Extension Service specialists review strategies following winter crop damage
As the winter damage to alfalfa and winter grain crops became evident in the past couple of weeks, Extension Service specialists have teamed to supply farmers with ideas on how to cope with the situation.
Reacting to widespread reports from throughout Wisconsin and southern Minnesota about alfalfa stand losses, forage agronomist Dan Undersander advised making sure that what appears to be "dead spots" in fields are really that or a case of delayed emergence from dormancy.
A quick test is to check the top four inches of the taproots - offwhite to turgid colors suggest the plant is alive while anything darker is not a good sign, he explained.
There is also a possibility that alfalfa plants could grow small shoots and then die, Undersander pointed out.
In any case, he recommends identifying the portions of the field that are affected and planting those areas with a 50/50 mix of annual Italian ryegrass and perennial ryegrass at 10 pounds per acre as soon as possible provided that only certain areas of a field are bare.
If it's a moderate percentage of the field that's affected and a first cutting is wanted, interseed 10 pounds of Italian annual ryegrass immediately and follow with a crop of corn to obtain top yield for the season, Undersander indicates.
In the southern half of Wisconsin, consider planting brown mid-rib sorghum sudangrass at 20 pounds per acre or, after Aug. 1, oats to be harvested as forage, he advises.
In cases where a large percentage of the alfalfa stand has been lost, plant corn or the BMR sorghum sudangrass at 20 pounds per acre by July 1, Undersander suggests.
He notes that corn will provide the most forage tonnage while the sorghum sudangrass is a good bet during dry and/or hot weather.
For additional current year forage, seed alfalfa at 10-12 pounds per acre along with a mix of six pounds of tall fescue and two pounds of Italian annual ryegrass.
If the alfalfa winterkill is so severe that the stand will be abandoned, there will still be one upside. It is that nitrogen credit can be taken for a subsequent corn crop, according to Extension Service soil fertility and nutrient management specialist Carrie Laboski.
Provided that the number of alfalfa plants was at least four per square foot going into the winter, the field should be considered as having had a good stand for nitrogen credits, Laboski indicates.
She notes that those credits should also be linked to the soil texture and the amount of alfalfa plant regrowth when a stand is taken out.
In the cases when a first cutting of alfalfa is taken within the approximately the next month, then the stand count after that cutting will dictate the amount of nitrogen credit that can be expected, Laboski cautions.
For red clover lost to winterkill, apply the same standards but the amount of nitrogen credit should be reduced by 20 percent compared to alfalfa, she states.
For a more accurate reading on nitrogen availability, take the pre-sidedress nitrate test, Laboski suggests. She notes that the details on that test can be found in chapter 5 of Extension Service publication A2809.
In new seedings of alfalfa, especially if cool and wet conditions continue, pythium will cause seedling blight and death while phythopthora root rot can take out entire stands in just a few days, Extension Service plant pathologist Damon Smith warns.
Smith explains that pythium can strike the seeds or the plant roots or stems at the early stages of growth. It can also damage mature plants by destroying the fine roots, he adds.
With phytophthora, the evidence on mature plants is a stunted, yellowed, or reddish purple appearance or perhaps wilting, Smith notes.
The other tell-tale signs are tan or brown lesions on the taproot and an eventual rotting or collapsing of the taproot, which allows an easy pulling of the plant, he observes.
In a related report based on the Extension Service's winter wheat plots, small grains specialist Shawn Conley and his support team have identified very strong genetic differences in their winterkill analyses conducted in late April.
He reported that stand losses are minimal at both Lancaster and Janesville.
At the Arlington plot, some wheat varieties had as little as 15 percent plant loss during the winter while others were close to 70 percent mortality.
The plot on Kolbe Seed Farms at Chilton averaged 25 percent stand loss with some varieties having close to 100 percent winterkill.
Because of the slow emergence of the crop from dormancy this year, Conley says it is still too early in some cases to declare that a wheat stand is dead but it is possible to determine if it is alive.
He notes that it is also too early to consider the application of a growth regulator and nitrogen applications should depend on a definitive calculation of stand density.