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3/15/2010 - 3/21/2010

Wet Spring Forage Planting Considerations

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 and possible flooding in 2010 has many producers wondering when they can get their forages planted.
Can spring forage stands still successfully be plant? 
The short answer is – yes, into the first ten days to two weeks of 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 one to three inches of the seedbed during the three to four 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.
Planting later than desired, adds to vulnerability 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 planted forages is set by both the planting window that provides for a six to eight 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 rain.
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 extended 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.

It’s Time to Scout for Winter Annuals

by Bob Hartzler, Department of Agronomy

In addition to wet fields and localized flooding, this winter’s record snow cover is likely to contribute to abundant winter annual weed infestations in no-till fields. In most years, winter annual infestations suffer significant mortality due to cold temperatures and freeze/thaw cycles, but the snow provided a blanket of protection. Thus, winter annual infestations will likely be more abundant and vigorous than in typical years.

Now is the time to scout fields to determine the need for herbicide applications specifically targeting winter annuals. The criteria used to determine if winter annuals warrant treatment is ‘fuzzy’ at best, but without scouting fields, the likelihood of efficiently managing these weeds is low.

The decision to treat winter annuals prior to planting should be based both on the species present and their distribution throughout the field. Winter annual identification skills of many agronomists are relatively weak, but knowing what you’re dealing with is essential for understanding the potential impact of the weed and selecting an appropriate treatment. An ID guide focusing on winter annuals and other early-season weeds is available from the University of Missouri Extension. The cost for Early Spring Weeds of No-Till Crop Production is $3.00, or it can be downloaded as a free PDF.

Fields that have a few, scattered patches of winter annuals normally do not warrant special treatment prior to planting. However, the burndown program should be adjusted to ensure complete control of these weeds at planting since they can be highly competitive with the emerging crop.

Fields with uniform infestations of winter annuals may benefit from burndown treatments made well ahead of planting. Benefits of early applications include weeds being easier to control than at planting, and preventing the weeds from accumulating sufficient biomass to interfere with planting operations or crop establishment.

If planting delays occur due to a wet spring, there may be large benefits achieved from controlling winter annual weeds in the next few weeks if conditions permit. As with any pest, proper identification of the winter annual weeds is critical in order to select an appropriate strategy.



Field pennycress is a common winter annual in no-till fields.


Bob Hartzler is a professor of agronomy with extension, teaching and research responsibilities.

This article was published originally on 3/22/2010 The information contained within the article may or may not be up to date depending on when you are accessing the information.

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