Now that we have a good working definition of what is considered a weed, let’s take a look at some of the specific manners in which weeds can affect our field crops. In the following video clip Dr. Namuth-Covert will describe four ways weeds can negatively impact crops.

Effects on Crop Yield

Now let’s discuss soil moisture. One idea to think about is that your soil has a limited amount of water present. Soil water increases when it rains or irrigation is applied, and decreases when used by plants. This moisture will either be used by the crop plants or by the weeds. Basically, whoever gets to it first is who will benefit. The obvious dynamic, especially early on, is if your weed pressure is high, the weeds will take away some of the moisture that your crops could utilize. This is a big concern especially in drier climates, where this can have tremendous negative effects on optimal crop yield in the end.

What is interesting is weeds seem to be able to grow in any kind of condition. Of course the weed population numbers are lower in environments with restricted water, light or nutrients, but typically there will be a type of weed present which can grow with less water compared to what a crop might need. In general the idea is that weeds are really tough and diverse. They can quickly adapt and survive with lower inputs, compared to what crops need.

Another concept to think about, too, is even during what might seem more like the off-season, such as in the fall and winter, any weeds present are still depleting some of the soil moisture that you might need in the following year. Therefore, it is important to think about your weed management over the entire 12 months of the year, not just during the growing season.