What Crops Are Grown in Iowa?

Corn and soybeans overwhelmingly dominate Iowa’s agricultural landscape, together covering roughly 85 percent of the state’s cropland in a typical year. But reducing Iowa to just two crops misses a more layered picture that includes oats, alfalfa, cover crops like cereal rye, a growing specialty produce sector, and a deep entanglement between crop farming and one of the densest hog populations in the country. The mix of what grows in Iowa is shaped as much by economics and infrastructure as by soil and climate.

The Corn and Soybean Duopoly

Iowa is the largest corn-producing state in the U.S. and typically ranks first or second in soybeans. Corn alone occupies around 13 million acres in a given year, with soybeans close behind at roughly 10 million. The reasons these two crops dominate are straightforward: Iowa sits squarely in the Corn Belt, with deep, fertile soils derived from glacial deposits and wind-blown loess, and a humid continental climate that delivers enough summer heat and rainfall to push corn yields well above the national average. Flat to gently rolling terrain makes large-scale mechanized planting and harvesting efficient, and a massive infrastructure of grain elevators, ethanol plants, and feed mills keeps demand local and transport costs low.

Most of the corn grown in Iowa is field corn, not the sweet corn you eat off the cob. It goes primarily into animal feed, ethanol production, and processed ingredients like corn syrup and starch. Iowa’s soybeans similarly feed the livestock and export pipeline, crushed into meal for animal feed and oil for food processing and biodiesel. A significant chunk of Iowa farmland is also devoted to hybrid seed corn production, which supplies the seed stock that farmers across the Midwest plant each spring.

Why Nearly Every Iowa Farm Rotates Between the Two

If you drive across Iowa in summer, you will notice a checkerboard pattern: a field of corn next to a field of soybeans, then corn again. This is not random. The standard Iowa rotation is corn one year, soybeans the next, repeated indefinitely. Soybeans fix nitrogen from the air into the soil through bacteria in their root nodules, which reduces the fertilizer a farmer needs for the following year’s corn crop. Corn, in turn, leaves behind residue and root mass that benefit the next soybean planting.

The yield penalty for skipping this rotation and planting corn after corn is real and well documented. A multi-location Iowa study found that continuous corn suffered yield losses ranging from about 11 to 28 percent compared to corn grown after soybeans, with the exact penalty depending on the specific location and soil type.¹ A separate analysis using both satellite imagery and field-level data confirmed the pattern, finding that corn rotated with soybeans yielded roughly 4 percent more than continuous corn on rainfed fields, while soybeans rotated with corn yielded about 10 percent more than continuous soybeans.² For soybeans, in other words, the rotation benefit is even larger than it is for corn.

These yield advantages translate directly into dollars, which is why the corn-soybean rotation is so deeply entrenched. Farmers who try to simplify by planting corn every year pay for it in lower yields and higher fertilizer bills. The economics have kept this two-crop cycle as Iowa’s default for decades.

Oats, Alfalfa, and the Case for Longer Rotations

Before the corn-soybean rotation took over in the mid-twentieth century, Iowa farms commonly grew oats, hay, and small grains alongside corn. Those crops have not disappeared entirely. Oats remain a modest presence, often planted as a “nurse crop” to establish alfalfa or other forages. Alfalfa, a perennial legume, is grown primarily for hay and fed to dairy cattle and horses. These crops occupy far less acreage than corn and soybeans, but they play an outsized role in soil health and in the economics of diversified operations.

A simulation study of Iowa farming systems found that a five-year rotation incorporating corn, soybeans, oats, and three years of alfalfa could increase net income by about 24 percent over five years compared to the standard corn-soybean cycle, even after accounting for government support payments that favor row crops.³ The catch is that growing alfalfa requires different equipment, different markets, and a different management mindset than row crops. Most Iowa farmers are set up for corn and soybeans, and the infrastructure to handle and sell small grains and forages has thinned out over the years. A farmer who wants to grow oats may find the nearest buyer inconveniently far away. These structural barriers, more than agronomic ones, keep longer rotations from spreading.

Cover Crops and Cereal Rye

One of the most significant shifts in Iowa cropping in recent years involves crops that are never harvested for grain at all. Cover crops are planted after the main crop is harvested in fall, grow through winter and early spring, and are terminated before the next planting season. Their purpose is to hold the soil in place, capture leftover nutrients, and improve soil structure. In Iowa, cereal rye is the dominant cover crop species because of its exceptional cold tolerance, strong fall and spring growth, and low seed cost.⁴ Oats are also used as a cover crop, though they typically winterkill in Iowa’s climate and provide less spring biomass.⁵

Adoption of cover crops has been growing, driven by state incentive programs and increasing awareness of soil health, but it remains far from universal. Farmers worry about how a thick mat of cereal rye residue will affect corn planting and early-season growth. The timing of when you kill the rye in spring matters enormously: terminate it too late and the corn seedlings struggle; terminate it too early and you lose much of the soil-protection benefit. The uncertainty around yield effects on corn keeps many farmers cautious, even though the environmental benefits are well supported by research.

Organic Farming in Iowa

Iowa has a small but economically interesting organic crop sector. Organic corn and soybean acreage has expanded, driven by premium prices that can be several times higher than conventional market prices. A long-term comparison at an Iowa research site found that organic rotations involving corn, soybeans, and oats produced dramatically higher economic returns than conventional corn-soybean rotations. Organic corn brought in roughly five times the per-hectare returns of conventional corn, and organic soybeans performed similarly well, with organic soybean returns averaging over $1,200 per hectare compared to about $235 per hectare for conventional soybeans.⁶

Those numbers look compelling, but they come with important caveats. Organic farming requires a three-year transition period during which yields may drop but organic premiums cannot yet be claimed. Weed management without herbicides is labor-intensive and skill-dependent. And organic price premiums depend on demand continuing to outpace supply; if every Iowa farmer switched to organic, those premiums would collapse. Still, for farmers willing to manage the complexity, organic cropping with extended rotations including oats and alfalfa can be substantially more profitable per acre than conventional corn and soybeans.

Specialty Produce and Fruits

Iowa may be synonymous with grain farming, but a growing number of producers raise fruits and vegetables for local and regional markets. Sweet corn, pumpkins, melons, apples, strawberries, tomatoes, peppers, and various greens are grown across the state, primarily for direct sale at farmers’ markets, roadside stands, and through community-supported agriculture programs. Research has examined the potential for Iowa’s farms to supply more fresh produce to the state’s metropolitan areas, which collectively house most of the population.⁷

The specialty crop sector remains tiny relative to corn and soybeans, but it punches above its weight economically on a per-acre basis. An acre of diversified vegetables can gross many times what an acre of field corn brings in. The constraints are labor, perishability, and market access rather than climate or soil. Iowa’s growing season is long enough for a wide range of temperate vegetables and fruits, and the state’s rich soils are well suited to them. The bottleneck is infrastructure: packing sheds, cold storage, and distribution networks that are well developed for grain but sparse for fresh produce.

How Livestock Shapes What Iowa Grows

You cannot understand Iowa’s crop mix without understanding its livestock industry. Iowa is the nation’s top hog-producing state by a wide margin, and it also supports significant cattle, poultry, and egg production. This matters for crops because livestock consume enormous quantities of corn and soybean meal, creating a guaranteed local demand that anchors the two-crop system. Much of Iowa’s corn never leaves the county where it was grown; it goes straight into nearby hog or cattle operations.

The relationship runs in both directions. Iowa’s dense hog population generates vast quantities of liquid swine manure, which is applied to cropland as fertilizer. A statewide assessment found that Iowa generally has more available cropland than it needs to absorb all the manure produced, but at the individual farm level the situation often reverses: farms near large hog confinements can have more manure than their fields can use, requiring transport to more distant fields.⁸ Manure is a genuine nutrient resource. An on-farm study found that corn yields responded well to liquid swine manure, averaging about 10.4 metric tons per hectare at the high application rate compared to 7.8 metric tons per hectare with no nitrogen input at all.⁹ However, the nitrogen in manure is harder to manage than synthetic fertilizer, and a portion is lost before the corn can use it, especially when manure is applied in fall and heavy spring rains wash nutrients away.

The timing and method of manure application have measurable effects on how much nutrient ends up stored in the soil rather than feeding the crop. Long-term application of higher rates during winter and spring led to significantly more residual phosphorus and nitrogen accumulating in the soil profile, raising questions about eventual runoff risk.¹⁰ This connection between livestock waste management and crop nutrient loading is one of the central environmental tensions in Iowa agriculture.

The Water Quality Question

Iowa’s cropping system has consequences far beyond the state’s borders. The heavy nitrogen fertilization required by corn, combined with the extensive network of subsurface tile drainage that makes productive farming possible on Iowa’s poorly drained soils, creates a direct pipeline for nitrate to reach streams and rivers.¹¹ That tile drainage is essential: without it, much of north-central Iowa’s most productive ground would be too waterlogged to farm. But the same drainage that makes the land productive also moves nitrate efficiently into waterways.

A 30-year analysis of Iowa stream data found that nitrate levels have been increasing. Nitrate yield per hectare was about 18 percent higher in the period from 2002 to 2016 compared to 1987 through 2001, driven in part by rising precipitation that amplifies nutrient transport.¹² Iowa’s nitrate contributions flow into the Mississippi River and ultimately to the Gulf of Mexico, where they contribute to the seasonal hypoxic zone, sometimes called the “dead zone.” Annual nitrate loads from Iowa have ranged enormously depending on rainfall, from about 66,000 metric tons in the drought year of 2012 to 567,000 metric tons in the extremely wet 2016.¹³

The trends are not uniformly bleak. A separate study found that when nitrate concentrations were adjusted for the influence of varying river flows, concentrations actually declined from 2000 to 2012 across multiple Iowa basins. That trend reflected both high-discharge years that diluted and flushed stored nitrogen and low-discharge years that reduced transport, with long subsurface residence times of eight years or more in some basins playing a role.¹⁴ Separating what is happening with actual nutrient management from what is happening with rainfall patterns turns out to be genuinely difficult, and researchers have gone back and forth on how much credit or blame to assign to farming practices versus climate variability.

Prairie Strips and Other Conservation Approaches

One promising approach to reducing the environmental footprint of Iowa’s corn-soybean system does not involve changing what is grown in the main fields at all. Prairie strips are narrow bands of native perennial grasses and wildflowers planted along contours within row-crop fields. Iowa State University research found that converting just 10 percent of a crop field to prairie strips reduced total water runoff by 37 percent, retained 20 times more soil, and captured over four times more phosphorus than fields without them.¹⁵ The strips also supported significantly more bird and pollinator species.

The appeal of prairie strips is that they ask farmers to give up only a small fraction of their productive land while delivering outsized environmental benefits. Federal programs now offer payments to farmers who install them. Combined with cover crops, reduced tillage, and improved nutrient management, these practices represent a toolkit for making Iowa’s dominant cropping system less damaging without overhauling the basic corn-soybean framework. Whether these voluntary, incentive-based approaches can move the needle fast enough to meaningfully reduce nitrate loading at the state scale remains an open and contested question.

Soil Erosion and Long-Term Productivity

Iowa’s famously productive soils are not invulnerable. The state has lost a significant fraction of its original topsoil since cultivation began in the 1800s, and erosion continues to be a concern on sloping land. A multi-year erosion-productivity study spanning 44 Iowa counties and 569 sites found that corn yields declined as the degree of past erosion increased, with soils derived from glacial till showing steeper yield losses from erosion than loess-derived soils. The organic matter content of the soils was closely tied to their erosion history.¹⁶ In other words, as topsoil erodes, it takes organic matter with it, and yields follow downward. This is a slow-moving problem that does not show up dramatically in any single season but compounds over decades.

The connection between erosion and cropping choices matters because row crops like corn and soybeans leave soil more exposed than perennial crops like hay or pasture. Fields in continuous corn with conventional tillage are among the most erosion-prone. Cover crops, no-till farming, and the inclusion of perennial phases in the rotation all reduce erosion risk, which is one more reason agronomists keep arguing for diversified rotations even when the immediate economics favor the corn-soybean default.

Weather Extremes and What They Mean for Iowa Crops

Iowa’s crops face increasing exposure to severe weather events. The August 2020 derecho, a fast-moving windstorm with gusts exceeding 100 miles per hour in some areas, flattened millions of acres of corn across central Iowa in a matter of hours. Corn is particularly vulnerable to this kind of damage because by late summer the plants are tall, top-heavy with developing ears, and easily snapped or uprooted by sustained high winds. Research on derecho impacts confirmed that corn condition vulnerability was further amplified when severe wind gusts coincided with drought or excessive wetness at the time of the event.¹⁷

Beyond single catastrophic events, Iowa farmers contend with a trend of increasing precipitation variability. Wetter springs delay planting and can waterlog fields even with tile drainage. Hotter summer nights accelerate corn respiration and reduce grain fill. Drought, while less common in Iowa than farther west, still strikes periodically and can devastate yields in counties without irrigation, which is most of the state. Iowa’s crop mix is unlikely to shift dramatically in response to these pressures in the near term because corn and soybeans remain the most profitable and logistically supported options. But the conversation about resilience, whether through crop diversification, improved drainage, or breeding for stress tolerance, is intensifying as weather volatility grows.

Seed Corn Production

One piece of Iowa agriculture that often flies under the radar is hybrid seed corn production. Iowa is a major center for growing the parent lines that are crossed to produce the hybrid seed sold to farmers across the country. Seed corn fields look similar to regular corn fields but are managed very differently: they involve detasseling (removing the pollen-producing tassels from one parent line so it can only be pollinated by the other) and require tighter quality controls including fungicide management. A study of commercial hybrid seed corn production in Iowa found that roughly 64 to 79 percent of fungicide treatments were profitable, depending on whether profitability was measured from the seed company’s or the grower’s perspective.¹⁸ The seed corn industry adds a layer of economic activity and employment that goes beyond commodity grain farming, particularly in central and north-central Iowa where major seed companies operate research stations and production facilities.