Horticultural Crops - Tree Fruit

Table of Contents

1. Orchard Site Preparation
2. Fumigation
3. Tree Density
4. Apples
5. Peaches
6. Soil Management
7. Cultivation/Cover Crops
8. Sod Systems
9. Herbicide Strips
10. Compaction

There is a need to develop fully-integrated orchard management systems that will promote production and be environmentally sound. Healthy and vigorous orchards produce high-quality fruit at the best possible cost and also, reduce the need for chemical treatments.

Best management practices for orchards include attention to: site preparation, soil management, water management including irrigation and drainage, nutrient management and pest management. Growers can adjust each component to maximize profits while protecting the environment.

Orchard Site Preparation

When planning a new orchard, select and prepare an appropriate site at least one to three years in advance. Consider soil testing, past levels of nematodes, organic matter levels, perennial weed control, drainage, soil depth, slope, stoniness and frost pockets.

Soil testing is a must prior to planting. Determine nutrient and pH levels and correct any problems.

Control nematodes, especially Root Lesion nematode. This is crucial to proper establishment of young fruit trees. Nematodes can damage roots and allow fungi to enter roots, disrupting water and nutrient absorption. To determine whether fumigation is necessary, look at the previous crop (corn, for example, increases nematodes), soil type (sandy soils tend to have higher populations than clays), rootstock's tolerance to nematodes and the results of soil samples. If counts are higher than 1,000 nematodes per kilogram of soil, treatment is recommended.

Figure 1. Plan ahead – consider soil test results, past levels of nematodes, weed control, drainage, soil depth, slope, stoniness and frost pockets.

Fumigation

Applying fumigants is usually done with a three-point hitch cultivator which places fumigants in a shallow band 1.75 metres wide and 15 centimetres deep. The entire field can be fumigated or just the strips where trees will be planted. Before applying fumigants, prepare a good seedbed. A new method uses a twin-shank subsoiler to deliver fumigant in a narrow band at 15, 30 and 45-centimetre depths. Establishing the sod cover in the summer before fumigation is recommended. Fumigating row strips through the sod allows better weed and erosion control. This may give better nematode control and also subsoils the planting area. The reduced tillage also preserves organic matter and reduces erosion.

Figure 2. Comparison of fumigation methods on one-year-old McIntosh apple seedlings (M26 Rootstock) (Dr. J.W. Potter, Ag. Canada Vineland).

Tree Density

Deciding how wide the tree rows should be and how far apart trees should be planted will affect productivity, nutrient management, pest management and water requirements. Before making a decision, consider equipment requirements, availability of skilled labour and availability of irrigation water.

Apples

Tree density has steadily increased over the years as dwarfing rootstocks replace standard rootstocks. The most cost-efficient systems in use are high-density training systems, such as slender spindle (1,750 trees per hectare) are in use. The advantages are:

• Earlier production with higher yields
• Orchard efficiency is higher (more fruiting wood is produced per hectare)
• Production costs per bin decrease
• Potentially higher-quality fruit
• Pesticide use may decline (tree row volume techniques)
• Cost recovery time is shorter

This system requires:

• High initial investment
• More professional skills and management are needed

Figure 3. A new fumigation method uses a twin-shank subsoiler to deliver the chemical in a narrow band at three depths.

Figure 4. An example of a highly coloured Empire crop resulting from good sunlight penetration into canopy.

Peaches

The standard for Ontario is 417 trees per hectare. This allows easy movement of standard equipment. The slender spindle system allows densities of 834 trees per hectare. Research completed in 1991 shows yields up by 17% compared to the standard system. Consider the following when making a decision:

• Higher costs to establish orchard
• Pruning methods will be different
• Training of trees is critical in the first and second years
• 75% of all work can be done from the ground

Figure 5. Peach training systems.

Soil Management

Good soil management in orchards should promote tree growth and good health, productivity and overall fruit quality while preserving soil structure. Issues include ground covers, organic matter and erosion.

Soil management systems include clean cultivation, cultivation plus cover crop, sod plus herbicide strip, sod plus mulch and intercropping between tree rows. In Ontario, growers usually use sod or cultivation plus cover crop. Clean cultivation decreases organic matter, degrades soil structure, increases erosion and increases the potential for winter injury.

Cultivation/Cover Crops (Peaches)

Soil is worked in April and cultivated regularly until early June. Cultivation reduces competition for moisture between trees, grasses and weeds and increases the air in the soil and soil temperatures (which may help reduce risk of spring frost). In mid June, a cover crop is planted.

Figure 6. Sod with a herbicide strip in these Spartan apples helps to maintain soil structure and prevent soil erosion.

When cultivating an orchard, leave some plant material on the soil. The purpose of cultivation is to suppress annual weed growth, not to overwork the soil.

Factors to consider when deciding on the cover crop include:

• Ease of establishment
• Dry matter produced
• Effect on nematodes and pests
• Nutrient interactions

The cover crop most widely used is annual ryegrass. It establishes quickly and will survive droughts by delaying establishment until conditions improve.

Sod Systems

Producers grow permanent sod between tree rows and mow sod for the life of the orchard. Advantages are:

• Decreased erosion
• Moderate soil temperatures
• Increased organic matter
• Decreased mechanical injury of roots
• Water penetrates soil more easily
• Easier orchard operations
• Decreased soil compaction

Figure 8. A permanent sod system in peaches.

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Grass Varieties for Orchards

Creeping Red Fescue

Characteristics:

• Harder to establish
  
• Drought tolerant
  
• Fine grass which requires less mowing
  
• Persistent
  
• Decreases nematode population

Perennial Ryegrass

Characteristics:

• Provides good cover, less weed growth
  
• Vigorous, fast establishment
  
• Suppresses nematode population
  
• Dwarfing varieties available

Tall Fescue

Characteristics:

• Very vigorous, giving good cover
  
• Requires more mowing
  
• Shorter types available

Italian (Annual) Ryegrass

Characteristics:

• Similar to perennial ryegrass
  
• Winterkills
  
• Decreases nematode populations
  
• Main use in vineyards and peach orchards (non-permanent cover)

Mixes

Characteristics:

• Includes all the above
  
• Preferred practice

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Some growers are trying to establish sod the year before planting. In the fall, sod in the tree row is killed with a herbicide. The following spring, trees are planted into the dead grass without cultivation.

Herbicide Strips

The objective of a herbicide strip is weed suppression during the critical growth stage from early spring to mid summer. A strip of bare ground is left at the base of the trees to reduce competition for moisture between trees and grasses and to aid in the control of voles and mice. The wider the strip, the better tree growth will be. However, a permanently bare strip creates soil problems, increases the possibility of roots being injured over the winter and encourages perennial weeds.

The best solution is to use mulches. Mulches are organic material that are placed within the tree row. Mulches should be applied early to allow decomposition before fall months.

Advantages are:

• Moisture is retained/conserved.
• Soil temperatures are moderated.
• Microbial activity is higher.
• More extensive rooting is encouraged.
• Soil structure improves.
• Enhanced nutrient availability.

Disadvantages are:

• Mulches may encourage rodents.
• Material and labour increases costs.
• Potential for excessive nitrogen.
• Introduction of weed seeds.
• Mechanical harvest of fall apples more difficult.

Possibilities for mulch include: straw, hay (legume hay may contain high levels of nitrogen which may increase late tree growth causing winter damage), wood chips and related products, decomposed organic wastes (e.g. grape pomace - Ministry of Environment permit required) and grass clippings. Apply mulches when soil moisture is high, usually in the spring.

Compaction

The constant movement of equipment between tree rows may compact soil and result in poor drainage. Subsoiling or mechanical aerators open up soil. However, care must be taken to prevent unwanted root pruning. Techniques should be used when soils are dry as working on wet soil will make problems worse.

Some growers are modifying their mowers to throw sod clippings into the row area as a mulch.

Figure 8. A strip of bare ground at the base of the tree helps to reduce competition for moisture from the sod and aids in vole and mice control.

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Horticultural Crop Production

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