An important practice in this area is fall applied weed control for troublesome perennial, winter annual and spring annual weeds. It is one of the most valuable passes we make each year and consistently delivers value to the farm.
An example of fall burndown, plus spring burndown with residual, is shown on the right. This shows an outside spray pass where the farmer needed to protect a neighbors sensitive crop.
Controls emerged weeds like winter annuals such as Pennycress and Shepard’s Purse as well as fall/spring annuals like Horseweed (Marestail). A fall pass allows you to size Horseweed (Marestail), which in turn makes it easier to control the smaller weeds in the spring, without much impact on planting dates.
Perennial Weed Control.
Difficult to control weeds in the spring and summer, like Thistle and Dandelion, are much easier to kill with a fall application. The first light frost signals the plants to mobilize nutrients from the leaves and move them to the roots. This a great time to include the herbicides as they move to the roots along with nutrition.
Alternate Host Plants.
Weeds like Purple Deadnettle, and to a lesser extent, Henbit, are alternative hosts for soybean cyst nematodes. Deadnettle is actually as/more efficient as a host than are soybeans. In a warm fall or spring, the SCN population can complete a life cycle on the alternate host plants.
Ground Cover reduction.
Winter and spring annual weeds help to shade soil. This keeps soil cooler and moister for longer periods of time. Chickweed can be especially troublesome when established as a ground cover.
Starting the spring clean in the fall allows for more efficient use of time in the spring. The Horseweed (Marestail) roots shown on the right had a tillage pass. However, they were too large and well established in the spring to be removed by simple tillage.
Products that contain both 2,4-D as well as dicamba are very efficient products and serve as the base of most fall programs. Glyphosate can be added to aid in control of emerged annual and perennial grasses. It also adds to the control of Chickweed, Dandelion and Thistle. Express® can be added for Chickweed, Dandelion and Thistle control as well.
Residual herbicides can be included as needed and bring value. Using residual allows the inclusion of alternative sites of action into the mix. It also allows you to spray earlier in the fall without being concerned about new weeds emerging. Sometimes nature shuts us down very early in the fall and limits spray activity. I encourage you to consider applications with residual starting October 10 each fall.
Residual choices can allow for flex rotation to either corn or beans. Products such as metribuzin, Basis® Blend and Autmn® Super can be used. Basis® Blend is especially effective on controlling bluegrass into the spring after a fall burndown. Annual Bluegrass is a major issue for many farmers.
PCT | Sunrise® BioBuild™ Digester
In addition to weed control, we also have an opportunity help aid in more rapid degradation of plant residue with the addition of PCT | Sunrise® BioBuild™ Digester.
BioBuild™ Digester physically etches into dead crop residue to allow naturally occurring residue digesters more access into the plants. This results in less residue on the soil surface next spring and potentially places more carbon into the soil for the following crops.
Less tire damage is a very important benefit. Minerals from plants start leaching back into the soil well before harvest and by harvest corn stalks have typically had 70% of their mineral component already returned to the soil.
Clearing Up Myths
One myth that is commonly promoted by many is that GMO stalks take longer to break down than does non-GMO stalks. Research has proven the exact opposite with GMO stalks breaking down quicker than non-GMO stalks.
This is purely logical as well, just few have taken the time to explain.
Bt in the plant is a protein and all protein processes are nitrogen dependent. As the corn plant matures there is less and less N available and the plant also naturally reduces the production of the Bt protein as well. This is true of both above ground and below ground Bt proteins.
In the picture of corn ears, it shows the facts very directly. All the ears shown are from the same field of refuge in bag corn. The larger ears are all from above ground protected Bt plants while the smaller ears in between are all from non-Bt but herbicide protected corn.
Recall there is little/no Bt protein in the plant during late grain fill.
Which plants had their stalks mined the most by grain fill?
Written By: Brian Mitchem, PCT | Sunrise Research Agronomist