Micronutrient Knowledge Base

Soybean is one of the most susceptible field crops to iron chlorosis(yellowing), and this problem is not uncommon in Kansas. Iron is a catalyst in the production of chlorophyll, so a deficiency of iron (Fe)displays as a yellowish or pale color in the leaves. Iron is an immobile nutrient in the plant so symptoms first appear on the youngest leaves. Iron chlorosis is usually caused by a combination of stresses rather than a simple deficiency of available soil Fe. Some of the soil chemical factors that play a role in Fe chlorosis include high pH, high carbonate levels, high salinity (EC), low available iron (DTPA-Fe), and high soil nitrate levels. Other factors that play a role include variety susceptibility and the presence of soybean cyst nematodes and root rotting fungi. Given all these factors, Fe chlorosis is a complex problem and not one that can be determined solely on the basis of a soil Fe test. One of the factors that can be involved in the development of Fe chlorosis in soybeans is high levels of soil nitrate. Iron is taken up in the ferric form (Fe), then is immediately converted within the plant into the ferrous form (Fe) (existing in the chlorophyll). High concentrations of nitrate-N seem to inhibit this conversion of Fe to Fe in the plant, contributing to Fe deficiencies. It is important remember that high soil nitrate levels alone will not cause iron chlorosis in soybeans, but is simply one additional factor that will magnify the problem.

Crop yield response to secondary nutrient sulfur (S) and micronutrient zinc (Zn) has been extensively studied, yet inconsistent results and a lack of context-specific guidelines limit widespread adoption. We conducted a meta-analysis of 152 data points from 27 studies to quantify the impact of S and Zn separately and in combination on maize, rice, and wheat grain yields. Using standard mean difference (SMD) as the effect size metric, S and Zn application significantly improved yields across all crops (SMD = 1.043, 95% confidence interval: 0.891–1.194, p < 0.001), with no significant differences among species. The greatest yield gain was observed under S + Zn (SMD = 1.797), especially without nitrogen (SMD = 2.115), while co-application with N had no significant effect (SMD = 0.614). Yield was 8.55% higher with single-dose versus split application, though not statistically significant. Early and mid-season application (SMD = 1.245) outperformed three-stage application (SMD = 0.465). Zinc sulfate (SMD = 1.036) and ammonium sulfate (SMD = 2.173) were the most effective Zn and S sources, respectively. Yield responses were stronger on medium- and coarse-textured soils and under hot climates. While the highest yield gain was generally observed under S + Zn application without nitrogen, this outcome may reflect specific experimental conditions rather than a universally optimal strategy. These results identify global trends in yield responses to S and Zn and underscore the importance of soil, climate, nutrient combinations, and timing. However, because most studies were conducted under nutrient deficient conditions, yield gains under more fertile or less responsive conditions could be overestimated. Keywords Micronutrients ・ Secondary nutrients ・ Cereal yield ・ Soil types ・ Climatic conditions ・ Crop species

Background: Boron (B) is an essential micronutrient for plants. Dicot plants respond to insufficient B supply by altering root architecture and root hair growth. How root systems of rather low-B demanding monocot species such as maize (Zea mays L.) respond to B deficiency in terra has not been experimentally resolved, yet. Aims: The study aims to investigate root responses and their physiological consequences under B deficiency during the vegetative growth of maize. Methods: B73 wild-type (WT) maize and its root hairless rth3 mutant were grown under varying B supply conditions in soil columns and in an automated root phenotyping facility. Biomass data, root system architecture traits, the mineral elemental composition and molecular B-deficiency responses were quantified. Results: Though having very low leaf B concentrations, no major growth deficit, apart from chlorotic stripes on leaves, was recorded on maize root and shoot development, with or without root hairs, on B-deficient conditions. Although leaf B concentration of the rth3 mutant is significantly lower under B-deficient and under B-surplus conditions compared to the WT, the rth3 mutant neither developed a larger total root length, more fine roots nor displayed a higher expression of B uptake transporters as compensatory adaptations. Conclusions: Strikingly, maize plants did neither react with an inhibited root growth nor by a compensatory root foraging behaviour to severe B-deficient in terra growth conditions. This is rather atypical for plants. The performance and altered leaf B concentrations of rth3 mutants may be biased by secondary effects, such as an overall reduced root growth. KEYWORDS boron deficiency, nutrient, phenotyping, root hairs, root, transport

Advances in plant nutrition can be achieved by improving the delivery of micronutrients to the plants. The objective of this research was to compare the efficiency of uptake of different sources of zinc, copper and manganese (sulfates, Ethylenediaminetetraacetic acid (EDTA) and oxides) and boron (boric anhydride and colemanite). We conducted all experiments in maize, repeated the experiment twice, using five replicates per treatment, and used two different media. Results showed that for cations, the soluble sources of micronutrients (sulfate and EDTA) in both media were more efficiently taken up. One-way ANOVA with post hoc Tukey for multiple comparisons of means (95% confidence level) was used for all statistical analyses. Sulfate sources were significantly different when compared to the negative control and to the oxide sources. EDTA sources were significantly different when compared to the negative control and to the oxide sources. Oxide sources were not significantly different from the negative control. For boron, we found a similar trend, with boric anhydride being significantly different when compared to the negative control and to colemanite. Colemanite was significantly different when compared to the negative control. This study generated important information about uptake of soluble and insoluble sources of four micronutrients that can be used for the development of new formulations. Keywords: zinc; copper; manganese; boron; sulfates; EDTA; oxides; boric anhydride; colemanite; nutrient uptake

This study investigated the agro-environmental effects of ZnO nanoparticles on soybean production. The research examined the impact of different ZnO nanoparticle concentrations applied via foliar spray on soybean growth, yield, and physiological characteristics under field conditions in comparison to conventional zinc fertilizer sources.