Horticultural Crops - Potatoes

Table of Contents

1. Soil Management
2. Water Management
3. Nutrient Management
4. Pest Management
5. Resistance Management
6. Alternative Tactics
7. Summary

Any practice considered for potato production must be cost-effective. But sustainability is more than just an economic issue, it also considers environmental factors. Best management practices bring together concerns for the environment and the need for efficient production of a high-quality product.

Soil Management

Potato production is hard on soil structure. Crop rotations can help. Try to rotate out of potatoes for at least a year. Avoid continuous potatoes. Use cover crops.

Compaction and poor soil structure can cause several problems:

• Soil crusting and reduced plant emergence.
• Poor aeration reduces crop vigour and leads to inconsistent yields.
• More misshapen tubers.
• Increased soil erosion by water.  

Figure 1. Potato harvest is highly mechanized, involving numerous trips over the field. Good soil management should be practiced to reduce the effects of soil compaction.

Hard pans can develop on sandy soils, particularly when there is heavy traffic on wet soil. Increasing potassium levels near the roots may help overcome some of the effect. Building organic matter levels will produce longer-term benefits. Use crop rotations, cover crops and manure. Good production depends on healthy, vigorous roots. Improving soil structure can improve yields.

A good practice is to plant a cereal crop in September or October and subsoil or chisel plow in late October or November when the ground is dry. This will break up hard layers but leave enough cover to prevent erosion.

Water Management

 Ask yourself the following questions about your water management practices:

• Do you have a rain gauge in every field and keep records of rainfall?
• Do you know the pH level of your water for consideration in irrigation and spraying?
• Do you regularly test your well for chemicals, bacteria and nitrates?

Many of the decisions a farmer makes to improve soil will also improve water quality. Water quality is important for spraying, irrigation and personal use.

Irrigation

More and more farmers are turning to irrigation to provide relief from droughts. Properly used, irrigation can help plants stay healthy and vigorous; however, leaching of nutrients and increased disease may result from over-irrigation. Consider the following when managing irrigation:

• Know your soil type and its capacity to hold water.
• Know how your crops store water. Demands change as crops develop.
• Use an irrigation scheduling method such as a tensiometer or the evapotranspiration model.
• Know the weather forecast.
• Monitor irrigation and use a rain gauge to measure the quantity applied.
• Watch for blight.
• On level fields with small hollows, use a "dammer diker". This machine makes small holes between the rows that trap the water where it is applied - preventing water flow to low spots.

As long as the soil is dry, subsoiling or chisel plowing a cover crop in mid-fall can help to break up plow layers. Take care to leave enough cover to prevent erosion.

Figure 2. Breaking up plow layers.

Irrigate when available moisture is below 50% of field capacity, wind speeds are less than 20 kilometres per hour, during evenings or calm, cloudy days. Irrigation can also be used to reduce soil blowing.

Nutrient Management

A healthy, well-nourished crop can withstand stress from drought, insects and weeds. Growers should supply the particular nutrients needed on a field by field basis. This prevents waste of fertilizer and lost yields.

Take soil tests - take samples carefully and map the field properly. Sample trouble areas separately.

• Establish yield goals based on your previous records; fertilize for a realistic yield goal and to improve your soil. Your own experience and the variety of potato will affect decisions.
• Leaf tissue test before bloom, particularly in poor areas.

Tuber test - take two weeks before harvest or at harvest to gauge storability of crop. Optimum levels of tuber calcium improve storability.

Keep good records - record all samples taken and make careful maps. Use records to correct problems and to refine programs.

Providing the required nutrients at each stage of growth, in the most effective way, is a challenge for all growers.

Sample Fertility Program (Example only)

Fall

• Broadcast 50% of potassium requirement.

Spring

• Broadcast, or band in planter, the remaining potassium.
• Split nitrogen 25% ppi (urea), 50% in the planter mix (ammonium sulfate/ammonium nitrate), 25% at second hilling (urea, calcium nitrate).

Planter Mix

• Band on either side of seed piece. Include phosphorus, magnesium, sulphur, zinc and calcium if needed.

Foliar Application

• If boron or zinc levels are low, apply in irrigation or sprayer. Manganese is most effective if applied this way.

Soil Applied

• Boron can be applied in a sprayer with pre-emergent herbicides at levels not higher than 9 kilograms per hectare.
• Lime may be spread in the fall at a rate of 2.5 tonnes per hectare.

The importance of secondary nutrients and micronutrients is often overlooked. Calcium is essential for internal quality and storability. If calcium levels test low, add a gypsum source to the planter mix to ensure that levels are adequate in the immediate vicinity of the tuber. Application of excess nitrogen, phosphorous or potassium will not correct problems with micronutrients.

Pest Management

Modern pest management uses both cultural and chemical controls to produce a quality product. A number of non-chemical controls are in use and others are being examined.

Figure 3. Newly hatched Colorado Potato Beetle larvae with eggs.

Cultural Control

Scout fields during the crop season, walk your whole field every two or three days. Keep records of weather, pests present, numbers and stage of development and crop condition. Use OMAFRA programs and information lines for pest updates.

Use a good crop rotation to break pest cycles.

Use a short fallow period to reduce weed pressure and reduce some soil-borne pests; but, beware of soil erosion.

Use good sanitation practices. Control weedy areas. Clean and disinfect storage and equipment. Bury or dispose of culls.

Figure 4. Defoliation by Colorado Potato Beetle.

Chemical Control

Manage your sprayer - calibrate the sprayer regularly. Regularly clean nozzles and components of sprayer. Use recommended rates of pesticides when applying. Mix spray as required. Be careful when working with chemicals.

Monitor water quality - be aware of pH levels and test water regularly.

Colorado Potato Beetle

Colorado Potato Beetle is probably the most frequent and serious pest. Good management is essential because this pest quickly becomes resistant to chemicals. The beetle's life cycle is:

• Adults emerge and lay eggs, approximately 300 per female.
• Eggs hatch in 5 to 10 days.
• Larvae 4 instars in 13 to 15 days.
• Larvae - enter the soil for 8 to 10 days. Emerge as adults.

Figure 5. Colorado Potato Beetle.

Resistance Management

Time spray when larvae are small, (their most vulnerable stage.) For best control, apply spray to first generation before third to fourth instar.

Use dip tests before spraying. These tests help to avoid applying ineffective materials.

Rotate chemical families to vary the mode of action against the insect. Use each chemical only once or twice a season.

For more information, refer to the Understanding the Basics section of this book.

Alternative Tactics

Rotation and isolation - to reduce the movement of Colorado Potato Beetle, isolation by streams or bush is necessary.

Microbial - it is effective on small larvae only.

Mechanical treatments - suction, flamers, ditches and traps.

Botanicals - a natural insecticide (e.g. Rotenone).

Trap cropping - plant some of the rows in the field to a crop preferred by the beetles so that control efforts can be concentrated on smaller areas.

Figure 6. Pesticide dip tests will help you to determine resistance and avoid applying ineffective materials.

Aphids can reduce yields and transmit viruses. Scout fields and use aphicides responsibly. Resistance has already been recorded.

Summary

Field scouting and good record keeping are important. To responsibly manage your crop, you must know soil type, fertility levels, weed pressures, cropping history, insect pressures, drainage patterns, pH levels, etc. Take notes and get advice.

Effective managers question all aspects of production, seek information and try innovative practices. A good crop rotation is important. Keep up with practices and developments in other areas that may assist you. Remember that a change in one part of your management system will affect the other parts. Plan ahead.

Horticultural Crop Production