Learn from Your Roots

By now, most of your mid-season in-field activities have taken place and hopefully you are on your way to a successful season. I want to discuss a few things that can be learned from getting out and conducting root digs in your corn fields. Taking a little time now can help you make management decisions later in the season.  

I recommend sampling roots throughout the field and getting representative samples with at least ten plants. Make sure to get as much of the root mass as possible and carry the soil of the root ball to the field edge or inspection location with you to wash and inspect the root balls.

Corn Rootworm larvae

You can either hand sort the soil on the roots above a drop cloth or tarp, or you can use my preferred method - the float method. Vigorously wash the roots off in a bucket of water to clean the soil off them. As you do this, the corn rootworm (CRW) larvae will float to the surface of the water for you to count. You want to take note if you find 2 or more CRW by the hand sort method or 8 or more by washing. You want to take action if these thresholds are met or exceeded. Action might include adult beetle control, rotating to a non-host crop next season, or adjusting corn rootworm management strategies. 

Corn Rootworm Feeding

If you are conducting root digs after CRW adult emergence, the float test and wash will not give a good indication of the severity of the problem. A better indicator is inspecting for evidence of feeding. In this instance, wash roots with a hose or pressure washer to clean them. Next, rate the level of feeding on the Node Injury Scale. This rates the first three nodes on whether they have been fed back to within 1.5” of the base of the root. Each node will be rated 0-1. A plant with one complete fed node and a half-fed node would score 1.5. Any corn rootworm trait with more than one Bt trait should be reported when scores are greater than 0.5. 

CompactionWhile digging roots it is also important to note irregularities in root development. The fibrous root system of the corn plant will try to find the path of least resistance. This can lead to misshapen root masses when you have diverse types of compaction layers in the soil profile. “Pancake” roots can develop when spring tillage in wet conditions cause a plow layer in the soil. In this instance, roots may not penetrate the layer. “Hatchet” roots occur when you have side wall compaction, and the roots grow entirely inside the seed trench. In either case, you might see symptoms of nutrient deficiency throughout the season due to the root having limited access to the soil profile and the nutrients in it. Limited root masses can also lead to increased instances of root lodging.  

Root StructureLastly take time to compare products and their root structures. Corn products with more robust root systems may be a better fit for more mellow prairie type soils. Hybrids known to have modest root structures are a better fit on tight clay soils. 

Hopefully, you can get out into your corn fields to take advantage of the information to be learned from your roots. While you are out there, take a look for any diseases that may be coming into your area. If you have any questions on these topics or any others, please contact your Burrus Representative.