By Dr. Heather Darby
In July, cornfields throughout the state were flooded, and their fate was unclear.
Some fields were pushed completely flat by the current of the raging water and died weeks later. Other fields were pushed near the ground and slowly, over time, they began to push themselves back up with clear determination to survive.
Fewer fields were flooded but did not get pushed down by the water. Regardless, all the corn was damaged, impaired and slow to recover as the soil remained saturated and wet weather continued until harvest.
Many farmers wondered if the silt left from the flood water would wash off the plants, if the plants would tassel and if ears would form. Would there be anything to harvest and would it be safe to feed to livestock?
Now the time has come, and farmers are starting to prepare for harvest. To assist with harvest management decisions, the University of Vermont (UVM) Extension Northwest Crops and Soils Team sampled corn from fields that had been flooded along the Lamoille, Winooski and Missisquoi Rivers.
Numerous corn plants were harvested at ground level from a set of fields and brought back to the Borderview Research Farm in Alburgh, UVM Extension’s research farm. At the farm, the corn from each field was divided into three piles. One pile represented corn harvested six inches from the ground, one 18 inches from the ground and one harvested just below the ear (snaplage).
Each sample was run through a chipper/shredder and a subsample collected for ash, mineral and mycotoxin analysis. The chipper/shredder was cleaned between each farm and each sample to avoid contamination.
The sample analysis revealed that a good portion of the silt that had contaminated the corn had been washed away over time (one benefit of the excessive rain). The highest ash content was 6.21 percent and from a field that had been nearly flat to the ground after the flood waters receded. This same cornfield had 15.5 percent ash content one month after the flood. More than half of the ash had been washed off these plants.
High-chop corn further reduced that ash, as would be expected since more of the stalk is left in the field. Most of the fields reached ash levels that are considered in the normal range for corn silage (3 to 4 percent ash on a dry matter basis).
The other concern was the possible growth of fungi on the plants that can produce harmful mycotoxins. Only corn sampled along the Winooski River contained the mycotoxin Deoxynivalenol (DON) produced by the Fusarium fungus.
The levels ranged from 0.50 to 4.8 parts per million (ppm). Depending on the livestock type, when DON concentrations reach 2 ppm it can negatively impact animal health.
Mycotoxins are complex organic compounds that are produced by some fungi to increase its impact on the plant. Once produced, these toxins cannot be destroyed by heat, time or fermentation.
The primary toxin-producing fungi within our area is Fusarium. Several toxins of great concern are produced by Fusarium and include vomitoxin (DON), fumonisin zearalenone and T-2.
A common scenario for high levels of Fusarium toxin infection in corn starts with wet conditions accompanied by damage to the plant. The longer corn is allowed to stand in the field after maturity, the greater the likelihood of significant toxin development.
Levels of Fusarium toxins can be the result of a continuous accumulation of toxin over time during the growth period and continuing after maturity and into storage until oxygen becomes limiting or, in the case of grain, moisture is reduced to less than 20 percent. Limiting oxygen is the key to successfully limiting toxin production during ensiling.
Oxygen is like a light switch. It can turn toxin production on and off during storage. Therefore, one of the best management strategies to mitigate further production of toxins is to create optimum fermentation conditions. It is wise to sample for mycotoxins once the feed is fully fermented and periodically as feeding begins.Source : uvm.edu