Corn: Tillage

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Pub 811: Agronomy Guide > Corn > Tillage

Excerpt from Agronomy Guide for Field Crops
Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

• Tillage
• Soil Texture and Drainage
• Crop Rotation
  • Table 1-1. Comparison of Two Tillage Systems on Grain Corn Yield
• Trials conducted following cereals (straw baled) or grain corn (1982-2007).
• Trials conducted on medium-or fine-textured soil (1982-2007).
• Table 1-2. Impact of Fall Tillage Systems on Grain Corn Yield
• Other Reasons for Tillage
• Conventional Tillage
• Fall Mulch Tillage
  • Table 1-3. Impact of Fall Tillage Systems Without Secondary Tillage on Grain Corn Yield
• Spring Mulch Tillage
  • Table 1-4. Tillage System Effects on Grain Corn Yield Following Soybeans
• Fall Strip-Tillage
  • Table 1-5. Fall Strip-Tillage for Corn After Winter Wheat (straw baled)
  • Table 1-6. Corn Yield Response to Application Method of Phosphorus and Potassium Fertilizer in Two Tillage Systems
• Deep Tillage
  • Table 1-7. Grain Corn Yield Response to Three Tillage Systems
  • Table 1-8. Effects of Tillage Systems on Corn Yields Following Winter Wheat
• No-Till Systems
• Soil Drainage
  • Table 1-9. Effect of Wheat Straw Levels on No-Till Corn Yields
• Crop Rotation
• Residue Management
• Weed Conrol
• Disease and Insect Management
• Fertilizer Placement
  • Table 1-10. Corn Yield Response to Phosphorus and Potassium Fertilizer Placement in Two Tillage Systems
• Table 1-11. Effect of Planter Model and Tillage on Corn Yield
• Soil Compaction
• Planter Performance

Tillage

Soil texture and crop rotation are the dominant factors that determine the need for tillage to successfully produce corn in Ontario. Soils in Ontario are usually saturated in early spring, and quick dry-down is necessary to ensure timely corn planting. Appropriate use of tillage can increase spring soil dry-down rates by loosening soil. This improves drainage and/or reduces residue cover, which increases rates of soil water evaporation.

Soil Texture and Drainage

Especially on soils with relatively slow internal drainage, tillage can significantly increase the rate of soil drying and warming, increasing the possibility for timely planting and fast uniform emergence. Generally, in Ontario, there is little corn yield response to tillage on coarse-textured soils (sand, loamy sand or sandy loams) that have good internal drainage characteristics (Drainage classification: rapid or well). This even occurs following crops that leave large amounts of residue cover, such as grain corn or cereals. Table 1-1, Comparison of Two Tillage Systems on Grain Corn Yield, provides a summary of Ontario tillage research for corn following either grain corn or cereals grouped according to soil texture. On the coarse-textured sites there was no consistent yield response to tillage. Tillage increased yield about 70% of the time on the medium-and fine-textured sites with an average yield response to tillage of 5%-7%.

Crop Rotation

A good crop rotation can replace a significant amount of tillage. Table 1-1, Comparison of Two Tillage Systems on Grain Corn Yield, summarizes Ontario tillage research for corn, conducted on medium-and fine-textured soils, grouped by previous crop. Generally, there is little corn yield response to tillage following forages. Including forages in crop rotations improves soil structure and may eliminate the need for tillage to improve seedbed tilth. The relatively low yield response to tillage following soybeans when compared to either cereals or grain corn is partially due to lower crop-residue levels following soybeans in no-till systems. High residue levels can reduce early-season soil temperature, resulting in delayed planting, slower corn growth and lower yield potential. The possibility that tillage increased corn yield following cereals or grain corn on medium-or fine-textured soils was about 75%, with yield increases averaging 5%-9%.

Other Reasons for Tillage

There are other reasons to perform tillage for corn production in addition to increasing soil dry-down rates:

• improved seedbed uniformity, resulting in more consistent planter performance and faster, more uniform corn emergence
• incorporation of surface-applied fertilizer or manure, resulting in increased nutrient availability and/or use efficiency
• termination and/or incorporation of weed or crop residue that can serve as hosts to increase populations of insect pests
• alleviation of soil compaction

Conventional Tillage

Conventional tillage for corn in Ontario consists of fall moldboard plowing followed in spring by secondary tillage, usually with a field cultivator or tandem disc. Most moldboard plowing is targeted to an operating depth of 15 cm (6 in.); plowing deeper often results in unwanted mixing of subsoil into the seed-bed. The more uniform and level a field is left after fall plowing, the greater the opportunities to reduce secondary tillage costs and improve planter performance. The lack of surface residue in conventional tillage exposes fields to greater erosion risks from water and wind. On complex slopes, tillage can be responsible for causing large quantities of topsoil to move to lower slope positions.

Fall Mulch Tillage

The chisel plow has been the most widely adopted fall mulch tillage tool in Ontario. Tandem and offset discs are also used extensively in some areas. Tillage research trials conducted across Ontario over the past 20 years have generally shown that disking often resulted in more favourable soil conditions and higher corn yields than chisel plowing. Table 1-2, Impact of Fall Tillage Systems on Grain Corn Yield, summarizes the corn yield data from these sites.

Chisel plowing with twisted shovel teeth may leave the soil quite ridged. This can lead to extra costs in secondary tillage (more passes), uneven seedbeds and occasionally excessive soil drying. Using sweep teeth on all or part of the chisel plow overcomes some of these problems, as does adding a levelling bar or harrows to the rear of the chisel plow, or timely secondary tillage in the spring.

When disking is done to leave the soil surface level in the fall, single-pass corn planting (no secondary tillage) becomes a viable option in the spring and is a good technique for reducing tillage costs. Table 1-3, Impact of Fall Tillage Systems Without Secondary Tillage on Grain Corn Yield, out-lines research conducted in Ontario where this approach was taken. On those sites where fall chisel plowing and secondary tillage were compared, the tandem disc-only treatment generally produced higher yields and had significantly lower operating costs. On average, using only the tandem disc yielded within 0.31 t/ha (5 bu/acre) of the conventional tillage system.

Spring Mulch Tillage

The best practice for reducing erosion and input costs is to not perform fall tillage. Producers working on fine-textured soils where crop residues are high following corn, wheat or other crops may be apprehensive about leaving soils untouched in the fall. However, following soybeans, there is little justification for doing fall tillage on most fields in Ontario. Table 1-4, Tillage System Effects on Grain Corn Yield Following Soybeans, illustrates that even on finely textured soils, spring tillage alone (two passes of a field cultivator) was generally sufficient when corn followed soybeans in the rotation. Other demonstration trials established on medium- and coarse-textured soils have shown the same.

When corn follows soybeans, systems that involve more than spring cultivation often do not produce enough extra corn to pay for the fall tillage operation.

Grower experience with spring mulch tillage systems has shown that working undisturbed soils in the spring obtained better results when using high-clearance tines, narrow teeth and/or when packers or rollers were used in conjunction with the field cultivator.

Fall Strip-Tillage

Performing fall tillage confined to narrow zones that correspond to next year's corn rows has received considerable attention in the past few years. The strips of soil are loosened, cleared of residue and hopefully somewhat elevated, while leaving the rest of the field covered with protective crop residue. The next spring, the strips are drier, less dense and more suited to "no-till" planting.

Research conducted at the University of Guelph over the period 1994-96 compared a Trans-till zone tillage tool to conventional and no-till systems in winter wheat stubble. Table 1-5, Fall Strip-Tillage for Corn After Winter Wheat (straw baled), next page, indicates that on fine-textured soils, strip-tillage in the fall generally produced yields that were better than no-till. Only at Wyoming did fall strip till yields equal those obtained with the conventional moldboard system. Subsequent Ontario research has supported the observations shown in Table 1-5; that on fine-textured soils following wheat, fall strip-tillage generally gave higher corn yields than no-till and equal yields to those of conventional tillage systems. Research results have not consistently shown a yield advantage for fall strip-tillage systems over no-till on medium-textured soils or when following soybeans.

¹ Trials were conducted on fine- (Wyoming) and medium- (Centralia) textured soils (1994-96).
² Moldboard and chisel-plowed plots were cultivated and packed in spring. Fall disc and zone-till plots were planted directly without any secondary tillage in spring. All treatments were planted the same day.

Early spring moisture measurements conducted on University tillage plots generally showed that fall strip-tilled zones were consistently drier in early May compared to the undisturbed no-till plots (Table 1-5).

Yield responses in side-by-side trials have not always indicated a benefit to fall strip-tillage, but producers with large acreage, poorly draining soils or high surface residues may gain a consistent benefit from strip-tillage in terms of planting timeliness, emergence uniformity and early corn growth. Performing secondary spring strip-tillage in fall strip-tillage zones has increased yields in instances where fall strip-tillage yields are less than those in conventional tillage systems. If conducting spring strip-tillage, do not exceed a tillage depth of 10 cm (4 in.), in order to minimize the risk of excessive soil drying that can occur, especially in dry planting seasons.

1. Average of 5 trials conducted on medium-textured soils with medium soil test K ratings (1 trial with a low soil test K rating).
2. Fall phosphorus (40 lb P₂O₅/acre on medium testing sites and 125 lb P₂O₅/acre on the low testing site) and potassium (100-125 lb K₂O/acre) were fall-surface broadcast in the no-till system and banded 6 in. deep in the fall strip-till system.
3. Planter phosphorus (30 lb P₂O₅/acre) and potassium (30 lb K₂O/acre) were applied in a band 5 cm (2 in.) beside the row, 5 cm (2 in.) below seeding depth.
   

Strip-tillage systems also provide an opportunity to band fertilizers that in a no-till system must be broadcast. Applying fertilizer using the strip-tillage system may also replace the need to apply banded starter fertilizers through the planter. Table 1-6, Corn Yield Response to Application Method of Phosphorus and Potassium Fertilizer in Two Tillage Systems, shows that fall banding of phosphorus and potassium in strip-tillage systems can produce higher yields than when similar rates of fertilizer were broadcast in no-till systems. However, corn yields from using strip-tillage systems to band-apply phosphorus and/or potassium in the fall have generally been lower than when P and K have been applied through the planter.

Deep Tillage

Increasing axle loads of farm machinery and the general concern that soils have become more compacted have increased the use of deep tillage systems. The main reason offered for deep tillage is that elimination of compacted sub-soil layers and/or tillage pans will promote rapid and deep root growth and improve drainage. However, in Ontario, subsoils loosened using deep tillage are often easily recompacted by wheel traffic. Moreover, it is possible that deep-tilled soils that receive wheel traffic end up with poorer drainage and are less favourable for root growth because deep tillage destroyed the natural pores created by worms or previous crop roots.

In Ontario, use of the disk ripper to conduct deep (30-35 cm or 12-13 in.) tillage has increased significantly. Table 1-7, Grain Corn Yield Response to Three Tillage Systems, summarizes the results of a study that evaluated corn yield response to deep tillage using a disk ripper in medium-textured soils. On these productive soils, with little evidence of severe subsoil compaction, there was little yield advantage and no economic advantage over a fall strip-tillage system where soils were tilled at about half the depth. Following wheat, both the disk ripper and fall strip-tillage systems produced yields that were 5% over no-till, but all of the yield response from tillage could be obtained using a fall strip-tillage system with a tillage depth about half that of the disk ripper. Some growers have claimed benefits from deep tillage on areas with poor drainage or severe soil compaction (such as headlands). The need for deep tillage in Ontario is often only associated with fields or areas of fields with severe drainage limitations or soil compaction.

The strip-tillage system has also been presented as an opportunity for reducing compaction and/or improving drainage by conducting deep tillage. In some cases, recommendations are made to till as deep as 30-35 cm (12-14 in). University of Guelph researchers tested deep in-row ripping in 1998-2000 at sites near Granton and Ridgetown. Table 1-8, Effects of Tillage Systems on Corn Yields Following Winter Wheat, illustrates that deep loosening either provided no yield benefit or not enough to pay for the cost of the deep tillage operation. The advantage of using a strip-tillage system to perform deep tillage is that wheel traffic does not occur on the deep tilled strips until the next harvest, which allows extra time for soil stabilization before being exposed to wheel traffic again.

No-Till Systems

In no-till systems, tillage is not used to prepare a seedbed. Minimal soil loosening in a narrow band immediately ahead of the seed opener is performed by planter-mounted coulters and/or residue clearing devices. Successful no-till corn production is partially dependant on effective use of alternative production practices and field management strategies that deal with yield limiting factors that otherwise would have been corrected with tillage.

For successful no-till corn production, pay attention to:

• soil drainage
• crop rotation
• residue management
• weed control
• disease/insect management
• fertilizer placement
• soil compaction
• planter performance

Soil DrainageS

Without the soil loosening and residue incorporation associated with tillage, soils experience slower spring drying rates in no-till systems. This can delay planting and possibly decrease the number of days available for timely planting. Effective tile drainage is necessary for many Ontario soils to ensure a reasonable opportunity for timely no-till corn planting and a favourable seedbed environment for rapid, deep root growth. Producers often discover that no-till is very difficult to do successfully in fine-textured soils that are not systematically tile drained. These fine-textured fields with inadequate tile drainage will require some type of fall tillage to maximize yield potential.

¹ Average 1994-96. Wyoming, Ontario.
² Stubble heights were approximately 25-30 cm (10-12 in.) except for plots where stubble was cut and removed.

Crop Rotation

In Ontario, no-till corn generally produces similar yields to tilled systems when following crops that produce low residues, such as soybeans, dry edible beans or forages that were harvested as hay or haylage. For soils with relatively slow internal drainage, increasing the amount of surface residue cover can slow soil drying, resulting in a reduced opportunity for timely planting and seedbed conditions that promote fast, deep, early-season root growth. Improved soil structure and higher earth worm activity associated with soils following forages may contribute to the success of no-till corn production following forages.

No-till corn grown on medium- and fine-textured soils, following crops that produce high residue, often struggle to achieve successful crop yields regardless of what else is done correctly. Following high-residue crops, such as grain corn or cereals, if it is not possible to remove residue (i.e., straw or stover baling), some tillage will probably be required to increase the chance of timely planting and maximum yield potential.

Residue Management

Reducing tillage costs for corn, improving net profits and enhancing the long-term health of the soil requires decisions about how best to handle crop residues, particularly wheat straw. Where no-till or reduced till corn is to follow wheat, remove the wheat straw from the field. Table 1-9, Effect of Wheat Straw Levels on No-Till Corn Yields, summarizes the corn yields from tillage trials where three different levels of straw were left on the field and corn was no-till planted the following year. Removing straw from fields, especially in high-yielding wheat crops and on heavier-textured soils, increased the potential for no-till corn yields to equal those of moldboard plowing.

Where straw removal is not an option, uniform spreading of the straw and chaff is critical for no-till or reduced tillage success in corn. Even where straw is to be left in the windrow, it is important to spread the chaff as widely and evenly as possible during combining. In cool, wet springs, the lower soil temperatures, poorer growth and potential slug damage brought on by mats of decaying wheat residue often result in yield losses that may have been avoided by uniform residue spreading.

Where the risks of water and wind erosion are low, the benefits of incorporating all the straw might outweigh the advantages of reducing tillage. For farms where erosion potential is higher, adopting a reduced tillage system, even with the need to remove some straw, is probably more sustainable. Another option is using a system where wheat fields receive a small amount of tillage to partially incorporate straw while still leaving the soil surface largely protected.

The impact of adding nitrogen to assist in straw breakdown was tested by researchers at the University of Guelph. Results indicate that where nitrogen was spread on wheat straw in the fall, it did not cause straw to decay more quickly. In addition, the soil nitrogen levels the following spring were not higher compared to where no nitrogen was applied.

Weed Control

For corn yield potential to be realized, optimum weed control is required. Extra management in no-till cropping systems may be needed to control perennial weeds and weed species that are new to the system (due to a shift in weed populations). Spring pre-plant burndown treatments are critical in allowing the crop to develop without interference during critical early growth phases.

Disease and Insect Management

Certain insect pests (i.e., armyworm, black cutworm) can be more of a problem in no-till systems, because lack of tillage can increase the probability that host plants are present, allowing populations of these pests to establish and multiply. Risk of damage from insect pests that over-winter or establish because host plants are present in no-till fields can be minimized by using fall burn-down herbicides. These effectively kill any weeds or perennial crops that would have otherwise over-wintered and started to regrow the following spring. More details on control measures for insects, pests and diseases for corn can be found in Chapter 13 and Chapter 14.

Fertilizer Placement

Studies in Ontario indicate that nutrient stratification (nutrients concentrated near the soil surface) may occur in long-term, no-till fields. Without the option to incorporate or mix dry fertilizer material in the no-till system, fertilizer placement becomes increasingly important.

Source: G. Stewart, OMAFRA, and K. Janovicek (University of Guelph).
¹ Average of 3 trials with high soil test K rating; 2 trials with a medium soil test K rating and 1 trial with a low soil test K rating.
² Fall phosphorous (40 lb P₂O₅/acre on low and moderately responsive testing sites and 125 lb P₂O₅/acre on the highly responsive testing site).
³ Potassium (100-125 lb K₂O/acre) was surface fall broadcast and incorporated in the fall moldboard system and fall broadcast and not incorporated in the fall strip-till system.
⁴ Planter phosphorous (30 lb P₂O₅/acre) and potassium (30 lb K₂O/acre) was applied in a band 5 cm (2 in.) beside the row, 5 cm (2 in.) below seeding depth.

Table 1-10, Corn Yield Response to Phosphorus and Potassium Fertilizer Placement in Two Tillage Systems, summarizes the results from a series of studies that evaluated phosphorus and potassium fertilizer placement in conventional and no-till systems. Generally, applying phosphorus and potassium in starter fertilizer bands decreased yield differences between fall moldboard and no-till systems, especially when soil test K levels were medium or low. Planter-banded phosphorus and potassium were utilized more efficiently compared to fall surface broadcast in no-till systems. However, on high response sites, a combination of broadcast and planter banding may be necessary to maximize no-till yields.

These results are consistent with other Ontario and U.S. Corn Belt research under similar conditions that has shown that planter-banded potassium reduced corn yield differences. Cooler and less aerated soils in no-till systems often have a slower rate of nitrogen mineralization compared to conventional tillage systems. This is often overcome by applying 35 kg/ha (31 lb/acre) of nitrogen in the starter fertilizer.

Applying 35 kg/ha (31 lb/acre) of nitrogen in the starter on no-till corn planters has been shown to over-come the slower nitrogen mineralization often present in no-till soils, when the balance of the nitrogen is applied in a side-dress application.

Soil Compaction

Soil compaction is often cited as one of the reasons no-till may yield less than conventional tillage corn. An option for enhancing corn yields in reduced tillage systems may include extensive loosening deeper into the soil profile. This can be done without disrupting much of the crop residue on the soil surface and can be confined to zones where next year's corn rows will be planted (i.e., strip-tillage).

Usually the most effective method to minimize compaction risk is to reduce the number of field operations and/or minimize use of equipment with heavy axles (e.g., grain buggies) wherever possible. Avoiding field traffic when soils are excessively wet will also help minimize compaction.

Planter Performance

Optimal planter performance is necessary to maximize corn yield potential in any tillage system. However, planter performance and/or suitability are especially critical in no-till systems due to the lack of tillage that results in greater variability in near-surface soil properties and residue cover. Table 1-11, Effect of Planter Model and Tillage on Corn Yield, suggests that yield differences between moldboard and no-tillage systems can be reduced by using newer model corn planters. There was less variability in emergence associated with the newer model planter in the no-till system, which probably explains why no-till yields were higher for this model. See Table 1-22, Effect of Planter Type on Corn Spacing Variability, for more detailed information on the effect of plant spacing and emergence variability on corn yield. Ensuring that planting equipment is properly maintained or upgraded to models better suited for no-till planting conditions will lessen corn plant stand and emergence variability, and increase no-till yields.