Field crops


How late will corn yield respond to nitrogen fertilizer?

There will be good response until at least tassel, probably 10 days after tassel. In six on-farm trials in 2010, rescue nitrogen was applied at the tassel stage and the average yield response was 34 bushels per acre. These fields had been fully fertilized but lost nitrogen due to wet weather. In three Missouri research station trials, a single nitrogen application at silking stage gave a yield response from 35 to 50 bushels per acre. No fertilizer was applied before the silking stage. In a Nebraska research station trial, a single nitrogen application at 10 days after tassel gave a yield response of 43 bushels per acre. No fertilizer was applied before 10 days after tassel.

— Answer by Peter Scharf

What are the economics and availability of natural gas for corn drying assuming lack of heat units delays corn maturity?

With the late-planted 2015 corn crop, producers might be in a situation where they must harvest corn at a much higher moisture percentage than has occurred for the past several years. The cost of harvesting higher moisture corn will come either through discounts for the sale of high moisture corn to a grain elevator or through increased drying costs for on farm drying. For those interested in current LP prices, the U.S. Energy Information Administration (EIA) provides current pricing information on Missouri LP prices at: For those interested in the economics of drying corn, there are two spreadsheets available from MU Extension at: . These spreadsheets can be found under the crop and fertility management section.

— Answer by Scott Brown

Cover crops

What are the best cover crops for nitrogen fixation if planted on prevent-planting acres?

Hairy vetch, crimson clover, alsike clover, arrowleaf clover and Austrian winter pea are the most commonly used legumes for cover crops in Missouri. Arrowleaf clover and Austrian winter pea are less likely to overwinter than the others. Soybean might also be an option for short-term use.

Photosynthesis provides the energy needed to drive nitrogen fixation. As a result, no legume fixes significant amounts of nitrogen until plants become relatively large. Although rhizobial infection and nodule formation begins two to three weeks after planting, fixation during this period is limited by photosynthetic capacity (leaf area). Further, soil temperature regulates the activity of the enzymes responsible for nitrogen fixation. The optimum soil temperature is around 75 to 80 degrees Fahrenheit. Nitrogen fixation ceases once temperatures drop much below 50 degrees Fahrenheit.

Most of the nitrogen fixed is stored in plant parts. Nitrogen accrual for the cover crop legumes mentioned above range from 40 to 150 pounds per acre annually under Missouri conditions. To capture most of this nitrogen, the biomass of the cover crop must break down and be released from the organic matter; it will not be available instantly.

— Answer by Rob Kallenbach and Bill Wiebold

For more information on cover crops, see MU Extension publication G4161, Cover Crops in Missouri: Putting Them to Work on Your Farm.

More resources about cover crops from the Missouri division of the USDA:


Given the poor growing conditions, does it make sense to continue spending money on inputs for grain crops?

Two considerations need to be taken into account to answer this question.

First, is the crop insured? If the crop is insured, you are under obligation to use “good farming practices.” Good farming practices incorporate the opinions and published materials of agricultural experts. So if you can find an expert opinion or published material indicating you should not continue rescuing the crop, you need to save that opinion to justify your action. Otherwise, you probably are obligated to attempt to optimize your production. If you choose to abandon the crop, you should call your insurance agent and ask for an adjuster’s opinion.

Second, from an economic perspective, the question involves weighing the benefit against the cost. Costs you have already sunk such as fertilizer and seed are not important in this decision. The question becomes: Am I expected to get more money in increased production than I spend in rescuing the crop? For example, assume that you have lost a lot of nitrogen and your corn crop is suffering as a result. It has been recommended that you add another 100 pounds of nitrogen to the crop and this will cost you $64 per acre. You expect the value of the crop at harvest to be $4 per bushel. If the additional nitrogen is expected to increase your yield by 16 bushels ($64 divided by $4) you should add the nitrogen. Even if you will lose money on the crop as a whole (considering the cost of inputs already used), you should make the additional investment if you expect the benefit to exceed the cost.

— Answer by Ray Massey


Is foliar applied fertilizer an effective alternative if fields are too wet to apply other forms?

Foliar applied fertilizer is not going to supply enough nitrogen (N), but it is better than nothing. Results from 2010 MU Extension study:

N source N rate N timing Application method Yield response
CoRoN 7.5 pounds N per acre (label rate), twice V10, V13 Broadcast foliar 13 bushels per acre
Urea + Agrotain 20 pounds N per acre, twice V10, V13 Broadcast dry 34 bushels per acre

For more information on the study, see

— Answer by Peter Scharf

Please provide information of aerial application of fertilizer service providers.

Unfortunately, aerial applicators have shifted heavily toward fungicide application at this time. It will be difficult to acquire aerial application of fertilizer. If it is possible, it will only be possible if a large number of acres are lined up.

— Answer by Peter Scharf

Has this year’s weather increased the amount of soil tests we need to take to prepare for next season?


— Answer by Peter Scharf


Alfalfa has not been cut for hay in a timely fashion. What are the consequences for quality and winter survival? Should management change from normal?

If alfalfa is cut after 10 percent bloom, it will be stemmy and too low quality for dairy feed. However, it will have the quality to meet maintenance requirements for dry cows and pleasure horses. If fed with an energy supplement, lower quality alfalfa can also work for beef stockers and replacement heifers.

At this point in the year, there is no consequence for winter survival. Management should include cutting and baling the current crop of alfalfa to enable growth for the next cutting.

— Answer by Craig Roberts

Late harvest and heavy leaching from rain have caused low-quality hay. What are some possible solutions for low hay quality?

The first step in dealing with over-mature or rain-damaged hay is forage testing. Forage testing results provide the information needed to accurately balance animal rations.

Low-quality grass hay can be baled and treated with ammonia in a procedure known as ammoniation. Ammonia treatment should only be applied to low-quality grass hay. Ammonia breaks linkages in the fiber that prevent forage digestion; the result of ammonia treatment is increased fiber digestibility and high energy.

According to research at the University of Missouri, ammonia treatment also degrades ergovaline and other ergot alkaloids produced by the tall fescue endophyte. Ammonia-treated fescue is far less toxic than untreated fescue.

The procedure for ammoniation can be found at Take note that this bulletin shows bales stacked as two on the bottom and one on top. Some of our producers have stacked four on the bottom and three on the top. Also, please be aware that this bulletin does not account for changes in cost of anhydrous ammonia over recent years.

Another option is to provide grain or grain by-product supplements to meet the nutritional needs of the animals. There are lots of good supplemental feed options, but the best results require knowledge of forage nutritive value.

Another option is to treat the low-quality hay with calcium hydroxide or calcium oxide. Recent work at MU showed that these treatments can be successful for those with the equipment to do it. For more information, see

Lastly, fertilize cool-season grass hay fields in mid-August autumn. Good quality cool-season grass pastures this autumn can be used to supplement poor quality hay. A strip grazing program, where a few days of grass and a few bales of hay are fed at the same time, can stretch the good quality pasture while using some of the hay. For the best results, move stock to a new strip of grass and provide a new bale or two when the original hay bales are 80 percent consumed.

— Answer by Craig Roberts and Rob Kallenbach

What are the recommended scouting methods to quantify the risk from ergot poisoning in hay, pasture and other forages?

There are no hard and fast rules for scouting ergot or determining thresholds. We first recommend walking the field and looking for sclerotia in the seed heads. Sclerotia are chocolate-colored ergot bodies that look like mouse droppings. Be sure to walk the entire field. If sclerotia are present, they will appear in the seed heads of nearly all pasture grasses and small grains in June and July. For more information, watch this video:

In our judgment, if 20 percent of the seed heads contain sclerotia, the field should be considered highly toxic. But this is merely our judgment based on years of experience. 

— Answer by Craig Roberts

How do you repair hoof damage to wet soils?

The best repair for cool-season grass fields damaged by hoof traffic is to implement good grazing practices. Avoid grazing hoof damaged pastures until the regrowth reaches 8 to 10 inches in height. Once the pastures recover, be careful to not allow stock to graze the pasture to a height of less than 3 inches.

— Answer by Rob Kallenbach and Craig Roberts

Are there short-season, summer-annual forages that can be planted this late to produce some hay? What about silage?

Yes. Small grains (rye, oats, wheat) and/or annual ryegrass could be planted in late summer for hay or silage. Turnips and other Brassica species can be planted for forage too, but they are difficult to store as hay or silage.

— Answer by Rob Kallenbach and Craig Roberts

Are preservatives or chemical dryers helpful for preserving silage, haylage or hay?

These products can either be used for speed drying (desiccants) or allowing the safe storage of moist hay (preservatives). Given the cost and hassle of applying these products, most are used for legume hay.

For more information on preservatives, visit

For more information on desiccants (as well as bit on preservatives), visit and

— Answer by Rob Kallenbach and Craig Roberts

If hay is recently cut, will the stand survive typical 90 degrees and higher summer temperatures?

For tall fescue and many other cool-season grasses, stand decline should not be much greater than normal. Cool-season grasses often go through a summer dormant period. Over the years, many tall fescue-based pastures and hayfields have been through several wet and drought cycles. For fields of smooth bromegrass, leaving a 4-inch stubble would be advisable as that species elevates its growing point as it matures.

Although this might be a tough year for many legumes, harvesting now would help them more than leaving the forage standing. Legume stand thinning might occur, but that would be due to the wet weather and grass competition, not because of the harvest timing.

— Answer by Rob Kallenbach and Craig Roberts

Hay is flooded and contaminated with dirt and other stuff. Will this contamination affect the animals?

Perhaps. Most often animals will refuse forage covered with soil or other contaminants. The greatest threat will be when livestock are forced to eat forage they would otherwise refuse.

— Answer by Craig Roberts and Rob Kallenbach

Will moldy hay affect animals? Is there something to decrease impact?

It can, but it is unusual. Often animals will refuse moldy hay if there are other sources of feed. Be most careful feeding moldy hay to horses because it can cause colic. Diluting the diet with other non-moldy feedstuffs can lessen the impact.

— Answer by Craig Roberts and Rob Kallenbach

Should additional nitrogen fertilizer be applied to cool-season grass pastures in July after hay is made?

Given what we expect regarding the nutritive value of hay this year, we would recommend fertilizing (mainly with nitrogen) cool-season grass hay fields in mid-August. Fertilizing before mid-August typically does not help much because dry conditions and warm temperatures in summer limit cool-season grass growth. Good quality cool-season grass pastures this autumn can be used to supplement poor-quality hay. Strip grazing programs, where a few days of grass and a few bales of hay are fed at the same time, can stretch the good quality pasture while using some of the hay. Move stock to a new strip of grass and provide a new bale or two when the original hay bales are 75 percent consumed.

— Answer by Craig Roberts and Rob Kallenbach

Grain sorghum

Will grain sorghum yield response to late application of nitrogen?

MU Extension has no data for this question, but Jason Kelley from Arkansas Extension says early boot is the latest stage at which he’d apply nitrogen.

— Answer by Peter Scharf


Atrazine was applied to corn land, but the corn was never planted. With all the rain, will the atrazine be diluted enough to plant something else this year? What about planting a forage this fall?

You must follow the planting interval restrictions listed on the label. Please follow this link for additional information:

— Answer by Kevin Bradley


Are crop roots permanently damaged from water-logged soils? Will crops be more prone to lodging?

Roots require oxygen for growth. Because water in soil pores replaces oxygen, roots will not grow into water-logged soils. However, many field crops have the ability to produce aernchyma in their roots. This is tissue with large air spaces. Rice plants produce this tissue, so oxygen reaches roots when submerged in water. It takes days for crop plant roots to adjust to water-logged conditions and even if aerenchyma forms, root growth will be slow.

Several root rot fungi favor water-logged soils. In some incidences, plants might not survive heavy fungi infection.

As water drains from soil, oxygen will return. Crop plant roots will resume growth. Roots compete with above ground parts for sugars and other nutrients. The competition increases to roots disadvantage with increased plant size and during grain filling. Plants might be vulnerable to lodging until adequate anchorage is established.

Hot temperatures increase water evaporation from leaves. Plants with reduced root systems will likely exhibit symptoms of drought stress on hot days.

Stomata of newly flooded plants will close. If this happens while air temperatures are hot, the newly flooded plants are vulnerable to heat stress and death. If the plant survives, plants will adapt and stomata function should return to near normal after 24 to 48 hours.

— Answer by Bill Wiebold


What is the availability and costs of germination and vigor testing for soybean held to next spring?

Missouri Crop Improvement Association can run accelerated aging tests in our Columbia lab at any time, provided we have germinator space available. However, we recommend testing later this winter or early next spring to give a more accurate representation of the quality and vigor of the seed after it has been exposed to individual storage conditions. A standard warm germination test is $14.25 and an accelerated aging test is $19.25.

Standard cold tests would be another option, but we do not offer that test in our lab due to lack of demand.

Regardless of the test method, vigor test results should be viewed in conjunction with standard warm germination test results to give an idea of maximum germination potential under both ideal and high-stress conditions.

— Answer by Richard Arnett


When is it too late to plant soybean?

It is difficult to answer this question because nature doesn’t work in a straightforward manner. Soybean maturity is controlled by photoperiod (modified by temperature). I wrote about planting soybean in mid-July in this article: Risk from frost and low yield are two risks involved, but both of these vary among years and are highly dependent on summer and fall weather.

— Answer by Bill Wiebold

Farmers have soybean seed treated with fungicides and/or insecticides. Because of prevent planting, the seed will not be used for planting, but dealers are not accepting returns. What should farmers do with treated seed?

The Missouri Department of Agriculture has released the following statement related to proper disposal of treated seed:

Storing soybean seed from one year to the next is not easy to do. Temperature and moisture are enemies of stored seed, and soybean seed is susceptible to germination and vigor loss during storage. Storage facilities that ensure cool temperatures and low humidity are the best opportunity for safe soybean seed storage. As temperature and humidity increase, the risk of vigor loss also increases.

Vigor and germination are two different, but important, components of seed quality. Germination percentages on seed tags or performed in seed analysis labs are measured using nearly ideal germination temperatures. Sometimes they are called warm germination percentage. Seed tags are required to display them. However, seeds are often planted in less than ideal conditions including cool soil temperatures. There are several tests that attempt to predict emergence from stress environments. These tests are often called vigor tests, and several tests include some exposure to cold temperature. The best test of soybean seed vigor is called accelerated aging. This test includes exposure to warm, humid conditions. Seed, especially seed stored in poor conditions, can exhibit adequate germination percentage but test poorly for vigor. This seed should not be planted in stress conditions that are common in spring.

— Answer by Bill Wiebold

If you plant soybean, knowing it will likely freeze before they are able to harvest, when is the best stage to bale?

If possible, harvesting at the early pod stage gives the best compromise between yield and nutritive value. If a frost is imminent, then harvesting at that time would be better than waiting.

— Answer by Craig Roberts and Rob Kallenbach

Should soybean seed be inoculated with rhizobium when planting next year?

Inoculation of soybean seed with rhizobium is not necessary unless soybean will be planted in a field in which soybean had not been planted for three years or if the field had been flooded for at least a month. Rhizobium bacteria require oxygen to live in soil (without a host), so flooding might reduce numbers. Success from inoculating with new highly potent rhizobium strain can be difficult because of the large number of naturally occurring bacteria. Wild rhizobium will often out compete applied rhizobium because of number differences.

— Answer by Bill Wiebold

Soybean plants in water-logged soils have turned yellow. Is the damage permanent?

Probably not. Rhizobia infect soybean roots through root hairs. Root hairs occur near the tips of actively growing roots. Roots will not grow in the absence of oxygen, so few nodules will form in water-logged soils. Nitrogen fixation requires oxygen for energy. For these reasons, nitrogen fixation might be reduced to near zero in water-logged soils. Once water drains from soil and oxygen returns, nitrogen fixation should begin. Risks of permanent damage or reduced yield increase with length of yellow symptoms or the age of the plant. Yellowing because of slow nitrogen fixation is more harmful during seed filling than vegetative growth.

— Answer by Bill Wiebold


Should farmers manage weeds in prevented planting fields to reduce weed seed bank?

Farmers should do some form of weed control in prevented planted fields to prevent weeds from producing seed, if possible.

— Answer by Kevin Bradley

How should large weeds be controlled in prevented plant acres?

There are a few options. One would be tillage prior to seedhead and viable seed production. A second option would be to try to establish a cover crop now to achieve some sort of cover over the soil to prevent weed encroachment. The third option would be through the use of herbicides. As a lot of money has already been spent for weed control on many of these fields and we have to be aware of herbicide carryover to next year’s crop with any applications made at this point in the season, the question of which herbicide program to use becomes much more complex. Standard burndown type of programs that include glyphosate + dicamba or glyphosate + 2,4-D or glyphosate + Sharpen should be considered. These would be some of the cheaper choices and would not cause problems for corn or soybean planted next season.

— Answer by Kevin Bradley

How should you control large weeds in corn and soybean fields?

In corn, there are really no legal options for most post-emergence herbicide applications at this time. Once corn reaches about 30 inches or so in height, our options for weed control become very limited. Making an off-label herbicide application at this point to large weeds will more than likely not provide adequate control of that weed, and you also run the risk of disrupting kernel set and overall corn ear damage. In soybean, although it is certainly not ideal, there are options of glyphosate (in Roundup-ready soybean) plus group 14 (PPO) herbicides. Some of the more common trade names include Prefix, Cobra, Flexstar and Ultra Blazer to name a few.

— Answer by Kevin Bradley

More information on weed management:

ARC, PLC and CTAP Acreage Maintenance
Producers enrolled in Agriculture Risk Coverage (ARC), Price Loss Coverage (PLC) or the Cotton Transition Assistance Program (CTAP) must protect all cropland and noncropland acres on the farm from wind and water erosion and noxious weeds. Producers who sign ARC county or individual contracts and PLC contracts agree to effectively control noxious weeds on the farm according to sound agricultural practices. The Missouri Farm Service Agency State Committee has approved volunteer stands of weeds on idle acres to protect from wind and water erosion, but weeds must be chemically or mechanically controlled to prevent seed formation. The deadline to control weeds is August 10. Producers should make every effort to control weeds as soon as possible.


What is the best way to prepare this season’s wheat for planting this fall?

There are questions about the advisability of saving seed from this year's crop for planting this coming fall. With the high levels of scabby kernels and the overall lower quality of grain, this is not a good year to consider saving seed for planting. If this alternative is still being considered, there are certain steps to take in making the decision of whether to use saved seed for planting. For more information on evaluating winter wheat seed quality for possible planting use, see

— Answer by Laura Sweets

What is vomitoxin?

This answer is developed from an excellent document prepared by Dwight Aakre and others with NDSU Extension Service at North Dakota State University. For more information, see

Vomitoxin is a common name for the chemical deoxynivalenol (DON). This mycotoxin is produced by the causal agent of Fusarium head blight (scab), Fusarium graminearum (Gibberella zeae).

I explain Fusarium head blight in more detail in the following article:

— Answer by Laura Sweets

Where can you have grain or plants analyzed for vomitoxin and other toxins? What do tests cost?

The MU Veterinary Medical Diagnostic Lab provides a Summary List of Services and Fees at

The test we are interested in is toward the end and called “Mycotoxin screen in feedstuffs (aflatoxin B1, ochratoxin A, vomitoxin, zearalenone; quantitative)” under Toxicology. It is $75.

— Answer by Tim Evans

Is grain or leaf dust from wheat infected with Fusarium fungi hazardous for humans to breathe? What about contact with the skin?

This answer is based on a document prepared by Ohio State University:

Vomitoxin is not found “freely floating” in the air. However, it is present in dust particles from wheat chaff and grain in elevators, bins, seed houses, grinding facilities, etc. A dust mask should be worn whenever handling contaminated grain. Read the article by Jepsen and Fleming, Dust Mask Protection from Wheat Dust, ( for information on the health effects associated with the inhalation of dust particles.

Although mycotoxins are of the greatest concern when ingested with contaminated food products, some toxins, including vomitoxin, can be absorbed through the skin. And remember, vomitoxin might not be the only toxin present in moldy grain. Gloves (preferably latex/nitrile) should be worn and handlers should wash hands and other exposed skin thoroughly after handling molds grain. The biggest danger is touching your mouth with hands that have touched scabby grain.

— Answer by Bill Wiebold

What is the process to make a crop insurance claim for vomitoxin-contaminated wheat?

Please this see this Risk Management Agency Fact Sheet, “Vomitoxin Testing” at

— Answer by Bill Wiebold