Tillage

To successfully produce corn in Ontario, it is important to consider factors such as soil texture and crop rotation. Factors that will influence tillage options include risk of erosion, availability of equipment and labour and impact on soil health.  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. 

The guiding principle behind conservation tillage and soil erosion reduction in corn productions should be to maintain 30% of the soil surface covered with crop residue, or living cover, throughout the entire year.

Soil Texture and Drainage

In Ontario, course-textured soils (e.g., sand, loamy or sandy loams) that have good internal drainage characteristics show little yield response to tillage (drainage classification: rapid or well). Even for crops that leave large amounts of residue cover, such as grain corn or cereals, there is often little response to tillage.  On heavy-textured soils with relatively slow internal drainage, tillage can significantly increase the rate of soil drying and warming. This increases the possibility for timely planting and rapid uniform emergence. Table 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. Tillage increased yield about 70% of the time following cereals, grain corn or soybeans on the medium- and fine-textured sites with an average 5%–7% yield increase.

Crop Rotation

A good crop rotation can replace a significant amount of tillage. Table 1 summarizes Ontario tillage research, 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.
• 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. Tillage increases corn yield about 75% of the time when following cereals or grain corn on medium- or fine-textured soils, with yield increases averaging 5%–9%.

Table 1. Comparison of Two Tillage systems on Grain Corn Yield

Comparison	Type	# Sites	No-Till	Mouldboard	Yield Response	Mouldboard Win: Loss
Soil Texture1	coarse	11	8.22 t/ha (131 bu/acre)	8.16 t/ha (130 bu/ac)	-0.9%	45:55
	medium	79	8.66 t/ha (138 bu/acre)	9.16 t/ha (146 bu/acre)	5.6%	72:28
	fine	42	8.60 t/ha (137 bu/acre)	9.16 t/ha (146 bu/ac)	6.5%	71:29
Previous Crop2	forages	13	8.84 t/ha (141 bu/acre)	8.91 t/ha (142 bu/acre)	0.7%	54:46
	soybeans	50	8.98 t/ha (143 bu/acre)	9.04 t/ha (144 bu/acre)	0.9%	56:44
	cereals (straw-baled)	75	9.23 t/ha (147 bu/acre)	9.60 t/ha (153 bu/ac)	4.1%	71:29
	grain corn	49	7.72 t/ha (123 bu/acre)	8.41 t/ha (134 bu/acre)	9.1%	76:24
1 Trials conducted following cereals (straw baled) or grain corn (1982–2007) 2 Trials conducted on medium- or fine-textured soils following various crops (1982–2007). Source: Tillage Ontario Database, 2008 .

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 mouldboard plowing followed in spring by secondary tillage, usually with a field cultivator or tandem disc. Most mouldboard plowing is targeted to an operating depth of 15 cm (6 in.); plowing deeper often results in unwanted mixing of subsoil into the seedbed. 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, disc-ripper and discs (either tandem or offset) have been the most widely adopted fall mulch tillage tools in Ontario. Tillage research trials conducted across Ontario over the past 30 years have generally shown that disking often resulted in more favourable soil conditions and higher corn yields than chisel plowing. Table 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. Adding a levelling bar or harrows to the rear of the chisel plow, or timely secondary tillage in the spring can also avoid this. The same approach should be considered with any fall mulch tillage operation.  Leaving the soil surface level in the fall allows for single-pass corn planting (no secondary tillage) to become a viable option in the spring. This is a good technique for reducing tillage costs and improving soil structure.  Soil surfaces are often left too rough in the fall so that multiple passes of spring tillage are required to make the field fit for planting.

Fall mulch tillage systems should leave the soil surface smooth enough that spring secondary tillage can be minimized.

Table 2. Impact of Fall Tillage Systems on Grain Corn Yield

Location	County	Soil	Previous Crop	No. of years	Tillage Systems: 1 Corn Yield
					Mouldboard	Chisel	Fall Tandem Disc Only
Alvinston	Lambton	Clay	soybeans	3	5.96 t/ha (95 bu/acre)	5.39 t/ha  (86 bu/acre)	5.71 t/ha  (91 bu/acre)
Fingal	Elgin	silty clay loam	soybeans	3	9.97 t/ha  (159 bu/acre)	9.66 t/ha  (154 bu/acre)	9.66 t/ha  (154 bu/acre)
Centralia	Huron	silt loam	wheat straw baled	3	9.16 t/ha  (146 bu/acre)	8.72 t/ha  (139 bu/acre)	8.84 t/ha  (141 bu/acre)
Wyoming	Lambton	silty clay loam	wheat straw baled	3	9.97 t/ha  (159 bu/acre)	9.72 t/ha  (155 bu/acre)	9.85 t/ha  (157 bu/acre)
Average				12	8.78 t/ha  (140 bu/acre)	8.41 t/ha  (134 bu/acre)	8.53 t/ha  (136 bu/acre)
Source: T. Vyn, K. Janovicek, D. Hooker and G. Opuku, University of Guelph.
1  Mouldboard and chisel plots received spring secondary tillage; fall tandem disc-only plots were planted directly in the spring without any secondary tillage.

Vertical Tillage

Vertical tillage is used to reduce any pushing or smearing action that may be caused by tillage tools that engage the ground in the horizontal plane.  Many vertical tillage tools are designed to break apart residue into more manageable pieces and distribute crop residue, while causing some soil fracturing and mixing of soil with residue at the surface. Classic vertical tillage tools include a range of implements from shanks (parabolic or straight) that generally are without sweeps or wings, to straight or wavy coulters that run parallel to the direction of travel. Quite a number of tillage tools embrace the concept of “vertical” tillage but have employed shallow concavity discs, low profile sweeps and extensive harrows to provide some additional soil disturbance, while attempting to remain true to the idea of tillage without significant inversion and soil smearing.

The most effective uses of vertical tillage tools for corn production fall into three categories:

1. Effective secondary tillage where mulch tillage has taken place the previous fall.
2. Single pass residue management and seedbed preparation for corn in lower residue situations (e.g., after soybeans or winter wheat where straw is removed).
3. Residue management and shallow tillage in corn after corn where vertical tillage may occur both in the fall and then again in the spring.

Spring Mulch Tillage

The best practice for reducing erosion and input costs is to eliminate 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 2. Impact of fall tillage on grain corn yield, 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 results. Producer 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.

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

Fall Strip Tillage

Performing fall tillage confined to narrow zones that correspond to next year’s corn rows has received considerable attention in recent years. The strips of soil are loosened, cleared of residue and often 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.

Table 3. Fall strip-tillage for corn after winter wheat (straw removed), summarizes Ontario research comparing a trans-till zone tillage tool to conventional and no-till systems in winter wheat stubble. These data indicate that on fine-textured soils, strip-tillage in the fall generally produced higher yields than no-till systems. Only at the Wyoming, ON location did fall strip till yields equal those obtained with the conventional mouldboard system. Subsequent research has supported the observations shown in Table 3, that on fine-textured soils following wheat, fall strip-tillage generally resulted in 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.

Table 3. Fall Strip-Tillage for Corn After Winter Wheat (Straw Removed)

Tillage System	Soil Moisture in Early May	Yield
		Fine- Textured Soil	Medium-Textured Soil
Fall mouldboard	23.3%	9.97 t/ha (159 bu/acre)	9.22 t/ha (147 bu/acre)
Fall zone-till	25.6%	9.97 t/ha (159 bu/acre)	8.72 t/ha (139 bu/acre)
No-till	29.8%	9.35 t/ha (149 bu/acre)	8.47 t/ha (135 bu/acre)
Source: T.J. Vyn, 1997, University of Guelph.

Early spring moisture measurements on the same tillage plots generally showed that fall strip-tilled zones were consistently drier in early May compared to the undisturbed no-till plots (Table 3). 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.

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. 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 (P) and/or potassium (K) in the fall have generally been lower than when P and K have been applied through the planter. This is especially evident when P and K soil fertility levels were medium or low. 

Spring Strip Tillage

Spring strip tillage offers an opportunity to prepare fine, residue free seedbeds in which the corn planter can operate.  Most spring strip tillage operations are restricted to the lighter textured soils, though in some cases well drained, medium textured soils are suitable for this one pass tillage option.  The spring strip tillage operation usually precedes the planter by no more than 6–12 hours in order to prevent the seed zone from excessively drying out.  Spring strip tillage has also been used as a technique for applying all or part of the corn crop’s nitrogen (N), P and K requirements.  To avoid seed or seedling burn from fertilizer placed in the seed zone three approaches can be taken:

1. Reduce the amount of fertilizer to rates that are similar to the planter banded safe rates, see Maximum safe rates of nutrients in fertilizer.
2. Disperse the fertilizer throughout the strip to avoid any concentrated zones.
3. Use fertilizer products that are less likely to cause salt or ammonia injury (i.e., coated urea).  Spring strip tillage systems that include a fertilizer application option can reduce the cost and complexity of a typical conservation tillage corn planter (e.g., no coulters or row cleaners are required, reduced down pressure requirement and the elimination of dry fertilizer).

From a soil conservation perspective, if implemented up and down the slope, spring strip-tillage also offers the advantage of eliminating the presence of fall strips that can potentially funnel water and be susceptible to erosion. Global Positioning Systems (GPS) can further add to the soil erosion controlling benefits of strip tillage (fall or spring) if the strips run on the contour of sloping fields, see Figure 2.

Deep Tillage

Deep tillage has increased due to heavier axle loads of farm machinery and the general concern that soils have become more compacted. The main benefit of using deep tillage is the elimination of compacted sub-soil layers and/or tillage pans.  Deep tillage will promote rapid and deep root growth and improve drainage. However, in Ontario, sub-soils that loosened using deep tillage are often easily re-compacted by wheel traffic. Moreover, it is possible that deep-tilled soils receiving wheel traffic will end up with poorer drainage and less favourable root growth.  This occurs because deep tillage often destroys the natural pores created by worms or previous crop roots.

In Ontario, use of the disk ripper to perform deep, 30–35 cm (12–14 in.), tillage has increased significantly. Table 4. 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 benefit 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% higher than no-till, but all of the yield response from tillage could be obtained using a fall strip-tillage system with a tillage depth of about half that of the disk ripper. Some producers have claimed benefits from deep tillage on areas with poor drainage or severe soil compaction (e.g., 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.

Table 4. Grain Corn Yield Response to Three Tillage Systems

1  Trials were conducted on medium- (loam or silt loam) textured soils following soybeans (4 sites) and winter wheat (8 sites) (2002–05).
Tillage1	Soybeans	Wheat
	t/ha (bu/acre)
Fall disk ripper 30-35 cm (12–14 in.)	9.73 t/ha (155 bu/ac)	9.73 t/ha (155 bu/ac)
Fall strip-tillage 15-20 cm (6–8 in.)	9.48 t/ha (151 bu/ac)	9.73 t/ha (155 bu/ac)
No-till	9.54 t/ha (152 bu/ac)	9.29 t/ha (148 bu/ac)
Source: Ontario Tillage Database, 2008

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, it has been suggested to till as deep as 30–35 cm (12–14 in.). Researchers tested deep in-row ripping at sites near Granton and Ridgetown. Table 5. 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. This allows extra time for the soil to stabilize before it is exposed to wheel traffic again.

Table 5. Effects of Tillage systems on Corn Yields Following Winter Wheat

Tillage System	Granton (loam–clay loam soil)	Ridgetown (clay loam soil)
	t/ha (bu/acre)
Fall mouldboard	11.35 t/ha (181 bu/ac)	7.78 t/ha (124 bu/ac)
Deep fall zone-till 30 cm (14 in.)	10.79 t/ha (172 bu/ac)	8.15 t/ha (130 bu/ac)
No-till (3-coulters)	10.73 t/ha (171 bu/ac)	7.65 t/ha (122 bu/ac)
No-till (row cleaners)	10.85 t/ha (173 bu/ac)	7.78 t/ha (124 bu/ac)
Source: T. Vyn, B. Deen, K. Janovicek, Univ. of Guelph;, D. Young, Univ, of Guelph, Ridgetown Campus (1998–2000).

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 dependent on effective use of field management strategies which may include alternative production practices that compensate for what tillage provides in other systems. For successful no-till corn production, the following issues must be carefully addressed:

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

Soil Drainage

Soils experience slower spring drying rates in no-till systems due to the lack of soil loosening and residue incorporation associated with tillage. 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.  Good drainage also helps to provide a favourable seedbed environment for rapid, deep root growth. Producers on fine-textured soils often discover that successful no-till is very difficult in fields that are not systematically tile drained. These fine-textured fields with inadequate tile drainage will often require some type of fall tillage to maximize yield potential.

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 harvested as hay or haylage. For soils with relatively slow internal drainage, increasing the amount of surface residue cover can slow soil drying, and delay the opportunity for timely planting and conditions that promote fast, deep, early-season root growth. Improved soil structure and higher earthworm 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 that follow crops producing high residue often struggle to achieve optimum yields, regardless of careful management for other parts of the production system.

If the choice is made to maintain residue cover following high residue crops such as grain corn or cereals, some tillage will likely be required.  This will increase the chance of timely planting and maximum yield potential.

Residue Management

Reducing tillage costs, improving net profits and enhancing long-term soil health 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 6. Effect of wheat straw levels on no-till corn yields, summarizes 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 mouldboard plowing.

Table 6. Effect of Wheat Straw Levels on No-Till Corn Yields

Tillage System/Straw Level1,2	Yield
No-till/ all straw and stubble remain	9.16 t/ha (146 bu/acre)
No-till/ straw baled but stubble remains	9.35 t/ha (149 bu/acre)
No-till/ straw baled and stubble cut and removed	9.91 t/ha (158 bu/acre)
Mouldboard/ straw baled but stubble remains	9.97 t/ha (159 bu/acre)
Source: T. Vyn, G. Opuku and C. Swanton, University of Guelph.
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.

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 spreading of residue.

The benefits of incorporating all of the straw might outweigh the advantages of reducing tillage. For farms where erosion potential is higher, adopting a reduced tillage system is likely more sustainable, even with the need to remove some straw. 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.

Researchers examined the impact of adding nitrogen to assist in straw breakdown. Results indicate that straw did not decay more quickly where nitrogen was spread on wheat straw in the fall. 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. Additional 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 weed interference during critical early growth phases.

Disease and Insect Management

Tillage can play a role in preventing or suppressing certain pest and disease issues. Weeds, volunteer plants from the previous crop, and certain cover crops left on the soil surface through the winter and early spring can increase the risk of some insect pests.  Low lying weeds such as chickweed are ideal for egg laying by black cutworm moths that fly in from the southern United States (U.S.) in early spring. Cereal aphids can transmit vector viruses from volunteer wheat plants and infect the newly planted cereal crop. Corn planted into a rye cover crop increases the risk of armyworm infestations. Achieving good weed and cover crop management through herbicide applications in the fall and tillage in early spring at least 3 weeks prior to planting can avoid some of these pest risks. Tillage can be used in attempt to reduce populations of wireworms and grubs by bringing them up to the soil surface, exposing them to their natural enemies. However, caution is warranted as several passes are required and may not provide adequate control. Tillage can actually increase the risk of one particular pest, seedcorn maggot, if weeds, manure or cover crops are incorporated into the soil shortly before planting. Incorporation needs to occur at least 3 weeks prior to planting to ensure that the adults are no longer attracted to the decaying vegetation.

Some diseases are more prone to no-till systems as tillage can help in disease management. Tillage helps the soil to warm up and dry quickly, reducing the risk of seedling diseases. Some stalk rot diseases can also be managed through tillage though in some cases, crop rotation and hybrid selection play a larger role in disease management.

More details on insect pests and diseases of corn can be found in Chapter 15 and Chapter 16.

Fertilizer Placement

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.

Studies done in Ontario and the U.S. cornbelt have shown that applying phosphorus and potassium in starter fertilizer bands resulted in yield response in no-till systems to be similar to fall mouldboard systems. This is especially evident in cases when soil tests indicated low to medium soil fertility levels of K. Planter-banded phosphorus and potassium were utilized more efficiently compared to fall surface broadcast in no-till systems. However, on sites with low fertility, a combination of broadcast and planter banding may be necessary to maximize no-till yields.

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 (30 lb/acre) of nitrogen in the starter fertilizer.

Soil Compaction

The best option for preventing soil compaction is to avoid field operations when soils are wet. Soil compaction is often cited as one of the reasons no-till corn may yield less than conventionally tilled corn. An option for enhancing corn yields in reduced tillage systems may include incorporating deep rooted crops into the rotation, and/or extensive loosening of soil 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 (e.g., strip-tillage).

Usually the most effective method to minimize the risk of deep compaction, 35–45 cm (15–18 in.) depth 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 wet will also help minimize compaction. 

Tire management can help reduce soil compaction in the root zone (top 20 cm (8 in.)). Increasing floatation by minimizing inflation pressures can reduce the impacts of tires, especially in the surface soil layers. This requires three key steps:

1. Know the axle load that each tire is carrying.
2. Know the manufacturers specifications for that tire.
3. Adjust inflation pressures down to the minimum acceptable pressure for soil conditions (speed, load type, duals, etc.).  A good target for tire inflation pressures to reduce soil compaction is 1 Bar (14.5 PSI).

Planter Performance

Optimal planter performance is necessary to maximize corn yield potential in any tillage system. Planter performance and/or suitability are especially critical in no-till systems. Absence of tillage results in greater variability in near-surface soil properties and residue cover, therefore ensuring that planting equipment is properly maintained and adjusted for no-till planting conditions will lessen variability in corn plant stand and emergence and increase yields in no-till systems.