Overview
How we test
Our rating scale
Overview
Root strength, a genetic trait, is a measure of the size, structure and mass of the permanent root system. It is an indication of the plant's ability to resist root lodging.
There are two root systems in the plant: seminal (seed) and permanent. Seminal roots are the first structures to emerge from the seed. They support the plant until approximately V5-V7 leaf stage, upon which the permanent root system takes over. Growth of the permanent roots continues until tasseling, after that point little to no root development occurs.
The permanent root system is composed of: the underground portion, and the above ground brace roots. Root systems have two functions: 1. Locate and transport water and nutrients to the plant, and 2. Anchor and support the plant. Even hybrids with a lower root strength rating can do an excellent job of performing the first function. Larger, more developed root systems do a better job of anchoring and supporting the plant, thus reducing the likelihood of root lodging.
Beyond genetics, other factors affect root development. These include: soil compaction, soil density, moisture availability, fertility and insects (especially rootworm).
Several factors conspire to cause root lodging. Tall plants; higher, heavier ears; and/or abundant late season rains followed by high winds create the most likely scenario for plants to go down. Really, it's just physics at work.
Bt hybrids have unique properties affecting root lodging. The stalks of these plants normally remain intact through harvest. Under high winds, the tops may come out of non-Bt hybrids, making them less likely to root lodge. Not so with the Bts. The plant can act as a "sail" to catch the wind and go down. Strangely enough, many of today's highest yield hybrids have smaller root systems.
How we test
iCORN root ratings are compiled from visual examinations. After tasseling, plants are uprooted and scored for root mass and size. The root rating is relative to plant height and ear height. A shorter plant with lower ear placement can be well supported by a smaller root system. The same size root system may not be adequate for a taller plant with higher ear placement.
Our rating scale
Our rating scale ranges from 0 to 9, with 9 being the best score. iCORN doesn't offer hybrids rating 5 or less on root strength. Here's the definition of our ratings.
- Can experience root lodging under certain conditions.
Use caution in the following situations:
- Compacted soils, or
- Black, productive prairie soils producing tall plants and high yields under high populations.
A 6 does not imply the hybrid is low yielding or has poor drought tolerance.
- Normally, root lodging is not a concern. Extreme conditions can result in some sporadic (15% or less) root lodging. Sometimes a 7 may go down in compacted areas of a field.
Caution: in dark, highly productive soils of Northwest Indiana and Northern Illinois, consider lowering populations of 7-rated Bt hybrids.
- Root lodging would be a rare occurrence. Even for tall plants an 8 root system will likely withstand high winds.
- Virtually no concern with root lodging. These hybrids exhibit large, fully developed root systems that provide excellent anchoring in nearly all conditions. Understand that rootworm damage can undermine the root strength of the hybrid.