Why did the plants root lodge?
First, hybrids vary in their tolerance to lodging. Second, root lodging can be directly tied to rootworm larvae feeding. Third, plants may lodge simply because of strong winds and saturated soils (may or may not exhibit rootworm damage). Warm, dry conditions during corn's vegetative period result in deep root penetration while cool, wet conditions result in shallow root systems. The latter would result in corn that is more prone to root lodging from strong winds and saturated soils.
Roots act as guy ropes and props that anchor corn plants against lodging. Initially both windward and leeward roots play a role with slow wind speeds, however, as wind speeds increase, the role of the windward and leeward roots change. During high wind events, windward roots are pulled from the soil while leeward roots are pushed into the soil. Although it might make sense that lodging comes from windward roots that fail to hold fast to the soil, the fragile link in rooting structures is the weakness in compression of the leeward corn roots from bearing large downward loads. A rotation of 10 degrees is enough to cause the leeward roots to buckle and the plant to lodge (Ennos et al.).
Root mass reaches its maximum at silking (R1). Brace roots provide support to the stalk and are of considerable importance in "resurrecting" plants root lodged by strong winds. Fortunately, plants root lodged before R1/R2 are somewhat able to compensate for the canopy disruption caused by the lodging. After a couple of days, the upper portions of these plants resume a vertical growth pattern, "goosenecking." Although this rearrangement of the crop canopy may limit potential yield losses, it does make harvesting slower and increases the potential for ear loss during harvest.
How will root lodging affect yield?
An Iowa State study forced V10-stage corn to "lodge" at a 45° angle in plots with and without rootworms. Grain yield of lodged corn without rootworms yielded 11 and 40 percent less than the control in the two years of the study while lodged corn with rootworms yielded 12 and 28 percent of the control. Years made a big difference in yield response. It was concluded that lodging was more detrimental to biomass accumulation and yield than corn rootworm larval feeding itself. In a separate study with natural root lodging, lodged plants intercepted 28 percent less light than un-lodged plants.
This gives us some idea of the wide variation in years and among treatments at V10. Simulated root-lodging work from the University of Wisconsin addresses the yield impact when lodging occurs at silking. Corn was lodged in two years at three different growth stages each year (see Table 1).
|Lodging treatments in Year 1||Grain yield (bu/acre)||Lodging treatments in Year 2||Grain yield (bu/acre)|
|LSD (0.05)||20||LSD (0.05)||10|
Table 1. Simulated root lodging. University of Wisconsin.
Lodging did not affect plant development, but it did increase the number of barren plants. The yield loss varied across the two years, with losses in the first year up to 30 percent and half of that in the second year. Overall, yields were reduced 2-6% when corn was lodged from V10/V12, 5-15% when corn was lodged from V13/V15, and 12-31% when corn was lodged on or after V17. We would expect less yield reductions after R1 since VT/R1 are the most critical stages for leaf loss, plant loss, etc. to occur.
What can we learn that will reduce root lodging in the future?
- Identify whether the lodging was primarily caused by rootworm larvae feeding, poor root development (due primarily to cold, wet soil conditions), poor seed placement at planting (too shallow of root mass), late-season stalk rot (see the Image Gallery for pictures of late-season lodging) or due to other circumstances. Understanding the cause will provide valuable information when managing this field in the future.
- In areas where rootworm larvae feeding was the cause of the root lodging, use soil insecticides, crop rotations, or Bt hybrids resistant to rootworm feeding.
- Hybrids vary in their susceptibility to lodging, select hybrids that withstand root lodging.
References cited here and/or may be helpful resources:
Carter, P.R. and K.D. Hudelson. 1988. Influence of simulated wind lodging on corn growth and grain yield. J. Prod. Agric. 1:295-299.
Ennos et al. 1993. Journal of Experimental Botany. 44:147-153.
Lipps, O.R. Mullen, and P. Thomison. 2004. Will poor root development impact corn yield potential in 2004? Corn Newsletter, Ohio State University Extension. 5 July 2004.
Portions of this text, written by Roger Elmore originally appeared in the Integrated Crop Management extension newsletter on pages 161-162 of the IC-494(21) - August 1, 2005 issue.