Horticultural Crops
Muck Crops

Muck Crops

Organic soil is a valuable resource but must be protected to maintain good yields of high-quality vegetables. These soils are very susceptible to wind erosion. As water is drained, organic matter is "eaten up" by microorganisms and soil gradually disappears in a process called subsidence.

Pesticides are necessary to produce the vegetables that consumers demand. Yet, a number of steps will help reduce the use of chemical pesticides. These materials are expensive so reduced usage is also cost-effective. Best management practices must make economic sense, be practical and fit present farm operations.

Subsidence or decreasing soil level is a problem with organic soil. The stake on the right with the cross pieces marking different levels, illustrates the rate of subsidence on the Bradford Marsh.

Soil Management

Subsidence - Organic soils such as muck or peat are very high in organic matter content — from 30 to 98%. The organic matter begins to disappear as soon as soils are exposed to air. When organic soil is drained and farmed, soil levels decrease. To slow the rate of loss, two possibilities are:

• Copper application - Copper is required by crops such as onions and lettuce and also helps reduce subsidence by slowing the growth of microorganisms. Apply copper to new muck at a rate of 14 kilograms per hectare (56 kilograms/hectare copper sulphate) each year for three years. Afterwards, apply five kilograms per hectare (20 kilograms of copper sulphate) to the soil with broadcast fertilizer every second or third year.
• Water table control - Draining organic soils exposes soil to the air and increases loss. By keeping as much of the soil profile as possible under water, subsidence decreases. Recommended water table levels are shown in the diagram/chart (below). The water table can be controlled by keeping water in drainage tiles or filling ditches and storage tanks and allowing water to flow back into tile drains as shown in the diagram. This also provides water to the roots of the crop which is cheaper than overhead irrigation and reduces the risk of spreading certain diseases (e.g. Septoria late blight of celery).

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Wind Erosion

Erosion also increases soil loss. Blowing soil can bury seed too deeply, cut young seedlings and fill ditches. High winds may even blow away seed with the soil. To reduce erosion, seed barley, or another cereal crop, on the same day as the crop is planted.

A broadcast seeding of barley provides the best wind protection. Make sure to kill the barley before it competes with the crop. Row seeding works well if the wind usually blows in one direction. The rows should be at right angles to the prevailing winds. Plant one row of barley per four to eight rows of onions.

*Seeding rate will depend on seed quality. Lower rates may be used if germination rate is high.

Seeding on ridges also reduces wind erosion. It works especially well for carrots but can work with lettuce and onions if the soil is not too dry. Growers use bed shapers to form the ridges. Ridges are 66 to 88 cm wide and 20 cm in height. Equipment is also available to form ridges when the crop is transplanted.

Winter cover crops reduce wind and water erosion as well. Ideal cover crop choices for muck soils die out completely over the winter and do not leave tough roots or leaves to get tangled in the seeder. Possibilities include oilseed radish, spring barley and annual ryegrass. Seed the cover crop between August 15 and September 15. Be prepared to mow or chop oilseed radish, if it starts to flower, to prevent seed set.

Row seeding of a cereal crop provides good protection if damaging winds usually come from one direction. Broadcast seeding provides better wind protection.

Tillage

It is important not to over-cultivate muck soils.

• In the spring, disk the soil to mix in fertilizer then deep cultivate to a depth of 20 to 30 centimetres.
• Leave the land as rough as possible while making sure there are no clumps that will interfere with the seeder.
• Conserve as much moisture as possible.
• Try not to overdrain the land. However, it may be necessary to cultivate low spots or wet fields twice, to dry land enough for seeding.
• After seeding, do not disturb the soil until the crop is established. The thin crust formed will help to resist wind erosion.
• Only plow once every two or three years in the fall, particularly after growing carrots. This turns carrot tops under and exposes a small amount of peat soil.
• If there is a drainage problem, use a subsoiler in the fall every second year.

Seeding on ridges works especially well for carrots and does provide some wind protection.

Water Management

As stated previously, water table control is particularly important. Subirrigation from below roots is good in most cases although it can increase the concentration of salts in the soil. Overhead irrigation increases the risk of some diseases and should be done at night if possible.

Avoid water erosion on flooded fields. In the spring, drain water through soil and into drainage tiles. Don’t let water run off the surface. Replacing drainage ditches with header tiles also helps. Watch the natural flow of water before installing header tile.

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Nutrient Management

Annual soil tests are important. Newly-developed muck soils tend to be low in most plant nutrients except nitrogen. After muck soils have been farmed for many years, levels of potassium and phosphorus can increase and may become excessive.

Muck soils usually lack micronutrients. A complete soil analysis is a good investment. Add any required micronutrients to spring fertilizer or as a foliar spray. Check the OMAF Vegetable Production Recommendations Publication 363 for the correct timing and application method for each micronutrient and crop.

Keep good records of soil tests each year to see if changes are occurring in either nutrient or pH levels. The best pH level for vegetables on organic soils is 5.5 to 6.5 but onions will produce well at a range of 5.1 to 7.0.

Applying the correct amount of fertilizer according to a soil test is the best approach. Too much fertilizer reduces yield and quality and costs money.

To drain land, the square metal trap is removed and water flows out drainage pipe. If necessary, excess water may be pumped out this way if water rises to the height of the tile. For subirrigation, metal cover is closed, causing cistern to be filled above the level of the tile. Excess subirrigation water flows into top pipe and into drainage tile.

Pest Management

Growers can reduce the use of pesticides by taking the following steps:

• Use varieties of vegetables that resist pests. This is the only possibility for diseases such as Fusarium yellows in celery or pink root in onions.
• Rotate crops. Onions and carrots are a good combination. Avoid growing carrots after lettuce or potatoes because soil-borne diseases such as Sclerotinia and Rhizoctonia will be worse.

Make full use of alternative control methods such as:

• Root-knot nematode is the most significant problem nematode on muck crops. Grains and grasses are not hosts of this nematode. Cover cropping with grasses can help to control the population.
• Oilseed radish may suppress nematodes. (Till under at green pod stage.)
• Late plowing when there’s a crust of frost to reduce nematode populations.
• Winter flooding with a thin layer of water to reduce Onion white rot, Sclerotinia white mold on carrots, possibly even carrot weevil and nematodes.
• Removing cull piles off the field.

Oilseed radish shows promise as a cover crop for muck soils; it does not overwinter, it is inexpensive and it may help to suppress nematodes.

Schedule sprays to be most effective by:

• Walking your fields regularly or hiring a pest management scout.
• Ensuring your sprayer is calibrated to operate efficiently.
• Listening to the local Agriphone for recommendations.
• Spraying according to pest management thresholds.

Summary

These best management practices provide solutions to everyday problems. In most cases, the cost is minimal, especially when compared to long-term benefits. When BMPs are in use, soil and water essential to crop production are being protected for the future.  

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