Rotation Benefits From Alfalfa to Corn Depend on Successful Alfalfa Stand Termination

Sep 04, 2020

By Jeff Coulter

There are many benefits to corn when it is planted after alfalfa, including greater yield, reduced nitrogen (N) requirement from fertilizer or manure, and reduced pest pressure compared to when corn is planted after other crops. In long-term trials in Wisconsin and Iowa, grain yield of first-year corn following alfalfa was as much as 8% higher than that of corn following soybean, and 9 to 18% higher than that of continuous corn. In these trials, the rotation effect also carried over to second-year corn following alfalfa, which yielded 6 to 8% more than continuous corn. However, successful termination of alfalfa is necessary to fully achieve its rotational benefits and avoid competition with corn for water and N.

Benefits of fall termination

Shorter rotations, where alfalfa is rotated after three to five years (including the establishment year), have been found to be most profitable in Wisconsin, Manitoba, and western Canada. When using a planned rotation, farmers are faced with deciding whether to terminate alfalfa in the fall or spring. When compared to spring termination of alfalfa, fall termination results in earlier decomposition of alfalfa residue and potential for earlier N release during the next growing season. As a result, N fertilizer rate guidelines for first-year corn following alfalfa on medium-textured (loamy) soils and fine-textured (clayey) soils are slightly lower when alfalfa termination occurs in the fall rather than the spring. Terminating alfalfa in the fall can also facilitate earlier drying and warming of soil in the spring, enabling earlier corn planting. Fall termination also reduces field operations in the spring. However, fall termination of alfalfa can result in less cover to protect against soil erosion during the winter, and does not provide farmers with the option of assessing the stand to determine whether alfalfa could be productive for another year.

Alfalfa can be terminated using tillage, herbicides, or a combination of both. Tillage implements such as a chisel plow with overlapping sweeps or moldboard plow, which completely cut off all alfalfa roots, are effective at terminating alfalfa, but may not be suitable for all fields due to concerns about soil erosion. Tillage implements that do not completely cut off all alfalfa roots will be unable to provide complete alfalfa termination unless herbicide is applied before tillage.

Fall herbicide applications to terminate alfalfa should occur before the first killing freeze (28 degrees Fahrenheit or lower for a few hours) when alfalfa regrowth since the last harvest is at least 4 to 6 inches, otherwise there may be poor herbicide translocation to roots.

If fall tillage is desired after an herbicide application for alfalfa termination, tillage can generally begin within three to four days following herbicide application, but some labels require a longer interval before tillage.

A highly effective herbicide option for fall termination of alfalfa is 2,4-D amine or ester alone or tank-mixed with a dicamba product. If grasses are present with alfalfa, a good option is to tank-mix glyphosate with 2,4-D. High rates of glyphosate alone for alfalfa termination often result in only partial kill (60 to 90% kill with fall applications, or 40 to 80% kill with spring applications).

Source : umn.edu

Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.