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Farming Without Chemicals in Ohio
A Case Study Report

Author: Keith Dix
Innovative Farmers of Ohio
in cooperation with the Citizens Policy Center

6. How do organic farmers control weeds?

There seems to be universal agreement among organic farmers that the most serious problem they face is the control of weeds. Their solution to this problem lies in substituting mechanical control of weeds for chemical control. Since organic certification prohibits the use of all chemical herbicides, organic growers rely on tractor drawn implements such as field cultivators and rotary hoes. It is also true that these growers have found that, over the years, the integration of cover crops in an organic rotation significantly helps reduce weed pressure. This is true for many weed species, but not all. Organic growers who do a good job of weed control are very conscious of the timing of various operations during the crop year. Some say that "timing is everything." It should also be mentioned that, while totally weed-free fields might be a laudable goal, most organic farmers understand that some weed pressure can be tolerated without significant losses in crop yields.

Nelson and Lynn W. Taking a crop of corn first, the Wengers explain how they plant it and manage the weeds:

Let's start in the spring with plowing. First, I haul manure on my old hay(alfalfa) ground, probably in the fall and in the spring. Then I try to plow in April some time, then let the ground lay to let some weeds germinate. I field cultivate it once before I plant with a Glencoe field cultivator with Danish tines. That way it tears up the germinating weeds.

Then we plant about the 10th of May. Before we plant, we either finish disk it or cultimulch it and then we plant. We don't usually rotary hoe much but last year we did and we did that just within a week after we planted. When the corn gets about 4 inches tall we cultivate the first time and then when it gets 6 or 8 inches tall we go through and cultivate the second time and that's it. We get pretty good weed control doing that if we get the first cultivation done right. The secret is getting that first generation of weeds done before you plant.

The secret to getting good weed control is to have your shields set so you roll the ground up on both sides of the row, up to the plant, the first time over. You can cover up the weeds the first time over. That will hold them back enough so that when you come back the second time you can really throw ground, really move. You take the shields off and really throw ground in the row. We do have some problem spots and if its really weedy its hard to cover the little ones (weeds ) up in the row. We usually try to harvest in October or November and that's about it with corn. Then we disk it with an off-set disk. We got a shredder this year so we're going to start shredding the stalks after harvest and then put lime on to get it ready for beans and alfalfa later. No winter cover.

Jeff D. He makes full use of the rotary hoe in the year that he's planting soybeans. I will moldboard plow the cover crop, some people don't like that, for one year for the beans to be planted. I plow it in the spring and let it sit for a while, let it mellow out a little bit, let the weeds come up, work them down with a field cultivator.

I have a newer field cultivator that has enough trash clearance and has a real good harrow on the back. I don't need to disk it at all, hopefully. I rarely use the disk anymore. The field cultivator tends to aerate the ground more and leave a better structure than a disk. So I'll field cultivate twice, maybe three times and then plant the beans the first week of June.

Every year, I hear farmers say, "I'm not going to plant before Memorial Day." Well, things get nice and you hear them say, "I wish I hadn't planted so early." As close to Memorial Day as you can get, that seems to be the weekend. If we have a really early year, I might get in four cultivations before planting beans. If the weeds keep germinating, you can keep killing them off every 4 or 5 days or a week.

Two or three days after getting the beans in, I'll rotary hoe them and then wait for them to come up where the rotary hoe isn't going to hurt them, rotary hoe them again, wait just a couple of days and rotary hoe them again;so I'll get three rotary hoeings in and then by that time you can see the row real good and I'll cultivate. I set my cultivator so the sweeps aren't running real close to the row but they're throwing dirt. I try to push as much dirt around the beans as I can without burying them. You want to cover up the weeds in the row but you don't want to bury the beans. I'll cultivate when they're a foot tall or so. They're done until fall.

From this account of his mechanical weed control regime, Jeff admits that he must make two to four pre-planting passes with the field cultivator and about five trips after planting&emdash;three with the rotary hoe and two with the cultivator. If the moldboard plowing and actual planting are included, he might be making as many as eleven trips across his bean fields. When asked if he notices any signs of soil compaction from these operations he said, "No, because the soil is dry by this time, and the soil is full of live organic matter. This organic matter makes the ground like a sponge that springs back. You can only believe it by seeing it!"

Dean Mc. He takes a different approach to weed management in his two-year, spelt-soybean rotation. Dean says "...our weed control for this year's bean crop really started last year." Red clover is seeded into the spelt in March. After the spelt is harvested:

We will mow weeds that are in the field in late August and we start working up those fields in September or October, whenever the soil's right. The red clover is incorporated. That was a hard thing for me to overcome. Why would you tear up the ground in the fall when you want to protect it over the winter? Why would you destroy a cover crop in the fall when it would continue to grow in the winter and early spring? The reason is, it takes time for it to digest and if you wait until spring to plow that huge mass down there just isn't enough time to have it break down. Also, it will hold the moisture in the ground longer.

Dean was asked about the advisability of leaving the fields bare over the winter. Wasn't he concerned about soil erosion?

It appears to be bare but in reality with the use of an offset disk or chisel plow the ground is not completely bare. You've just mixed the residue with the top six inches of soil and there's a lot of wicking action. The soil can hold a lot more moisture than ground that is planted to a fall crop, for example. The erosion on those fields has been surprisingly minimal. I see more erosion where we have fall-seeded crops like in our spelt fields. Those don't get fluffed up as much. They're packed down and water will pool in those fields before in other places.

Steve B. uses winter rye in the wheat (or spelt) and soybean rotation on his 1,050 acres in Seneca County. After the wheat or spelt is harvested, usually in July, Steve begins preparing his ground for the next season:

We can start with wheat harvest or spelt which is usually done in July and as soon as we get the harvest over with we'll go over it with the offset disk, get it disked up good and then come in with a field cultivator or a tandem disk after letting it sit for a week or two. We work it down and get the straw incorporated and let it lay and then let the weeds come up and then field cultivate it, maybe once or twice in August or September.

Some time around September 10 or 15, we'll drill our rye cover crop in there. We'll let that grow all fall and winter and then go in, depending on the spring, mid to late April and plow the rye under. We may use the offset disk this year but don't know how that will work. We've always moldboard plowed it. And then disk it. We're in the process of getting a big rotovator so we can get it worked down immediately after plowing it. We don't want to lose any more moisture than we absolutely have to.

Then we'll field cultivate it, usually with a packer after the cultivator. Ideally, we'd like to let it lay after we plow it a couple of weeks, maybe three, hopefully to get a crop of weeds to germinate and then work it under. We'll start planting soybeans between May 20 to June 1. We always try to be done by the 1st of June. We have planted as late as the middle of June. I don't like to wait that long.

We'll cultivate as soon as the beans are up, a couple or three inches tall. Sooner if we have to. Our cultivator has cutaway disks that cut it away from the row. Our planter is rigged up with diggers that dig grooves. It's an eight-row planter and it's set to dig four grooves with a Danish tine and a spike. The cultivator has what I call "V" wheels that will follow those grooves. We can get down to a four inch ban with the cultivator with pretty good results. If you do a good job with the cultivator with the cutaway disks you can pretty much eliminate just about everything(i.e. weeds) except what's in the row.

We'll go back a couple of weeks later with the cutaway disks off when the beans are 18-24 inches tall. It's usually late June when we go back and do that. Once in a while we'll cultivate a third time but that's pretty rare.

Sometimes we'll rotary hoe before the first cultivation but that's rare, too. The reason I don't like to do that it distorts that groove that I've made with the planter. The rotary hoe will fill that trench in so I'm a little nervous about whether the cultivator will follow the groove or not. Our experience with the rotary hoe has not been real successful so we feel that if we can get in and cultivate as early as we can we can get the weeds stopped.