Good Agricultural Practices for the Production of Vegetable crops

Growers need to produce a high-quality product efficiently to remain competitive, however, soil and water resources must also be preserved. Healthy, productive plants require healthy soil and clean water.

Soil and Water Management

Intensive vegetable production, whether for processing or fresh market, returns little organic matter to the soil. Tillage used to prepare the seedbed increases the loss of organic matter. To maintain or increase organic matter levels:

• Use cover crops within the rotation. Following short-season vegetables, establish a cover crop as soon as possible. This green manure crop increases organic matter levels and also breaks some pest life cycles.
• For long-season vegetables, annual or cereal rye is usually the best cover crop. It grows well in cooler weather such as late autumn and early spring. Rye's large, fibrous roots help hold the soil together, preventing erosion. Tillage or herbicides will kill the rye prior to spring planting.
• When a cereal crop precedes vegetables, underseed the cereal with either clover or alfalfa to improve soil structure and reduce compaction. Legumes produce nitrogen, so make allowances in your nutrient applications.
• Reduce tillage and add manure, mushroom compost (a permit is required by Ministry of the Environment for the application of organic off-farm waste) and other plant waste. Take care not to increase soil compaction. Adjust the following year's nutrient application depending on the content of these materials.

Cereal crops like wheat make a good break in a crop rotation, helping to build and maintain soil organic matter and soil structure.

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Soil Compaction

Soil compaction is a growing concern for vegetable producers. Increased mechanization has led to larger and heavier equipment to ensure planting and harvesting are handled on time. 
Seedbed preparation and harvest operations under wet soil conditions are the major causes of soil compaction. Perishability and maturity of the vegetable crop are important to quality. Because staying out of wet fields is often not an option, research continues into solutions.

Crop Rotation

Crop rotation is a best management practice for vegetable growers. It will address loss of organic matter, disease, weed and insect pressures, soil nutrition, compaction and erosion. Two rules of thumb:

• The longer the rotation, the better.
• Rotate between different families of crops.

In designing a rotation, ask yourself the following questions:

• Is the rotation profitable?
• Are the yields sustainable?
• Does the sequence allow the use of cover crops?
• Does it make use of nitrogen produced by an earlier crop?
• Does it allow for timely planting and harvest?
• Are harmful herbicide residues left?

Recent tomato research shows that yields improve with good crop rotations. Building and maintaining soil resources should produce similar results for all vegetable crops.

Processing peas can be particularly hard on soil structure. Tightly scheduled planting and harvest seasons mean soil moisture levels may not be optimum when machinery, such as pea combines, are running over the soil.

Early or short season crops such as melons allow the use of cover crops and green manure crops to build and maintain soil organic matter.

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Wind and Water Erosion

Level sandy soils are at the highest risk of wind erosion while hilly fields are also subject to water erosion. Windbreaks, grassed waterways and other structures address problems in the long-term. Increased residue on the soil surface and use of cover crops will help in the short-term.

For precision-seeded crops, choose a field sheltered by a windbreak, woodlot or other means. Strip cropping with another crop will also cut down wind. The cereal will shelter the seedlings. A timely application of contact grass herbicide will kill the cover crop before it competes with the vegetable.

In some transplanted vegetable production systems, ground beds roughen the soil surface which slows water, wind and soil movement. Some growers are also managing cover crops on ground beds to control wind. Another alternative is the use of narrow grass strips spaced across a field to reduce the speed and soil-carrying ability of wind. 
A rye cover crop on beds can be managed with a timed application of herbicides to provide short-term wind protection in the spring. This system also minimizes the number of passes over the field in spring.

Irrigation

Average rainfall is irregular and sometimes is inadequate for vegetables. Irrigation can be profitable with high-value vegetable crops. Both overhead and sprinkler irrigation systems are being used in Ontario. Overall costs are comparable. Drip irrigation has two advantages: reduced water needs and uniform soil moisture; but, overhead irrigation is adaptable to any crop and can be used for frost protection. 
Irrigation is important after planting until seedlings emerge and during fruit development. Most vegetables have periods where a lack of water can affect yield and quality. Use a scheduling method such as the tensiometer or the evapotranspiration model to assist in irrigation timing.

Plasticulture

This practice combines plastic mulches with row covers and drip irrigation. The practice is costly and is only practical with fresh market vegetables.

Benefits include: early harvest, increased early season yield, improved quality and reduced soil movement due to erosion. Removing and disposing of plastic materials in land fills after harvest is a drawback.

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