Common uses of cover crops include reduction of soil erosion, weed prevention, nutrient scavenging and alleviation of soil compaction. They are most easily used after small grains, canning crops, and silage, but can also be used in the corn-soybean rotation.

The difficult growing conditions of 2011 provided a unique circumstance for collecting cover crop data. Researchers and educators from University of Minnesota Extension, University of Minnesota Southwest Research and Outreach Center, and Albert Lea Seed House partnered with North Central Region Sustainable Agriculture Research and Education (NCR-SARE) on the establishment of cover crop plots to be used for education and outreach.

The cover crop plots were established in areas that were too wet for spring 2011 planting; conditions were similar to those for prevented-plant acres. The year's weather extremes allowed us to study the agronomics of cover crops under both wet and dry conditions.

Cover crops included: tillage radish, oats, field pea, winter rye, sudangrass, sorghum-sudangrass, pearl millet, cowpeas, tillage radish-oats-field pea mixture, oats-cowpea mixture, oats-berseem clover mixture, and oats-crimson clover mixture. Site conditions included: after corn with standing water that prevented planting, after alfalfa with soil too wet to plant, and after oat harvest. Two planting dates were used: Aug. 17 and Sept. 9, 2011. Plant cuttings were taken Oct. 27, 2011.

Data showed that under the 2011 growing conditions in Lamberton, Minn., cover crops had the most above-ground growth when planted in mid-August with the previous cash crop of field corn, except in the tillage radish. No single cover crop species consistently had the most above-ground plant matter for each planting date or site.

The top plant-matter producer was the oats-cowpea mixture planted Aug. 17 with the previous cash crop of corn (4,539 pounds dry plant matter per acre). The lowest plant-matter producer under all plot conditions was the cowpeas (zero pounds dry plant matter per acre). No samples were taken from the plots planted in the 2011 oat field. Conditions were too dry for growth.

University of Minnesota researchers and Extension educators contributed to a cover crop decision tool that can be found at the Midwest Cover Crops Council website: http://mcccdev.anr.msu.edu. To join the Minnesota Cover Crop Listserv, email me at sacke032@umn.edu.

This single-generation per year insect normally affects alfalfa around the timing of the first cut for hay, although the actual timing varies from year to year as influenced by temperatures.

Daily temperatures are recognized as playing a significant role in how fast insects develop. Scientists have developed models for insects capable of causing large-scale economic losses. The models are referred to as degree day (DD) models. They use the daily average temperature and the experimentally determined lower developmental threshold temperature.

This knowledge is used to estimate the rate of physiological development and to forecast egg hatch and other biological events. They tend to be more accurate in predicting biological events than calendar dates, though not always.

An alfalfa weevil predictive model has been available for many years. University of Wisconsin Extension summarizes the model at www.soils.wisc.edu/uwex_agwx/thermal_models/alfalfa.

Alfalfa farmers who become familiar with the model will gain insight about when weevils, particularly the larvae, are most likely to be feeding. The goal of these models is to alert the crop manager to the need for timely field checks and to avoid missing an infestation.

Field observations from southern Minnesota indicate that the overwintering adult weevils began moving into alfalfa fields the week of April 15. The adults are there to feed and females to lay eggs in stems. The models would suggest that early larval hatch is underway and checking fields to determine population levels would be wise.

These early checks can provide an indication as to whether infestations at the field level are significant enough to warrant early cutting or insecticide treatments. Early cutting to avoid foliage loss is preferable when timing permits so beneficial insects that naturally suppress weevils are conserved.

As crop managers monitor alfalfa and weevil development, remember that warmer temperatures will accelerate development; cooler temperatures will slow it down. Moisture stress may also interact in the plant-insect relationship. If plants are not actively growing due to stress, the feeding injury can be significantly increased.

Using as many of the available tools as possible will help crop managers better understand the timing of biological events in the fields and lead to better management decisions.

More educational information for on forage crops can be found at www.extension.umn.edu/forages.

Federal law provides a zero tolerance for treated soybeans at market. That means that a single treated seed can contaminate a truck, bin or silo. Your elevator can hold you legally responsible for the contamination because of a problem that started with one treated soybean.

University of Minnesota Extension recommends that growers take these steps to avoid mistakes that can take place during the rush of planting:

• Make sure nobody on your farm dumps leftover soybean seed into a storage bin.
• Do not use the same equipment to transport treated seed and soybeans sold for grain.
• Clean all equipment that comes in contact with treated seed.
• Manage treated seed before and after planting to reduce the potential for problems.
• Buy only the seed you need to minimize dealing with leftover treated soybeans.
• Work with your seed supplier to develop a plan to dispose of any leftover treated seed.

In addition to avoiding costly penalties because of soybean contamination, handling treated soybeans with care is the right thing to do. Fungicides have a place in seed beds, but not on a dinner plate, which is why it's important to keep treated seed soybeans separate from your soybean harvest.

Take time this spring to pay attention to farm safety, both your personal safety and the safety of the crops that you grow. For more information for soybean growers, visit www.extension.umn.edu/soybean.

If you applied nitrogen last fall
Field conditions were less than optimum for nitrogen application last fall. The dry soil conditions made it difficult for fall anhydrous ammonia application and the incorporation of urea. At this time, we would not expect a large amount of conversion of ammonium to nitrate within the soil if the fall applications were done according to nitrogen best management practices.

Soil sampling for soil nitrate-nitrogen at this time is unreliable and will likely not give an accurate picture of what is still contained within the soil.

If you made fall nitrogen applications and are concerned about how much nitrogen is left, our recommendation at this point is to wait until late May to early June, then use the supplemental nitrogen decision tool found at www.extension.umn.edu/go/1102 (pdf) to determine if a side-dress application is necessary.

If you did not apply nitrogen last fall

• For sandy soils, you should not consider early application. The best practice for sandy soils is to apply nitrogen as part of the starter and a side-dress application.
• For heavier textured soils, you may want to consider using a soil test for nitrate this spring to determine the suggested nitrogen application rate. Since we had a dry fall and winter, there is a good chance that there is a significant amount of soil nitrate left that the corn crop could use. This is particularly true if the previous crop was corn or small grains.

The weather is warm now, but it is hard to tell what may occur a month or more later.

You can find details on soil nitrate testing, calculating supplemental nitrogen, and nitrogen application on the University of Minnesota Extension website at www.extension.umn.edu/nutrient-management/nitrogen-management.

This recharge also occurs with spring rainfall when most crops aren't in yet to consume the moisture. Data from the University of Minnesota's Southwestern Research and Outreach Center in Lamberton indicated that soil water recharge and crop usage is not in a normal pattern this spring.

When the ground froze last fall, there were about 3 inches of plant-available water in the 5-foot soil profile, with most of it below 2 feet. A normal profile would hold closer to 10 inches of plant-available water. Add to this the below-normal snowfall that did not add significantly to spring recharge.

Most tillage done last fall was aided by winter snowfall. Fall chisel plowing provided a rough surface that provides divots for water storage during snow melt and early spring rains.

Conservation tillage done last fall is also aiding in soil moisture retention by leaving significant residue in the fields, reducing soil water evaporation and increasing infiltration during spring rainfall. Last fall tillage was difficult at best because of the dry conditions. Large, hard clods were created with the fall tillage. It looks like the moisture we did get this winter mellowed the clods enough that a tillage operation will be able to create a good seedbed this spring.

Keep tillage minimal this spring to conserve soil moisture and maintain residue on the soil surface. Seedbed preparation must be the goal of spring tillage.

Any clods from last fall should be worked for good seed-to-soil contact at planting. Spring tillage is necessary in most cases, but take care not to get too aggressive because excessive tillage will dry out the soil and cause a dry seedbed. This will cause problems with plant stands and thus affect grain yield even if we receive adequate amounts of moisture during the growing season.

For more information, visit the University of Minnesota Extension website at www.extension.umn.edu/tillage.

Alfalfa will likely break dormancy in the next week to 10 days with forecasted temperatures 10 to 20 degrees warmer than normal, according to University of Minnesota Extension climatologist Mark Seeley.

A number of factors affect the likelihood of winter injury in alfalfa stands, including stand age, variety, soil pH, soil fertility and cutting management. Snow is an excellent insulator and temperature fluctuations are much less under snow cover. The lack of snow this winter is concerning, but, the relatively mild temperatures have helped reduce injury potential.

Alfalfa has a greater potential for winter injury or kill if the temperature near the crowns falls below 15 degrees. Spring-like temperatures in January and February followed by brief cold spells increased the injury potential. Current soil temperatures range from 20 to 30 degrees and will increase quickly.

Winter injury is difficult to predict and is usually a result of a combination of several environmental and plant stress factors, including cold soil temperatures, lack of snow cover, and alternating warm and freezing temperatures. Newer alfalfa stands that are well-fertilized, and varieties with superior winter-hardiness, are less susceptible.

Diagnose winter injury by digging up plants and examining roots after the spring thaw. Healthy roots are firm and white in color. Roots with winter injury are gray and appear water-soaked. If 50 percent or more of the root appears injured, the plant will most likely die during spring green-up or later in the year.

To estimate yield potential in injured stands, count the number of stems in a square-foot area. If more than 55 stems are found, yield is not likely to be affected; however, if fewer than 40 steams are found, yield will likely be severely limited.

Winter-injured stands require different management than healthy stands. If you decide to keep an injured stand, allow alfalfa plants to mature longer before cutting, increase cutting height, ensure fertility is adequate, control weeds, and do not take a late-fall cutting.

More educational information for on forage crops, including Minnesota Agricultural Experiment Station variety trial results for alfalfa, can be found at www.extension.umn.edu/forages.

The protein content of the soybean impacts the protein content of the soybean meal, and end users pay a premium for high-protein meal. Because these premiums get passed down through the value chain, higher-protein soybeans command a premium at the first point of sale, the local elevator. Normally, producers don't see this price differential because long-term variation in soybean quality is built into the local price as a part of the basis.

Occasionally, local protein levels can dip low enough that grain handlers begin docking for low-protein soybeans delivered to local elevators. This occurred in an area in south central Minnesota in the fall of 2011. There, many farmers accepted a 15-cent per bushel penalty for low-protein soybeans.

Soybeans grown in the northern and western ranges of the U.S. Corn Belt tend to have lower protein than soybeans grown elsewhere in the U.S. or in South America. This puts farmers in Minnesota and the Dakotas at risk of being penalized for low protein levels, but what can be done?

Farmers can have a direct impact on the quality of the grain that they sell in the fall by selecting the higher-protein lines from among the top-yielding varieties available. Because it is not always easy to identify high-yielding varieties with high-protein seed, it is critical for U.S. producers to educate end-users about other positive attributes of northern grown soybeans.

With the support of soybean checkoff organizations from Minnesota, South and North Dakota, University of Minnesota researchers have shown that the protein fraction from northern grown soybeans tends to be slightly enriched in the amino acids most important to swine and poultry.

While there may be less protein overall, it appears to be of a greater quality than once thought. In addition, there appears to be other minor constituents in the seed of northern grown soybeans that provide additional value to the end user. Researchers are currently quantifying these additional factors.

Farm leaders from Minnesota and the Dakotas will travel with me—a soybean agronomist with University of Minnesota Extension—to the Philippines, Thailand and China in March to educate end-users about the positive attributes of northern grown soybeans. If nutritionists can look beyond crude protein as a measure of quality, Minnesota farmers should soon see increased prices for their soybeans at market.

For more information, visit www.extension.umn.edu/soybean.

Glyphosate-resistant waterhemp was first confirmed in southern Minnesota in 2007 and continues to increase, likely due to the continued planting of Roundup Ready® crops and the exclusive use of glyphosate.

Waterhemp begins emerging near mid-May and continues through the beginning of August. Three factors make it especially difficult to keep under control: an ability to produce nearly 1 million seeds per plant, continual germination throughout the growing season, and an increased frequency of biotypes, or new weeds that are genetically adaptable to a diverse array of herbicide chemistries.

The longevity of waterhemp seeds in the seed bank is short compared to most species, with only 1 to 12 percent survival after four years. For that reason, complete control (zero seed production) of all waterhemp plants over a three- to four-year period should allow producers to take control of this difficult weed problem.

To reduce the selection pressure for glyphosate-resistant waterhemp, Extension crop specialists recommend using pre-emergence residual herbicides, increasing crop rotation diversity in the cropping system, and focusing on the use of Roundup Ready® crops in the rotation where the fewest alternative herbicides to glyphosate exist.

For more detailed information regarding crop rotation and herbicide effectiveness, see the Extension publication "Pre and Post Herbicide Diversification Options," (PDF) at www.extension.umn.edu/go/1096. For more information on how to proactively manage for waterhemp in sugarbeet, soybean, corn and wheat, visit www.extension.umn.edu/go/1097.

How to identify waterhemp
The stems of waterhemp plants have little to no hair compared to redroot pigweed, and the leaves are usually longer and narrower. Waterhemp seedlings have oval-shaped seed leaves and are hairless, appearing waxy or glossy-looking. Waterhemp can range from 4 inches to 12 feet high, but generally grows to about 4 or 5 feet in most field crop situations. In the mature stage, one way to differentiate waterhemp from the other pigweeds is to compare the seed heads. Redroot and smooth pigweed have denser, more compact seed heads than waterhemp.

For more Extension crops resources, visit www.extension.umn.edu/crops.

Media Contact: Catherine Dehdashti, U of M Extension, (612) 625-0237, ced@umn.edu

Climate outlooks currently favor more rain than normal this spring across much of the state, but it might not be enough, Seeley said: "Many areas are so deficient in stored soil moisture they will need 150 to 200 percent of normal rainfall during March and April to make up the difference."

Here are some measures farmers should consider for a planting-season drought:

1. Consider crop insurance. Producers who take out a loan for inputs are usually required to buy crop insurance. Kent Olson, Extension economist, says others will want to strongly consider it this year. March 15 is the standard deadline for finalizing a plan with your agent for crop insurance.
2. If soils remain dry, planting season could arrive early. Jeff Coulter, Extension corn agronomist, recommends that growers avoid planting corn before April 18 to reduce the risk of frost damage to young corn plants.
3. Conserve moisture in the seed zone. Uniform emergence is important for corn. This requires good seed-to-soil contact and adequate moisture in the seed zone, according to Coulter. If dry conditions persist at planting, he advises growers to prepare seed beds close to planting and avoid unnecessary tillage passes.
4. Consider pre-emergence herbicides to reduce weed competition with corn and soybean, since yield loss due to early-season weed competition is greatest in dry years. According to Jeff Gunsolus, Extension weed scientist, most pre-emergence herbicides are activated with just one-half inch of rainfall. This is similar to the amount needed to stimulate early-season weed flushes. Even if dry weather follows a pre-emergence herbicide, it can still be activated by later rainfall.
5. Target post-emergence herbicide applications to small weeds that are no taller than 2 inches, Gunsolus says. Larger weeds are more difficult to control if they are drought stressed and they also compete more with corn and soybean for water and nutrients.