Last Friday a severe hail storm passed through southwestern Wisconsin causing extensive damage to corn. The corn was just beginning to dent. Growers are currently asking questions about what effect hail has on grain yield at this stage in corn development and what options may exist for harvesting.

First of all and most importantly, growers should wait 7 to 10 days before making an assessment on hail damage. The corn plant has the capacity to compensate for various stresses and it would take this long before the plant has recovered to its remaining potential. If they have hail insurance, wait until the adjuster has made their measurements and injury determinations before making any decisions.

Secondly, an economic estimate should be made of the options (ie. corn grain, high-moisture corn, silage, snaplage, etc.) available in the grower's situation. Estimates of changes in yield and quality due to plant part loss should be taken into account. For corn grain yield, information from crop insurance hail adjusters tables would be a good source for making estimates. Little economic information on hail damage is available on other harvesting options such as silage, high-moisture corn, or snaplage. One approach would be to use yield and quality changes observed under normal development and conditions and adjust downward. Below is an example for corn silage.

Hail during kernel grain-fill can be very detrimental to grain yield. Depending on the stage of development and the amount of leaf loss, grain yield can be reduced from 0 to 41 percent after the soft-dough stage of development. Any losses due to ear dropping would increase this yield loss estimate .

The types of options available to farmers varies from farm-to-farm and field-to-field. On a farm basis, the decision hinges on availability of other corn handling systems involving drying capacity, silage storage facilities, high moisture corn handling equipment, snaplage equipment, etc. Using these later systems means that the harvested corn product will probably have to be fed on-farm to livestock.

On a field basis, things to consider are mold development, moisture levels for ensiling, and effects on maturation rate, yield and quality. If ears are damaged, easier entry of mold causing organisms into the ear can take place. If it is wet for the duration of the season, mold problems will probably increase. Drier weather may not promote growth of mold producing organisms. Safer storage of corn predisposed to mold causing organisms can be achieved by drying grain to 15.5% moisture, ensiling at the proper moisture for the silo type, or treating high moisture corn with propionic or acetic acid.

Hailed corn will usually achieve physiological maturity earlier, but take longer to dry-down than non-hailed corn. Yield and test weight will likely decrease when stressed by hail.

If ensiling, hail damaged corn should be stored separately from other silage already put up. Hail damaged corn may have lower quality, and by storing separately, the farmer will have the option of mixing poor and good silages to obtain a satisfactory ration, or feeding the damaged silage to animals that do not have high quality forage requirements. An estimate of silage yield and quality should be obtained to compare with the grain yield estimate.

Wiersma et al. (1993) looked at quality changes in corn silage at five stages of kernel maturity. These values would be for corn silage under normal conditions. With hail damage, loss of leaves and poor kernel fill would affect quality by increasing fiber content and decreasing yield, crude protein, and digestibility. This data may be helpful in assisting the decision to harvest corn for silage or leave for grain.

Whole plant dry matter, crude protein, ADF, NDF, and digestibility for corn silage at five stages of kernel maturity.
Maturity stage	Dry matter	Yield	Crude protein	ADF	NDF	Digestibility (in vitro)
	%	ton/A	%	%	%	%
Soft dough	24	5.4	10.3	27.2	52.7	77.1
Early dent	27	5.6	9.9	24.3	48.0	79.0
1/2 milkline	34	6.3	9.2	22.8	45.1	80.0
3/4 milkline	37	6.4	8.9	23.8	47.3	79.6
No milkline	40	6.3	8.4	24.0	47.3	78.6