Project Title

Field validation of 'best bet' fertiliser management strategies for cashews in North Queensland

Objective

• To foster the establishment of a sustainable, economically viable Australian cashew industry by providing information on the yield potential and possible economic returns from high-input management systems for cashew in North Queensland.

Australia imports $25–30 M worth of cashew kernels annually, but has sufficient soils suitable for growing cashews in northern Australia to become a net exporter of cashews. Recent fertiliser research suggests that current yields could be increased by improved fertiliser strategies. Verification of the field performance of the new fertiliser technologies under the farmer’s existing growing conditions would allow current growers and potential investors to undertake expansion and consolidation of the infant Australian cashew industry with confidence.

Research

There were three major thrusts to the research. Firstly, yields of nut-in-shell and kernels were compared between adjacent trees which received either (a) the current low input fertiliser strategy, or (b) the high input improved fertiliser strategy. Secondly, longer term effects of fertilisers on the chemical fertility of the soils were estimated by analysing soil samples from the adjacent virgin open forest, and from under the treated trees before and 12 months after application of fertilisers. Thirdly, leaf samples collected every 3 months allowed the nutritional status of the trees to be monitored throughout the study period.

Outcome

Application of the higher rates of fertilisers increased rate of growth of the canopy and number of nuts produced per unit canopy area. The result was an increase in nut-in-shell and kernel yields by about 50%. Rough estimates of the costs of the additional fertilisers and the value of the additional nut-in-shell and kernel yields suggest that the improved fertiliser technology would increase profitability by about $390 ha^-1 year^-1 if the yield was sold as nut-in-shell, or by about $450 ha^-1 year^-1 if the crop was sold as kernel.

Application of the higher fertiliser rates had no short term detrimental effects on the soil resources in terms of increases in acidity, sodicity, or soluble salts, but further studies would be needed to confirm if this situation continues into the longer term. With the exception of improved P and K fertility status, the higher fertiliser rates had no significant impact on the chemical fertility of the soils. With the exception of calcium, manganese, and possibly potassium, all trees were rated as having a low to marginal nutritional status for the major and minor nutrient elements, despite the higher fertiliser rates in the improved fertiliser strategy. Hence, further high inputs of fertilisers would be need to improve the nutritional status of the trees. If this was to occur, further improvements in tree growth, and nut-in-shell and kernel yields would be expected.

Implications

The improved fertiliser strategy has been validated under actual farmer’s growing conditions. By applying the new fertiliser technology, increased yields and improved profitability would result. For an investor considering establishing and growing cashews, a further benefit would occur, namely a decrease in the payback period – if the improved fertiliser technology was applied from the date of transplanting, the increased rates of growth of the canopy would decrease the time taken to reach a mature canopy size and to attain mature tree yields.

RIRDC Project No: CSO-11A

Researcher: Dr. Noel Grundon

Organisation: CSIRO

Tropical Forest Research Centre, PO Box 780, ATHERTON QLD 4883

Contacts: Phone: (07) 4091 8800 Fax: (07) 4091 3245

The effect of native vegetation on the cashew arthropod fauna with particular reference to the most important pest – Helopeltis pernicialis

Objectives

• To understand how physical and biological factors affect the dispersal, the distribution and the population fluctuation of Helopeltis pernicialis.
• To determine the control threshold of H. pernicialis.
• To characterise the impact of native vegetation adjoining the cashew plantation on the diversity of arthropods in the orchard and on the distribution and abundance of the main cashew insect pests and their natural enemies.

Several pilot cashew plantations established in the Northern Territory since 1985 have encountered serious insect pest problems. The work on the cashew insects at Wildman river suggested that there are four major insect pests, among which H. pernicialis is the most important pest that results in almost no yield.

The following aspects needed to be known before suitable control strategies can be implemented:

• The host range;
• the dispersal mechanism between cashew orchards;
• the distribution in different types of cashews;
• the relationship with other arthropods;
• the control threshold; and
• the effect of native vegetation on the dispersal of this species.

The study was conducted at two sites – Wildman River Cashew Plantation and Howard Springs Farm, with surveys, field observations, a field manipulative experiment, field and laboratory rearing and regular vacuum sampling.

Outcomes

A level of six to ten percent fresh damaged flushing shoots can be used as a control threshold for H. pernicialis. The green ant was determined to be the most important biological control agent against H. pernicialis and other main insect pests. Close contact between native vegetation and cashews played an important part in increasing the diversity of arthropods in cashews, enriching the natural enemy populations (especially the green ant) of the main cashew insect pests and increasing yields.

Implications

Native trees or some tropical fruit tree species could be used for intercropping or mixcropping with cashews to enhance/stabilise natural enemy populations (especially the green ant) to control cashew insect pests. Further research is needed to investigate the management and utilisation of green ants in cashew plantations.

RIRDC Project No: UNT-3A

Researchers: R.K. Peng, K. Christian and K. Gibb

Organisation: Faculty of Science, Northern Territory University, DARWIN NT 0809

Contacts: Phones: (08) 8946 6763; (08) 8946 6706; (08) 8946 6705 Fax: (08) 8941 0460

Project Title

Development of an Australian Cashew Industry information support system

Objectives

To foster the establishment and expansion of an Australian cashew industry by providing an Information Support System comprising

• a database and review of published literature on the culture, processing and marketing of cashews,
• an Australian Cashew Growers' Manual; and
• a mechanism for regularly updating the manual and maintaining ongoing contact within the Australian cashew industry.

Progress on each objective:

• 1305 references have been incorporated into a Procite (PC software) database and allocated to one or more of 52 subject matter areas. The first draft of a review of published literature on the culture of cashew relevant to Australian conditions is in preparation.
• Key resource persons from CSIRO, WADA, QDPI and NTDPIF and industry provided information drawn from Australian research and the published literature of the cashew database for the text of the Australian Cashew Growers' Manual at an information gathering workshop. The final draft of the manual will be forwarded to key resource personnel and sponsoring organisations for technical corrections by the end of May. Anticipated publication date is August 1998.
• RIRDC and QDPI have been requested to reach agreement on a mechanism for regular updating of the manual and maintaining ongoing contact within the Australian cashew industry through the QDPI Agrilink project.

Start Date: 15 April, 1997

Finish Date: 30 August, 1998

Researcher: Dr. Noel Grundon

Organisation: CSIRO Land and Water, Tropical Forest Research Centre, PO Box 780, ATHERTON QLD 4883

Contacts: Phone: (07) 4091 8800  Fax: (07) 4091 3245   E-mail: Noel.Grundon@tfrc.csiro.au

Cashew nutrition management strategies

Objectives

• To develop nutrition management strategies for cashew (A.occidentale)

The third of three years assessment of the affect of nitrogen (N) rate and timing on vegetative, floral and nut development was completed in 1997.

The analysis of 1995 and 1996 assessment data was completed and reported. Both years’ results show that N application can promote vegetative and floral development and that N timing influences the timing of nut drop. N application during the vegetative growth phase (December to April) caused pre-July vegetative and panicle development resulting in a greater proportion of pre-December nut drop. This is highly desirable because of yield loss from wet season rain after this month.

Leaf nutrient studies identified possible index leaves for assessing tree N status. Two leaf types, which will be studied further, were sensitive to N treatments and are easily recognisable and predicably available for sampling.

Post-harvest raw nut and kernel assessment procedures (moisture standards and kernel recovery methods) were resolved. A fourth year undergraduate study was organised with University of Queensland (Gatton College) to describe the nut drying dynamics of cashew. Information from this study will include conventional drying methods for raw nut and kernel.

RIRDC Project No: DAQ-145A

Start Date: 1 July, 1993

Finish Date: 31 October, 1998

Researcher: Mr. Patrick O’Farrell

Organisation: Department of Primary Industries (Qld), PO Box 1054, MAREEBA QLD 4880

Contacts: Phone: (07) 4092 8555  Fax: (07) 4092 3593   E-mail: ofarrep@dpi.qld.gov.au

Utilisation of the green ant, Oecephylla smaragdina, to control cashew insect pests

Objectives

• To develop the methods that can be used by cashew growers to utilise green ants as an effective biological control agent of the important cashew insect pests, which include the tea mosquito bug, the fruit spotting bug, the mango tip borer and the leafroller.
• Longer term objectives include the implementation of the biological control in order to reduce the use of pesticides and the associated costs and pesticide residues in the production of cashews.

Fierce fights between green ant colonies were identified as the major factor limiting the ant populations and their efficiency as biological control agents. In order to stabilise green ant populations in cashew orchards, experiments with full-, semi-, and no-isolation of existing ant colonies in cashew plantations were done in 1996 and 1997. In a related experiment, green ant colonies were transplanted from native vegetation to a cashew orchard in 1997.

Trees with ant colonies which were fully isolated from other colonies were significantly less damaged by the main insect pests and produced significantly higher yield than those with ant colonies which were partly isolated or were not isolated. This is because fighting events between fully isolated ant colonies were eliminated, and the populations of these colonies were stable throughout the cashew flowering and fruiting period. Trees in which green ant colonies were transplanted sustained little damage by the main insect pests and produced high quality nuts and panicles. Both experiments have been expanded in a large scale in 1998 with full support from cashew growers. Cashews Northern Territory has adopted the green ant technology for the insect pest control since 1997.

RIRDC Project No: UNT-4A

Start Date: 1 January, 1996

Finish Date: 31 December, 1998

Researcher: Dr. Renkang Peng

Organisation: Northern Territory University, PO Box 40146, CASUARINA NT 0811

Contacts: Phone: (08) 8946 6763  Fax: (08) 8941 0460

       Last updated: 25 August 1998 Copyright © RIRDC http://www.rirdc.gov.au/comp98/cas.htm