Guidelines for Nitrate Testing and Silage Options

Chad Lee, Extension Agronomist, University of Kentucky

The dry weather has many producers considering salvaging the corn crop as silage. The dry weather increases the risk of nitrate toxicity. An updated set of sampling guidelines and testing laboratories are now available online.

Just remember that the sampling procedure and handling of the sample can greatly influence the results of the test. Follow the guidelines as close as possible to avoid false readings from the tests.

One very good aspect of ensiling is that nitrates are reduced by as much as 50% by the ensiling process. If corn is to be ensiled, then samples should be tested for nitrates around 3 weeks after ensiling. However, to get proper ensiling, whole plant moisture must be at the proper levels. According to Donna Amaral-Phillips, bunkers require fresh chop to be between 30 to 35% dry matter (65 to 70% moisture). Upright silos and bags can be a little drier at 35 to 40% dry matter (60 to 65% moisture).

Farmers need to focus on whole plant moisture rather than growth stage to ensure proper ensiling this season. This means that some plants may be harvested early, with little to no grain. The lack of grain will change the feeding value  If possible, corn fields at the same maturity should be cut and ensiled together. Forage analysis will be necessary on all silage this season to allow proper adjustments in final feed rations.

Related Resources

• Nitrate testing in forages, June 29, 2012
• Reminders for Corn Silage Chopping Time: June 28, 2012, Donna Amaral-Phillips
• Harvesting drought corn early for silage: June 28, 2012, Donna Amaral-Phillips
• Ways to Cut Feed Costs with Narrow Profit Margins: June 28, 2012, Donna Amaral-Phillips

Drought Resources for 2012

Chad Lee, Extension Agronomist, University of Kentucky

We have put together a new website to house the 2012 drought information for corn and soybeans. This drought is widespread and we have included articles from other states as well as our resources here in Kentucky.

Websites that monitor the drought conditions and include some other information about weather are near the top of the page. Timely articles, including date published, from Kentucky are listed below the websites. Articles from other states come next. States as far north as Wisconsin are reporting drought concerns. Finally, there are some links to websites about irrigation and crop water use.

If you know of other resources that should be on this 2012 drought website, please let me know. Thanks.

2012 Drought Resources.

Drought Stress and Corn Pollination

Chad Lee, Extension Agronomist, University of Kentucky

Drought-stress corn in western Kentucky. Photo: June 25, 2012. 

Most of western Kentucky is in a severe drought status and that severity is likely to spread to central Kentucky on the next report. Most of the corn is going through tassel and pollination, which is well ahead of the five-year average, and the worst possible time to experience temperatures in the high 90's F (35 C or more). The high temperatures and low humidity dry out pollen and silks faster, both of which need moisture for successful fertilization of the ovules.

In addition to the need for moisture for pollination, the corn plant simply needs more water. Corn around tasseling and silking demands about 0.3 inches (7.7 mm) per day. Most of our fields were at a water deficit prior to tasseling and the water deficit is increasing. The lack of water could lead to the abortion of kernels.

Dry conditions prior to tasseling often result in the tassel emergence and pollen drop before silk emergence. In many cases, the resulting ears may have a few kernels develop near the base of the ear but very few to no kernels near the tip of the ear.

Could Sugar help Drought Stressed Corn?

Chad Lee, Extension Agronomist, University of Kentucky

The dry weather has farmers looking for any options to alleviate drought stress. Some are tempted to try sugar. Plants make glucose sugar through the process of photosynthesis. Crop scientists estimate that about 78 pounds of glucose is needed to produce one bushel of corn and 119 pounds of glucose is needed to produce one bushel of soybean.

To extend those calculations, 50 bushels of soybeans require about 5,965 pounds of glucose and 200 bushels of corn require about 15,580 pounds of glucose. In comparison, some of the products being sold are putting on 16 fluid ounces of product. Those products contain 34% sugar, which comes out to 5.44 ounces of sugar per acre. That is a very small amount compared to what the crops require.

I Hate Crying Wolf…… But Forewarned is Forearmed !!

Doug Johnson, Extension Entomologist

Twospotted spider mites (TSSM) are an occasional pest of soybeans and corn in Kentucky (KY). They are present every year but only important during hot, dry periods. Unfortunately, this is the type of weather we currently have and have had for several months. Additionally, states to the north of us, including Nebraska and Iowa, are already experiencing some problems. I have not received information about spider mites on KY field crops but have seen some large populations in fruit trees (different mite but same circumstances). I, therefore, think it wise for those with field crops interest to keep an eye peeled for this pest.

Twospotted spider mites on soybean leaf
Photo: Frank Peairs, Colorado State Univ.,
 Bugwood.org

TSSM are greenish-white with two dark spots on the back. Adults are about the size of salt grains. Juvenile TSSM have six legs, but adults have eight legs. Other species of spider mites also attack field crops.

Spider mites become active early in the spring and remain active throughout the summer. They live in thinly webbed colonies on the underside of leaves. Occasionally, you will see web strands between leaves. Hot, dry weather allows rapid population growth with each generation taking about five to seven days to complete.

Infestations tend to start on field margins near broadleaf weeds and/or the side from which the wind is blowing, as they may drift on a breeze. They may then spread out in ever enlarging spots if the weather allows.

In corn, damage presents as yellow stippling on the upper surface of the leaves. Heavy and / or prolonged infestations may cause premature drying resulting in loss of tissue, stalk breakage and kernel shrinkage.

In soybean, injury could resemble herbicide damage, foliar disease or nutrient deficiency. Feeding results in tiny yellow spots or stipples which may turn orange. Multiple damaged spots may merge in to larger areas of damage. With severe damage, leaves may turn brown and eventually fall off. Spider mites reduce yields by causing pod shattering, wrinkled seed and early maturity.

Scouting is best done in times of prolonged hot, dry (low humidity) weather. In soybeans the most important time is during the reproductive stages of R1-R5 and where a synthetic pyrethroid insecticide has been used. Shake plants over a piece of white paper and look for tiny white moving specks. A hand lens is very useful in determining if the specks are actually mites. In corn, scouting is much more difficult and less is known about making a control decision. The mites are no harder to find, simply follow the instructions for soybean but using corn leaves. One simply wishes to determine if the infestation is only on the outer edges or is across the field.

Large and widespread, mite infestations usually happen when hot, dry and low humidity conditions have occurred early in the season (like this year!). In these circumstances, scouting should start well before R1 (soybean) and in younger corn. Cooler temperatures and high humidity allow a natural fungus to control spider mites. Rainfall will help the plant tolerate the infestation but will not reduce the mite population. Application of synthetic pyrethroid insecticides and fungicides may worsen the infestation because these insecticides don’t work well on mites and the fungicide may hamper the natural occurring fungus that kills the mites.

If direct control is required, consider using an organophosphate insecticide like chlorpyrifos or dimethoate. If you must use a pyrethroid consider bifenthrin. An application is warranted when most plants are infested with spider mites and leaf speckling and discoloration are apparent.

Reference: Field Crop Insects. Iowa State Univ. CES. CSI 0014. Jan. 2012

Corn, Soybean and Tobacco Field Day

Chad Lee, Extension Agronomist, University of Kentucky


The Corn, Soybean and Tobacco Field Day is scheduled for August 9, 2012 at the University of Kentucky Research and Education Center in Princeton, KY. The morning program will begin at 7:30 am with registration and end at lunch. The lunch is sponsored by the Kentucky Corn Growers and the Kentucky Soybean Board.

The corn and soybean topics will all be discussed on the morning. Format of that program will be very similar to the wheat field days. Tobacco will have programs in the morning and afternoon.

Some of the topics to be discussed are corn row widths and yields, nitrogen management, and high yield soybean.

More Corn and Soybean Challenges in Fields

Chad Lee, Extension Agronomist, University of Kentucky

The images from field problems in Kentucky has been updated. Because the file was getting very large, you can access only the May 2012, June 2012 or the full version which includes wheat. If you access the full version, just be aware that it is 23.5 MB... and growing.

The most common symptom in corn is potassium (K) deficiency. In most cases, the K deficiency is the result of root restriction. Most of the root restriction is from compaction, whether it be sidewall or sub-surface. Areas of Kentucky had ample rain during corn planting and getting sidewall compaction would have been very easy to do. The general lack of rain now adds to the problem.

The compaction limits root growth, reducing the root interaction with nutrients. Water is needed for uptake of many nutrients, including compaction. The lack of water reduces the amount of K taken up by the plant. Either dry weather or compaction on their own can cause problem, but having both together causes even more troubles.