If you have been reading any of my suggestions from the past four years you know my passion for residue management. Again this year I am getting calls on how to manage the varied toxins that show up when climate is favorable for molds to propagate in grain fields. Ask the producer where these hot spots are located in their fields and the recurring answer is in low lying areas where residues accumulate and drainage is the least effective. Swine feed can safely be fed at 5 ppm providing this source is included at no more than 20% of the diet for a final 1% of the feed consumed.
Most of the barley and wheat varieties that we grow have little or no resistance to head scab. The fungus can be present on old corn Stover, and residues of old barley and wheat crops. What drives this disease is wet, warm weather during the flowering period. If the heads of barley or wheat are infected with the fungus (Fusarium graminearum) that causes head scab, that fungus can then produce several toxins that can contaminate the grain. These toxins are often referred to as vomitoxins because they can cause feed refusal in non-ruminant animals. The most common vomitoxin that is produced by the head scab fungus is deoxynivalenol or DON for short. DON production by the fungus is extremely variable depending on environmental conditions. The presence of scab on the grain does not mean that the grain has to have DON nor does high or low levels of scab relate to the amount of DON present. A high level of scabby kernels in the harvested grain means that DON will likely be present.
The lighter weight, smaller kernels can be screened or separated with increased air flow. I suggest we segregate infected areas of the field for separate harvest and screen and air separate outside the field. As with weed seed why do we reseed trouble areas while we combine the fields and then complain about trouble spots in the field next year?
Is there too much residue, too little decay, or not enough oxygen in the soil and to keep the microbes operating at their peak efficiency? Yes is the correct answer to all three questions. The first tillage practice each year is a combine set to start the process of breaking down the residue into small pieces and exposing the whole stalk to the elements for decomposition, not just the outside portions. As we get more soil to residue contact and supply a good carbon food source for the microbes the fungal colonies can rapidly go to work with the humics providing the “fizz” that releases the oxygen that the microbes thrive on! Organic acids from the mine I access run in the 600 range for Cat ion Exchange Capacity. This highly reactive material quickly becomes available to support Mycorrhiza activity in breaking down last year’s residue into next year’s slow release nutrition, while building organic matter and humus to aid is storing moisture and fertility to provide the new crop with an enhanced support system.
As the residue breaks down and the soil biology find the oxygen it needs, they in turn help destroy the molds and diseases that previously were given free housing and food supply to become active and plague our next crop. You wouldn’t continually utilize the farrowing, nursery, and finishing facilities without breaking the disease cycle, but many of us have done just that while growing our feed source.
Fusarium molds in one year’s corn crop can become a source for one of the many toxins that
Contaminate grain. Mycotoxin, Aflotoxin, and Deoxynivalenol or DON are the three main culprits we hear about most often.
As a bonus the soil biology will help aerate and separate clay particles so that drainage will improve, more oxygen can be stored in the soils and our decay system returns to doing its job of recycling, detoxifying, and nurturing the next crop to feed a hungry population, safe, nutritious pork that we all enjoy raising and serving to them!!
