The first step in converting to an organic system is to read and understand the organic standards from a chosen organic certifier.
With this knowledge you will be able to identify key changes required to the current production system, particularly relating to soil fertility, weeds, pest and disease management .
Setting up an organic system for mango production will take time. Organic standards require a minimum of three years, and this reflects the changes that must take place for an organic system to begin to function properly. This period will require serious commitment to understanding the different approach involved, especially in relation to the way plants are fed and how to manipulate biological processes – both above and below the ground.
Many growers start with a small area that is unlikely to have a significant impact on profit. By starting with a small trial dedicated to organic methods, growers can gain experience, knowledge and confidence about what works and where problems may occur.
One useful strategy can be to move towards a more biological approach for several years prior to considering organic production. Interest in developing a more integrated and biological approach can result in a reduced need for many of the conventional fertilisers and sprays normally used. This can mean that the transition into a fully organic certified system is unlikely to require dramatic changes to management practices and that crop quality and yields should remain relatively stable.
Growers who already use integrated pest and integrated weed management techniques may find the transition to organic less dramatic than otherwise.
Working in conjunction with a few other like-minded growers can speed the learning period by providing more scope for testing ideas and finding better solutions.
The transition toward an organic system can lead to some problems in the first few years. A familiar crop may perform differently under organic management. Some growers report that tree vigour may look a bit poor, but as the system establishes, tree health recovers and improves to better than previous conventional condition and good yields return.
Also in the first few years some pest or disease problems can get worse while others improve. However, over time those transitional problems diminish as changes in the biological dynamics progress toward a different equilibrium.
Existing orchard condition
The existing condition of an orchard can have a significant bearing on the likelihood of successful conversion to an organic system.
Listed below are some important considerations:
- Tree health - the existing condition of trees needs to be healthy. Successful conversion to organic management can be difficult to achieve with diseased trees or trees in poor condition.
- Weed status – existing serious problems with invasive perennial weeds can present a major difficulty and cost to control under organic systems. The usual course of action is to minimise these problem weeds before establishing an organic system. Ongoing vigilance is needed to ensure timely control of subsequent outbreaks.
- Varieties – it has yet to be determined which varieties of mangoes are more amenable to organic systems in WA. No specific varieties have been developed for organic production. Obviously, varieties that are less prone to problematic pests or diseases are desirable, as are varieties that typically are not treated with growth hormone to aid flowering. Market preferences and other agronomic traits must also be considered. Most mangoes grown in WA are Kensington Pride (also known as Bowen or KP). While this variety does well under organic management, it is known to respond to the growth regulator paclobutrazol, which is prohibited for use under organic standards.
- Orchard layout and tree structure - the best layout and pruning system may vary to suit regional conditions. High density plantings may be subject to less airflow and therefore more susceptible to fungal disease. However this may be offset with careful layout and pruning to facilitate good air flow. Pruning to an open structure that allows good airflow and adequate internal light without burning fruit can be important to minimise disease risk and assist good fruit colouration.
Selecting a site
Selecting a location isolated from potential sources of pest, disease or weed introductions is obviously desirable but not always possible. Sites that are away from conventional production areas allow for relative isolation to reduce the risk of contamination from adjacent land use and means the area needed for buffer zones between organic and conventional crops are minimised. On windy sites windbreaks may be required, not only to control spray drift problems but also to protect crops from wind effect and damage.
Selecting better quality soils is likely to be helpful and require fewer inputs than poorer soils. Loamy soils are likely to require relatively less nutrient inputs and lower water demands than sandy soil types. In addition, the clay content in loamy soils can accommodate organic matter, the development of good soil biological activity and humus formation suitable for organic production. Chemical or heavy metal residues in soil must not exceed limits set by organic standards.
Water requirements for mango production in WA vary according to location, size of trees and season. The total water requirement can exceed 10ML/ha per year. Consideration should be given to possible sources of unacceptable contamination or excessive nutrients in irrigation water.
Choosing a small initial block for organic conversion can reduce the commercial risk in the event of crop failure, while providing a commercially realistic scale to gain knowledge and experience in order to assess the commercial and technical feasibility for future expansion of the organic system.
Mature mango trees that are considered healthy with no major production problems relating to soil conditions, weeds, or disease are preferred and can mean establishing an organic system is unlikely to face serious problems.
Choosing mature trees is also considered an advantage, especially for Kensington Pride (KP) because older KPs are considered to have a reduced tendency for biennial bearing. The benefit to conventional production of using the growth regular paclobutrazol - commonly used to “even out” biennial cropping patterns - would be less pronounced than for younger trees. Therefore any yield disadvantage would be minimised. Weed management under mature trees is also easier due to greater shading and leaf litter, which suppress weed growth.