Can Corn Too Dry Due To Drought Rehydrate Enough For Silage?

September 19, 1996 3(25):147-148

Joe Lauer, Corn Agronomist

Corn in many areas of Wisconsin is dying prematurely due to drought. Corn is at R4 to R5 (dough to dent), and the bottom 1/3 to 1/2 of the plant has fired off. Many producers have found it is too dry to put into silage storage structures to get adequate fermentation. Adding water as the silo is being filled is difficult and usually does not work. Can corn that is too dry and dying prematurely, rehydrate enough after a rain to be at the proper moisture for fermentation in the storage structure?

Water movement in the plant is a passive process. The water conducting cells, called xylem, are dead cells and thus energy is not required for the uptake and transport of water within the plant. The plant is essentially a large "wick" and the amount of water transport is dependent upon soil water movement to plant roots and leaf transpiration.

The movement of water within the soil is dynamic and constantly changing. High evaporative and transpiration demands quickly deplete soil water around the roots. Most water uptake by the corn plant takes place in the upper 3 feet of the soil profile, although a corn root system will grow 5 to 7 feet deep and uptake will take place deeper in the profile. Dr. John Norman (UW-Soils) reports that soil water is low in the upper 3 to 4 feet of most Wisconsin soils, but is good to adequate at depths lower in the profile. Water will move from deeper, wetter parts of the soil profile to dryer, shallower levels and under low evapotranspiration conditions could adequately re-supply the water needs of the plant.

Nearly 80% of the dry weight of a corn plant near maturity is in the stalk and ear. These structure are typically the last to die on the plant. Corn which might be dying prematurely and be too dry for ensiling should have the ability to rehydrate following a rain or low evaoptranspiration conditions, as long as some green stalk or leaf tissue is present on the plant to drive the transpiration process.

Things to consider about corn dying prematurely and too dry due to drought for silage fermentation:

  • Corn should rehydrate to near normal levels following precipitation or low transpiration environments. The amount of rehydration will depend upon the ability of water to move to the roots, the amount of green stalk and leaf tissue, and precipitation.
  • No guarantee that rains or low transpiration environments will come while the plant is still living. Green leaf tissue is required for adequate transpiration and movement of water through the plant. Corn may have to be harvested for high moisture or dry grain.
  • Adding water as the silo is being filled usually does not work because the great amount of water required to change silage moisture percentage.
  • Producers may want to consider using oxygen limiting silos since corn silage can be ensiled at lower moistures.

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