BLOOMINGTON, Ill. — The prevented planting option is on the table as drenched soils have pushed planting into June, but to avoid problems later, producers should consider planting something to protect the fallow soil.
Karen Corrigan, independent agronomist and co-owner of McGillicuddy-Corrigan Agronomics, provided some recommendations of what to do with the cropless soil in a McLean County Farm Bureau-hosted meeting June 3.
“Make sure you keep the soil healthy. You don’t want to leave the soil black. We have really rich organic soils, and we want to make sure we keep those microbes alive. Bare soil can decrease productivity for the next year,” Corrigan said.
“Live roots will keep the soil ‘alive’ in better condition. Anytime you can keep those live roots out there, the soil is going to be more productive the next year. If you have left it black, you’re really going to take a big hit on yield next year.
“We also have to control the weeds. Weeds are not cover crops and should not be treated as such, and we definitely don’t want the revenge of plant 2019 to come back for the next several years.”
Tillage and herbicides are two options for controlling weeds on prevented plant acres, but Corrigan said in most cases they are not the best options.
Tillage, while an economical option, may keep the farmer busy, it is only effective on smaller weeds. Repeated tillage can damage soil structure, kill microbial activity and bring up more weed seeds to germinate.
“Tillage on larger weeds is not going to pull them out and kill them, and it’s not going to stop seed production. If you’re doing tillage, make sure the weeds are under 6 inches,” Corrigan said.
“Using herbicides will obviously be very costly with the application and product costs and will need to be repeated two or three times to be effective. Herbicides must be applied prior to seed formation. Residual herbicides sound good, but actually won’t last as long without a crop to compete.”
Cover Crop Option
Cover crops are an option many are considering for their fallow fields, but don’t plant them until the insurance dates have passed.
The seed supply may not meet demand, Corrigan noted.
“There’re rumors out there right now that supplies are low and that’s just because the millions of acres that we’re looking at in (prevented) plant. The cover crop companies were not expecting millions of acres in Illinois and Indiana to not be planted, and so generally when things like that happens, cover crop companies or salesmen seem to come out of the woodwork,” she said.
“We really want to make sure to choose a reputable one and one that you know has a good source. We want to make sure we don’t bring in any weed seeds from other areas that we then have to deal with.
“Over the last couple of years in Iowa there was pollinator mixes that had Palmer amaranth in them, and we want to definitely make sure that we avoid situations like that.
“Use a good, reputable company that’s been around and knows what they’re talking about, have clean seed. Check for contaminants and check for weed seed not from your area.”
Minivan Not Ferrari
If opting for cover crops to keep those fields active and healthy, Corrigan recommends keep it simple.
“You don’t have to spend a fortune. This is not something you have to spend $60 an acre on. You can have the Ferrari of cover crops, or you can have the old minivan that gets you where you need to go, and this is a situation where you don’t need the high-end,” she said.
When choosing a cover crop species, the first factor that should be considered is what herbicides were applied on a particular field.
Most cover crops are planted in the fall after harvest, so that is normally not a concern.
However, earlier planted cover crops could fall in the window and impacted by herbicides.
Corrigan reiterated that first-time cover crop users need to keep it simple and plant something that’s going to die over-winter taking away the spring management issues going into the next crop year.
“If you’ve used cover crops in the past, you know what mix to use and you know what you’re doing, how you’re going to kill it and already have it figured our then by all means do that,” she said.
Another consideration is determining what one wants to accomplish with cover crops beyond just covering and protecting the soil.
Some cover crops are best for erosion control with fibrous roots that hold the soil in place, others are best in building humus, some for scavenging nutrients that has spring growth and there are those that break up tight soils. In addition, there are cover crops with forage qualities that can be used for grazing after Nov. 1.
Timing of planting cover crops should also be considered Sorghum-sudangrass, buckwheat and cowpea are examples of cover crops that can be planted mid-summer, whereas the more traditional cover crops would be planted towards the end of July and at harvest.
“Oats and radishes are good cover crops for first-timers. They can be planted later in July, it winter kills, is a good combination prior to corn. The mix provides two different root types and depths. I will caution is the mix has a potential for nutrient leaching due to no spring growth, and the stench from radishes can be strong as they die and smell like natural gas,” Corrigan said.
“Rye as a cover crop is another option. It provides fibrous roots and loosens the soil. It’s great if going into soybeans. Rye does need more intense management if going to corn as it needs time to kill prior to planting corn.
“You need to make sure rye only gets so much growth in the spring and you want to kill it when it reaches one foot. Use extra nitrogen at planting to cover the corn’s needs until the residue releases it. It’s very good a suppressing weed control and scavenges nutrients. If you have particularly weedy fields this would be a good option to suppress those.”
With all of the rain, Corrigan said she’s been getting calls asking how much fertilizer is left in the fields.
“It kind of depends on what happened in your area. In most cases your phosphorous and potassium are fine. They don’t move much in the soil. However, if you’re in areas where there’s running water, it will move that soils and move nutrients,” she said.
“I don’t think a lot of our nitrogen leached down. We did have a lot of water, but we didn’t have moving water that moved down the profile. So, in most cases where we lost nitrogen was through denitrification and it went up as opposed to down. I would not assume that nitrogen is there for next year.”