When is it Too Late Plant Forages?

April 29, 2008
ICM News

By Stephen K. Barnhart, Department of Agronomy

Spring hay and pasture seedings are normally done from late February through late April in Iowa. The extended period of wet weather in 2008 has many producers still waiting to get their forages planted.

Can they still successfully plant forage crops? 

The short answer is – yes, into the first 10 days to 2 weeks into May. The ‘end of the spring forage planting season’ is limited by seedling development and growth into the summer months. Most forage seedlings  are emerging and growing root systems into the top 1 to 3 inches of the seedbed during the 3 to 4 weeks following germination. 

The increasingly dry and hot soil surfaces in late May and June increase the risk that the small forage seedlings do not establish. So, the risk depends on rainfall and soil temperatures from here on. If conditions turn normal or hotter and dryer than normal, the risk of late planted forage seeding failures increases.  If late May and early June conditions remain cooler and wetter than normal, then later-than-desired spring  forage seedings may survive very well.

If you do plant later than desired, be aware that you are still as vulnerable or more vulnerable to erosion and weed competition.  Keep cereal companion crop planting rates to half of a full seeding rate or less, and mow or clip new seedings several times during the early seedling development months to allow light to reach small developing legume and grass seedlings. Also scout for and manage potato leafhoppers in new alfalfa seedings.

What about skipping spring planting and planting the new hay and pasture fields in late-summer?

The success of ‘late summer plated forages’ is set by both the ‘planting window’ that provides for a 6 to 8 week establishment time requirement for seedlings before the first killing freeze of the fall, and the necessity of adequate existing soil moisture and likelihood of average or better fall rainfall. 

For alfalfa and other forage legumes, the seed should be planted by Aug. 10 for the northern third of Iowa, by Aug 20 for the middle third of the state and by late August or the first week of September for the southern third of the state. Cool-season forage grasses can be planted a few weeks later in each of these zones.

The risk of stand failure is high if seed is planted in dry soil, and rainfall patterns for the remainder of the fall season are erratic.

Can purchased seed be carried over until fall or next spring ?

Seed is perishable.Germination declines over storage time, and declines faster if seed storage conditions are warm and in high humidity. Certainly try to store carry-over seed in a cool, dry place. Even better, try to arrange for storage in a more desirable seed storage facility. If you do have concerns about the viability of carry-over forage seed, have a germination test done before planting, and adjust sowing rates to compensate for any germination percentage losses.


Stephen K. Barnhart is a professor of agronomy with extension, teaching, and research responsibilities in forage production and management.


Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on April 29, 2008. The information contained within may not be the most current and accurate depending on when it is accessed.