CT-4
Long-term research and farmer experience in the Midwest show traditional no-till planting (using one no-till coulter in front of each row) usually maintains or improves yield potential on well drained and very low organic matter soils. However in some cases, no-till planting may have a yield disadvantage compared to full-width or ridge-till systems. One or more of the following conditions are usually associated with reduced no-till yields: heavy residue levels, poor soil drainage, northern Corn Belt locations, very early planting, uneven residue distribution, or an uneven soil surface. Such conditions can result in reduced stand, uneven emergence, slow early-season growth, allelopathy, and delayed maturity-all potential yield limiting factors. These negative factors reduce corn yield more than soybean yield, since soybeans have a greater ability to overcome early season stress and to compensate for reduced stand.
To offset some of the limitations of traditional no-till planting, many farmers now use planter attachments to prepare a wider residue-free and/or tilled strip for each row not tilled before planting. One of the more popular "strip preparation" attachments is double disks or spiked wheels for residue removal. Another attachment is a set of two or three staggered, non-powered fluted coulters that loosen soil and partially incorporate residue in a 6- to 8- inch band ahead of planter units. Both types of attachments are often used on the same planter. Some farmers use other methods for improving the in-row area, either at planting or before planting in early spring or the previous fall. One method is planting in the old row middles with a single coulter or other attachments. This method avoids corn stalk stubs and the heaviest residue, often leading to more uniform seed placement. Other methods of loosening soil in the row include cultivator sweeps or powered rotary tillers set for strip tillage, either preplant or with the planter. Anhydrous ammonia applicators with "wings" attached to the knives are sometimes used in the fall to prepare strips for spring planting.
This publication reviews relevant research findings, discusses ongoing Purdue University research, and summarizes the challenges and opportunities with strip preparation practices for corn and soybean production.
Recent studies in the northern Corn Belt show an advantage for residue-free rows for corn. In Central Iowa, maintaining a 10-inch wide residue-free band for the row regained about 80 percent of the yield loss for no-till compared to a clean-tilled seedbed for continuous corn on silty clay loam soil.
Farther north, Minnesota researchers found that residue removal from the row area was successful for no-till corn in 1989 and 1990, but not in the drier spring of 1988. They concluded that greater than 20 percent in-row surface cover often lowers yield potential. With the longer growing season in western Kentucky, removing residue from the row area increased continuous corn yield in only one year out of four on a moderately well- drained silt loam soil.
Strip tillage for corn and soybeans is not a new idea, but evaluation in research plots is limited. Studies in Indiana (1967-70) and Ontario (1982-84) found that powered rotary tiller strips about 8 inches wide and 4 inches deep improved growth, maturity, and yield of continuous corn compared to traditional no-till planting into the previous year's rows. However, growth, maturity, and yield were still significantly better with full-width tillage, compared to the strip tillage method.
More recent comparisons of strip preparation techniques for no-till corn and soybeans in Indiana began in 1991 at the Agronomy Research Center near Lafayette. A conventional fall plow system was compared to no-till with the following planter attachments:
With these attachments, both corn and soybeans (in 30-inch rows) were planted into the previous year's rows in plots without any preplant tillage.
When corn followed corn, residue removal significantly increased soil temperature (Figure 1), and improved growth, maturity, and yield (Table 1). However, all these factors improved with fall plowing compared to no-till with residues removed. Corn showed little response to in-row tillage, with or without residue removal. For both corn and soybeans in rotation, there was very limited growth and maturity response, and no significant yield response, to residue removal or strip tillage, compared to traditional no-till planting.
Another study at the Agronomy Research Center compares fall vs. spring strip preparation methods and planting into the "old row" vs. between-row planting. Table 2 shows selected one-year corn following corn data from this study.
Shifting traditional no-till corn to row-middles, instead of planting in rows from the previous year, improved yield, primarily due to a better stand. Using strip preparation with the planter in row middles did not improve yield over traditional no-till. Fall strip preparation improved soil temperature, stand, and maturity, but yield was still significantly lower than fall plowed corn yield and little better than traditional no-till between rows.
In this same study spring strip preparation did not improve traditional no-till stand, growth, or yield when corn followed drilled soybeans.
Corn Corn Soybeans
after after after
Tillage corn soybeans corn
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bu/a.
Fall Plow 171 173 51
No-till 152 175 50
No-till + RR 159 177 50
3-coulters 154 172 51
3-coulters + RR 161 172 52
Mini-till 151 176 52
Mini-till + RR 154 171 50
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RR Residue removed
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Position Soil 50% Stand at Height 50%
b c
of rows Temp. Emergence 4 wk 8 wk Tassel Yield
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No-till in 62.5 21 21,500 38 84 163
No-till bet. 61.5 19 24,958 42 82 184
Spring strip-prep a bet. 62.2 19 22,958 43 82 177
Fall strip-prep bet. 63.4 17 25,708 43 80 189
Fall plow -- 65.8 15 25,667 57 78 223
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a Strip-preparation included row cleaners plus 3 fluted coulters per row.
b In or between last year's corn rows.
c Average daily soil temperature for first 5 weeks.
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Stand, Height, Harvest
Tillage 4 wks 8 wks moist Yield
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plants/a. in. % bu/a.
Spring chisel 23,125 57.8 26.2 156
No-till 24,667 57.1 26.5 153
Row cleaners 22,972 55.1 26.6 151
3 coulters 24,694 55.9 26.3 155
Mini-till a 23,875 56.8 26.1 157
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a Loosens a 4-inch strip of soil 4 inches deep, leaving residue
undisturbed.
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Strip preparation studies are also being conducted on two soil types at the Northeast Purdue Agricultural Center (NEPAC) near Columbia City, IN. Three- year data from Blount silt loam (Table 3) show no significant difference in yield among spring chisel, no-ftll, and strip preparation for corn following drilled soybeans.
In continuous corn on Rawson sandy loam at this same location, the spring chisel system produced the highest yield (Table 4), but planting between the old rows improved traditional no-till yield. Residue removal and strip tillage did not increase yield compared to traditional no-till planting between the old rows.
Some Indiana farmers apply anhydrous ammonia (and sometimes other nutrients) where the corn rows will be next spring, often using disks to form a small ridge of soil over the fertilizer band. They then no-till plant corn into these fall- prepared strips. One year's data at Lafayette, IN, planting into a 2 inch fall ridge, showed soil temperature, growth, and maturity advantages similar to other strip-preparation techniques.
Studies throughout the Corn Belt show planting into a 5- to 7- inch ridge made the previous year provides growth and yield almost equal to fall plowing, even in poorly drained, high- residue fields. It appears the success of this method of strip preparation depends on the ridge height, amount of seed zone elevation, and the resulting increase in soil temperature.
An advantage for this system could be the omission of starter fertilizer, since roots of young seedlings should have access to the fall-fertilized bands. However, fall applied nitrogen (N) often needs a nitrification inhibitor to minimize losses. Even with an inhibitor, fall applied N is usually less efficient than side- dressed N in the Eastern Corn Belt.
Moving residue from the row and/or loosening soil can cause serious water erosion problems if rows run up and down slope. Residue measurements in corn stubble have shown that fluted coulters and soil lifters usually leave enough soil cover for adequate erosion control and compliance with Food Security Act regulations. Use of attachments to provide residue removal in corn stubble, or any strip preparation in soybean stubble, may not leave soil with adequate protection from soil erosion. Consider the following suggestions for residue removal or strip tillage on highly erodible land:
Stand, Height, Harvest
Tillage 4 wk 8 wk moist Yield
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plants/a. in. % bu/a.
Spring chisel 25,375 69 21.0 157
No-till in row 23,500 62 21.1 142
No-till between rows 25,590 63 21.1 148
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Experience shows that both strip preparation techniques and traditional no-till planting have limitations in certain situations. Where soils stay wet under heavy residue, soil engaging tools throw soil from the row and form clods when the soil dries. When residues are removed from wet soil, the soil often sticks to planter depth gauge wheels causing variable seed depth. Spiked wheels may throw some wet soil from the row area, leaving a slight furrow in the seed zone.
The operating depth of both residue removal and strip tillage attachments can change as soil conditions change across a field. On-the-go adjustment of these attachments would be desirable.
In heavy cover crops or sod not killed several weeks prior to planting, non-powered strip tillage attachments may not perform satisfactorily. The vigorous root system of these crops holds soil firmly in place.
Wind often blows residues back into the row area lessening the desired warming/drying effects.
Where reduced stands or uneven seedling emergence limit traditional no-till yields, either planting beside/between last year's rows (in corn after corn) or using strip preparation should improve yield potential. In uneven crop residue or surface-applied manure, row cleaners should provide a more uniform seeding depth. Where previous wheel tracks create a non-uniform soil surface, zone tillage may also improve seeding depth uniformity.
If lower early season soil temperature and/or allelopathy cause slow growth and delayed maturity, row cleaners should improve yield potential. However, yields may not equal those with full-width tillage on dark, silty clay loam soils.
Since both erratic seedling emergence and slow early growth affect corn more negatively than soybeans, strip preparation is likely to improve corn yield more than soybean yield.
New 12/94
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agriculture Cooperating. H.A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to our programs and facilities.