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Alternative Tillage Strategies for Sweet Corn

Steve Groff
Cedar Meadow Farm, Holtwood, PA

Traditionally, full-scale tillage has been practiced in growing vegetables. Preparing a seedbed for transplants or seeds, to alleviate compaction, and weed control, has been the primary reason for tillage. With the increased awareness of environmental stewardship, newer tillage and planting equipment, and a desire to reduce imput costs, alternate tillage strategies are now beginning to prove viable.

Why do we till?

• Prepares seed bed
• Relieves compaction
• Used for weed control

How is tillage harmful?

• Subjects soil to erosion
• Burns up organic matter
• Addicts the soil to additional tillage
• Breaks down aggregation

With these aspects in mind we need to figure out how we can decrease the detrimental effects to the soil with our tillage passes and still grow a profitable crop. From a strictly soil perspective, tillage is the worst thing you can do to it. A good example is this - soil in woods. It is nice and soft, has high organic matter, and water infiltrates easily. Or, your lawn. Do you till it every year to make it grow better? When you shovel up a chunk of sod in your yard does the soil look nice and crumbly or is it tight and compacted. I like to think of tillage reduction this way. What can I use to replace steel as a way of preparing the soil for a crop? First thing that comes to mind is the use of cover crops. Having covers in your rotation can possibly eliminate a tillage trip or reduce cultivation needs due to weed suppression. Another aspect is by not destroying wormholes and old decayed root channels with tillage. This helps in crop roots being able to penetrate the soil better and for increased water infiltration. The bottom lines is- reduce tillage where practically possible on your farm with your equipment and with your knowledge and experience.

Here are some proven systems that you might want to consider that treat the soil better then full tillage.

Zone tillage is a 2 or 3 coulter in-row setup that goes before the planter either as a separate pass on it's own coulter cart, or on the planter itself. It tills an area 4-8" wide and 2-4" deep. Some farmers use the coulter cart a day or 2 before planting as a way to dry and warm the soil. I know a 150-acre sweet corn and pumpkin grower from Maine who uses this system quite successfully. It really shines in the cool wet soils of early spring. Usually no other tillage is used.

Strip tillage has shank or knife with a coulter in front to cut residues. It is more aggressive than zone till and can go 3-6" deep and creates a tilled strip 6-8" wide. Sometimes it is used in the fall in a way that makes a slight mound in order for drier and warmer planting conditions in the spring. I've seen a variation of this in Oregon where the vegetable producers use a stripped down rototiller that only has tines operating in the row to create a 4-8" tilled strip. This is very slow and take a lot of power but works well. Another variation is to have a deep till shank with coulters on either side to keep soil from being thrown out of the seedbed. A disadvantage with strip till is that it is difficult to do with stones and on hillsides.

No tillage is what I do. It leaves the residues on the soil surface and I try not to disturb any more soil then necessary to get the plants or seeds in the ground. Has the greatest savings in erosion potential, reduces the need of equipment and fuel, and if done correctly is the best for increasing the soil quality on most soils. The disadvantages are trying to overcome cold and wet soils in the spring and getting the right equipment to do the job.

Deep tillage is only needed when the subsoil is compacted. It's better if you can do it with an implement that will leave most of the residue on the surface. It's best to avoid causing the compaction in the first place if you can.

I started no tilling in the early '80s on about 15 field corn acres because we had some erosion problems and I didn't like having to fill in gullies before harvesting corn and I felt that wasn't right. In 1991 I began using a rye cover crop as another soil-conservation measure. In 1994 we stated no-tilling tomatoes and in 3 years, all of our 175 acres of 15 different crops were no-tilled. This "Permanent Cover Cropping System" is done successfully by using cover crops, intensive crop rotation, and long-term no-tillage. I can't say enough how these 3 components are the foundation to make this system work. No-till is not the "magic bullet". It is an equal partner with cover crops and rotation.

I use this system for 3 reasons:

• Increase profits
• Enhance soil quality
• Reduce pesticides

Increase profits

The economics of this system are positive. However, in the sweet corn year of my rotation I do not get nearly the same increase in profitability as I do in my other vegetable crops using this system. A saving in tillage is $50/A and $10/A for pesticides (average of the last 4 years). Increased costs are $40/A for establishment and seed of a cover crop, and $10/A for controlling the cover crop. It's hard to put a dollar value on the other benefits cover crops give such as erosion control, better soil quality, increased organic matter, and cleaner harvesting conditions, but it has to be factored in at least indirectly. On my farm I've been able grow my own cover crop seed and use a rolling stalk chopper to control the covers. This allows me to further reduce expenses. Our yields have increased the last several years and this adds to the profit.

Enhance Soil Quality

Soil erosion is the most detrimental aspect of agriculture. We can't turn our backs on soil erosion and call ourselves sustainable! No-till has some very attractive attributes especially when combined with cover crops and crop rotation. SOIL IS MEANT TO BE COVERED! Soil erosion on Cedar Meadow farm has been cut from 14 tons per acre per year to almost nothing. With the ground covered by plant residues and not loosened by vigorous tillage, the soil stays rather than getting washed away during heavy rainfall. The combination of cover crops and no tilling does more than cut erosion - it improves soil tilth, increases organic matter levels, enhances water infiltration and lessens pest problems. Organic Matter has gone from 2.7% to 4.3%.

Reduced Pesticides

A good thick mulch helps control weeds and has cut down on my herbicide bill somewhat. It's very important to have a consistent cover crop to make this work. Total pesticide usage on the whole farm has decreased 50%. Beneficial insects have increased.

How the System Works

The foundation of this system is the establishment of a cover crop in late summer or in the fall. My favorite for early sweet corn right now is a mix of oats (1.5 bu.) and soybeans (1 bu.) planted in August. The beans give N for the oats. This mixture will then winter kill and provides a nice dead residue to plant the early sweet corn into. I have found that when planting into this dead residue that I need to use nearly as much herbicide as I would in a conventional system. A few weeds or volunteer oats are generally present so 1/2 - 1 pint of Roundup is used with 1.5 pints of Bicep. If broadleaves break though I will use 1/2 ounce of Permit or Basagran. For the later plantings I will plant into a mix of hairy vetch (25 lbs.) and rye (30 lbs.), straight hairy vetch (25lbs.), or straight rye (2 bu.). I have successfully no-tilled sweet corn into corn and soybean residue with excellent results, however more herbicides and fertilizers are needed to control weeds and provide N. I credit rye/vetch giving #50lb. of N and straight vetch #75lb. of N. Vetch seed is expensive so I grow my own with rye. I have seed to sell.

I wanted to control covers mechanically and in a way that flattens them near the soil to help their decomposition. I ended up buying a 10-foot Buffalo Rolling Stalk Chopper in 1996. It's designed to flatten and chop cornstalks, on a scale between a flail mower and a disk. The machine has two rows of rollers, four in front and four in back, with eight 23-inch blades per roller. The turning rollers crimp up the cover and push it right down. It can be run at 8-10 miles per hour, so it's fast and economical. I added parallel linkage so each roller floats independently.

The versatile machine has been used on over 500 acres in 4 years. I roll the covers with it, and get good control of hairy vetch and rye if it has flowered. It is important to roll the cover before wind blows it in various directions so it is laid parallel to the direction of planting. I always roll soon after the rye is 4 feet tall, which is around May 10th unless the cover is thin, and will not blow down. The cover will regrow somewhat and then I spray with 1/2 pint of Roundup and 1.2 - 1.5 pints of Bicep before emergence.

After sweet corn harvest, I use the rolling stalk chopper to roll down the stalks and immediately plant another cover crop. I use a customized Kinze no till planter with Monosem row units to seed the sweet corn. This machine has Rawson coulters, Ausherman row cleaners, Yetter parallel linkage, Martin spading closing wheels, Keeton seed firmers and foam markers. When planting early into the dead mulch I use a 2" eight wave coulter on either side of the row and clean the row so the soil dries out and warms up quicker. It is basically a zone - till setup. Later on I change the coulters to a 1" 13 wave style. Each setup applies 80lbs. of N on the row - 40 lbs. on each side. I also put 3 gallons of popup fertilizer in the seed trench and add T-22 to the seed.

I've also customized an RJ Equipment carousel no-till transplanter for no-till transplanting of sweet corn seedlings into killed cover crops. I'll seed into 288 trays on April 1 and then plant the 4 leaf seedlings around April 25th. By adding row covers I can up the first harvest date by at least 10 days before the first early direct planted sweet corn. This transplanter has a spring-loaded 20-inch, turbo coulter, followed by a double-disk opener and a short shoe to place the transplant in. Angled press wheels tuck the soil firmly around the plant. The package leaves virtually no soil showing after the crop is planted, giving good full coverage mulch for the whole season.

Fertilizer management evolves, as you have become more committed to the use of no-till, cover crops and the overall concept of sustainable ag. Any synthetic N I use is mainly ammonium sulfate. I need the sulfur it supplies, as well as its low volatility. I side-dress by broadcasting 40 - 80 lbs. of dry N (depending on contribution of cover) when the corn is 12" tall. I tend to credit my higher organic matter soils of giving me 25lb of N or so from release of additional N.

I do some foliar feeding as well. Soil Compaction is to be avoided at all costs! However, once you've no-tilled for several years the soil becomes noticeably less susceptible to compaction. Cover crops are key to this in building soil structure. I'm real fussy about when lime and manure trucks can get on my fields. If you ever need to alleviate compaction, do so with as little surface disturbance as possible.

I just purchased a customized 2 shank Unverferth ripper/stripper to go through my field driveways after harvest. This tool has a narrow shank that penetrates 12 inches deep and has a 2-inch wide wavy coulter on either side of the shank. This keeps soil from being thrown away from the shank and chops it up a bit. A 12-inch wide rolling basket follows to further break up clods. I am able to plant behind this without needing to disk.

Controlling perennial weeds can be a challenge in no till but I have found that with intensive crop rotation and occasional spot spraying, weeds can be managed effectively. Perennial weeds are not a problem on our farm.