Margaret A Smith, PhD
Albert Lea Seed Agronomist

Key points are boxed below.

When to Plant Spring-seeded Small Grains

The common guideline for spring planting small grains in the northern U.S. is, “as soon as you can get in the field.” As soon as you can get in the field isn’t early at all this year!

Select Minnesota, Iowa, or Wisconsin below to see an oat planting graph comparing this year’s progress (red), last year’s progress (blue), and a 10-year average (green). As you can see we are far behind planting progress compared to last year at this time, when spring was very warm and dry, or even to the previous 10-year average.

Minnesota

Iowa

Wisconsin

Long-term average optimum seeding times vary by latitude—earlier farther south and later farther north in the upper Midwest. In most areas, the optimum period spans a 7- to 10-day period. Optimum planting dates have been defined by several universities, using both research data and field observations. The University of Minnesota suggests these planting date ranges for spring small grains (Table 1).

Table 1 – Optimum seeding dates and last recommended seeding dates for small grains in Minnesota

Area of Minnesota Optimum Seeding Date Last Planting Date
South of U.S. Highway 23 First week of April First week of May
South of MN Highway 210 Second week of April Second week of May
South of U.S. Highway 10 Third week of April Third week of May
South of U.S. Highway 2 Fourth week of April Fourth week of May
South of Canadian border First week of May First week of June

Source: University of Minnesota’s Late Planting Spring Small Grains

North Dakota State University recommends planting before May 15 in the northern areas of the state and by April 30 in the southern areas of the state. University of Nebraska suggests planting between March 15 and April 1, with the optimum seeding time the third week of March.

Key Point: What is Your Optimum Seeding Date Range?

Not sure where you fall in these geographic ranges? The closest you can get to localizing these recommended dates for your farm is to use past experience on the farm and in your surrounding area. Your observations are important due to microclimatic differences, such as in the coulee regions of the Driftless Area and near the Great Lakes.

What is a long term, early average planting day for small grains you or your neighbors grow? Perhaps not the earliest planting date you’ve ever experienced, but early! The optimum for your farm is likely between that date and 7-10 days following. Yields drop fairly consistently after that optimum period for about 30 days, after which small grain yields will likely drop quickly with each day’s additional delay in planting.

This impact on grain development and yield is due largely to temperatures during early development, pollination and grain fill. The ultimate “last planting date” (based on agronomic considerations) for your area will vary from year to year, based on the summer daytime AND nighttime temperatures during grain flowering, pollination and seed fill. The challenge in picking that “last day” is our inability to adequately predict what those temperatures will be.

Growth Stages of Cereal Grains

Spring-planted cereal grains are cool-season annuals that thrive in temperatures below 70 o -75o F. Minimum soil temperatures for germination of small grains are:

  • 35 o-37o for spring wheat
  • 36o F for barley
  • 40o F for oats

Ideally, daytime air temperature highs would reach 60º F and overnight temperatures would not drop below 40º F for a great small grain stand within 8-10 days after planting. Fortunately, small grains are resilient through germination and emergence; during seedling emergence, the plant crown can survive temperatures down to at least 28º F. Oats planted on two farms in northern Iowa in late March this year withstood an extended wet, cold period and didn’t emerge for 30 days, but now have excellent stands.

Cereal grains pass through two development stages: during the first, vegetative stage, leaves, the plant crown, and tillers are initiated and roots begin development. After cereals complete this early growth stage, and sufficiently long days (hours of sunlight per day) and Growing Degree Days (GDD) are accumulated, they enter their second, reproductive stage. To reproduce (produce seed) the plant’s main stem and tillers elongate, plants flower, pollinate and fill seed.

Impacts of Delayed Planting on Cereal Grain Development and Grain Yield and Quality

With delayed planting, average temperatures tend to increase, forcing cereal grain plants to move through their growth stages more quickly—often at the cost of potential yield. While early warmth promotes plant growth, unusually high temperatures can stress the plant. Growing too quickly means that plants produce fewer tillers, develop smaller heads and fewer spikelets per head, and have smaller kernels and lower test weight. Additionally, if plants lack adequate moisture in summer heat, they will preserve water by closing their stomata, reducing photosynthesis, which also is detrimental to yield.

Oats in the upper Midwest generally are planted in early April and harvested in mid-July, but the wet, cold spring weather this year has delayed planting. Planting now may push the grain fill stage into the hottest part of the growing season with high temperatures posing a potential threat to grain yield. Several days of temperatures above 75°F during panicle emergence and the milk stage reduces yields. Night temperatures above 70 o F during grain fill in July or August increases plant respiration and reduces grain fill.

On average, late-planted cereal grain yields decrease 1 to 1½ percent every day past the optimum planting date. After about 30 days, the rate of decline in yield and test weight accelerates. As grain yields decline, the percent protein in the grain tends to increase. This can be good or bad depending on your market. High protein is desirable for bread wheat, but undesirable for malting barley. For oats, delayed planting also decreases the percentage of plump kernels and increases the incidence of crown rust infection.

Key Point: How Late Can You Still Plant Spring Grains?

Your decision to plant small grains beyond the 30-day extended planting window is based on three major factors, and you may have others:

  1. The agronomic knowledge about grain yield quality decline. You may be satisfied with a lower grain yield, but food-grade quality will be more difficult to meet. Do you have an alternate market for light-test weight small grains?
  2. The value of the small grain in 2022. Oat and wheat are at near market highs for the last 10 years. Can you accept lower yield with these higher prices?
  3. The importance of small grains in your rotation. Organic growers, in particular, often rely on their small grains in the rotation to prepare for a following corn crop. A legume or mixed cover following the small grain harvest is critical to their corn production. Conventional growers may have more flexibility in their rotation.

Key Point: Planting Oats, Barley, and Wheat Late—Management Options

  1. You may want to consider an alternative crop instead of risking the probability of a small grain harvest with reduced yield and quality.
  2. If you do plant late, increase the seeding rate by 1 to 1.5 percent for every day past the optimum planting date up to 1.6-1.8 million seeds per acre. Since tillering will be reduced with warmer temperatures, the increased seeding rate will promote more main stem development to help overcome tillering loss. Even so, summer heat stress is likely to affect final test weight, even in a thickly planted stand.
  3. If temperatures warm rapidly during seed set and early grain fill and grain yield potential seems poor, consider harvesting your small grain for forage.

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