It's amazing how something as small as weeds can play with your yields, and therefore wallet.  Here are some interesting statistics regarding growing corn in the midwest.

  Early season weed control is vital to both future yields and profitability, because early weed flushes compete intensely with corn for both nitrogen (N) and water. Dense weeds can also shade soils and make them cooler so that corn grows more slowly.

  So, when does early season weed control need to be done before it’s too late to stop yield loss? According to weed research, conducted across the Midwest including South Dakota, given that you start with a clean field, the most competitive weeds in corn will be about 3-4 in. high when corn reaches the V3-V4 growth stage. If you don’t remove those 3-4-in. weeds promptly, you’ll be losing about 3 bu./acre for every day you delay. Minnesota studies over three years show corn lost between 12-13 bu./acre within the first week and 27-29 bu./acre within the second week if weeds were allowed to remain in the field after they reached 4 in. in height.

  A big yield loss early in the season could mean the difference between making or losing money, Depending on soil moisture and fertility levels, waiting to control weeds until corn reaches the V3-V4 growth stage can push you over the economic threshold for profitability. At about 4-6-in.-tall corn and weeds, is when producers typically pass the breakeven mark and start losing money to lost yields from weed pressure after factoring in the cost of the herbicide application.


  These statistics were taken from