when Zn was applied after flowering time, e.g., at early milk plus dough stages. Foliar Zn spray offers a practical and useful means for an effective biofortification of rice grain with Zn. This practice consistently and significantly contributed to increases in grain Zn of rice irrespective of cultivars, environmental conditions and management practices in 5 different countries.

Effects of Combined Phosphorus-Zinc Fertilization on Grain Zinc Nutritional Quality of Wheat Grown on Potentially Zinc-Deficient Calcareous Soil

A 2-year field experiment was conducted (i) to study the effect of combined P and Zn fertilization on the Zn nutritional quality of wheat grown on potentially Zn-deficient calcareous soil and (ii) to identify which soil Zn fraction had the greatest effect on grain Zn concentration. Results showed that Zn fertilization increased grain Zn concentrations by 13% in 2006–2007 and 15% in 2007–2008. However, the application of 200 kg P2O5 ha−1 combined with Zn fertilizer reduced grain Zn concentrations by 38% in 2006–2007 and 17% in 2007–2008 compared with the control (no fertilizer treatment). The phytic acid (PA) concentration and the PA:Zn molar ratio in wheat grain increased as P fertilizer application rate increased, regardless of the Zn fertilizer application rate. Zinc fertilization alone increased diethyltriaminepentaacetic acid–Zn by 220% in 2006–2007 and 470% in 2007–2008 compared with the no Zn fertilizer treatment. The combined application of P and Zn also increased diethyltriaminepentaacetic acid–Zn and loose organic matter–bound Zn, but the increase became smaller as the P fertilizer application rate increased. In conclusion, P fertilizer application rates to the potentially Zn-deficient calcareous soil used in this study should be less than 100 kg P2O5 ha−1 to ensure the efficacy of the Zn fertilizer. Among the soil Zn fractions in this study, loose organic matter–bound Zn had the greatest correlation with grain Zn concentration.

Interactive effect of N fertilization and tillage management on Zn biofortification in durum wheat (Triticum durum)

Gao, X. and Grant, C. A. 2011. Interactive effect of N fertilization and tillage management on Zn biofortification in durum wheat ( Triticum durum ). Can. J. Plant Sci. 91: 951–960. A 3-yr field study was conducted at two locations in southwestern Manitoba, Canada, to determine the interactive effect of application of four sources of N fertilizer and two tillage management systems on grain Zn concentration of durum wheat. There was a significant year-to-year variation in grain yield and grain Zn concentration, indicating a strong environmental influence. Soil type also had a dominating effect, with grain Zn concentration generally being higher at the clay loam location than the fine sandy loam location, reflecting the native soil Zn status. Tillage management showed little influence on grain Zn, suggesting that reduced tillage practices can be adopted by local farmers without decreasing mineral concentrations in grain. Compared with the control treatment, which did not receive extra N fertilizer, N fertilization at 60 kg ha−1decreased grain Zn concentration in 4 of 6 site-years. Grain Zn accumulation was, however, generally not affected by extra N fertilization, in spite of a positive fertilization effect on grain yield. The four N sources did not differ in their effect on grain yield and grain Zn, indicating that at the rate of N applied there were no differential fertilizer source effects on Zn availability. The results of the present study suggest that for wheat production on Canadian prairies, a regular N fertilization rate using the currently registered cultivars is not likely to produce wheat grain that meets the recommended dietary allowance for Zn. Application of Zn fertilizer, in combination with optimum N fertilization or other agronomic practices that can increase grain Zn, is required to produce improved grain quality for human health.

Teff (Eragrostis tef) production constraints on Vertisols in Ethiopia: farmers' perceptions and evaluation of low soil zinc as yield-limiting factor

Teff (Eragrostis tef (Zucc.) Trotter) is a major food crop in Ethiopia and Eritrea. It is well adapted to Vertisols. Yields are low (around 1000 kg ha−1) despite fertilization with urea and diammonium phosphate. The objectives of this study were to understand farmers’ perception on teff production constraints and to evaluate on-farm yield response of teff to zinc (Zn) fertilization. We conducted a farm survey and a participatory fertilization experiment in three teff-based sites (peasant associations) on Vertisols in the mid highland and lowland agroecological zones in Ethiopia. Per site 10 farmers participated in the survey and on-farm experiment. Poor soil fertility in the mid highland and moisture deficit in the lowland agroecological zones were mentioned by farmers as major teff production constraints, respectively. On-farm application of Zn fertilizer at a rate of 8 kg Zn ha−1 increased teff grain and straw yields by 14% and 15% on average, respectively, which could be economically profitable. Not all plots showed a positive response, however, indicating the necessity for enhanced insight in indicators for soil Zn bioavailability as a yield-limiting factor. Our study indicates the importance of Zn in teff production on Vertisols. We propose further research on management options to prepare for effective interventions based on the farm survey and on-farm experiment.

Impacts of phosphorus and zinc levels on phosphorus and zinc nutrition and phytic acid concentration in wheat (Triticum aestivum L.)

Zinc (Zn) and phytic acid content in grain crops are directly related to their nutritional quality and therefore human health. To investigate the nutritional influences of phosphorus (P) and Zn levels on wheat (Triticum aestivum L.), plants were grown hydroponically to maturity in chelator-buffered solutions. Appropriate amounts of P, coupled with sufficient Zn, increased P and Zn concentrations in wheat grain. The Zn supply decreased both phytic acid and the molar ratios of phytic acid to Zn in wheat grain with respect to the Zn(0) treatment. Furthermore, proportions of Zn and P content in the grain relative to that of the whole plant were improved. With increasing P, the proportion of Zn and P content in the grain relative to the whole plant decreased. P and Zn acted antagonistically in roots. Excess P inhibited Zn uptake in roots, while Zn decreased the transfer of P from roots to shoots. For P that had been transported to the shoots, supplemental Zn facilitated its transfer to the grain. Excess P decreased the distribution of Zn in grain, while Zn enhanced the uptake of Zn and P in grain, The combined application of Zn fertilizer with the extensive use of P fertilizer can effectively increase the P and Zn concentration and Zn bioavailability of wheat grain, and hence Zn nutritional quality.

Zinc fractions and availability to soybeans in representative soils of Northeast China

Limited information exists about the zinc (Zn) status of major soils in northeast China, and their ability to supply Zn to soybeans. This study aims to establish the critical concentrations of Zn in soil for plant growth, to characterize the Zn forms in soil, to correlate the concentration of various Zn forms with Zn uptake by soybeans, and to identify the most effective means of Zn application. Thirty-three soil samples were collected from farmland in 11 districts/sites (covering six soil groups) of northeast China. Zinc fractions and DTPA-extractable Zn concentrations of the soils were determined. A pot experiment was also carried out to study the effects of Zn application method on Zn uptake, yield and use efficiency of soybeans. The concentrations of total Zn in these soils ranged from 60 to 84 mg kg−1 while the DTPA-extractable Zn concentrations ranged from 0.77 to 2.16 mg kg−1 and were highly correlated positively with both concentrations of exchangeable Zn (Ex-Zn) and organically bound Zn (OM-Zn). Soybean yields correlated positively and best with concentrations of Ex-Zn, followed by those of OM-Zn. In addition, soybean growth correlated positively with concentrations of all Zn forms except for Fe-oxide bound Zn. When concentrations of DTPA-extractable Zn were less than 1.0 mg kg−1, Zn deficiency occurred and the application of Zn fertilizer increased the yield of soybeans significantly. Foliar sprays and seed coatings resulted in greater yield responses and Zn-use efficiency than other methods. Surface application of Zn after flowering was ineffective. The soils at seven out of 11 field sites were deficient or marginally deficient in Zn. DTPA-extractable Zn provides a good indicator of Zn availability to soybeans with a critical concentration of 1.0 mg kg−1 soil. Foliar sprays and seed coatings should be recommended for the correction of Zn deficiency.

Physiological limits to zinc biofortification of edible crops.

It has been estimated that one-third of the world’s population lack sufficient Zn for adequate nutrition. This can be alleviated by increasing dietary Zn intakes through Zn biofortification of edible crops. Biofortification strategies include the application of Zn-fertilizers and the development of crop genotypes that acquire more Zn from the soil and accumulate it in edible portions. Zinc concentrations in roots, leaves, and stems can be increased through the application of Zn-fertilizers. Root Zn concentrations of up to 500–5000 mg kg−1 dry matter (DM), and leaf Zn concentrations of up to 100–700 mg kg−1 DM, can be achieved without loss of yield when Zn-fertilizers are applied to the soil. It is possible that greater Zn concentrations in non-woody shoot tissues can be achieved using foliar Zn-fertilizers. By contrast, Zn concentrations in fruits, seeds, and tubers are severely limited by low Zn mobility in the phloem and Zn concentrations higher than 30–100 mg kg−1 DM are rarely observed. However, genetically modified plants with improved abilities to translocate Zn in the phloem might be used to biofortify these phloem-fed tissues. In addition, genetically modified plants with increased tolerance to high tissue Zn concentrations could be used to increase Zn concentrations in all edible produce and, thereby, increase dietary Zn intakes.

Effect of combination use of Zn and N fertilizers on yield and Zn content in winter wheat

为比较石灰性土壤氮锌配施对不同小麦品种生长及锌营养的影响, 选10种本地主要种植小麦品种, 进行连续两年的田间试验, 测定小麦产量及锌含量。结果表明, 在石灰性土壤上单施锌肥和氮锌配施对小麦产量、籽粒锌含量的影响因品种而异。单施锌肥及氮锌配施处理可显著增加土壤有效锌含量, 但单施锌肥处理仅增加“西杂1号”、“武农148”、“郑麦9023”籽粒锌含量; 氮锌配施增加除“小偃22”外其余9种供试小麦品种籽粒锌含量, 增幅为7.3%~54.7%。单施锌肥对小麦锌累积量增加的效果不明显; 氮锌配施可显著增加小麦地上部锌累积量, 两季分别增加6.5%、29.8%。单施氮肥可显著增加小麦锌吸收, 但其主要累积在小麦茎叶部。在石灰性土壤上, 单施锌肥虽显著增加了土壤有效锌含量, 但对小麦产量及籽粒Zn含量增加有限, 氮锌肥配施可取得较好效果。

Critical Soil Zinc Deficiency Concentration and Tissue Iron: Zinc Ratio as a Diagnostic Tool for Prediction of Zinc Deficiency in Corn

ABSTRACT Zinc (Zn) fertilizer application is most economic if based on soil test and plant analysis information. The aim of this study was to determine the soil test [diethylenetrinitrilopentaacetate (DTPA) and ethylenetriaminepentaacetic acid (EDTA) extractable] Zn-critical levels and tissue Fe/Zn ratio for corn (Zea mays L.). A greenhouse experiment with 12 soil series and two Zn fertilizer treatments (0 and 15 mg Zn kg−1 as zinc sulfate) was conducted. Critical Zn deficiency levels were determined using the Cate-Nelson procedure. Relative corn yield varied from 0.59 to 1.64. Critical deficiency levels based on the Cate-Nelson method were 1.50 and 1.17 mg kg−1 for DTPA and EDTA-extracted soil Zn, respectively. No accurate critical deficiency level could be established using the shoot Zn concentrations. The critical iron (Fe)/Zn ratio in the corn shoot was 3.9. Values greater than 3.9 indicate hidden Zn deficiency and probable response to applied Zn.

Selecting Zinc‐Efficient Wheat Genotypes with High Grain Yield Using a Stress Tolerance Index

There is no reliable indicator for identifying Zn‐deficiency tolerant genotypes with high grain yield. The aim of this investigation was to compare the grain yield response of 30 spring and 20 winter bread wheat (Triticum aestivum L.) genotypes to Zn fertilization under field condition and to select high grain yield Zn‐deficiency tolerant genotypes using a stress tolerance indicator. The stress tolerance indicator is a stress tolerance index (STI) used to identify genotypes that produce high yields under both nonstress and stress environments. Two individual trials, each consisting of two field plot experiments, were conducted during the 2006–2007 growing season. Spring wheat genotypes (Trial l) and winter wheat genotypes (Trial 2) were planted in two different locations. Two Zn rates, 0 and 40 kg Zn ha−1, using ZnSO4·7H2O were evaluated. Grain yield varied significantly (P < 0.01) among wheat genotypes regardless of Zn treatment. Application of Zn fertilizer increased grain yield of spring wheat genotypes an average of 883 and 913 kg ha−1 in Karaj and Isfahan locations, respectively, although considerable variation was found among genotypes in response to Zn fertilization. Zinc efficiency (ZE) significantly differed among wheat genotypes and ranged from 69% to 95% for spring wheat and from 62% to 105% for winter wheat genotypes. Most of the wheat genotypes were placed in group A (genotypes that are not affected by stress) and D (genotypes with low yield in both stress and nonstress environments) based on the STI. The results showed that the STI could be a better selection criterion compared with ZE for identifying high‐yield stress‐tolerant genotypes.

Zinc crops 2007: improving crop production and human health

Zinc (Zn) deficiency is recognized as a serious threat to both crop production and human health globally. It has been estimated that half of the cereal-cultivated soils have insufficient Zn to support high crop yields and to provide grains of high nutritional quality. As a result, Zn deficiency in humans tends to be prevalent in regions with Zn-deficient soils, particularly in the developing world. Currently, one-third of the world population is at risk of Zn deficiency causing severe health complications, such as impairments in physical development, immune system and brain function (Hotz and Brown 2004). Continuous reliance on high proportion of cereal-based foods with low amount and availability of Zn appears to be the major reason for the widespread occurrence of the Zn-deficiency problem in humans. Enrichment of cereal grains with Zn through both genetic (e.g., breeding) and agronomic (e.g., application of Zn fertilizers) biofortification is, therefore, a high priority area of research, and will contribute to minimizing Zn-deficiency-related health problems in human populations (Bouis 2003; Cakmak 2008). The Zinc Crops 2007 Conference, held in Istanbul, Turkey, on May 24–26 in 2007, has been organized to review and discuss the latest knowledge and best agricultural practices in addressing Zn deficiency and its impact on global crop production and human health. Distinguished keynote speakers have been invited to deliver speeches on the following conference topics:

Enrichment of cereal grains with zinc: Agronomic or genetic biofortification?

Zinc deficiency is a well-documented problem in food crops, causing decreased crop yields and nutritional quality. Generally, the regions in the world with Zn-deficient soils are also characterized by widespread Zn deficiency in humans. Recent estimates indicate that nearly half of world population suffers from Zn deficiency. Cereal crops play an important role in satisfying daily calorie intake in developing world, but they are inherently very low in Zn concentrations in grain, particularly when grown on Zn-deficient soils. The reliance on cereal-based diets may induce Zn deficiency-related health problems in humans, such as impairments in physical development, immune system and brain function. Among the strategies being discussed as major solution to Zn deficiency, plant breeding strategy (e.g., genetic biofortification) appears to be a most sustainable and cost-effective approach useful in improving Zn concentrations in grain. The breeding approach is, however, a long-term process requiring a substantial effort and resources. A successful breeding program for biofortifying food crops with Zn is very much dependent on the size of plant-available Zn pools in soil. In most parts of the cereal-growing areas, soils have, however, a variety of chemical and physical problems that significantly reduce availability of Zn to plant roots. Hence, the genetic capacity of the newly developed (biofortified) cultivars to absorb sufficient amount of Zn from soil and accumulate it in the grain may not be expressed to the full extent. It is, therefore, essential to have a short-term approach to improve Zn concentration in cereal grains. Application of Zn fertilizers or Zn-enriched NPK fertilizers (e.g., agronomic biofortification) offers a rapid solution to the problem, and represents useful complementary approach to on-going breeding programs. There is increasing evidence showing that foliar or combined soil+foliar application of Zn fertilizers under field conditions are highly effective and very practical way to maximize uptake and accumulation of Zn in whole wheat grain, raising concentration up to 60 mg Zn kg−1. Zinc-enriched grains are also of great importance for crop productivity resulting in better seedling vigor, denser stands and higher stress tolerance on potentially Zn-deficient soils. Agronomic biofortification strategy appears to be essential in keeping sufficient amount of available Zn in soil solution and maintaining adequate Zn transport to the seeds during reproductive growth stage. Finally, agronomic biofortification is required for optimizing and ensuring the success of genetic biofortification of cereal grains with Zn. In case of greater bioavailability of the grain Zn derived from foliar applications than from soil, agronomic biofortification would be a very attractive and useful strategy in solving Zn deficiency-related health problems globally and effectively.

Sufficiency and Deficiency Indices of Soil Available Zinc for Rice in the Alluvial Soil of the Coastal Yellow Sea

To determine the sufficiency and deficiency indices of soil available Zn by the Agro Services International (ASI) method (ASI-Zn) for Zn fertilizer recommendation in rice production in the alluvial soil of the coastal Yellow Sea, the relationship between relative rice yield and soil available ASI-Zn concentration was analyzed from a ten-field experiment with various soil test classes ranging from low to high fertility in 2005 and 2006, and nine Zn fertilizer application rates (0, 7.5, 15, 22.5, 30, 37.5, 45, 52.5 and 60 kg Zn/ha) arranged at random with three replications in each field. There was a significant quadratic relationship between soil available ASI-Zn and rice yield, and a significant linear relationship between soil available ASI-Zn concentration and Zn fertilization rate. For rice variety Wuyujing 3, soil available ASI-Zn was deficient when the value was at lower than 1 mg Zn/L, low at 1 to 2 mg Zn/L, sufficient at 1 to 2 mg Zn/L, excessive at higher than 7.5 mg Zn/L. Thus, Zn fertilizer recommendation could be done according to the sufficiency and deficiency indices of soil ASI-Zn. For most of alluvial soils of the coastal Yellow Sea in the study, the available ASI-Zn was lower than 1 mg Zn/L, and then the optimum application rate of Zn fertilizer was about 20 kg Zn/ha.

Effects of Soil and Foliar Application of Zn Fertilizer on Yield and Growth Characteristics of Bread Wheat (Triticum aestivum L.) Cultivars

In order to investigate role of zinc application (soil + foliar application) on growth traits, yield, its concentration and accumulation in wheat leaves and grains, two common cultivars of wheat namely Tajan and Nye 60 have been selected. Four zinc fertilizer levels including Zn0 (no zinc fertilizer), Zn1 (5 kg Zn ha-1 in soil + 300 g Zn ha-1 in foliar application), Zn2 (10 kg Zn ha-1 in soil + 600 g Zn ha-1 in foliar application) and Zn3 (15 kg ha-1 in soil + 900 g Zn ha-1 in foliar application) both from zinc sulfate source have been applied in planting and booting stage in soil and as foliar application. A pot experiment was conducted as a factorial design with 3 replications during 2005. Results showed that using zinc caused increasing effects on grain yield, total dry matter, yield, 1000 grain weight, number of tiller, grain zinc content, flag leaf zinc content, plant height, number of node, protein content and grain Fe content. Number of tiller, grain zinc content and percentage of protein were higher in Tajan cultivar than Nye 60. In other hands, Nye 60 had higher grain yield and 1000 grain weight than Tajan, however, other measured traits showed no significant difference.

Salinity and Zinc Application Effects on Phytoavailability of Cadmium and Zinc

Salinity and Zn deficiency in soils are two factors that may change the phytoavailability of Zn and Cd. The aim of this study was to determine the effects of salinity and Zn application on soil Cd and Zn solubility and their concentration in wheat shoots. A greenhouse experiment with wheat (Triticum aestivum L. cv. Rushan) consisting of two levels of Zn (0 and 15 mg Zn kg−1, in the form of ZnSO4), and five salinity levels of irrigation water (0, 60, 120, and 180 mM NaCl, and 120 mM NaNO3) in triplicate was conducted. Wheat was seeded in pots. After 45 d of growth, the shoots were harvested, and Zn and Cd concentrations were determined. After harvesting, electrical conductivity (EC), pH, and concentrations of anions and cations were determined in soil saturation extracts. Concentrations of Cd and Zn species in soil solution were predicted using the speciation program MINTEQA2. Increasing salinity increased total Cd (CdT), Cd2+, CdCl+, CdHCO3+, and CdCl20 concentrations in the soil solution, whereas no such effect was found for the NaNO3 treatment. Higher salinity decreased the total Zn (ZnT) and free Zn2+ concentrations in the soil solution and decreased Zn concentrations in the wheat shoots. With application of Zn fertilizer, shoot Cd concentrations decreased by 11 to 90%, whereas Zn concentration increased by 75 to 103%. Increasing salinity of irrigation water decreased shoot dry matter, especially if no ZnSO4 was applied. Application of Zn had a positive effect on salt tolerance of plant and increased dry matter of shoot.