Most of the recommendations made in this column are intended to be applicable over a wide area, including the need to carefully select crop varieties and the benefits of timely planting. Some crop management recommendations, however, vary from region to region. One advantage of writing for a regional publication such as Farming is that the climatic differences aren’t huge, but they still exist. I’ll present a couple of examples, but first: a timely tip before you head for your fields with the corn planter.
A few years ago I broke my wrist in a fall from a 25-foot ladder while doing some tree work that I had no business doing in the first place. Prior to the surgery to piece things back together, the physician at the hospital who was doing my pre-op exam said, “Just because you can do it doesn’t mean that you should do it!”
Much the same can be said for corn planter speed. The operator’s manual may state that the corn planter will plant at 8 mph, but what most manuals don’t say is that this will often be at the expense of a uniform plant population.
Maintaining a moderate planting speed is especially important in fields where stones or uneven ground will make the corn planter bounce around a bit. You may not plant quite as many acres in a day, but you’ll wind up with a more uniform plant population – and perhaps fewer repairs.
Bt hybrids for European corn borers
The Bt trait for corn borers has been around longer than the one for corn rootworms, but we haven’t had the development of insect resistance that has been encountered with the rootworm trait. However, entomologists are now questioning whether farmers in much of the northeastern U.S. need to worry about corn borer control.
It’s generally accepted that the threshold for control is one corn borer per plant, but I’ve yet to see this infestation level in the Northeast. Some years ago, we did two years of research at Miner Institute (Chazy, N.Y.) on the use of the Bt corn borer trait, comparing a borer-resistant hybrid to one that was genetically identical except for the Bt gene.
In the first year of the trial, 25 percent of the non-Bt corn plants were infested with at least one corn borer, while none of the corn plants with the Bt trait had any corn borers. This isn’t surprising, since entomologists state that 99.9 percent of corn borers are expected to die when feeding on plants containing the Bt corn borer toxin. In spite of the difference in corn borer numbers, the Bt hybrid’s yields were only slightly higher.
In the second year of the trial, 46 percent of the non-Bt corn plants were infested, and once again none of the Bt plants had any borers. However, when we measured yields, there was no significant difference between Bt and non-Bt corn; in fact, the small yield difference we found was in favor of the non-Bt hybrid! This shouldn’t be surprising, since a 46 percent infestation level is still much lower than the one borer per plant that’s considered the action threshold.
Now questions are being asked as to whether corn borer control is still needed in areas where the Bt corn borer event had previously resulted in less stalk lodging and higher yields. Aided at least in part by the years of control provided by genetically modified hybrids, the number of corn borers is down considerably. Several years of on-farm research by Pennsylvania State University found that corn borer infestation levels were low enough that non-Bt hybrids yielded just as well as the Bt hybrids. Before spending the money for the Bt corn borer trait, farmers should scout their non-Bt cornfields late in the summer and/or rely on crop consultants for guidance, and then ask: Is this trait really necessary?
Fall alfalfa management
It’s logical that the more severe the winter conditions, the more important fall management of alfalfa becomes. Less-than-ideal soil drainage can also cause alfalfa overwintering problems. Winter conditions for alfalfa are usually more challenging in the northern half ofFarming magazine’s circulation area. This is because of two factors, one well-recognized and the other not so much. The first factor is simply the winter temperatures in northern New York and northern New England compared to, for instance, much of Pennsylvania, southern New England and the Delmarva area.
Alfalfa crowns can suffer damage from extended direct exposure to temperatures of 0 degrees Fahrenheit and below. The key phrase here is “extended direct exposure.” That’s why in northern states it’s recommended to leave 6 inches or so of stubble during the last fall harvest, or harvest early enough that there’s sufficient regrowth to collect snow and thereby protect the crowns.
Older alfalfa stands (more than 2 years old) are more susceptible to freezing injury because many of the crowns have already been damaged by field traffic. Subzero temperatures are much less likely south of the Mason-Dixon Line, providing farmers there with somewhat more flexibility in fall management.
Another reason why fall alfalfa management may differ between North and South is that during the last Ice Age, a glacier covered the Lake States in the Midwest, plus most of New York and New England, but only a small portion of northern Pennsylvania and none of the Delmarva area.
This glacier, which according to geologists receded over 10,000 years ago, was miles thick in some areas and caused soil compaction that soil scientists say has never completely disappeared. A zone of compacted soil beginning about 20 inches below the soil surface – though it may be shallower than this where wind or water erosion has resulted in soil loss – may affect the rooting depth of plants, including alfalfa. This can affect the yield potential of crops and may be why on these once-glaciated soils we almost never get the 8-ton-per-acre alfalfa yields we sometimes read of in national farm magazines.
On many of these soils, it’s simply more difficult to grow alfalfa and have it last a long time, which is one of several reasons why I prefer alfalfa-grass to straight alfalfa. Few farmers realize it, but that ancient glacier is one reason why straight alfalfa is much more common in Pennsylvania and the Delmarva area than it is in New York and New England.