Zn-deficient Soil Research Articles

Zinc oxide nano particles increases Zn uptake, translocation in rice with positive effect on growth, yield and moisture stress tolerance

Zinc (Zn) is one of the important micronutrients required for plant growth and development. Soil Zn deficiency is a major problem and hence adequate Zn supply during crop developmental stages are recommended to improve the nutrient content in the edible parts and also improve productivity. However, excess use of traditional Zn fertilizers has detrimental effect on soil and plant health. Hence, there is a need to have formulations of Zn with improved use efficiency for the better crop performance with less input. In this context, we investigated the impact of Zn Oxide (ZnO) nano particles on Zn uptake, translocation and growth performance in rice in comparison to conventional Zn fertilizer (ZnSO4). Seed priming with 1000 ppm of ZnO was found to be optimal for increasing seedling vigour index. Significant improvement in growth of pot grown rice plants was observed with ZnO treatment compared to ZnSO4, particularly with seed priming followed by foliar application. Plants treated with nano ZnO showed improved plant height, chlorophyll content, biomass, tiller number and yield. The Zn content in leaf and seed is also higher in ZnO nano treated plant samples compared to ZnSO4 treatment. With increased Zn levels in leaves, substantial up regulation of Cu/Zn SOD was observed. Under moisture stress conditions, the ZnO nano particles application improved the tolerance by maintaining the membrane stability and showed higher expression of Cu/Zn SOD. This signifies that optimum levels of Zn enhances cell metabolism leading to improved growth and stress tolerance. Overall the study demonstrates the positive effects of ZnO nano particle in improving the plant growth.

Biochemical indicators of root damage in rice (Oryza sativa) genotypes under zinc deficiency stress.

Zn deficiency is one of the major soil constraints currently limiting rice production. Although recent studies demonstrated that higher antioxidant activity in leaf tissue effectively protects against Zn deficiency stress, little is known about whether similar tolerance mechanisms operate in root tissue. In this study we explored root-specific responses of different rice genotypes to Zn deficiency. Root solute leakage and biomass reduction, antioxidant activity, and metabolic changes were measured using plants grown in Zn-deficient soil and hydroponics. Solute leakage from roots was higher in sensitive genotypes and linked to membrane damage caused by Zn deficiency-induced oxidative stress. However, total root antioxidant activity was four-fold lower than in leaves and did not differ between sensitive and tolerant genotypes. Root metabolite analysis using gas chromatography-mass spectrometry and high performance liquid chromatography indicated that Zn deficiency triggered the accumulation of glycerol-3-phosphate and acetate in sensitive genotypes, while less or no accumulation was seen in tolerant genotypes. We suggest that these metabolites may serve as biochemical indicators of root damage under Zn deficiency.

Response of Miscanthus sacchariflorus to zinc stress mediated by arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi have the ability to promote growth of the associated plants by enhancing water and nutrient uptake. In the present study, we aimed to explore the performance of Miscanthus sacchariflorus under different soil zinc (Zn) levels in association with inoculated AM fungi. M. sacchariflorus was grown in a greenhouse with three doses of added Zn (0, 100 and 1000mgkg−1 soil) in combination with or without association of AM fungi, and its growth, oxidative stress levels, and ultrastructure were observed. The additions of medium levels of Zn (100mgkg−1) did not show significant effects on mycorrhizal colonization; however, when the Zn addition level was 1000mgkg−1, the mycorrhizal infection rate slightly decreased in comparison to the no Zn addition treatment (control). Inoculation of AM with 100mgkg−1 Zn addition increased chlorophyll concentration, Fv/Fm, total dry mass, concentrations of indole acetic acid, total nitrogen and total phosphorus, and content of Zn, whereas activity levels of peroxidase and indole acetic acid oxidase, and H2O2 levels were low when compared with the other two treatments. 1000mgkg−1 Zn addition resulted in lower Zn contents in the aerial parts of inoculated compared to non-inoculated plants. Zn crystals in the root parenchyma of mycorrhizal plants were observed. These results open the possibility of using arbuscular mycorrhizal fungi symbiotic Miscanthus plants in phytoremediation as well as to grow them in Zn-deficient soils.

Apple pomace improves the quality of pig manure aerobic compost by reducing emissions of NH3 and N2O

In this study, the effects of apple pomace (AP) addition (0%, 5%, 10%, and 20% on a dry weight basis, named as control, AP1, AP2, and AP3) and citric acid (CA) addition on nitrogen conservation were investigated during aerobic composting of pig manure. Gaseous emissions of NH3 and N2O were inhibited by AP and CA addition, with AP’s effect greater. The inhibition improved with increasing AP addition. The AP3 treatment was the most effective on NH3 adsorption and transformation to {{bf{NH}}}_{{bf{4}}}^{{boldsymbol{+}}}-N, improved with subsequent transformation to {{bf{NO}}}_{{bf{3}}}^{{boldsymbol{-}}}-N, and inhibition of N2O and {{bf{NO}}}_{{bf{2}}}^{{boldsymbol{-}}} production. Compared with control, AP3 showed the highest inhibition of accumulated NH3 and N2O emission, by 57% and 24%, respectively, and with a 19% increase of total Kjeldahl nitrogen in the compost. The further pot experiment proved the application of the AP amendment compost could improve the yield and trace element nutrient accumulation in Chinese cabbage when planted in a typical Zn-deficient soil. This study illustrates that AP application benefits both compost nitrogen conservation and fertilizer quality.

Zinc uptake by roots and accumulation in maize plants as affected by phosphorus application and arbuscular mycorrhizal colonization

Phosphorus (P) application reduces the zinc (Zn) concentration of cereal grain, but the mechanisms, including root Zn accumulation, remain controversial. Field and pot experiments were conducted to determine the degree to which root Zn accumulation, root arbuscular mycorrhizal (AM) colonization, and other factors contribute to the negative interaction between P and Zn. Root Zn accumulation was positively related to shoot Zn accumulation. In responding to P application, root Zn accumulation was more affected by changes in AM colonization than by changes in root dry weight (RDW). In the pot experiment without Zn supply, root Zn concentration (RZnC), RDW, and AM colonization together explained 98% (adjusted R2 value) of the decrease in root Zn accumulation with P application, while AM colonization and RDW explained 66% (adjusted R2 value) of decrease in total Zn accumulation. In the pot experiment with Zn sufficient supply, RZnC and RDW explained 89% (adjusted R2 value) of the decrease in root Zn accumulation with increasing P application, while RDW, RZnC, and AM colonization explained 53% (adjusted R2 value) of the decrease in total Zn accumulation. Especially in Zn-deficient soil, root Zn accumulation explains much of the negative interaction between P and Zn, and root Zn accumulation is greatly affected by AM colonization.

Combined Zinc and Nitrogen Fertilization in Different Bread Wheat Genotypes Grown under Mediterranean Conditions

The combined application of nitrogen (N) and zinc (Zn) appears to be a promising agronomic strategy for the biofortification with Zn. To evaluate such efficiency, a field experiment was conducted in south-eastern Portugal under Zn-deficient soil. Four advanced breeding lines and two commercial varieties of bread wheat (Triticum aestivum L.) were fertilized with five treatments: i) control, ii) two foliar Zn applications, iii) one foliar Zn+N application, iv) soil and two foliar Zn applications, and v) soil and one foliar Zn+N application. Grain Zn content varied greatly across treatments and INIAV-1 and the commercial varieties were the most interesting cultivars in all the treatments. Grain Zn concentrations higher than the target level of 38 mg Zn kg−1 were obtained only when two foliar Zn applications were applied, alone or in combination with soil Zn applications, and grain Zn bioavailability also was more adequate (phytate:Zn ratios similar to 15). Soil Zn application resulted in grain yield increases between 7–10%, which virtually offset the extra application cost. The combined soil and two foliar treatment could be a good option for biofortifying bread wheat under Zn-deficient soils.

Effects of synthetic Zn chelates on flax response and soil Zn status

Throughout the world, flax (Linum usitatissimum L.) is often grown in Zn-deficient soils, but appropriate fertilizer management can optimize both crop yield and micronutrient content. A greenhouse experiment was conducted on Typic Haploxeralf (pH 6.1) and Typic Calcixerept (pH 8.1) soils to study the relative efficiency of chelated Zn using two application rates of three different Zn sources [Zn-EDDHSA, ethylenediamine-di-(2-hydroxy-5-sulfophenylacetate of Zn); Zn-HEDTA, N-2-hydroxyethyl-ethylenediaminetriacetate of Zn; and Zn-EDTA, ethylenediaminetetraacetate of Zn]. Dry matter /DM) yield, Zn concentration, chlorophyll content, crude fiber and tensile properties were monitored and the soil-Zn status (available-Zn, Zn-fractions and total-Zn) was assessed. Zinc chelate applications increased the most labile forms of Zn in soils and Zn concentrations in plants. The low rate of Zn generally had a beneficial effect on DM yield and tensile properties. The exception was Zn-EDTA in the weakly acidic soil, where the highest Zn concentrations were observed in leaves and whole shoots; this coincided with the largest concentrations of labile Zn in soil. The most efficient fertilizers were Zn-EDDHSA (in both soils) and Zn-EDTA (in the calcareous soil). The relatively large amounts of labile and available Zn present in both of the soils fertilized with Zn-EDTA points to the applying this chelate at lower rate than 5 mg Zn/kg; this should, in turn, reduce the cost of Zn fertilization and minimize environmental pollution risk.

Natural Genetic Variation of Seed Micronutrients of Arabidopsis thaliana Grown in Zinc-Deficient and Zinc-Amended Soil.

The quality of edible seeds for human and animal nutrition is crucially dependent on high zinc (Zn) and iron (Fe) seed concentrations. The micronutrient bioavailability is strongly reduced by seed phytate that forms complexes with seed cations. Superior genotypes with increased seed Zn concentrations had been identified, but low micronutrient seed levels often prevail when the plants are grown in Zn-deficient soils, which are globally widespread and correlate with human Zn-deficiency. Here, seed Zn concentrations of Arabidopsis accessions grown in Zn-deficient and Zn-amended conditions were measured together with seed Fe and manganese (Mn), in a panel of 108 accessions. By applying genome-wide association, de novo candidate genes potentially involved in the seed micronutrient accumulation were identified. However, a candidate inositol 1,3,4-trisphosphate 5/6-kinase 3 gene (ITPK3), located close to a significant nucleotide polymorphism associated with relative Zn seed concentrations, was dispensable for seed micronutrients accumulation in Col-0. Loss of this gene in itpk3-1 did neither affect phytate seed levels, nor seed Zn, Fe, and Mn. It is concluded that large natural variance of micronutrient seed levels is identified in the population and several accessions maintain high seed Zn despite growth in Zn-deficient conditions.

Valuing increased zinc (Zn) fertiliser-use in Pakistan

Background and aimsUse of zinc (Zn) fertilisers may be cost-effective in increasing crop yields and in alleviating dietary Zn deficiency. However, Zn fertilisers are underutilised in many countries despite the widespread occurrence of Zn-deficient soils. Here, increased Zn fertiliser-use scenarios were simulated for wheat production in Punjab and Sindh Provinces, Pakistan. Inputs and outputs were valued in terms of both potential yield gains as well as health gains in the population.MethodsThe current dietary Zn deficiency risk of 23.9 % in Pakistan was based on food supply and wheat grain surveys. “Disability-adjusted life years (DALYs) lost” are a common metric of disease burden; an estimated 245,000 DALYs y−1 are lost in Punjab and Sindh due to Zn deficiency. Baseline Zn fertiliser-use of 7.3 kt y−1 ZnSO4.H2O was obtained from published and industry sources. The wheat area currently receiving Zn fertilisers, and grain yield responses of 8 and 14 % in Punjab and Sindh, respectively, were based on a recent survey of >2500 farmers. Increased grain Zn concentrations under Zn fertilisation were estimated from literature data and converted to improved Zn intake in humans and ultimately a reduction in DALYs lost.ResultsApplication of Zn fertilisers to the area currently under wheat production in Punjab and Sindh, at current soil: foliar usage ratios, could increase dietary Zn supply from ~12.6 to 14.6 mg capita−1 d−1, and almost halve the prevalence of Zn deficiency, assuming no other changes to food consumption. Gross wheat yield could increase by 2.0 and 0.6 Mt. grain y−1 in Punjab and Sindh, respectively, representing an additional return of US$ >800 M and an annual increased grain supply of 19 kg capita−1.ConclusionsThere are potential market- and subsidy-based incentives to increase Zn fertiliser-use in Pakistan. Benefit-Cost Ratios (BCRs) for yield alone are 13.3 and 17.5 for Punjab and Sindh, respectively. If each DALY is monetised at one to three fold Gross National Income per capita on purchasing power parity (GNIPPP), full adoption of Zn fertiliser for wheat provides an additional annual return of 405–1216 M International Dollars (I$) in Punjab alone, at a cost per DALY saved of I$ 461–619.

Impact of foliar zinc application on agronomic traits and grain quality parameters of wheat grown in zinc deficient soil

Zinc (Zn) is an important micronutrient for the growth and development of plant and humans, and dietary Zn shortage is a global wide nutritional problem. A field experiment was conducted to investigate the effects of foliar Zn application at different growth stages on grain yield, grain mineral nutrients and its relation to phytic acid content in spring wheat grown on Zn-deficient soil during the 2013–2014 growing season at Maragheh University research field, Iran. Results showed that foliar spray of zinc sulfate at different growth stages, in general, had non-significant effect on thousand grain weight and harvest index, while considerably increased grain yield, number of grains per spike, fertile spikelet per spike and plant height. Zinc and ascorbic acid contents in the grain consistently increased with the timing of the foliar Zn application and were highest at early grain filling stage. However, the timing of the Zn application had no effect on copper and phytic acid contents, but changed grain iron and manganese concentrations, and decreased phytate to Zn molar ratio of wheat grains. Results indicated that foliar Zn application at the booting + milking stages significantly increased agronomic traits, grain Zn content and bioavailability in wheat grown on Zn deficient alkaline soils, thereby improving the wheat grain’s nutritional quality for humans.

Influence of foliage-sprayed zinc sulfate on grape quality and wine aroma characteristics of Merlot

Three concentrations of zinc sulfate were foliage-sprayed in Vitis vinifera cv. Merlot growing on Zn-deficient soils over successive years, 2013 and 2014, to investigate the effect on grape quality and wine aroma characteristics. Headspace solid-phase microextraction with gas chromatography–mass spectrometry (HS-SPME-GC/MS) was used for qualitative and quantitative analysis of aroma compounds. Zinc sulfate treatments significantly increased the concentrations of total soluble solids, total phenols, flavonoids, flavanols, tannins and anthocyanins in matured berry. A total of 53 compounds were identified and quantified from all the eight wines of the 2 years. Zinc sulfate treatments increased the variety of volatile compounds in wines, especially in the aged wines of 2013. Besides, total concentration of the volatile compounds was also enhanced by treatment of 4.0 g/L ZnSO4·7H2O in both years. Principal component analysis indicated that 1-nonanol, 1-butanol-3-methyl acetate, ethyl hexanoate, ethyl phenylacetate, ethyl benzoate, ethyl palmitate, p-hydroxyl ethyl cinnamate and β-damascenone were the eight most characteristic components of Zn-treated wines in both 2013 and 2014. Among those, β-damascenone and ethyl hexanoate were also two of the most odor-active compounds. Moreover, among the nine described aroma categories in the sensory analysis, intensities of fruity, vegetative, spicy, nuts and toasty were influenced by Zn treatment.

Effects of increasing rates of zinc fertilization on phytic acid and phytic acid/zinc molar ratio in zinc bio-fortified wheat

A two-year field trial was conducted to investigate the effect of increasing rates of zinc (Zn) fertilization on Zn accumulation and phytic acid contents in winter wheat (Triticum aestivum L. cv. Yang Mai 16) grown on location without soil Zn deficiency. The rates of ZnSO4·7H2O were as follows: 0 (control), 300, 600, 900, 1200, and 1500kg/ha, and Zn was added as base fertilizer. The Zn concentrations in different wheat organs were significantly improved and exhibited positive correlations with the Zn fertilizer rates. Phytic acid (PA) concentrations in wheat grains were significantly decreased, and the PA/Zn molar ratio dropped below 15 after Zn application. After harvest, the residual Zn concentrations in the soil were still at high levels with 272.9mg/kg. According to our results, very high application rates of soil zinc fertilizers (such as 300kg/ha ZnSO4·7H2O) would be effective for the implementation of Zn biofortification strategy to mitigate Zn malnutrition in human health.

English

Fields experiment was done to investigate the effect of a typical water saving irrigation technique, namely non-flooding controlled irrigation (NFI), on the extractability, solubility, and bioavailability of zinc (Zn) in a non-polluted paddy soil. The Zn contents in the soil solutions, soil extractions by modified BCR (European Community Bureau of Reference) sequential extraction procedure, and the plant digestions were measured. Compared with the Zn in flooding irrigation (FI) soil, Zn contents in extractable (EXT) form and Zn contents in soil solutions was increased in 0–20 cm NFI soil, accompanied with a little reduction of soil Zn in oxidizable (OXD) form. That confirmed the Zn in OXD form was released into soil solution under the wetting-drying cycle condition in NFI fields, and hence resulted in high extractability and solubility of Zn in top surface soil. As a result, Zn contents in the rice plant parts in NFI fields were higher than in FI fields. It can be concluded that NFI irrigation is help to enhance soil Zn bioavailability and food Zn nutrients status in the soil without Zn-pollution and Zn deficiency, but might led to soil Zn depletion in Zn deficient soil or rice foodstuffs pollution in Zn-polluted soil. © 2015 Friends Science Publishers

Effect of Sources, Methods and Time of Application of Zinc on Productivity, Zinc Uptake and Use Efficiency of Oats (Avena Sativa L.) Under Zinc Defficient Condition

A field experiment conducted at the Indian Agricultural Research Institute, New Delhi, India showed that oats (Avena sativa L.) responded (grain yield increase) to zinc (Zn) fertilizer and coating of oat seeds with Zn sulfate or Zn oxide is the best practice. Zinc fertilizer applied to soil, deep placement (5 cm below the seed placement) was superior for growth and yield than soil surface (broadcast) application. Delaying Zn application to 25 days after sowing (first irrigation) was inferior to Zn application at sowing. Partial factor productivity (PFP) of applied Zn varied from 700–2,024 kg grain kg Zn−1, agronomic efficiency (AE) varied from 62–428 kg grain increase kg−1 Zn (applied) and physiological efficiency (PE) of Zn varied from 1,822–3,221 kg grain kg−1 Zn (absorbed). The crop recovery efficiency (CRE) varied from 3.1–17.7%. Thus, adequate Zn fertilizer of oats can lead to higher grain yield and higher Zn concentration in grain (improved quality for human nutrition) under Zn deficient soil.

Zinc fractionation of tropical paddy soils and their relationships with selected soil properties

Knowledge of zinc (Zn) distribution among various fractions will help to predict the potential of the soil to supply sufficient Zn for crop production. The present study was done to investigate Zn fractions, Zn availability factor (AF) and their relationship with soil properties of Zn-deficient tropical paddy soils. The samples of two soil orders (six soil series) were sequentially extracted with chemical extractants in two different growth stages of rice (maximum tillering and flowering stages). The proportion of Zn fractions extracted at the maximum tillering stage followed the order, water soluble plus exchangeable (WE) < crystalline sesquioxide (Cry) < manganese oxide (MN) < organically bound (Org) < amorphous sesquioxide (Amor) < residual Zn (Res), whereas the order at the flowering stage was as follows: WE < Mn < Cry < Org < Amor < Res. Cation exchange capacity (CEC), clay content and organic carbon (OC) were the most important factors controlling the distribution of Zn in soils. The AF was low in Tok Young (1.79%), high in Telemong (17%) and medium in the rest of soil series (around 8%). A stepwise multiple linear regression and principal component analyses showed that OC, clay content and CEC were the main variables that explained the predictability of Zn fractions. The result of the length of submerging showed that the WE, Org and Cry concentrations decreased, while Amor, MN, and the sum of all Zn fractions increased with increase in the flooding period. The extractability and solid-phase fractionation of Zn in two different times of soil sampling showed the importance of timing of Zn fertilizer application and flooding or pre-flooding in Zn availability.

Yield and Zinc, Copper, Manganese and Iron Concentration in Maize (Zea mays L.) Grown on Vertisol as Influenced by Zinc Application from Various Zinc Fertilizers

Zinc (Zn) deficiency in soils and field crops is widespread across the world, including India, resulting in severe reduction in yield. Hence, soil application of Zn fertilizers is recommended for ameliorating Zn deficiency in soil and for obtaining higher crop yield and better crop quality. Zinc sulfate is commonly used Zn fertilizer in India because of its solubility and less cost. However, good quality and adequate quantity of zinc sulfate is not available in the market round the year for farmers' use. Field experiments were therefore conducted during rainy season of 2010 and 2011 at research farm of Indian Institute of Soil Science, Bhopal, India to assess the influence of Zn application through zinc sulfate monohydrate (33% Zn), zinc polyphosphate (21% Zn) and Zn ethylenediaminetetraacetate (EDTA) (12% Zn) on yield and micronutrient concentration and uptake by maize (Zea mays L.). In both the years, grain and vegetative tissue (stover) yield of maize increased significantly with successive application of Zn up to 1 kg ha−1 added through zinc sulfate monohydrate and zinc polyphosphate. Addition of 2.5 kg Zn ha−1 did not increase yield further but resulted in highest stover Zn concentration. Zinc, copper (Cu), manganese (Mn), and iron (Fe) concentration in maize grain varied from 22.2 to 27.6, 1.6 to 2.5, 3.5 to 4.7 and 19.9 to 24.5 mg kg−1 respectively in both the years. Maize stover had 25.9 to 36.2, 7.9 to 9.8, 36.7 to 44.9 and 174 to 212 mg kg−1 Zn, Cu, Mn, and Fe, respectively. Zinc application did not influence Cu, Mn and Fe concentration in both grain and stover of maize. Transfer coefficients (TCs) of micronutrients varied from 0.72 to 0.95, 0.18 to 0.30, 0.08 to 0.13 and 0.10 to 0.15 for Zn, Cu, Mn, and Fe respectively. Total Zn uptake significantly increased with Zn application from 0.5 to 2.5 kg ha−1 supplied through zinc sulfate monohydrate and zinc polyphosphate. Recovery efficiency of Zn declined with increased Zn rates.

Promoting effect of foliage sprayed zinc sulfate on accumulation of sugar and phenolics in berries of Vitis vinifera cv. Merlot growing on zinc deficient soil.

The effect of foliage sprayed zinc sulfate on berry development of Vitis vinifera cv. Merlot growing on arid zone Zn-deficient soils was investigated over two consecutive seasons, 2013 and 2014. Initial zinc concentration in soil and vines, photosynthesis at three berry developmental stages, berry weight, content of total soluble solids, titratable acidity, phenolics and expression of phenolics biosynthetic pathway genes throughout the stages were measured. Foliage sprayed zinc sulfate showed promoting effects on photosynthesis and berry development of vines and the promotion mainly occurred from veraison to maturation. Zn treatments enhanced the accumulation of total soluble solids, total phenols, flavonoids, flavanols, tannins and anthocyanins in berry skin, decreasing the concentration of titratable acidity. Furthermore, foliage sprayed zinc sulfate could significantly influence the expression of phenolics biosynthetic pathway genes throughout berry development, and the results of expression analysis supported the promotion of Zn treatments on phenolics accumulation. This research is the first comprehensive and detailed study about the effect of foliage sprayed Zn fertilizer on grape berry development, phenolics accumulation and gene expression in berry skin, providing a basis for improving the quality of grape and wine in Zn-deficient areas.

How important is the mycorrhizal pathway for plant Zn uptake?

Formation of arbuscular mycorrhizas can enhance plant uptake of immobile nutrients such as zinc (Zn) and phosphorus (P). Enhancement of Zn uptake by arbuscular mycorrhizal (AM) fungi on Zn-deficient soils has been studied previously, however, the quantity of Zn that is contributed by the AM pathway of uptake to the plant has not previously been reported for soil of any Zn status. We grew a mycorrhiza-defective mutant tomato (Solanum lycopersicum L.) genotype (rmc) and its mycorrhizal wild-type progenitor (76R) in pots containing a hyphal compartment (HC) accessible only by the external hyphae of AM fungi, and containing the radioisotope 65Zn. This was repeated at three soil Zn concentrations, ranging from low to high. We estimated the amount of Zn delivered via both the AM and direct (root) pathways. Up to 24 % of Zn in the shoots of the AM plants was delivered via the AM pathway at the lowest soil Zn treatment. This decreased significantly, to 8 %, as soil Zn concentration increased. No 65Zn was detected in the tissues of the non-mycorrhizal genotype. The relative contribution to shoot Zn by the AM pathway of uptake was highest when soil Zn was low, and decreased with increasing soil Zn concentration.

Relative Efficiency of Zinc-Coated Urea and Soil and Foliar Application of Zinc Sulphate on Yield, Nitrogen, Phosphorus, Potassium, Zinc and Iron Biofortification in Grains and Uptake by Basmati Rice (Oryza sativa L.)

Two on-farm trials conducted one each in Aligarh and Meerut districts of the state of Uttar Pradesh, India on zinc (Zn) deficient soils during the rainy season (July-October) showed that Zn application increased not only Zn concentration and uptake by rice but also increased protein content of rice kernels and concentrations of Fe, N, P and K due to the overall improvement in crop growth. Foliar application of Zn was better from the viewpoint of Zn biofortification of rice kernels; nevertheless much of the foliar applied Zn was retained in husk. Since, foliar application of Zn is made at a late stage of crop growth, hence it was not as effective as soil application in increasing yield attributes, yield and concentration and uptake of Fe, N, P and K in rice. This study brought out that adequate soil application of Zn sulphate followed by its foliar application is the best approach. Zn coated urea applying less than half the amount of Zn as applied through soil + foliar application was very close to it and is quite promising.

Germination-enhancing and zinc-sparing roles for selenium in broccoli

Large areas of China have soils low in both available selenium (Se) and zinc (Zn). In order to investigate whether Se supplied as either selenate or selenite can increase germination and growth compared with low-Se controls we used broccoli, an important vegetable with anticancer effects, especially when biofortified with Se. Broccoli was grown under both Zn adequacy and Zn deficiency to determine whether interactions between these minerals affect plant growth. Selenite and selenate at a wide range of doses increased the speed and extent of germination. Both inorganic Se forms increased early root and shoot growth at low concentrations, with selenite having a stronger effect than selenate. A sand culture trial showed a similar growth increase due to low-dose Se under Zn deficiency but not under Zn adequacy. Conversely, at high Se levels, the results provided evidence from biomass, water use, photosynthesis and gas exchange that broccoli growth was inhibited at high Se levels, with selenite being more toxic than selenate. In this broccoli trial, the two Se forms were equally effective in increasing leaf Se concentration, whereas in most plants selenite is largely converted to organic Se forms and stored in the roots. This study suggests that Se, supplied either as selenate or selenite, may improve germination and growth in broccoli, especially on Zn-deficient soils. Field trials conducted on soils which are very low in both plant-available Se and Zn are needed.