Fertilizer International 524 Jan-Feb 2025
22 January 2025
Maximising soybean crop yields
CROP NUTRITION
Maximising soybean crop yields
Nearly 400 million tonnes of soybean are harvested globally every year and processed to yield oil and meal, a major source of animal protein. Its cultivation in Brazil, the US and other countries requires large applications of potash and phosphate. Growers are, however, increasingly turning to biostimulants and micronutrients such as boron to achieve incremental yield gains.
Advances in plant genetics and agronomy have allowed farmers in Brazil and the US to achieve record soybean yields in recent years. Record-breaking soybean harvests are being accompanied by the ever high uptake and removal of secondary nutrients and micronutrients such as sulphur, magnesium, boron and zinc. This is making the need for season-long macronutrient and micronutrient availability greater today than ever before. Fortunately, fertilizer producers have responded to this challenge by developing innovative, new fertilizer products and designing sophisticated, tailored fertilizer programmes for soybean.
Soybeans are known for their efficient use of residual soil nutrients, although modern, high-yielding varieties require more careful nutrient management and higher nutrient inputs.
Proper and well planned crop nutrition is known to be one of most effective ways of influencing both soybean yield and quality. Fertilizer management, and the alleviation of soil acidity, for example, generally have commercially valuable and positive effects on the oil and protein levels of soybeans. Maintaining soil fertility also protects soybean plants from environmental stresses such as weather, disease and nematodes.
In soybean production, soil pH has been singled out for its influence on soil fertility and plant growth. Soybeans thrive at soil pH between 6.0 and 6.8, and both nutrient uptake and yield are maximised at this pH range.
ICL
Biostimulants in soybean: a Brazilian success story
Introduction
Soybean [Glycine max (L.) Merrill] is Brazil’s most economically important crop – and is well known for its sophisticated and sustainable cultivation practices.
The continuing success of soybean growing in Brazil is attributable to investments in new technologies, the use of efficient management practices, and the adoption of innovative products that enhance plant performance. The use of biostimulants, in particular, is one innovation that has expanded rapidly and contributed significantly to improvements in the country’s soybean productivity.
Biostimulants
Plant biostimulants are synthetic or natural compounds that are applied to soil, foliage, or seeds. They improve soybean yield and quality by stimulating plant metabolism, enhancing nutrient absorption, and increasing resilience to biotic and abiotic stresses.
The main categories of plant biostimulants include microorganisms, humic and fulvic acids, amino acids, plant extracts, and algae extracts. ICL, a leading biostimulant producer, offers all of these product types. The company has been a biostimulant market pioneer.
Sustainability
Sustainability is a key pillar of soybean production systems – benefitting both growers and the planet, respectively, by making soybean products more competitive and reducing the environmental impacts of farming.
One clear example of sustainable cultivation is the widespread use of inoculants for biological nitrogen fixation (BNF) in Brazilian soybean growing. This agricultural practice is adopted on 44 million hectares of soybeans and – by fixing atmospheric N instead of applying synthetic nitrogen fertilizers – avoids 240 million tonnes in CO2 equivalent emissions1 .
Soil management
In Brazil, soybeans are typically cultivated on nutrient-depleted soils which require careful management to maintain their fertility and ensure high crop productivity. The successful cultivation of a fast-growing crop like soybean relies on several essential factors – these including nutrient-rich soils, the absence of compaction, a high organic matter content, and an active soil microbiota.
ICL biostimulants for soybean management
Phusion is a phosphate fertilizer that incorporates micronutrients and humic substances. It is recommended at planting to nourish crops and aid root development. Phusion also increases phosphorus availability by containing a polymer that helps prevent the adsorption of this major nutrient by soil particles.
Bioz Diamond contains bioactive compounds and organic acids that stimulate soil microbiota diversity. It promotes vigorous root system growth by balancing nutrient mineralisation and root interaction. This improves nutrient uptake efficiency and helps plants become more resilient to environmental stresses. Overall, the product is designed to enhance soil health and reduce environmental and crop management-related damage to soils.
ICL offers a range of products to enhance biological nitrogen fixation (BNF) and ensure robust growth in soybean – starting with seed treatment all the way through to the grain filling stage.
Inoculants based on Bradyrhizobium (Actibio Brady) and Azospirillum (Actibio Azos), for example, enhance BNF and root growth. Studies show annual inoculation with Bradyrhizobium increases productivity by about 8%, while adding Azospirillum can boost this gain to 19%2 . A third inoculant product, Actibio Phos (Pseudomonas bacteria), produces metabolites that aid P and K mineralisation and root system development.
The biostimulant Bioz Topaz, meanwhile, is recommended as the best option for maintaining seed vigour and ensuring proper rooting. It is composed of an algae extract, alongside micronutrients such as Ni, Co, and Mo, and supports nitrogen-fixing bacteria activity as well as providing balanced crop nutrition.
Valuably, Bioz Topaz is compatible with other biological products used in seed treatment, including inoculants, insecticides, and fungicides. In soybean cultivation, Bioz Topaz has been shown to increases the number of nodules per plant by 66% and soybean yields (productivity) by 11% in research carried out by ICL’s Innovation Center and ESAPLq/ USP (Figure 1).
The BNF process is not limited to seed inoculation or the initial stages of soybean growth. In fact, peak demand for nitrogen actually occurs at the R1 growth stage of the soybean plant, making it essential to keep root nodules active throughout the entire plant growth cycle. To achieve this, however, optimising both photosynthesis and plant metabolism is necessary.
Using Bioz Nephrite in nutrient management, for example, increases the photosynthetic activity of plants and promotes the accumulation of carbon in the aerial parts.
This is then transported to the roots, intensifying nodule activity and ensuring nitrogen fixation.
A 15N isotope study has shown that a combined application of Bioz Topaz + Bioz Nephrite increased BNF by 33% – by improving the volume, weight, and number of nodules – as well as enhancing soybean productivity (Figure 2).
Strategies for climate stress mitigation
Brazil faces climatic challenges such as extreme weather events with high temperatures and water deficits. Amino acids play a crucial role in mitigating these stresses through their role in vital plant processes. Foliar application of the following two amino acid products can enhance plant resistance to stress by improving the absorption of nutrients and other agricultural chemicals:
- Bioz Moonstone is a foliar fertilizer with a unique amino acid complex that mitigates abiotic stresses and promotes rapid plant recovery.
- Bioz Kellus contains nutrients such K, Cu, Mn, and Zn that are complexed with amino acids. This ensures stable solutions, rapid nutrient absorption, and increased antioxidant enzyme activity (Figure 3).
Improving plant structure and flower retention
During vegetative growth, many growers seek to control soybean plant height to optimise the number and arrangement of lateral branches and nodes. The biostimulant Bioz Sapphire, by stimulating cell division, improves plant structure, promotes better branching and, valuably, in doing so increases light interception.
During the soybean’s reproductive stage, it is common for some flowers to be lost due to abscission. This can be a major issue with some 20-80% of flowers susceptible to the abscission process, depending on the environmental conditions and plant genetic characteristics.
To protect against this, the application of Bioz Onyx has proven to be effective at increasing flower set and pod retention. This product contains organic and biostimulant components and promotes the synthesis of essential flowering and fruiting hormones such as gibberellins and cytokinins.
During the 2021/22 and 2022/23 growing seasons, ICL commissioned soybean trials with Bioz Onyx across different producing regions (n=13) in collaboration with universities and external consultancies. Results demonstrated an 8% average increase in soybean productivity, equivalent to an average yield gain of 288 kg per hectare, confirming the significant economic benefits of Bioz Onyx for growers.
Grain filling and nutritional quality
Inorganic biostimulants such as Nutriduo are also available for soybean cultivation in addition to traditional organic-based biostimulants. This product is applied during the grain filling stage and contributes to the biofortification of the crop by enriching the grain with selenium (Se). It also contains amino acids.
The nutritionally balanced composition of Nutriduo (N, P, K, Mg, B, and Zn) is designed to mobilise sugars from the leaves to the grain. The presence of Se is an additional benefit as it improves plants resilience, especially under saline, heat, and water stress conditions.
The future of biostimulants
ICL believes biostimulants have a promising future ahead, thanks to emerging research innovations and a growing range of practical applications. This product group complements and enhances the action of fertilizers and other agrochemical inputs, improving sustainability as well as the quality and yield of agricultural produce.
Looking ahead, the integration of genetic engineering, precision agriculture, big data, artificial intelligence, and regenerative agriculture will have a positive impact on farm productivity and profitability.
The use of biostimulants in crops such as soybean is a great success story for Brazilian agriculture. Yet challenges do remain – particularly when it comes to product regulation. In our view, robust regulation of the biostimulants market, with greater standardisation and the implementation of clear protocols, is essential and necessary to increase producer confidence and expand the use of these innovative and valuable products.
References
About the authors
- Karla Martins – Technical Development Consultant, ICL Brazil
- Deyvid Bueno – Product Manager, ICL Brazil
- Guilherme Souza – Technical Development Manager, ICL Brazil
- Patrick Haim – Lead Agronomist, ICL
U.S. BORAX
Boron in soybean nutrition
Boron uptake by soybean
Agronomists have investigated the patterns of nutrient uptake, partitioning, and remobilisation in soybean cultivation for many years. Recent studies have shown that the potential for nutrient uptake by soybean crops has increased significantly as productivity (yield) levels have risen. This has resulted in higher overall demand for nutrients – including for boron.
Crop research carried out by the Brazilian Agricultural Research Corporation (EMBRAPA), for example, shows that new soybean varieties (SYN 1039 and DM 6563) accumulate and export more boron compared to the variety (BRS 184) traditionally grown (Table 1). These data reinforce the fact that precise knowledge about nutrient uptake and demand, and how this varies for different soybean varieties planted in different regions, is essential when it comes to better crop nutrient management.
Similarly, results obtained for total boron uptake by soybean plants and boron removal by soybean seeds from a U.S. study (Table 2) do differ from those observed in Brazil. Indeed, such variations in boron uptake are to be expected, as these reflect differences in the growing environment, climate conditions, soil type, and soybean cultivation techniques.
An important parameter provided by the U.S. study is the maximum boron accumulation rate, essentially a measure of peak boron demand. U.S. researchers found that the maximum soybean demand for boron occurs during the R4 reproductive period, with a peak accumulation value of 5.18 g/ha being observed (Table 2).
These results demonstrate the importance of using fertilizer sources – such as Granubor ® (sodium tetraborate pentahydrate) – that release all their boron over the growing season and therefore guarantee gradual and consistent boron supply, this being particularly important during those soybean growth stages with the greatest boron demand.
The 2016 EMBRAPA study also determined boron accumulation curves for three soybean varieties. Results show that soybean demand for boron starts in the vegetative phases (V1-V6) and then progressively increases during the crop’s reproductive period – particularly between periods R2 and R5 – reaching maximum accumulation between the R4 and R5 phases (Figure 1).
Soybean cultivation research studies commissioned by U.S. Borax, and carried out with different agronomic research institutions in Brazil, show that using Granubor® as a source of boron delivers an average incremental yield improvement of 277 kg/ha. Results were obtained using reliable experimental designs and determined from rigorous statistical analysis, such as ANOVA and mean tests. This provides a high level of confidence in the crop recommendations for Granubor® and the resulting yield improvements.
Granubor®: a high agronomic efficiency fertilizer
To evaluate boron release from different fertilizer sources, U.S. Borax carried out percolation experiments using columns filled with soil under controlled laboratory conditions (see main photo). Water was applied daily to the individual columns, each of which contained a boron dose from different fertilizer sources. The boron sources tested were standard boric acid (17.5% B), Granubor® (15% B), and five types of ulexite from different regions. The results obtained for ulexite have been described previously (Fertilizer International 521, p26).
The volume of drained (percolated) water was collected each day and analysed for soluble boron content. Experimental conditions were as follows:
- 300 g of topsoil (clayey soil) around 10 inches deep (classified as well drained) was placed in 12’’ x 2” PVC pipes
- Soil content: < 0.1 ppm of B
- 250 g of soil placed in a tube followed by 1 g of boron equivalent fertilizer, covered by 50 g of soil
- Watered 100 ml/day
- Boron concentration in percolated solution was measured by inductively coupled plasma (ICP) analysis.
Results (Figure 2) show that 100% of the boron present in the boric acid percolated after 63 days (9 weeks), while 98.1% of the boron in Granubor® percolated after 140 days (20 weeks). These results confirm that boric acid percolates faster than Granubor® due to its more rapid solubilisation. Therefore, in practice and from a field application perspective, standard boric acid may not fully meet the boron demands of soybean throughout the growing season.
Whereas for Granubor® , in contrast, the pattern of boron release strongly matches the period of greatest boron demand from soybean plants (Figure 2). It can supply boron to the soybean crop when it’s most needed, if applied at the correct time.
Soybean is a global crop and its nutrient needs in different regions will vary according to soil type, climate conditions and soybean variety etc. Nonetheless, U.S. and Brazilian soybean growers have observed significant corrections in boron deficiency symptoms on farms using Granubor® .
In our view, Granubor® provides the best solution for soybean growers requiring a soil-applied boron fertilizer, based on the rigorous analysis of extensive field data collected from numerous research studies (Figure 3).
References
About the authors
Fabiano Silvestrin is Principal Advisor, Global Market Development Agriculture, and Eduardo Saldanha is Agriculture Development Specialist, Latin America, at U.S. Borax.
