Soil Management: Reducing Losses of Organic Matter

 

| Corn | Soybeans | Forages | Cereals | Dry Edible Beans |
| Spring and Winter Canola | Other Crops | Soil Management |
| Soil Fertility and Nutrient Use | Field Scouting |
| On-Farm Stored Grain Management | Weed Control |
| Insects and Pests of Field Crops | Diseases of Field Crops | Appendices |

Pub 811: Agronomy Guide > Soil Management > Reducing Losses of Organic Matter

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

 

Reducing Soil Erosion

Soil erosion occurs to some extent on most agricultural soils. Factors affecting erosion include soil texture, intensity of rainfall, slope steepness, length of slope and management factors such as crop rotation and tillage practices. A number of the measures already mentioned in this chapter can help control or reduce the amount of soil lost from a field. Minimizing the amount of tillage used can reduce tillage erosion. Minimum till, no-till, improved drainage and crop rotation, including cover crops, can go a long way to reducing wind and water erosion. Table 8-13, Soil Management Practices to Reduce Soil Erosion, shows benefits of various practices to water, wind and tillage erosion.

In some situations, these measures are not enough, especially where water flow is concentrated, and other soil conservation practices become necessary. A number of structures can be used to control a concentrated flow that is causing a gully or rill in a field. These structures will require less maintenance if combined with minimum till or no-till. Improved tillage and cropping practices can also reduce the size of the structure required. Strip cropping is another option for protecting the soil from water erosion. This practice involves planting alternating strips of row crops with a cereal or forage. Combining conservation tillage with strip cropping will increase the width of the strips required.

See the booklets Best Management Practices: Soil Management, Order No. BMP06E, Best Management Practices: Field Crop Production, Order No. BMP02E, and the OMAFRA website at www.ontario.ca/crops, for more information.

Table 8-12. Management Considerations for Various Crop Rotations

Crop	Previous Crop
	Corn	Soybeans	Forages
Corn	yield depression corn rootworm European corn borer slugs may cause damage in no-till	European chafer (on light-textured soils)	wireworms following grassy sod
Soybeans	slugs may cause damage in no-till	yield depression soybean cyst nematode root diseases degrades soil	weed escapes may be difficult to control slugs may reduce stand
Forages	heavy residue may interfere with seed placement in no-till	check for herbicide carry-over	forage diseases could increase autotoxicity of alfalfa
Spring cereals			wireworms (following grassy sod)
Winter cereals	increased risk of fusarium head blight	European chafer (on light-textured soils)	weed escapes reduced growth no-till into quackgrass
Dry edible beans		white mould root rots soybean cyst nematode (maybe)	weed escapes slugs in no-till
Canola	slugs may cause damage in no-till harvest is too late for winter canola planting check for herbicide carryover	white mould check for herbicide carryover	slugs may reduce stand
Legend:	Recommended		Caution

 

Crop	Previous Crop
	Spring Cereals	Winter Cereals	Dry Edible Beans	Canola
Corn	heavy residue in no-till may delay soil drying and warming	heavy residue in no-till may delay soil drying and warming		may adversely affect crop growth
Soybeans	slugs and delayed planting could affect no-till	slugs and delayed planting could affect no-till spider mites following clover cover crop	white mould degrades soil soybean cyst nematode (maybe)	white mould can adversely affect crop growth
Forages
Spring cereals	leaf diseases yield depression	leaf diseases yield depression		may be slight reduction in growth
Winter cereals	take-all leaf diseases	take-all leaf diseases yield depression		may be slight reduction in growth
Dry edible beans	slugs may cause damage in no-till	slugs may cause damage in no-till	yield depression root rots white mould soil structure	white mould may adversely affect crop growth
Canola		slugs may cause damage in no-till	white mould	white mould blackleg root rots yield depression check herbicide carryover
Legend:	Caution	Not recommended

Table 8-13. Soil Management Practices to Reduce Soil Erosion

Practice	Effect	Other Benefits	Water	Wind	Tillage
Reduced tillage	leaves residue on the soil surface, effectively controlling erosion loosens less soil prevents soil from being moved down slope by tillage implements	improved water infiltration reduced organic matter loss improved soil structure	x	x	x
Adding organic materials	protects the soil from erosion by leaving material on the soil surface promotes soil tilth (better water infiltration equals less runoff) and larger and more stable aggregates (less erosion), due to higher organic matter levels in soil	added nutrients increase of organic matter levels improved soil structure improved soil life	x	x
Crop rotation	protects the soil by keeping the soil surface covered year round (grass and legume forage crops) helps hold soil in place with the extensive root systems (perennial crops) helps protect the soil from fall through to harvest (fall-planted annual crops such as winter wheat)	improved soil structure and less soil compaction because of root systems improved water infiltration higher yields reduction in insect and disease build-up	x	x
Cover crops	protect the soil by covering it when it might otherwise be left bare help improve soil structure to resist erosion and improve infiltration, less runoff due to added organic matter soil held in place by the roots	increase organic matter levels help hold onto nutrients from recently applied manure provide forage weed and nematode supression	x	x

Stream and Ditch Protection

Ditch and stream banks are often a significant source of sediment in water. Unprotected banks will continue to erode, cutting into valuable farmland. Increasing pressure to protect groundwater and surface water underlines the need to protect this resource. A number of measures can protect stream and ditch banks as well the water flowing in them. High stream flows, cattle and machinery can subject banks to erosion. Concentrated flows entering a watercourse can cause rill or gully erosion. Buffer strips, tile outlet protection or header tile, drop pipes and rock chutes can help stabilize streambanks and ditches.

Restrict livestock from all watercourses; many fencing options are available. Bridges, culverts or low-level crossings are some of the options available to move livestock and machinery safely.

See the Best Management Practices booklets listed at the end of this chapter.

Windbreaks and Shelterbelts

Often additional protection from the wind is necessary when there is not enough residue to hold soil in place. Windbreaks and shelterbelts can provide that protection by slowing down wind speeds near the ground. Windbreaks also create a micro-climate, raising soil and air temperatures adjacent to the trees, reducing drying winds and accumulating more snow. These effects also provide crop yield increases. See Figure 8-2, Windbreaks Provide Protection to Crops.

Fragile Land Retirement

Occasionally, the erosion cannot be controlled on a field or part of a field. The erosion may be too extreme, or the field has some other limitation, making it unprofitable or unsustainable to farm. Fragile land could include areas along creeks, lakes and wetlands that may be subject to flooding or other land that is subject to severe erosion. This land should be retired from production to forest or pastureland.

Preventing Compaction

As discussed earlier, compaction occurs easily with the use of heavy farm equipment, especially when soils are wet.

A number of management options can help prevent soil compaction:

• Keep off the field when the soil is wet, particularly with heavy equipment. The carrying capacity of dry soil is much greater than that of moist soil.
• Ensure tillage operations are performed when the soil is at proper moisture conditions at tillage depth.
• Install tile drainage in fields with variable or poor drainage.
• Use longer crop rotations that include forages/-cereals.
• Leave forage crops in for more than 1 year.
• Alternate tillage depth so that tillage pans are not created.
• Minimize the amount of traffic on a field.
• Use radials, large tires or tracks that create a long narrow footprint to restrict compaction.
• Reduce the tire pressure to reduce the force on the surface of the soil. This will only be effective with radial tires and with large enough tires to carry the equipment at the reduced pressures. Check with the manufacturer that the tires are rated to operate at low pressures.
• Avoid high axle loading, which will cause compaction in the subsoil, even with low tire pressure. Keep equipment weight and loads as low as practical (below 4.5 tonnes/axle or 5 tons/axle). As often as possible, limit traffic with heavy equipment to laneways rather than tracking the entire field.

Subsoiling or Deep Tillage

Subsoiling is often used to try to loosen compacted areas of fields where heavy loads have passed. Generally, subsoiling does not provide any long-term benefits. Always check for the presence of compaction using a tile probe or soil pit and check the moisture at depth before subsoiling. See Soil Health Check, for a description of how to detect soil compaction. Deep tillage where the soil is not compacted will not provide any benefit and may damage soil structure or drainage tile below the normal depth of tillage.

Change soil management, harvesting and manure application practices to avoid further problems. These changes include using lighter loads and staying off the soil when it is wet below the surface.

Reducing Tillage

Soil is tilled for a number of reasons. Those include weed control, soil levelling, burying of crop residues, incorporation of fertilizer and manure and seedbed preparation. The advent of herbicides greatly reduced the need for tillage to control weeds (except in the organic system) and the development of equipment to plant into crop residues means that crops can be planted successfully with little or no tillage. Generally, performing primary tillage operations in the spring will leave the soil less prone to erosion than tillage in the fall. Try to use the least amount of tillage necessary to achieve the goal.

See the tillage sections of each specific crop in this publication for additional information.

Moldboard Plow

From a soil quality perspective, the moldboard plow is the least desirable tillage method because it leaves little residue on the soil surface, requires multiple passes of secondary tillage and is energy and labour intensive. Plowing and secondary tillage pulverize aggregates, making the soil more prone to crusting and erosion. If moldboard plowing is used, set the plow to stand the furrows on edge and try to leave some residue on the surface. Also minimize the number of secondary tillage passes to reduce the breakdown of soil aggregates

Chisel Plow

The chisel plow will leave more residue on the surface than the moldboard plow, depending on how it is set up, amount of crop residue and the amount of secondary tillage used. Chisel plowing with twisted shovel teeth will leave the soil ridged, which is good for soil erosion control but can require extra tillage passes in the spring and lead to uneven soil moisture in the seedbed. Many of these problems can be overcome by:

• using sweep teeth on all or part of the chisel plow
• adding a levelling bar or harrows to the rear of the chisel plow
• timely secondary tillage in the spring

The chisel plow can also be an effective tool for incorporating manure.

Disc

The disc, like the chisel plow, will leave more residue on the soil surface than the moldboard plow. Using this tool when the soil is too wet can cause soil compaction. Too many passes will break down soil aggregates and increase the loss of soil organic matter and risk of crusting. A good planter set up to handle some residue and a rougher seedbed can help reduce the number of secondary tillage passes in any tillage system.

No-Till, Zone Till and Strip Till

No-till systems provide the greatest opportunity to leave protective crop residues on the soil surface. They also have the greatest potential for reducing tillage costs, offset somewhat by the need to control weeds in nearly all cases with a preplant "burndown" herbicide application. Numerous options exist both in the original design and in the modifications available for row crop planters or seed drills to be considered "no-till" capable.

In Ontario, the term "no-till" generally describes planting the crop into a field with no previous tillage passes, with just the seed opener or with one coulter in front of the seed opener. Planting into the soil the spring after fields were tilled in the fall and left ready to plant is not no-till.

Zone tillage systems usually have two or three coulters in front of the seed and fertilizer openers and may also include trash wheels.

Strip tillage utilizes a toolbar with coulters in front, followed by a shank and a couple of disks at the back. It may be used in the fall, spring or both to prepare a seedbed. The shank typically operates at a 10-15 cm (4-6 in.) depth.

The success of no-till systems is often dependent on a range of factors other than the equipment design. Two of these - soil drainage and crop rotation - have a significant influence on the performance of all no-till systems. Reduced tillage systems present the greatest challenge for planting corn. Tillage systems are described in more detail in Chapter 1, Corn.