Ontario Corn and Soybean Micronutrients Knowledge Hub

This University of Minnesota Extension blog post (Dan Kaiser, 2020) examines whether boron (B) deficiency is a problem for Minnesota crops, including corn and soybean. Boron is needed in small quantities and, since deficiencies are not widespread across the Corn Belt, data establishing reliable tissue sufficiency thresholds is lacking, making recommendations difficult to generate without an actual deficiency to calibrate against. For corn specifically, a three-year AFREC-funded study (ending 2018) across nine irrigated and nine non-irrigated Minnesota locations broadcast boron at 3 lb/acre. Average corn grain yield was the same with or without boron at all locations. Leaf boron concentrations as low as 4 ppm at the V10 growth stage showed no yield increase, so the study could not establish a lower sufficiency threshold for tissue B in corn; the need for boron fertilization in corn was concluded to be less widespread than recent reports suggested. For soybean and dry bean, these crops are highly sensitive to boron toxicity, so boron fertilizer application should generally be avoided. Multiple Minnesota soybean research trials found yield was not increased at most sites, and was actually decreased at a few sites. Boron toxicity symptoms have also been observed in dry bean following foliar boron application. Reports of low soybean/dry bean tissue boron from sandy soils have occurred, but there is insufficient evidence to support boron application, and tissue tests are not considered a reliable indicator of true B deficiency in these crops. Overall recommendation: outside of sandy soils, boron deficiency is unlikely in Minnesota field crops, and growers should be cautious applying boron given toxicity risk, particularly for soybean and dry bean, where excess boron can reduce yield.

This Iowa State article addresses in-season (post-emergence) fertilization of soybean, primarily discussing phosphorus and potassium; explicit micronutrient content is limited to one set of field trials. About 100 replicated Iowa trials (1994-early 2000s) tested foliar sprays of low-salt fluid fertilizers (3-18-18 and 10-10-10 N-P2O5-K2O, with or without sulfur) applied with or without the micronutrients boron (B), iron (Fe), and zinc (Zn), at rates of 2-6 gal/acre from V5 to R3, sometimes tank-mixed with glyphosate. Foliar fertilization increased yield in only about 15 percent of fields on average (range 15-30 percent depending on trial set/year), with the best treatment averaging just 0.7 bu/acre gain across all fields. Critically, adding sulfur or micronutrients (B, Fe, Zn) to the fertilizer mix did not produce higher yields than the base fertilizer alone. Responses were more likely under conditions restricting early root growth or nutrient uptake (ridge-till/no-till, cool wet soils), not from micronutrient deficiency per se. A related five-trial (2005-2006) study of foliar fertilizer plus fungicide found no consistent yield benefit from the fertilizer component (fungicide alone drove the yield gains observed). Recommendation: in-season fertilization of soybean, including micronutrient-containing foliar blends, is seldom cost-effective in Iowa; economic response is unlikely unless deficiency symptoms are visually confirmed alongside a deficient soil test, or unless soil/climatic factors (other than drought) are clearly limiting nutrient uptake early in the season. The article does not identify B, Fe, or Zn deficiency as a driver of soybean response in these trials; their inclusion in blends showed no advantage over N-P-K-only mixtures.

Within the last decade, studies involving numerous crops provide strong evidence that seed Fe concentration ([Fe]) is useful for identifying genotypes possessing superior resistance to Fe deficiency. It is our opinion that using seed [Fe] is equivalent or superior to using visual chlorosis score as a measure of Fe efficiency, that seed [Fe] can be used to identify resistance to Fe deficiency in the absence of Fe deficiency or in the presence of Fe deficiency exacerbated by applying high rates of fertilizer N, that conventional plant breeding can be used to increase seed [Fe] as a strategy for improving resistance to Fe deficiency, and that planting seed [Fe] can be used as a predictor of successful (nonchlorotic) seedling establishment. International agricultural agencies, such as HarvestPlus (CIAT, Cali, Columbia), have promoted using plant breeding as an intervention strategy focused on increasing micronutrient concentrations and bioavailabilities in crops consumed by populations with known micronutrient deficiencies. Can conventional plant breeding be used to increase seed [Fe] as a strategy to reduce Fe deficiency in soybean [Glycine max (L.) Merr.] Evidence presented in this paper combined with earlier reports indicates that Fe-efficient and Fe-inefficient varieties appear to have seed [Fe] maxima that are distinctly different and seldom exceeded; that is, soybean plants tend to maintain [Fe] in the grain within predetermined, genetically controlled limits. Seed [Fe] can be regarded as an integrated measure of resistance to Fe deficiency that is manifest at maturity and that involves the coordinate expression of several genes regulating Fe reduction and uptake, transport, and storage.

Many of today's innovative materials used to carry trace elements (TEs) are derived from chelates. Most of the materials used for this purpose have been produced on the basis of EDTA, which is not considered to be environmentally friendly due to its high persistence. Research is therefore being carried out to produce materials that do not pose an environmental risk. Therefore, a study was carried out to determine the effects of newly developed innovative materials with embedded biodegradable and environmentally safe chelates (IDHA-iminodisuccinic acid-and N-butyl-D-gluconamide ligands) containing copper, molybdenum and iron on the yield, biometric characteristics and chemical composition of soybean and selected soil properties. It is difficult to find publications on their effects in soybean cultivation. The greatest increase in soybean leaf greenness index (SPAD) was found after the addition of pure Salmagsup® (Sal.sup®). The effect of the chelates on the SPAD index was lower, with Sal.sup® + Fe chelate having the greatest effect during the vegetative development stage and Cu chelate having the greatest effect during the flowering stage. Sal.sup® + Cu, especially with Fe, accelerated pod and seed ripening in the last vegetative stage of soybean. Sal.sup® + Cu had the most favourable impact on plant height, pure Sal.sup® on the pod number per plant, Sal.sup® + Fe on the seed number per pod, Sal.sup® with Mo and Fe chelates on soybean seed yield, and pure Sal.sup® on fresh weight remaining above-ground part yield, while pure Sal.sup® and Sal.sup® + Fe had the most favourable impact on dry weight aerial yield. The fertiliser materials (especially Sal.sup® + Cu) generally increased the N content of the tested soybean organs and the Cu content of the other above-ground soybean parts (especially those containing chelates) and had an antagonistic effect on the Mg content of the soybean above-ground parts. Sal.sup® + Cu also had a negative effect on the Fe content of other above-ground soybean parts. Sal.sup® + Fe had a positive impact on the iron content, and Sal.sup® + Mo had a positive impact on the molybdenum content of soybean. The applied fertilisers had little effect on the contents of Cu, Mo and Fe in the soil. There was only a significant increase in the Cu content of the soil after the addition of Sal.sup® + Cu and a significantly smaller increase under the influence of Sal.sup® without chelates, as well as an increase in the Mo content of the soil with Sal.sup®. The present study confirms the beneficial impact of the novel materials with chelates. It has been demonstrated that the presence of materials containing Mo and, in particular, Cu has a considerable effect on the yield and quality characteristics of soybeans.

The aim of the study was to determine the influence of the soil type and differential sulphur rates used with or without Basfoliar 36 Extra on the soil pH as well as the amount of available forms of copper, zinc and manganese based on the micro plots field experiment. Moreover, the relationship between the studied microelements was examined. The experiment was performed in two-factor design; the first-order factor was the soil type (Typic Hapludolls, Typic Hapludalfs, Typic Haplorthods, Typic Endoaquolls), while the second-order factor - fertilization with sulphur and compound fertilizer - Basfoliar 36 Extra. The plant tested was Rota cultivar maize. The use of sulphur and sulphur combined with Basfoliar 36 Extra changed the classification of the soils in terms of their pH. In the soils under study, as a result of the 10-years application of sulphur and/or foliar fertiliser with NPK fertilization as well as growing maize in monoculture showing a high uptake of macro-and micro-nutrients, there was reported a clear decrease in the content of zinc, copper and manganese, as compared with the initial content. With that in mind, one shall assume that growing maize in a 10-year monoculture is connected with an intensive use of soils, which can result in a clear deficit of the elements studied in soil.

Strip intercropping is the practice of growing two or more species of plants in strips wide enough for independent mechanical cultivation, yet narrow enough to allow interaction between the species. This can affect not only crop yield but also competition in the uptake of nutrients and thus the chemical composition of the plants. The aim of this study was to assess the impact of strip intercropping and three methods of weed control on the content of zinc and copper in maize and on uptake of these components by maize. The study was conducted in 2004-2006 on a private farm located in the village of Frankamionka in the administrative district (powiat) of Zamosc. It was based on a field experiment conducted on clayey silt soil with grain-size distribution of clay and a moderate Zn and Cu content. The experiment design was a split-plot randomized complete block in four replications. The factors taken into account were two methods of cultivation: sole cropping and strip cropping (common bean, dent maize, and spring wheat in adjacent strips) and three methods of weed control: mechanical - weeding of interrows twice; mechanical-chemical the herbicide Gesaprim 90 WG 1.5 kg ha(-1) + weeding of interrows once; and chemical the herbicides Gesaprim 90 WG 1.5 kg ha(-1) + Milagro 040 SC 1.5 L ha(-1). Fodder maize was grown for silage and harvested during milky-wax maturity. The content of copper and zinc in the dry matter of maize was determined by atomic absorption spectrophotometry (AAS) after digestion in HNO3 (extra pure) in accordance with PN-EN ISO 6869:2002. On average for the experiment, strip cropping of maize with common bean and spring wheat reduced zinc content in maize, but in successive years of the study, the impact of the cultivation methods was varied. Strip cropping significantly increased the copper content in the plants in comparison with sole cropping. Zn and Cu content varied depending on the location of a row in strip cropping. Location adjacent to a strip of beans was more favourable to zinc accumulation in the biomass of maize, while copper content was the highest in maize plants from rows adjacent to wheat, and lowest when grown next to a bean strip. Strip cropping significantly decreased zinc uptake by maize, but the influence of cropping methods on copper uptake was not significant. The uptake of zinc and copper was the highest when the chemical weed control method was used, and resulted mainly from the high biomass of maize. The results confirm the impact of strip cropping on competition. in the uptake of nutrients and on their content and total uptake.

Legumes, due to their symbiosis with papillary bacteria, can receive nitrogen from the air. The remaining nutrients must be supplied in fertilisers, either soil or foliar. In the pot experiment, we recorded the responses of two soybean cultivars (Annushka, Pompei) to the foliar application of micronutrients (control, Zn, Fe, Cu, Mn, B, or Mo). The physiological properties were expressed as net photosynthetic rate (PN), intercellular CO2 concentration (Ci), transpiration rate (E), stomatal conductance (gs), maximum quantum yield of photosystem II (Fv/Fm), maximum quantum yield of primary photochemistry (Fv/F0), photosynthetic performance index (PI), and the development of soil plant analyses (SPAD), which were analysed. The effects of individual micronutrients on nodulation, plant growth, and condition were also investigated. Micronutrient fertilisation had a positive effect on plant fresh weight and no negative effect on plant condition. It was shown that elements such as B, Fe, and Mo had the most beneficial effect on nodulation compared to the control, regardless of the cultivar analysed. The application of single-component foliar fertilisers improved the physiological parameters of the plants. The relative chlorophyll content was most favourably affected by the application of Mn, B, and Mo in the Annushka cultivar, and Fe, Mn, and Mo in the Pompei cultivar. Similarly, in the case of chlorophyll fluorescence, the most stimulating effect was found for Mn and B, regardless of the cultivar. In the case of gas exchange, the application of Fe, Mo, and B for the Annushka cultivar and Cu for the Pompei cultivar had the most favourable effect on physiological measurements. The results obtained indicate that the foliar application of the evaluated micronutrients is justified in soybean cultivation and does not disturb the nodulation process.

Strip cropping is a form of intercropping in which two or more species of plants are grown in adjacent strips. Strips should be wide enough for independent mechanical cultivation, but sufficiently narrow to allow for interaction between species. This may affect not only the size and structure of yield, but also the chemical composition of the plants. The aim of this study was to assess the impact of strip cropping and different weed control methods on the content of iron and manganese and uptake by dent maize. The study was conducted on a private farm in the village of Frankamionka in the district of Zamosc. It was run from 2004 to 2006. It consisted of a field experiment established on soil with an average Fe and Mn content. The experimental factors were two methods of cultivation: sole cropping and strip cropping (common bean, dent maize, and spring wheat in adjacent strips), and three methods of weed control: mechanical (inter-row cultivation applied twice), mechanical-chemical (the herbicide Gesaprim 90 WG 1.5 kg ha(-1) + single inter-row cultivation), and chemical (the herbicides Gesaprim 90 WG 1.5 kg ha(-1) + Milagro 040 SC 1.5 L ha(-1)). Maize was grown for silage and harvested at the milky-wax stage. Iron and manganese in the dry matter of maize were determined by atomic absorption spectrometry (AAS) after digestion in HNO3 (extra pure) in accordance with PN EN ISO 6869:2002. On average for the experiment, strip cropping of maize with common beans and spring wheat increased the iron and manganese content in maize crop in comparison with sole cropping. The Fe and Mn content varied depending on the position of a row in strip cropping. Location adjacent to beans was more conducive to iron accumulation in maize, but reduced the manganese content. Strip cropping significantly increased the uptake of both iron and manganese by maize. The iron content was the highest where mechanical weed control was applied, while manganese was the highest where herbicides alone were used. The uptake of iron and manganese was the highest under the chemical weed control method. The results confirm the impact of strip cropping on the uptake of these minerals by maize and their content in the maize.

Effects of seed priming with zinc (Zn) plus manganese (Mn), boron (B), and phosphate (P) on growth and nutritional status of maize were studied. Nutrient seed priming significantly increased seed contents of primed nutrients. In nutrient solution (NS) lacking Zn and Mn, growth of maize plants primed with Zn + Mn increased by more than 50% and 100%, respectively, as compared to control treatment. The primed nutrients were efficiently translocated to the growing shoot and could maintain Zn and Mn supply for at least three weeks of the culture period. In soil culture, plants suffered from P and Zn deficiency, which was mitigated to some extent by P and Zn + Mn priming. Particularly, translocation of Zn seed reserves to the shoot tissue was negatively affected by the highly calcareous soil. In the field experiment, Zn + Mn seed priming increased grain yield by 15%, demonstrating the potential for long-lasting effects of nutrient seed priming.

Prevalent on calcareous soils in the United States and abroad, iron deficiency is among the most common and severe nutritional stresses in plants. In soybean (Glycine max) commercial plantings, the identification and use of iron-efficient genotypes has proven to be the best form of managing this soil-related plant stress. Previous studies conducted in soybean identified a significant iron efficiency quantitative trait locus (QTL) explaining more than 70% of the phenotypic variation for the trait. In this research, we identified candidate genes underlying this QTL through molecular breeding, mapping, and transcriptome sequencing. Introgression mapping was performed using two related near-isogenic lines in which a region located on soybean chromosome 3 required for iron efficiency was identified. The region corresponds to the previously reported iron efficiency QTL. The location was further confirmed through QTL mapping conducted in this study. Transcriptome sequencing and quantitative real-time-polymerase chain reaction identified two genes encoding transcription factors within the region that were significantly induced in soybean roots under iron stress. The two induced transcription factors were identified as homologs of the subgroup lb basic helix-loop-helix (bHLH) genes that are known to regulate the strategy I response in Arabidopsis (Arabidopsis thaliana). Resequencing of these differentially expressed genes unveiled a significant deletion within a predicted dimerization domain. We hypothesize that this deletion disrupts the Fe-DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT)/bHLH heterodimer that has been shown to induce known iron acquisition genes.