By Kelsey Banks, Agronomist
AgriNews Contributor

Have you ever spoke with an agronomist about almost any type of crop issue you may be experiencing, and they ask you, “What crop was in the field previously?” There is a reason for this question to be asked. The reason is that they are asking if you are rotating crops in your fields. Rotating your crops is important for many reasons, and the lack of crop rotation can be one of the primary reasons for issues with crops growing in season.

Crop rotation is important for three primary reasons – soil health, grain or feed quality, and crop yield. The soil provides each plant a home and a place to maximize its growth potential; a place where each individual plant will be fed its nutrients and will be provided moisture when it is needed; it also stores moisture, where many nutrients are cycled all below the soil surface that affect plant growth. However, sometimes there are crops like alfalfa that may be in a field for longer than one season; they build nitrogen and help alleviate compaction in the soil, making other nutrients more available, and they also improve soil structure. Crop rotation is a contributor to ensuring you have healthy, profitable crop growing soils.

Crop rotation can be a large part of an integrated pest management (IPM) plan as well. An IPM plan is typically implemented to prevent and manage pests including weeds, insects, and disease. These pests cause stress on the crop and prevent it from reaching its maximum yield and quality. An IPM plan involves using a targeted mix of cultural, physical, biological, and chemical controls.

Throughout the growing season there may be some negative stressors that we cannot control such as poor environmental conditions. However, there are some negative stressors that crop rotation, as a part of an IPM plan can reduce plant stress and help increase grain or feed quality and yield. Some soil-borne diseases such as soybean cyst nematode (SCN) or white mould can be problematic and seen in the crop, both in-season and at harvest. If crop rotation occurs, pests like SCN and white mould build up in the soil can be mitigated, thereby reducing the negative impact on yield and quality.

All pesticides (herbicides, fungicides, and insecticides) are registered for a target and a host. The target being what is trying to be controlled and the host being the crop being grown that the target may be affecting. Crop rotation can also help with the weed management part of an IPM plan. Each herbicide falls into a group that represents a specific mode of action that is taken to control the target. As you rotate your crops, your herbicide groups used, typically rotate as well. Consequently, there is lower weed competition from those problem weeds for nutrients, sunlight, or moisture that the crop needs to grow, to reach its maximum quality and yield.

Crop rotation is also important in relation to pesticide rotation, as it assists with rotating the modes of actions in the products applied on the soil or in the crop. If the same chemical program is used every year, there is a risk of creating herbicide resistant pests. This is already an issue that needs to be kept in mind each year as product decisions are made. For example, in Carleton County, there has been group 2 herbicide resistant common ragweed discovered in some fields. The fields that have this confirmed resistance, will have to plan for non-group 2 herbicides to control these resistant weed species.

If you have questions about crop rotation, the benefits of crop rotation, how to better implement it into your field management planning, or about IPM planning, please contact your agronomist.