Organic Tree Cropping

The Big Picture

The term organic means the production of safe, wholesome food by natural means that are as sustainable as possible, and to leave the soil in an improved state of health.
The return to such methods is partly a reaction to the use of toxic pesticides, fungicides, herbicides and fertilisers, and also to the over-use and loss of natural fertility of soil.

Because the term organic means different things to different people, consumers have looked for an assurance that produce conforms to standards. At present (2000) there are two organisations which provide that assurance by the certification of organic production for export and within NZ:

• The NZ Biological Producers and Consumers Council Inc. (trademark BIO-GRO NZ).

• Bio Dynamic Farming and Gardening Association in NZ Inc. (trademark DEMETER).

Organic growing requires growers to be in tune with what is happening in their orchards and have an overall plan for the sustainable management of fertility, pests and diseases. Organic methods do not eliminate pests and diseases, they manage them at acceptable levels by means that are as natural as possible.

Principles Of Organic Production

(As outlined by The NZ Biological Producers & Consumers council Inc)

Organic production, which includes such terms as biological husbandrv eco-agriculture, natural, sustainable and bio-dynamic, seeks to produce food of optimum quality. Also to manage productive ecosystems according to a total concept that endeavours to make them sustainable and non-polluting of the environment, while providing an appropriate level of income to the producer(s), families and communities.

Some of the main principles and methods that are employed aim to:

• Foster beneficial processes and interactions such as occur in natural ecosystems thus encouraging internal stability rather than heavy reliance on external control measures.

• Reduce external control to the absolute minimum required for maintaining the chosen state of production. Inputs used should aim to work as far as possible in conjunction with natural cycles, rather than trying to dominate such cycles.

• Achieve cycles/flows of nutrients and materials that have as few; losses as possible This requires the conservation and recycling of nutrients and organic material.

• Sustain and enhance the fertility and life supporting ability of the production medium including its biological, physical and chemical components. For land-based production systems great emphasis is placed on the importance of soil organic matter, and soil flora and fauna.

• Minimise any deleterious environmental effects of particular management practices including any that may reduce the natural diversity to the detriment of plants and wildlife habitats.

• Use appropriate stocking rates, consider animal welfare, sound rotations using the diverse stock and cropping strategies with the extensive but rational use of animal manure and other vegetative residues.
• Use appropriate cultivation techniques, avoid soluble mineral salt fertilisers, and prohibit nearly all chemical pesticides. These form the basis of organic agriculture and horticulture.

Three Factors to Consider For Tree Cropping

1. The Soil
2. The environment above the soil (plants, animals, insects, birds etc.)
3. The Genetic lnfluence

The soil:

Basic tenet of soil management – add organic matter. Sandy soil is thus given body and clay becomes friable. Worms, fungi and bacteria multiply and the microflora and fauna come alive. Moisture retention and penetration improve and root plates develop.
Our treatment of the soil should encourage the total health of plants, animal life, insects and microflora and probably a number of other things we don’t understand.

The following methods are used to improve the soil organically. (Note: Our Grandfathers used animal manures, seaweed, compost and green crops but our modern monocultural systems make pure organic options difficult to achieve.)

Compost:

Compost is the material resulting from the controlled microbiological transformation of organic materials. A range of plant and animal ingredients forms the basis of good compost, whether mixed in a heap or a bin.
Adequate moisture and regular turning will provide the aerobic conditions and heating necessary to kill weed seeds and produce a stable, friable humus full of nutrients and microflora and fauna. The addition of compost will improve any soil type.

Green Manure Crops:

Green manure crops are grown quickly and then cultivated into the soil. They improve soil structure and provide humus and balanced nutrients thus improving future plant health. eg Legumes – Lupins, Broadbeans, Clover, Lucerne. Cereals – Oats and Barley. Grasses, Mustard and Phacelia are also ideal. Phacelia is frequently grown as a green crop because it is very fast growing, and breaks down well when worked back into the soil. The blue flowers attract many insects and its pollen is of a very high quality and plentiful. It is early and long flowering allowing Hover Flies to mature more and produce more eggs/larvae to eat the aphids.

Mulches:

A mulch is a protective cover spread over exposed soil. This enhances conditions for root growth and activity of soil organisms. These organisms incorporate organic mulches into the soil to provide nutrients for plants. Mulch protects the soil from the impact of raindrops, temperature variations, wind erosion, sun and suppresses weed growth. Good examples are cut mixed herb lays, pea straw, seaweed, sawdust mixed with chicken litter, lucerne hay, etc.

A mixed herb ley can be a grass/clover mix with flower plants and herbs with roots that penetrate to different depths breaking up hard pans and drawing up nutrients. Species can include Tall Fescue, Prairie Grass, Brown Top, Cocksfoot, Timothy White & Red Clover, Lucerne, Chicory, Yarrow, Borage & others. Diversity is important to provide a permanent source of balanced plant nutrients when sown between rows of trees, cut and used as mulch on the tree row. It is especially ideal for lighter soil types, as they continually need replenishing with nutrients.

The Environment

In horticulture we modify and create the environment by the spacing, orientation, pruning, thinning, of shelter trees, and watering, around covers and monoculture or companion planting. We may also erect artificial structures to create an environment. All these modifications effect the presence or absence of insects, birds, disease, temperature, relative humidity and sunlight strength.

We do not fully understand the habitats of all natural insects and pest predators but some guidelines are evident.

A truly organic system really needs the input of animals and birds to complete the nutrient cycle. As long ago as 1926 researchers observed that uncultivated orchards were less severely, attacked by pests than cultivated ones. It was found that the presence wild flowers in apple orchards particularly the flowers of the Umbelliferae family (such as cow parsley , carrot, parsnip) were attractive to many parasitic wasps.

Incorporating flowering plants into tree cropping ventures provides habitats for beneficial insects that fit into integrated pest management programmes and help maintain a natural balance without chemical intervention.

The Genetic Influence

The genes in your plants and trees have a major influence on how healthy and fruitful they are. Rootstocks must be from healthy virus free material suitable to the conditions in which they are to be grown e.g. rootstock performance varies according to soil types and drainage. Select cultivars suitable for your site and climate e.g. Woolly apple aphid is controlled by using resistant rootstocks. Any trees obviously diseased or infested should be remedied, or removed and burnt.

Many fruit and nut crops can be grown without using insecticides and herbicides. These are Hazelnut, Walnut, Chestnut, Blueberries, Figs, Feijoas, Pears, Nashi, Plums, Kiwifruit and Apples. Disease will be contained by the tree’s natural resistance and your good husbandry. The trees will not be entirely pest and disease free and are therefore unacceptable for export unless hand sorted and packed. Black Spot will be a problem in some European Pears and Apples, but can be controlled even in export varieties. The selection of cultivars with disease resistance is advisable, but consideration should be given to the requirements of the market to be supplied. More disease resistant varieties are becoming available in the near future.

How to Apply these Lessons to Growing Tree Crops

Soil Management:

Apply a layer of compost around each tree, then a layer of mulch. Mixed herb ley grown between rows then cut and then placed around trees form an excellent mulch. Take leaf samples annually to monitor nutrient levels of crop trees. Soil analysis should be taken before developing the block so the pH levels can be corrected if necessary. Do this gradually as large doses of lime can seriously damage sensitive microflora and fauna.

Weed Control:

Use mulches, mechanical weed eaters, mowing, flame weeders or steam. Keep irrigation nozzles clear to allow even distribution of water. One option is to hang the lateral tubing from the tree trunks to keep it above the vegetation.

The Environment:

Encourage beneficial Predators and Parasites by providing suitable habitats. Plant Umbelliferae species in the shelterbelt lines. Shelterbelts are not just for wind reduction but an essential part of the biological husbandry system. Plant a diverse shelterbelt such as Alders as the tree layer, Tagasaste as the shrub species layer, (both nitrogen fixing) and Cow Parsley and Phacelia as the herb layer.

The degree of shelter should be considered. While crop protection is necessary, adequate airflow will assist to reduce fungal diseases. The removal of some internal shelter may improve airflow while giving the opportunity to provide further natural predator habitat.

Other methods of environmental manipulation in an organically acceptable manner, are the use of viral or bacterial sprays to control specific varieties of caterpillar, and the use of pheromones to confuse the mating of specific pests.

Advantages of Growing Organic Tree Crops

• Environmental consideration
• Careful use of resources
• Pest and Disease balance
• Water and Nutrient balance
• Several studies indicate that nitrate levels of organically grown food are lower than those grown using conventional methods, and that the resulting food is higher in vitamins and minerals.
• Market potential. Growth rate for Certified Organic Food is predicted to be 50% over the next 5 years
• If quality is maintained it is expected that the returns will be 20% higher than the conventionally grown product.

Disadvantages

• More labour intensive
• More time consuming
• Less tidy looking orchard
• Costs of certification
• You are restricted to using materials and practices that are acceptable to certification organisations.

Changing to organics takes time. Allow for at least 2-3 years (or longer) transitional period for beneficial insects to build up, plus additional workloads and organic management techniques to be used. It does, however, offer a healthier alternative to chemical residues in our food chain and provides a much healthier orchard environment to work in.

New Zealand Has Two Organic Certification Organisations:

Bio Dynamic Farming and Gardening Association

They have the International certification trademark Demeter, which assures buyers that the produce is biodynamically grown.

Bio-Grow NZ

This is the trading name of the NZ Biological Producers & Consumers Council Inc. They have developed a set of standards for organic production, which are internationally recognised, and are the leading organic certification agency in NZ.

Further information was obtained from:
Steve Wratten & Bob Crowder, Lincoln University;
Howard Wearing, Hort Research, Clyde;
Chris Wheeler, Soil & Health Association;
Viv Milne, with some reservations.

Contributed by: Linda Gardner and Ross Jamieson (Quality Tree Co – no longer trading)

First published January 2000
Privacy removals and proprietory format conversion – December 2007

This crop guide was produced with the latest information available at the time of publication. This should not be considered the ultimate in information for New Zealand growing conditions: it is just a basic guide on the subject.