Corn: Tillage Systems

Excerpt from Agronomy Guide for Field Crops (Chapter 3)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Introduction
2. Tillage Systems
3. Conventional Tillage
4. Fall Mulch Tillage
   • The Impact of Fall Tillage Systems on Grain Corn Yield - Table 3-1 (Metric) (Imperial)
   • The Impact of Fall Tillage Systems on Grain Corn Yield - Table 3-2 (Metric) (Imperial)
5. Spring Mulch Tillage
   • Tillage System Effects on Grain Corn Yield Following Soybeans - Table 3-3
6. Fall Strip Tillage
   • Strip Tillage for Corn After Winter Wheat - Table 3-4
7. No-Till Systems
   • Soil Drainage
   • Crop Rotation
   • Residue Management
     • The Effect of Wheat Straw Levels on No-Till Corn Yields - Table 3-5
   • Weed Control
   • Fertilizer Placement
   • Soil Compaction
     • The Effects of Tillage Systems on Corn Yields Following Winter Wheat - Table 3-6
8. Updates on Corn:Tillage Systems
9. Related Links...

Introduction

Corn is grown widely across Southern Ontario. Over the years 1996-2000, grain corn acreage averaged 717,000 ha (1.77 million ac) with an average yield of 7.34 t/ha (117 bu/ac). An additional 121,000 ha is grown as corn silage for livestock feed. Grain corn produced within the province is used for both feed (65%) and industrial uses (35%). The total commercial value of the Ontario corn crop exceeds $800 million annually.

Tillage Systems

| Conventional Tillage | Fall Mulch Tillage | Spring Mulch Tillage | Fall Strip Tillage | No-Till Systems |

Conventional Tillage

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

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Fall Mulch Tillage

The chisel plow has been the most widely adopted fall mulch tillage tool in Ontario with tandem and offset discs also being 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 3-1, The Impact of Fall Tillage Systems on Grain Corn Yield (Metric) (Imperial), summarizes the corn yield data from these sites.

Source: T. Vyn, K. Janovicek, D. Hooker and D. Young, University of Guelph.

Source: T. Vyn, K. Janovicek, D. Hooker and D. Young, University of Guelph.

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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. Practising timely secondary tillage in the spring is also advantageous.

When disking is done in such a way as to leave the soil 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 3-2, The Impact of Fall Tillage Systems on Grain Corn Yield, outlines 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 5 bu of the conventional tillage system.

Source: T. Vyn, K. Janovicek, D. Hooker and G. Opuku, University of Guelph.

Source: T. Vyn, K. Janovicek, D. Hooker and G. Opuku, University of Guelph.

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Spring Mulch Tillage

The best practice for reducing erosion and input costs is to refrain from fall tillage. Producers working on heavy 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 3-3. Tillage System Effects on Grain Corn Yield Following Soybeans, illustrates that even on finely textured soils, spring tillage alone (using a field cultivator for 2 passes) was generally sufficient when corn followed soybeans in the rotation. Other demonstration trials established on medium- and coarse-textured soils have arrived at the same conclusion.

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

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Fall Strip Tillage

The concept of performing fall tillage confined to narrow zones corresponding to next year's corn rows has received considerable attention during the past few years. The method is to prepare strips of soil that are loosened, cleared of residue and hopefully somewhat elevated, while leaving the rest of the field covered with crop residue and therefore protected. The next spring, these strips are drier, less dense and more suited to "no-till" planting. Research conducted at the University of Guelph over the period 1994-96 employed strip tillage in the fall in winter wheat stubble.

Table 3-4. Strip Tillage for Corn After Winter Wheat, indicates that on fine textured soils, strip tillage in the fall generally produced yields that were better than no-till, but only at Wyoming did they equal yields obtained with the conventional moldboard system. Both producers and researchers have done a wide range of testing with strip tillage systems. Results do not consistently show a yield advantage for the strip tillage system over no-till. However, when soil moisture levels were measured in the university plots, the strip-tilled zones were consistently drier in early May than in the undisturbed no-till plots. Yield responses in side-by-side trials have not always indicated a benefit to strip tillage, but producers with large acreage, poorly drained soils or high surface residues may gain a consistent benefit from strip tillage in terms of planting timeliness, emergence and early corn growth.

Source: T.J. Vyn, 1997, University of Guelph.

The strip tillage system can also provide 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.). There is limited evidence to support deep strip tillage for corn. However, a strip tillage system automatically eliminates traffic on the deep-tilled zones at least until the next harvest, allowing for some soil stabilization before being again exposed to wheel traffic.

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No-Till Systems

Key management issues within no-till systems for corn are:

• soil drainage
• crop rotation
• residue management
• weed control
• fertilizer placement
• soil compaction
• disease/insect management (see the section No-Till Systems)

Soil Drainage

Good internal drainage improves the probability that soils will dry and allow for timely planting of corn in a no-till system. Drainage lessens the risk that soils will become saturated and prone to poor root growth and function, especially early in the season. Producers often discover that no-till is very difficult to do successfully in fine textured soils that are not systematically tile drained.

Crop Rotation

Rotations can be viewed as replacement for tillage. Narrow rotations such as continuous corn do not lend themselves to no-till regardless of what else is done correctly. Sound crop rotations, including a wider range of crops such as legumes and forages, improve soil structure and generally make no-till more successful.

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Residue Management

Reducing tillage costs for corn, improving net profits and enhancing the long-term health of the soil requires corn producers to make decisions about how best to handle crop residues, particularly wheat straw. Many of these decisions require some action before heading to the wheat field with the combine. Where a producer's intention is to manage wheat straw to facilitate no-till or reduced tillage corn production, it is best to remove the wheat straw from the field. Table 3-5. The Effect of Wheat Straw Levels on No-Till Corn Yields, outlines 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 increases 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 left in the windrow, ensure that chaff is spread as widely and uniformly 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 could have been avoided by uniform residue spreading.

Where the risks of water and wind erosion are low, the benefits of returning 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, the straw did not decay faster. In addition, the soil nitrogen levels were not higher on these plots when tested the following spring compared to the plots that did not receive nitrogen.

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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 (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.

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. Results have shown that the size of the yield response to planter-banded potassium (K) in no-till often exceeds the response on side-by-side moldboard plots.

Another important factor to consider is that no-till soils are often cooler and less aerated than in conventional tillage. These conditions lead to a rate of nitrogen mineralization that is slower in no-till than in tilled ground.

Applying 35 kg/ha (31 lb/ac) of nitrogen in the starter on no-till corn planters is recommended in order to overcome the slower nitrogen mineralization often present in no-till soils.

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. University of Guelph researchers tested deep in-row ripping in 1998-2000 at sites near Granton and Ridgetown. Table 3-6. The 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. Some growers have claimed benefits of deep ripping on poorly drained areas or in areas where soil compaction was excessive, such as headlands.

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Updates on Corn: Tillage Systems

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