There are countless ways for farmers to control weeds. Tillage of all types, various herbicides, mowing, and even cover crops that can suppress weed populations. Weeds have been on my mind lately because the wet spring has kept most equipment that can deal with weeds off the soft soils.
While driving home earlier this week I noticed the stark difference between one of our fields and the adjacent field that belongs to a neighbor. Take a good look at the picture below. Our field is on the right half, and the neighbor farms the land on the left.
Can you see a slight difference between the two fields? Obviously our neighbor is dealing with very few weeds in his field, and we have a solid mat of chickweed on our ground. Why would that be? We both farm conventionally, and it’s quite obvious we farm in the same area. What weed management practices can be attributed to such a stark difference?
I asked my neighbor what he has done to this field since harvest last fall. He ran a disc chisel over the corn stalks after harvest. Later manure was injected into the soil with a Balzer Magnum. This spring he applied a burndown for weeds consisting of glyphosate, 2, 4-D, and atrazine. So his ground has seen some mechanical control via tillage in the fall, followed by a very common spring herbicide application.
Alright so why do I have a ton of weeds compared to my neighbor? I’m not a bad farmer, it’s just that the piece of land pictured has been under quite a different program than the other field. In fall of 2011 my field was planted with winter wheat which was harvested in June of 2012. We planted soybeans directly into that wheat stubble. The soybeans would have received an application of glyphosate during the summer to control any weeds that popped up after the wheat was removed. Beyond that, only the combine has been on this ground since then.
So we haven’t had any mechanical weed control, or the expense of fuel, labor and equipment, in this field since before wheat was planted nearly 18 months ago. And we didn’t have any fall herbicide applied in 2012. So with all the wet weather this spring chickweed was able to take hold. Will this be a problem for us? No not really. This field is going to remain no-till. Actually the wheat was only in 30 acres of a much larger field that is also no-till, but all that acreage has cover crops following 2012 corn harvest which have kept the weeds at bay. Since the wheat ground is to remain no-till we will use herbicide to control the weeds with a burndown application very similar to our neighbor’s. In fact that was done yesterday, so all the weeds you see are on their way out as I type. We could till the wheat ground, but tillage won’t kill all the chickweed. Rather it will just slow it down for while meaning either herbicide or tilling between the soybean rows later, and we stopped doing row crop tillage in crop a long time ago. I’ve actually never seen a cultivator in a soybean field but rather corn fields.
My neighbor and I still fight many of the same tough weeds each year. Giant ragweed is always a tough customer, and has been for a long time. Marestail seems to be on the rise, and there are now marestails that are resistant to glyphosate. 2,4-D will burn those resistant weeds up quick though. Since we grow popcorn and waxy corn we actually have quite a few acres of our corn crops that are not Roundup Ready. This means were are rotating herbicide modes of action which is a very important factor in avoiding resistant weeds. Not all herbicides kill by the same mechanism so I believe rotating your chemistry is nearly as important as rotating your crops.
Here we are doing a little mechanical tillage before Plant 13 gets serious.
So what if a farmer can’t use herbicide like my neighbor and I can? As it happens my friend Tim Zweber farms organically with his wife Emily up in Minnesota at Zweber Farms, LLC. Tim was kind enough to answer some of my organic weed management questions so all you readers could get another perspective from a farmer on weed control.
Brian: What crops do you raise?
Tim: On our farm we grow Corn, Barley & Peas for forage, A hay mix of Alfalfa, Red Clover and grasses, and pasture.
Brian: Describe your weed management program.
Tim: Our weed management program consists mostly of crop rotations and mechanical controls. Biggest problem weeds in the corn are grasses in the low areas that are hard to control through cultivating if I can’t get in to cultivate on time due to rain.
In our hay fields we plant a Barley/Pea cover crop with the hay mix underseeded. The cover crop is fast establishing and shades out weeds. We have quite a few weeds in the second cutting of new seedings mostly grasses like foxtails and quack and lambsquarter and pigweed. We cut the second cutting while the weeds are immature and chop or make baleage from it. The resulting feed tests well and cows find it very palatable but there will be some sorting of woody parts of pigweed if weather keeps us from cutting it early enough. Have to clean the feedbunks more often but there are worse things in the world.
Brian: Do you have specific problem weeds?
Tim: The only weed we have problems with in our pasture ground is thistles. To be specific Carduus acanthoides or the plumeless thistle. No other thistle is as prolific of seed producer and absolutely unpalatable to cattle. We control them through clipping pastures and trimming under fencelines. Unfortunately due to their ability to continuously produce flowers we have had trouble controlling them.
Biggest problem weeds in the corn are grasses in the low areas that are hard to control through cultivating if I can’t get in to cultivate on time due to rain.
Brian: Do any of your problem weeds become more prevalent under a particular management practice?
Tim: The biggest causes of weed problems on our farm are weather related. Actions must take place on time to ensure weeds aren’t able to survive to the reproductive stage and rain can really mess that up for us. Cattle damaging ground cover due to wet conditions or heat stress is another contributor to weed management issues.
Among the three systems described above I can tell you that weather is a major factor for all of us. When things are wet like they are things spring, you can either go to the field or you physically just can’t do it. And there’s that in between time when you have to decide if treating weeds while it’s just a little wet is a good idea or not. Do you wait for conditions to change and let weeds grow, or do you leave some ruts in the field?
I’ve chatted with Tim about organic no-till systems. In that kind of system an organic farmer is losing the mechanical control Tim uses, and the herbicides I use are certainly not in play. My understanding is that the farmer would plant a cereal rye cover crop. The rye would be allowed to grow enough to be killed with a roller-crimper, and the planter would plant directly into the mat of rye. Rye has allelopathic tendencies that provide a chemical defense against weeds. This is one of the reasons we have started using rye cover crops on our farm. The mat suppresses further weed growth, however I have read that a pass with a wide sweep row cultivator maybe be needed to undercut the roots of weeds that appear. Not a true no-till system, but that type of tool does not move a great deal of soil either.
The final point I want to make is that weeds and other problems like pests and disease are things all farmers battle. We might use different tools in our fight, but that often just means the weeds, pests, and disease adapt to our efforts. Conventional, organic, or in between nature always has a strong hand to play!