How to check roots
Root digs during the growing season can tell you what's going on with your corn plants. Bob Streit, a Boone, Iowa, crop consultant, gives five tips on how to properly do root digs and how to decipher the findings.
1. Start Early
You can begin digging roots early, even when plants are in the V3 to V4 growth stages. This is when early root rots start to turn crown roots brown. Tracking disease now lets you know if the disease is advancing or slowing.
Later root digs following tasseling can enable you to split the entire crown lengthwise with a sharp knife. This helps you assess if crown rot has moved up the stalk. If rot is present, target this field for early harvest before lodging occurs, advises Streit.
Ways to prevent future crown rot infestations include deep tillage if a penetrometer test identifies hardpan. Roots that grow in a zigzag pattern also reveal compaction, since roots are under extreme pressure to push deeper into the soil, says Streit. Other remedies include boosting drainage, correcting nutrient deficiencies, and using seed treatments.
Early-season root digs can also verify adequate seeding depth. Seeds planted too shallow end up with fewer roots for nutrient and water uptake.
2. Know root type
Three root types exist, says Streit.
• Broad and flat roots enable plants to withstand winds. They aren't as beneficial, however, in extracting nutrients deep in the soil.
• Deep penetrating roots extract nutrients and water deep in the soil but do not anchor plants as well as flat roots.
• A combination of the two types.
Knowing root type and your hybrid's genetic family enable you to better form an appropriate fertility program, says Streit. This includes rates, placement, and timing.
3. Check root health
Healthy roots should be long and white with soil clinging to a noticeable white film or slime. Dry and bare roots reveal below-ground problems, says Streit.
4. Check if roots tap nutrient bands
If you band or sidedress fertilizer, root digs can verify if roots have tapped nutrient bands. You can do so by washing off roots to see if a prolific root mass has formed in the nutrient-concentration zone.
5. Look for rootworms
Root digs also will reveal the corn rootworm egg hatch and development of early instar stages. The hatch typically begins after 625 growing degree days. Adult rootworm treatment via liquid insecticides can pay if levels reach economic thresholds.