| SUBSCRIBE MARKETS WEATHER LINKS HOME |
|
Plant-to-plant variability affects your corn yieldToo much variability is a sign of stress and stress causes yield loss. But there are criteria to measure the amount of variability and thus gauge the stress your crop is experiencingby PAT LYNCHWere you satisfied with your corn yields this year? Were there some fields or farms that yielded significantly lower than others or lower than you thought they should have done? Some of the clues to solving this problem may have been in the field all year.Corn has to get off to a good start to reach its potential. Over the past 20 years, we have collected notes on plant-to-plant variability in cornfields. Too much variability is a sign of stress and stress causes yield loss. The variability is not the cause of yield loss but is a symptom of stress. The more variability, the more stress and the lower the final yield. The amount of stress can be measured by the amount of variation. This hypothesis can never be proved or disproved since you cannot set up research to measure it. Variability can mean uneven emergence or uneven early growth. This variability can be through the whole field or just in parts of it. This year, we had producers who had yield variation of 100 bu/ac in the same field. In other years, there was a variation of 20-30 bu/ac. on this land. This yield variation was due to the stresses in the field. Typically, if a field is worked too deeply, planted too soon or both, it will emerge unevenly. If a crop emerges under stress, it will continue to be uneven. This unevenness results in different stages when the crop is sprayed. Some post-emerge products are stage specific. If the crop is quite variable, it will be hard to spray when the entire crop is at the right stage. One of the criteria for all post-emerge products is that the crop must not be under stress. If the crop is under stress, as shown by its unevenness, then post-emerge products can further affect yield. Some researchers believe that corn plants at different stages act like weeds. Plants that emerge later compete for water, sunlight and nutrients, but do not add yield. There are criteria that you can use to measure the plant-to-plant variability of young corn crops. How variable is the population from row to row? How many doubles are you dropping? What is the range in early corn development? One of the criteria that Francis Childs, a U.S. farmer who has produced 442 bu/ac, strives for is even emergence. You can check this by measuring the variation in number of leaves on adjacent plants when the corn is small. Ideally, you will have a crop that has no doubles, row to row variation of less than 2,000 plants per acre and field variation of less than 3,000 plants per acre from one part of the field to another. And ideally you will have a harvestable ear on 98-99 per cent of the plants, and very small variation in the number of kernels per ear.
The table indicates what we have seen in the field. We do populations at the two-to-four leaf stage in a minimum of four adjacent rows. Average populations are calculated in representative areas of the field. We do a second staging at the six-to-eight leaf stage. Our experience has been that uneven stands typically yields less. The numbers in the table represent significant areas of a field. All fields will have the variation that is in the table, but if it occurs in a significant part of the field, it will affect yield.
There has been a lot of research done in Ontario and the United States in measuring the plant-to-plant space variation. Researchers in both countries are arguing whether or not that variation causes a yield loss. Perhaps this variation that they are measuring is a symptom of other factors that are causing a yield loss. BF Pat Lynch, CCA (ON,) is head agronomist for Cargill in Ontario
|