DO CORN TILLERS HELP OR HURT GRAIN YIELDS?

It was common belief in the early 1900’s that tillers would suck nutrients from the main plant. The term “sucker” came from this notion. Plant Physiologists at the University of Wisconsin found that little movement of food takes place between the main plant and tillers before tasselling. However, immediately after silking and during grain fill, substantial amounts of food moved from leaves of large tillers without ears to the ear on the main plant. There was little food movement when ears were on both the tiller and main plant. The only time when food moved from the main plant to the tiller was when there was an ear on the tiller and there was no ear on the main plant. This is not a condition likely to occur in the field. In most situations where you have small shaded tillers without ears under a full stand, tillers will have little influence on grain yield. If there is a slight influence on grain yield, it would most likely be in the positive direction.

TILLERS IN CORN ARE LATERAL BRANCHES THAT DEVELOP FROM BELOW GROUND NODES.

Further up the plant these branches will develop into ears. The amount of tillering is controlled by the genetics of the hybrid, plant population, spacing within the row, soil fertility and early season growing conditions. In other words, corn hybrids will take advantage of available soil nutrients and moisture by forming one or more tillers where stands are thin, where there are skips in the row or at the ends of the row. Some hybrids with a strong tillering trait may form one or more tillers even at high plant populations if the soil fertility and moisture supplies are ample. Excessive tillering may also occur when the growing point has been injured from hail, insects, frost, herbicides or diseases.

ROOT OBSERVATION IS IMPORTANT WHEN DIAGNOSING EARLY SEASON CORN PROBLEMS.

Often we forget to examine the roots of the corn plant and consequently don’t make an accurate diagnosis. The roots are the other half of the plant and may contain the answer to the problem.

THERE IS NO FORMULA FOR A CORN REPLANT DECISION

The decision to replant depends upon the facts surrounding each situation. First gather all the facts: plant stand, plant distribution, original planting date and possible replant date. Date of planting studies by the University of Florida show that final grain yield declines 1/2 bushel per acre per day during the first 4 weeks from when soils are warm enough to start planting. After that, the decline increases to 1 - 1.5 bushels per day. If it is not a clear decision, check with your corn rep about the ear flex ability of the hybrid you planted. A hybrid with a good ear flex score will compensate for lower populations by putting on a larger ear. A "Rule- Of-Thumb" is: If you have a 70 to 75 percent stand, leave it.

WHAT IS THE EFFECT OF SKIPS AND DOUBLES ON CORN YIELD?

Both skips and doubles result in plant spacing variability, but their effect on yield can be quite different! To more accurately characterize the yield effects of skips and doubles, a study was conducted by Dr. Emerson Nafziger at the University of Illinois. The results of this study show it is better to have doubles than skips.

SKIPS: Grain weight of individual plants increased when next to a skip or second from a skip. This effect occurred at all populations, but was greater at the lower populations. Though neighboring plants do compensate for skips, the compensation is not enough to avoid overall yield losses.

DOUBLES: Yield is reduced in plants next to doubles, and in the doubles themselves. However, the additional weight of the extra plant in the double compensates for the reduction in the neighboring plants. The yield of doubles is not reduced drastically, even at high populations.

Skips resulted in appreciable yield reductions, from 18 bu/acre at the low population to 34 bu/acre at the high population. Doubles, on the other hand, resulted in yield increases of 19 bu/acre or more, even at the high populations. In addition, plants did not become barren when doubled at high populations. The bottomline is, unless doubles result in above-optimum populations, doubles should not be a cause of concern for growers.