Companion Crops and New Alfalfa: When More First-Year Hay Costs You the Stand

By Jon Paul Driver

Companion crops can increase first-year tonnage while reducing alfalfa density, forage quality and stand longevity.

Planting alfalfa is an investment in several future harvests, not merely the first cutting. A choice that adds forage during the seeding year may look profitable immediately but leave fewer alfalfa plants—and fewer productive years—behind.

Research from Dr. Carson Roberts, assistant research professor and state Extension specialist in forage agronomy at the University of Missouri, clarifies that tradeoff. Roberts compared alfalfa established alone and with oat companion crops across several irrigation levels. His findings frame companion crops as management tools—not traditions that automatically belong in every new seeding.

Why Growers Use Companion Crops

An oat companion crop can serve several purposes. Its fibrous root system can stabilize erosion-prone soil while alfalfa seedlings develop. Fast oat growth may suppress weeds, and the mixture can produce substantially more forage during the establishment year.

The catch is simple: oats and alfalfa share the same field, water, sunlight and nutrients. Oats grow faster and taller, allowing the crop intended to “help” to become the alfalfa’s strongest competitor.

Alfalfa has weak seedling vigor. A thin first-year stand begins with fewer plants available to survive winter injury, traffic, disease and natural thinning. The real question is whether enough alfalfa will remain in years four, five and six.

Start by Defining a Successful Stand

Roberts recommends approximately 25 to 30 emerged alfalfa plants per square foot during establishment. Survival is much lower than emergence. “After that first year, around 60 to 80% of those seedling alfalfa plants die,” he explains. Natural thinning leaves a productive mature stand with perhaps four to eight plants per square foot.

Once plants become larger and individual crowns are difficult to distinguish, stem density becomes the better measurement. Approximately 50 stems per square foot is an important benchmark. Below that level, yield potential generally begins to decline.

These numbers help growers judge companion crops correctly. A heavy oat cutting can hide weak alfalfa underneath. The field may appear productive when viewed from the windrow, even though the crop intended to remain for several years has already been compromised.

Moisture Changes the Answer

Water availability was central to Roberts’ research. His Utah trials used line-source irrigation, which created a gradient ranging from fully irrigated ground to dryland conditions. This allowed the same treatments to be compared across several moisture levels.

Under full irrigation, oats reduced alfalfa stem density at the first cutting. By the second cutting, much of that density difference disappeared because the alfalfa had enough water to recover after the oats were removed. Even then, the companion crop still reduced alfalfa yield during the establishment period.

The dryland results were less forgiving. Where moisture was limited, alfalfa planted with oats produced a weaker stand than solo-seeded alfalfa. The effect remained evident at the second cutting, showing that early competition left more than a temporary visual difference. Even alfalfa planted without oats or herbicide performed better than the oat treatment in some dryland comparisons. Clean, herbicide-managed alfalfa produced the strongest dryland stand.

The practical explanation is straightforward. A companion crop cannot manufacture water. Where growing-season precipitation is scarce, every oat plant draws from the same soil-moisture account as the alfalfa. When that account is nearly empty, the faster-growing crop gets paid first.

Preserve Moisture Before Planting

On our northeastern Washington farm, establishment begins long before the drill enters the field. We often complete tillage, packing and nutrient incorporation in fall, then leave a stale seedbed through winter. Early spring planting avoids reopening the soil and sacrificing stored moisture during another tillage sequence.

No-till drills can also place seed into firm soil with good depth control. In a stable no-till or stale seedbed, seed may sometimes be placed slightly deeper to reach moisture than it could in freshly tilled soil. That is not permission to bury alfalfa. It is a reminder to evaluate actual field conditions instead of following one depth setting everywhere.

Roberts reduces establishment to three essentials: seeding depth, seed-to-soil contact and moisture. “As long as you can get those three things right, it doesn’t matter what you did to the field,” he says. No tillage system can compensate for seed placed below its ability to emerge or above the moisture required to germinate.

More Tons Do Not Always Mean More Value

Companion crops complicate economics because they change both yield and quality. In Roberts’ fully irrigated research, solo-seeded alfalfa managed with herbicides produced roughly 3,500 pounds of forage per acre. Adding oats increased production to more than 6,000 pounds.

The oat mixture, however, tested closer to fair-quality hay, while the solo-seeded alfalfa produced premium-quality forage. During the wet, lower-priced 2019 market, the oat mixture was valued near $86 per ton and generated about $260 per acre in gross sales. Premium alfalfa near $170 per ton generated approximately $280 per acre. The solo-seeded system also avoided the cost of oat seed.

The relationship reversed during the dry 2021 market. Feed supplies were tight, buyers needed tonnage, and the price gap between fair and premium hay narrowed. Fair-quality forage near $235 per ton generated approximately $705 per acre from the higher-yielding oat treatment. Premium alfalfa near $265 per ton generated about $437 per acre.

They demonstrate why growers should compare dollars per acre rather than price per ton or yield alone. Seed, herbicide, harvest cost, forage quality, expected market and establishment risk all belong in the calculation.

Feed Needs Do Not End the Analysis

Livestock producers often defend companion crops by saying they need the additional feed. That may be true, but it does not eliminate opportunity cost. A producer who can grow and sell premium alfalfa may be able to purchase more lower-quality forage with the proceeds. High-quality forage can also be blended with straw or another inexpensive feed ingredient, depending on the ration.

The correct comparison is not “feed versus no feed.” It is the quantity and feeding value produced by each system, the value of alternative feeds, and the consequences for the permanent alfalfa stand. A short-term forage shortage should not automatically justify a practice that increases the chance of replanting the field early.

A Practical Decision Rule

In dryland conditions—especially where little rain falls during the growing season—the safest general recommendation is to establish alfalfa without a companion crop and control weeds directly. Limited water should be reserved for the crop expected to remain.

Under dependable irrigation or reliable in-season rainfall, an oat companion crop becomes more defensible. It may control erosion, add first-year production and improve gross returns when the market rewards tonnage. Growers should still monitor alfalfa density, account for lower forage quality and recognize that adequate water reduces competition risk rather than eliminating it.

Companion crops are neither heroes nor villains; they are competitors that sometimes earn their place. Roberts offers a blunt warning: “If you’re going to make a stand fail to get a few extra dollars, don’t come complaining to me when you have to replant.” The best decision protects establishment first and measures value per acre over the life of the stand.