Soybeans are genetically modified primarily to survive being sprayed with herbicides that would otherwise kill them, giving farmers a simpler and cheaper way to control weeds. That single trait, herbicide tolerance, accounts for the vast majority of GM soybean acreage worldwide. But the reasons have expanded over the past three decades to include insect resistance, improved oil profiles, drought tolerance, and disease resistance. With GM soybeans planted on roughly 100 million hectares globally and an adoption rate above 70%, the crop is the most widely grown genetically modified plant on earth.
Weed Control Started It All
The first commercially successful GM soybean, introduced in the mid-1990s, carried a single foreign gene called CP4 EPSPS, sourced from a soil bacterium. That gene produces a protein that lets the plant tolerate glyphosate, a broad-spectrum herbicide sold under brand names you probably recognize. Without the gene, glyphosate kills the soybean along with the weeds. With it, a farmer can spray an entire field after the crop has emerged and wipe out almost everything green except the soybean itself.1The Journal of Nutrition. The Expressed Protein in Glyphosate-Tolerant Soybean, 5-Enolpyruvylshikimate-3-Phosphate Synthase from Agrobacterium sp. Strain CP4, Is Rapidly Digested In Vitro and Is not Toxic to Acutely Gavaged Mice
Before glyphosate-tolerant soybeans, weed management typically involved applying several different herbicides at different times, each targeting different weed species, often combined with mechanical tillage. The appeal of one spray that handles nearly everything was enormous. Farmers saved money on herbicide programs, simplified their schedules, and in many regions shifted to planting without tilling the soil at all, because the herbicide replaced the plow as the primary weed-removal tool.2PubMed Central. The relative importance of herbicide use for conservation tillage adoption by U.S. corn and soybean producers
The economic logic was straightforward. Glyphosate was off-patent, cheap, and effective against a wide range of weeds. Pairing it with a tolerant crop meant farmers could treat weed control as a single line item instead of juggling multiple products, application windows, and equipment passes. A second generation of GM herbicide-tolerant soybeans, offering the same glyphosate tolerance plus higher yield potential, became available in the United States and Canada around 2009 and pushed average farm income gains even higher.3PubMed Central. Economic impact of GM crops The global income and production effects 1996–2012
Insect Resistance Came Next
Herbicide tolerance solved the weed problem, but soybeans also face serious insect pests, particularly caterpillars that chew through leaves and pods. In tropical and subtropical growing regions like Brazil, the damage from species such as the velvetbean caterpillar and soybean looper can slash yields dramatically. To address this, breeders stacked genes from the bacterium Bacillus thuringiensis (Bt) into soybean lines. These genes produce proteins that are toxic to caterpillars but harmless to mammals.
Brazil approved a pyramided GM soybean expressing three Bt proteins, Cry1A.105, Cry2Ab2, and Cry1Ac, combined with herbicide tolerance. Field and lab studies evaluated its performance against the key caterpillar pests that plague Brazilian soybean fields.4Journal of Economic Entomology. Performance of Genetically Modified Soybean Expressing the Cry1A.105, Cry2Ab2, and Cry1Ac Proteins Against Key Lepidopteran Pests in Brazil Stacking multiple Bt genes in one plant is a deliberate strategy. Using several proteins with different modes of action makes it much harder for insect populations to develop resistance to any single one. This is the same principle used in Bt corn and Bt cotton, applied to soybeans a generation later.
The Numbers Behind Adoption
The global footprint of GM soybeans is hard to overstate. In 2023, GM soybeans covered about 101 million hectares worldwide, representing a 72% adoption rate among soybean growers globally.5Journal of Integrative Agriculture. Trends in the global commercialization of genetically modified crops in 2023 That makes GM soybean the most widely planted biotech crop by area, ahead of GM corn.
The economic gains have accumulated to staggering levels. Between 1996 and 2024, GM crop technology across all four major crops (soybean, corn, cotton, canola) increased farm incomes by roughly $385 billion. GM technology added an estimated 459 million tonnes to global soybean production over that period. About 52% of total income gains went to farmers in developing countries, with 48% to those in developed nations. Roughly two-thirds of the gains came from yield and production increases, and the remaining third from cost savings.6PubMed Central. Genetically modified (GM) crop use 1996-2024: farm income and production impacts
For soybeans specifically, the earlier generation of herbicide-tolerant varieties delivered most of their benefit through cheaper weed control rather than higher yields. But as new trait combinations and second-generation varieties arrived, yield gains became a larger share of the benefit. By the 1996–2012 period, GM herbicide-tolerant soybeans had generated an estimated $37 billion in cumulative farm income, with about 38% from yield gains and 62% from cost reductions.3PubMed Central. Economic impact of GM crops The global income and production effects 1996–2012
Conservation Tillage and Soil Health
One of the less obvious reasons GM soybeans spread so quickly is that they enabled a shift in how farmers prepare fields. Conventional farming involves plowing and tilling to bury weeds before planting. Tillage works, but it breaks up soil structure, increases erosion, and releases stored carbon. Conservation tillage, which leaves crop residue on the surface and disturbs the soil as little as possible, reduces all of these problems. The catch is that without turning the soil over, you need another way to kill weeds before planting.
Herbicide-tolerant soybeans filled that gap. Farmers practicing conservation tillage treat a higher share of their acreage with pre-emergence herbicides than those who still plow, effectively replacing the plow’s weed-killing function with chemical weed control.2PubMed Central. The relative importance of herbicide use for conservation tillage adoption by U.S. corn and soybean producers This trade-off, less soil disturbance in exchange for more herbicide, is central to the debate over whether GM soybeans are truly better for the environment. The soil benefits are real: less erosion, better water infiltration, and improved habitat for soil organisms. But the herbicide side of the ledger has its own complications.
The Weed Resistance Problem
Heavy and repeated use of a single herbicide creates intense selection pressure on weed populations. Any weed plant that happens to survive glyphosate, through a random mutation or a quirk of timing, gets to reproduce in a field emptied of competitors. Over the years, glyphosate-resistant weeds have emerged across soybean-growing regions. Argentina and Brazil, where the massive adoption of no-till farming and glyphosate-tolerant soybeans created especially uniform herbicide regimes, have been particularly affected. Species like Johnsongrass in Argentina and wild poinsettia in Brazil developed resistance that forced farmers back toward more complex and expensive weed-management programs.7PubMed. Glyphosate-resistant weeds of South American cropping systems: an overview
Data from the United States tell a consistent story. On average, adopters of glyphosate-tolerant soybeans used about 28% more herbicide by weight per hectare than non-adopters. When those herbicides were weighted by environmental impact rather than raw volume, the gap narrowed to roughly equivalent levels, because glyphosate is less toxic per kilogram than many of the herbicides it replaced. But the trend over time showed GT adopters using increasingly more herbicide relative to non-adopters, a pattern consistent with farmers spraying more glyphosate as resistant weeds proliferated.8PubMed Central. Genetically engineered crops and pesticide use in U.S. maize and soybeans
This is the central tension of herbicide-tolerant crops. The technology works beautifully in the short run but creates its own obsolescence when used without rotation or complementary weed control strategies. Companies have responded by developing soybeans tolerant to additional herbicides, so farmers can rotate chemistries, but the arms race between herbicide traits and weed evolution continues.
Redesigning the Oil
Herbicide tolerance and insect resistance are about protecting the plant in the field. A different category of genetic modification aims to change what is inside the harvested bean. Soybean oil is one of the most widely consumed vegetable oils in the world, but conventional soybean oil is relatively high in polyunsaturated fats like linoleic and linolenic acid, which oxidize easily and limit shelf life. For food manufacturers, this meant soybean oil often needed to be partially hydrogenated, a process that created trans fats.
Genetic engineering offered a workaround. By silencing the gene for a key enzyme (FAD2) in the fatty acid pathway, researchers dramatically shifted the oil profile. In transgenic soybean lines, oleic acid content jumped from around 20% to roughly 80%, while linoleic and linolenic acid dropped correspondingly.9PubMed. Improved oil quality in transgenic soybean seeds by RNAi-mediated knockdown of GmFAD2-1B A separate approach used sequence-specific nucleases to knock out the same FAD2 genes, producing high-oleic, low-linolenic oil without introducing any foreign DNA at all.10PubMed Central. Direct stacking of sequence-specific nuclease-induced mutations to produce high oleic and low linolenic soybean oil High-oleic soybean oil is more heat-stable, longer-lasting, and does not require hydrogenation. Several high-oleic soybean varieties are already in commercial production, and the oil has found its way into frying operations, food-service supply chains, and packaged foods.
Feeding Livestock More Efficiently
Soybeans are the world’s dominant source of protein in animal feed, but their amino acid profile is not a perfect match for what chickens and pigs need. Soybean protein is relatively low in sulfur-containing amino acids like methionine and cysteine, which are essential for livestock growth. Feed manufacturers compensate by adding synthetic methionine, but this adds cost. Engineering soybeans with higher levels of sulfur-rich storage proteins could reduce or eliminate the need for that supplement, lowering feed costs and simplifying rations.11Crop Science. Engineering Soybean for Enhanced Sulfur Amino Acid Content
Another target is anti-nutritional compounds. Soybeans contain oligosaccharides called raffinose and stachyose that humans and monogastric animals cannot digest, leading to gas and reduced nutrient absorption. Genome editing has been used to knock out the genes responsible for producing these sugars, creating soybean lines in which raffinose and stachyose drop below detectable levels.12The Crop Journal. Multiplex genome editing targeting soybean with ultra-low anti-nutritive oligosaccharides Beans like these could improve digestibility for both livestock and human consumers.
Preparing for a Hotter, Drier Climate
As growing seasons become less predictable, drought tolerance has moved near the top of breeders’ wish lists. Conventional soybean breeding for drought resistance has been slow because the trait is controlled by many genes interacting with environmental conditions. Genetic engineering offers a shortcut. Researchers transformed soybeans with a gene for a sunflower transcription factor called HaHB4, which had previously shown drought tolerance in other species.13PubMed Central. Successful field performance in warm and dry environments of soybean expressing the sunflower transcription factor HB4
Field results were encouraging. Across 27 experiments spanning a wide range of growing conditions, the transgenic soybean line outyielded its conventional parent by an average of about 4%, with the advantage reaching as high as 43% under the most stressful conditions. The yield bump came from producing more seeds per plant, even though individual seeds weighed slightly less.14Journal of Experimental Botany. Successful field performance in warm and dry environments of soybean expressing the sunflower transcription factor HB4 – Section: Results Argentina became the first country to approve a drought-tolerant GM soybean for commercial cultivation, and the technology signals a future where GM traits are aimed not just at fighting weeds and bugs but at keeping yields stable as the climate shifts.
Are GM Soybeans Safe to Eat?
This is the question that hovers over every discussion of GM crops. For soybeans specifically, the evidence is reassuring. The CP4 EPSPS protein, the only foreign protein in the original glyphosate-tolerant soybean, breaks down rapidly when exposed to digestive conditions and showed no toxicity in animal feeding studies.1The Journal of Nutrition. The Expressed Protein in Glyphosate-Tolerant Soybean, 5-Enolpyruvylshikimate-3-Phosphate Synthase from Agrobacterium sp. Strain CP4, Is Rapidly Digested In Vitro and Is not Toxic to Acutely Gavaged Mice
On allergenicity, a direct comparison found that the rate of IgE sensitization (the immune response behind allergic reactions) was identical between GM and conventional soybean extracts at 3.8% of allergic adults tested. The allergen profiles matched across multiple analytical methods, and none of the subjects reacted to the purified EPSPS protein itself.15PubMed Central. Evaluating the allergic risk of genetically modified soybean The European Union requires that GM plants considered allergenic undergo assessment for unintended increases in endogenous allergens before they can be sold.16PubMed. Assessment of endogenous allergenicity of genetically modified plants exemplified by soybean – Where do we stand? This regulatory framework exists precisely because the concern is legitimate in principle, even though the evidence so far has not shown increased allergenicity in approved GM soybean varieties.
Disease Resistance on the Horizon
Soybean rust, caused by the fungus Phakopsora pachyrhizi, is one of the most destructive soybean diseases worldwide. It can cut yields by more than half in bad years, and resistance bred through conventional crosses has been difficult to sustain because the pathogen evolves quickly to overcome single resistance genes. Researchers are now pursuing transgenic approaches and RNA interference to build more durable defenses, aided by recent sequencing of the rust pathogen’s genome.17PubMed Central. Soybean-Phakopsora pachyrhizi interactions: towards the development of next-generation disease-resistant plants While no rust-resistant GM soybean is on the market yet, this is one of the traits most likely to drive the next round of GM soybean development, particularly in Brazil and other tropical producers where rust pressure is highest.
CRISPR and Gene Editing Are Changing the Toolkit
Most commercially planted GM soybeans carry foreign DNA, a bacterial gene for herbicide tolerance or Bt genes for insect resistance. Gene editing with CRISPR/Cas9 is different. It allows breeders to make precise changes to the soybean’s own genome without inserting foreign genes. CRISPR is already being used in soybean research to alter fatty acid composition, protein content, flavor, digestibility, seed size, and seed-coat color.18PubMed Central. Recent advances in the improvement of soybean seed traits by genome editing
The regulatory implications are significant. In many countries, gene-edited crops that do not contain foreign DNA are regulated differently from traditional GMOs, sometimes falling outside GM regulations entirely. This could accelerate the development of improved soybean varieties with traits that consumers and food manufacturers actually want, like better taste, improved nutrition, or reduced allergens, without triggering the labeling and approval hurdles that slow down transgenic varieties. Whether these gene-edited soybeans are considered “genetically modified” in a regulatory sense varies by country, but biologically, the tools are converging on the same goal: a soybean that performs better in the field and delivers more value after harvest.
Who Owns the Genes
One reason GM soybeans generate controversy has nothing to do with biology and everything to do with intellectual property. The genes inserted into GM soybeans are patented, and farmers who buy GM seed sign technology agreements that limit the use of the seed to a single crop. Saving harvested seed to replant the following year, a practice as old as agriculture, is restricted under these contracts. The agreements spell out patent numbers, agronomic recommendations, penalties for non-compliance, and the fact that the farmer is purchasing a limited-use license for the gene, not ownership of it.19Revista de Economia e Sociologia Rural. Economic governance of property rights: comparative analysis on the collection of royalties in genetically modified soybean seeds
This licensing model has been a flashpoint, particularly in countries where seed-saving is deeply embedded in farming culture. In the United States, the legal framework is well established and enforced. In South America, enforcement has been more uneven, and the economics of royalty collection have varied by country. The broader point is that GM soybean adoption is not purely a decision about agronomy or economics. It ties farmers into a commercial relationship with the trait developer that shapes their seed choices, planting flexibility, and long-term costs in ways that conventional seed does not.