Issue # 10, August 31, 2004

• Coping With Late Maturing and Frost Damaged Crops

• Options for Frost Damaged Corn

• Drying Wheat During a Cool & Wet Harvest

Coping With Late Maturing and Frost Damaged Crops

    Due to the recent early frost, NDSU Extension Specialist put together a web site that has identified web sites and other information concerning frost affects on maturing crops.  The site has identified nine areas.  This include; Corn chopping listing, Predicting crop maturity, General frost information, Economic considerations, Hay, pasture and other feeds, Soybeans, Sunflower, Dry edible beans and Corn.  This site should help get current information on what options are available.  Click on the following link to access this site.

Coping with Late Maturing and Frost Damaged Crops

Options for Frost Damaged Corn 

The widespread frost in the state (15-21 August) affected a significant number of acres of corn.  The following are answers to questions that have been coming in this past week about frost damage corn. 

Will corn continue to grow after frost damage?

The answer to this question will of course depend on the severity of the damage and the stage of crop development. Most reports indicate that the frost last week damaged the upper leaves and the tassel.  Certainly if the lower leaves are still green, the corn plant will continue to grow and develop.  The rate of growth may be slowed, however.  Furthermore, reserves in the stalks can be translocated to the ear even after leaves have been damaged.  Yield will be reduced proportionally to the amount of leaf damage and hail damage charts can be applied to estimate the likely yield loss.  If the stalk was killed by the freezing temperatures, then there will be no additional corn growth.  If corn was in the process of flowering, there is a good chance that the anthers or the silks were damaged and/or the pollen was killed.  Frost damage at this stage may result in barren ears.  To determine if pollination has occurred in these late flowering fields, cut through the husk leaves of several ears to check to see if silks have detached from the developing kernels.  Silks detach from the kernel within 2 to 3 days of fertilization, but will remain attached for an extended period if no fertilization has occurred.  Nielson (2004) describes in detail a technique that can be used to determine if silks are attached or not (Early Detection of Ovule Fertilization Progress in Corn. http://www.agry.purdue.edu/ext/corn/news/articles.04/EarShake-0711.html).  If you plan to use your damaged crop for silage or grazing, dry mater will in most cases continue to increase unless most of the green tissue was damaged. 

What can I do with damaged corn that will likely not produce significant grain?

If the crop is insured before doing anything, contact your insurance company and a obtain a release.  The following are some potential uses of frost damaged immature corn:

• Ensiling – ensiling can be an excellent option for immature damaged corn. However, you must have a close market (probably within less than 30 miles of your field) in order for it to be profitable.  Good silage can be made from immature corn, though corn with little or no grain development will be lower in quality than silage produced later in the season.  The optimal moisture content for making corn silage is between 60 and 70%.  Immature corn usually contains between 80 and 85% moisture and will need to dry before it can be properly ensiled.  Since most of the moisture is in the stalk, immature corn plants can take longer than mature plants to dry. 
• Haying – Haying not a good option as it is difficult to dry stalks sufficiently to make good quality hay.  Wet bales will result in molding and spontaneous combustion.  The moisture content of the corn stover must be below 20% for preservation as “hay.” In the range of 20% to about 50% moisture content, browning reactions produce heat and reduce the feed value of the corn. The heat produced increases the rate of reactions creating an upward spiral in temperature that eventually may result in spontaneous combustion.  Effective ensiling in a bale requires the exclusion of oxygen. Deterioration will continue even if baled at the proper moisture content if oxygen is not excluded. Oxygen can be excluded by placing the bale at about 50% to 60% moisture content in a sealed bag to create baleage.  Drying stalks to below 20% moisture may be possible if the stalks are crushed or split with a flail or other special equipment.
• Grazing – Grazing corn that is too wet to ensile can be a good option.  Grazing costs less than ensiling, though temporary fencing is needed to reduce trampling of standing stalks.  Nitrate toxicity should not be a problem in frost damaged corn unless the leaves are killed and the roots and stalks remain alive for several weeks before being grazed. 
• Incorporating the crop into the soil – Destroying the crop and tilling it into the soil (or spreading the residue in the case of zero till systems) may be the most cost effective way of dealing with frost damage corn, especially in farms that are not integrated with or near livestock.  The nutrients taken up by the corn crop will be returned to the soil when a crop is tilled under.  A 30 lb N credit to the subsequent crop is given when an immature corn crop is incorporated as a green manure. Corn residue generally can be chopped and incorporated without too much difficulty using a heavy tandem disk.  Greener stalks are more easily cut and incorporated that those that have dried. 

Prepared by Joel Ransom
NDSU Extension Agronomist – Cereal Crops

Drying Wheat During a Cool & Late Harvest
Kenneth Hellevang, Ph.D., P.E.
Extension Engineer, Professor
Agricultural & Biosystems Engineering Department

Air will be warmed by 4 to 5 degrees as it passes through the fan on a bin of wheat operating at a static pressure of 6 to 7 inches of water gage. During an "average" year, this heat added from the fan will likely contribute to over- drying the wheat. Wheat will dry to about 13.3% with air at 69°F and 60% relative humidity, which is the average for August across the state of North Dakota. When this air is heated 4 degrees by the fan, the wheat will dry to about 12.2%. After passing through the fan, the average August air entering the grain will be 73°F and 52% relative humidity. During an average year, it is very important to run the fan during the night when the relative humidity is higher to reduce the amount of over-drying.

Wheat will dry to about 13.0% moisture during average statewide September weather conditions of 58°F and 65% relative humidity. The moisture content of the wheat would be 14.5% without the fan heat. However, the fan warming the air just 4 degrees, from 58 to 62°F, reduces the relative humidity from 65% to 56%. Therefore, even with the cooler and damper air, it is best to run the fan 24-hours per day. Supplemental heat is not generally needed even for the cooler damper conditions.

Running the fan just during the warmer and drier portion of the day will cause the wheat to be over-dried and lengthen the drying time. The estimated drying time is 26 days to dry wheat from 18% to 13% using an airflow rate of 1.0 cfm/bu with September conditions of 58°F and 65% relative humidity. The air is 62°F and 56% relative humidity after being heated 4 degrees by the fan. It will take 47 days to dry the wheat if the fan is operated during the warmer 12 hours each day. In addition, the wheat will dry to about 11.5% moisture. The air will be about 64°F and 55% relative humidity during the warmer 12 hours of the day, and about 68°F and 48% relative humidity after being heated by the fan. If these conditions existed 24 hours per day, the drying time would be reduced to about 23.5 days. However, since the fan is only operated half time, it takes 47 days to complete the drying and the wheat is over-dried.

Even for conditions that may occur in the northern part of the state in late September to early October, the air only needs to be warmed about 7°F to reduce the relative humidity from 70% at 50°F to the desired 57% at 57°F to dry the wheat to 13.5% moisture. Since the air is warmed about 4 degrees by the fan, only an additional 3 degrees needs to be provided by a supplemental heater. A rule-of-thumb on wheat is that 1 Kw of heater per horsepower of fan motor will warm the air about 5 degrees. Therefore, only about a 3 Kw heater is needed for a 5 hp fan to provide the desired amount of heat.

The drying time will be longer at cooler temperatures, because the cooler air cannot hold as much moisture. It will take about 27 days to dry wheat from 17% to 12.2% with an average August air temperature of 69°F and an airflow rate of 0.75 cfm/bu. It will take about 32 days to dry wheat from 17 to 13.0% with an average September temperature of 58°F and the same airflow rate. 

Please Contact Our Office For Additional Information
E-mail: john.swenson@ndsu.edu
Go to the 2003 AgAlert Index Page