Pre-Harvest Thoughts – Corn
Harvest is quickly approaching and while we can see the light at the end of the tunnel, there is still a lot going on in corn to think about before combines get rolling.
Water Use – Corn that is at ½ milk line requires about 2.25 inches of water (or 0.1-0.2 inches per day) to reach physiological maturity (black layer). Once corn reaches black layer it stops accumulating dry matter and does not require water.
Disease – Heavy late season rains have let to another year of late season diseases in corn. Diseases such as Physoderma Node Rot, Dipoldia Ear and Stalk Rot, Fusarium Kernel and Stalk Rots and Gibberella Ear and Stalk Rot have been found throughout the sales territory already this season. Contact your seed representatives to discuss any hybrid sensitivity to late season diseases and focus on susceptible hybrids first.
Scout regularly and use the PUSH or PINCH tests to indicate stalk issues. For PUSH – Push the plant tops away from you at a 30 degree angle. If they don’t return to vertical or they snap, they may be compromised by a stalk rot. For the PINCH test – Pinch the lower internodes of the plant. If they are crushed easily by your hand their integrity has been compromised. If 10% or more plants fail these tests consider harvesting the field early to reduce possible losses. Once you find plants that fail either of these tests it is important to cut the stalk open in order to understand exactly what disease you are looking at to help with future management decisions.
Ear rots are generally brought on by damp weather after pollination and during grain fill which most of us have had this year. For a full field picture, ideally you would sample 20 ears in 5 different locations by pulling back the husk and using a crop diagnostic guide or you Jacobsen Seed Representative to help you identify the specific pathogen. Hybrids or fields that are diagnosed with ear rots should be harvest early, segregated and dried quickly to lower than 15% moisture to slow fungal progression. For long term storage dry grain to less than 13% and cool to below freezing. Certain ear rot pathogens such as Fusarium and Aspergillus can also produce mycotoxins that are harmful to livestock and humans. Contact your local grain handling facility about tests for mycotoxins.
Fertilizer – Recent studies have shown that fertilizing after corn and in front of soybeans brings profitable yield increases to most soybean acres. Fertilizing after corn is even more important when corn stover is taken from the field (silage, stalk bales) because a majority of potassium is stored in plant material. Potassium removal rates can be as high as 5x higher when taking plant material compared to grain only. It is important to return the potassium through manure application if continuing with corn or adding additional dry fertilizer in the form of potash. Potassium is often associated with the movement of water, nutrients, and sugars within the plant. It also plays an important role in the opening and closing of stomate structures, stalks strength in corn and nodulation in soybeans. Soybeans especially like free potassium 1.2 pounds of potassium nutrient leave the field with every bushel of soybean. An average 60 bu/ac soybean crop will remove 72 pounds of nutrient from the farm at harvest time. Making sure to have enough potassium available is crucial to consistent, successful soybean crops.