Developing sustainable banana production systems: a case study from tropical Australia

The north Queensland banana industry is under pressure from government and community expectations to exhibit good environmental stewardship. The industry is situated on the high-rainfall north Queensland coast adjacent to 2 natural icons, the Great Barrier Reef to the east and World Heritage-listed rain forest areas to the west. The main environmental concern is agricultural industry pollutants harming the Great Barrier Reef. In addition to environmental issues the banana industry also suffers financial pressure from declining margins and production loss from tropical cyclones. As part of a broader government strategy to reduce land-based pollutants affecting the Great Barrier Reef, the formation of a pilot banana producers group to address these environmental and economic pressures was facilitated. Using an integrated farming systems approach, we worked collaboratively with these producers to conduct an environmental risk assessment of their businesses and then to develop best management practices (BMP) to address environmental concerns. We also sought input from technical experts to provide increased rigour for the environmental risk assessment and BMP development. The producers' commercial experience ensured new ideas for improved sustainable practices were constantly assessed through their profit-driven 'filter' thus ensuring economic sustainability was also considered. Relying heavily on the producers' knowledge and experience meant the agreed sustainable practices were practical, relevant and financially feasible for the average-sized banana business in the region. Expert input and review also ensured that practices were technically sound. The pilot group producers then implemented and adapted selected key practices on their farms. High priority practices addressed by the producers group included optimizing nitrogen fertilizer management to reduce runoff water nitrification, developing practical ground cover management to reduce soil erosion and improving integrated pest management systems to reduce pesticide use. To facilitate wider banana industry understanding and adoption of the BMP's developed by the pilot group, we conducted field days at the farms of the pilot group members. Information generated by the pilot group has had wider application to Australian horticulture and the process has been subsequently used with the north Queensland sugar industry. Our experiences have shown that integrated farming systems methodologies are useful in addressing complex issues like environmental and economic sustainability. We have also found that individual horticulture businesses need on-going technical support for change to more sustainable practices. One-off interventions have little impact, as farm improvement is usually an on-going incremental process. A key lesson from this project has been the need to develop practical, farm scale economic tools to clarify and demonstrate the financial impact of alternative management practices. Demonstrating continued profitability is critical to encourage widespread industry adoption of environmentally sustainable practices

Poor adoption of ley-pastures in south-west Queensland: biophysical, economic and social constraints.

The present review identifies various constraints relating to poor adoption of ley-pastures in south-west Queensland, and suggests changes in research, development and extension efforts for improved adoption. The constraints include biophysical, economic and social constraints. In terms of biophysical constraints, first, shallower soil profiles with subsoil constraints (salt and sodicity), unpredictable rainfall, drier conditions with higher soil temperature and evaporative demand in summer, and frost and subzero temperature in winter, frequently result in a failure of established, or establishing, pastures. Second, there are limited options for legumes in a ley-pasture, with the legumes currently being mostly winter-active legumes such as lucerne and medics. Winter-active legumes are ineffective in improving soil conditions in a region with summer-dominant rainfall. Third, most grain growers are reluctant to include grasses in their ley-pasture mix, which can be uneconomical for various reasons, including nitrogen immobilisation, carryover of cereal diseases and depressed yields of the following cereal crops. Fourth, a severe depletion of soil water following perennial ley-pastures (grass + legumes or lucerne) can reduce the yields of subsequent crops for several seasons, and the practice of longer fallows to increase soil water storage may be uneconomical and damaging to the environment. Economic assessments of integrating medium- to long-term ley-pastures into cropping regions are generally less attractive because of reduced capital flow, increased capital investment, economic loss associated with establishment and termination phases of ley-pastures, and lost opportunities for cropping in a favourable season. Income from livestock on ley-pastures and soil productivity gains to subsequent crops in rotation may not be comparable to cropping when grain prices are high. However, the economic benefits of ley-pastures may be underestimated, because of unaccounted environmental benefits such as enhanced water use, and reduced soil erosion from summer-dominant rainfall, and therefore, this requires further investigation. In terms of social constraints, the risk of poor and unreliable establishment and persistence, uncertainties in economic and environmental benefits, the complicated process of changing from crop to ley-pastures and vice versa, and the additional labour and management requirements of livestock, present growers socially unattractive and complex decision-making processes for considering adoption of an existing medium- to long-term ley-pasture technology. It is essential that research, development and extension efforts should consider that new ley-pasture options, such as incorporation of a short-term summer forage legume, need to be less risky in establishment, productive in a region with prevailing biophysical constraints, economically viable, less complex and highly flexible in the change-over processes, and socially attractive to growers for adoption in south-west Queensland.

Do elasmobranch reactions to magnetic fields in water show promise for bycatch mitigation?

Elasmobranchs are under increasing pressure from targeted fisheries worldwide, but unregulated bycatch is perhaps their greatest threat. This study tested five elasmobranch bycatch species (Sphyrna lewini, Carcharhinus tilstoni, Carcharhinus amblyrhynchos, Rhizoprionodon acutus, Glyphis glyphis) and one targeted teleost species (Lates calcarifer) to determine whether magnetic fields caused a reaction response and/or change in spatial use of an experimental arena. All elasmobranch species reacted to magnets at distances between 0.26 and 0.58 m at magnetic strengths between 25 and 234 gauss and avoided the area around the magnets. Contrastingly, the teleosts showed no reaction response and congregated around the magnets. The different reactions of the teleosts and elasmobranchs are presumably driven by the presence of ampullae of Lorenzini in the elasmobranchs; different reaction distances between elasmobranch species appeared to correlate with their feeding ecology. Elasmobranchs with a higher reliance on the electroreceptive sense to locate prey reacted to the magnets at the greatest distance, except G. glyphis. Notably, this is the only elasmobranch species tested with a fresh- and saltwater phase in their ecology, which may account for the decreased magnetic sensitivity. The application of magnets worldwide to mitigate the bycatch of elasmobranchs appears promising based on these results.

Analysis and Modelling of the Effects of Water Stress on Maize Growth and Yield in Dryland Conditions.

It is essential to provide experimental evidence and reliable predictions of the effects of water stress on crop production in the drier, less predictable environments. A field experiment undertaken in southeast Queensland, Australia with three water regimes (fully irrigated, rainfed and irrigated until late canopy expansion followed by rainfed) was used to compare effects of water stress on crop production in two maize (Zea mays L.) cultivars (Pioneer 34N43 and Pioneer 31H50). Water stress affected growth and yield more in Pioneer 34N43 than in Pioneer 31H50. A crop model APSIM-Maize, after having been calibrated for the two cultivars, was used to simulate maize growth and development under water stress. The predictions on leaf area index (LAI) dynamics, biomass growth and grain yield under rain fed and irrigated followed by rain fed treatments was reasonable, indicating that stress indices used by APSIM-Maize produced appropriate adjustments to crop growth and development in response to water stress. This study shows that Pioneer 31H50 is less sensitive to water stress and thus a preferred cultivar in dryland conditions, and that it is feasible to provide sound predictions and risk assessment for crop production in drier, more variable conditions using the APSIM-Maize model.

Adaptation and management of Australian buffalograss cultivars for shade and water conservation

Soft-leaf buffalo grass is increasing in popularity as an amenity turfgrass in Australia. This project was instigated to assess the adaptation of and establish management guidelines for its use in Australias vast array of growing environments. There is an extensive selection of soft-leaf buffalo grass cultivars throughout Australia and with the countrys changing climates from temperate in the south to tropical in the north not all cultivars are going to be adapted to all regions. The project evaluated 19 buffalo grass cultivars along with other warm-season grasses including green couch, kikuyu and sweet smother grass. The soft-leaf buffalo grasses were evaluated for their growth and adaptation in a number of regions throughout Australia including Western Australia, Victoria, ACT, NSW and Queensland. The growth habit of the individual cultivars was examined along with their level of shade tolerance, water use, herbicide tolerance, resistance to wear, response to nitrogen applications and growth potential in highly alkaline (pH) soils. The growth habit of the various cultivars currently commercially available in Australia differs considerably from the more robust type that spreads quicker and is thicker in appearance (Sir Walter, Kings Pride, Ned Kelly and Jabiru) to the dwarf types that are shorter and thinner in appearance (AusTine and AusDwarf). Soft-leaf buffalo grass types tested do not differ in water use when compared to old-style common buffalo grass. Thus, soft-leaf buffalo grasses, like other warm-season turfgrass species, are efficient in water use. These grasses also recover after periods of low water availability. Individual cultivar differences were not discernible. In high pH soils (i.e. on alkaline-side) some elements essential for plant growth (e.g. iron and manganese) may be deficient causing turfgrass to appear pale green, and visually unacceptable. When 14 soft-leaf buffalo grass genotypes were grown on a highly alkaline soil (pH 7.5-7.9), cultivars differed in leaf iron, but not in leaf manganese, concentrations. Nitrogen is critical to the production of quality turf. The methods for applying this essential element can be manipulated to minimise the maintenance inputs (mowing) during the peak growing period (summer). By applying the greatest proportion of the turfs total nitrogen requirements in early spring, peak summer growth can be reduced resulting in a corresponding reduction in mowing requirements. Soft-leaf buffalo grass cultivars are more shade and wear tolerant than other warm-season turfgrasses being used by homeowners. There are differences between the individual buffalo grass varieties however. The majority of types currently available would be classified as having moderate levels of shade tolerance and wear reasonably well with good recovery rates. The impact of wear in a shaded environment was not tested and there is a need to investigate this as this is a typical growing environment for many homeowners. The use of herbicides is required to maintain quality soft-leaf buffalo grass turf. The development of softer herbicides for other turfgrasses has seen an increase in their popularity. The buffalo grass cultivars currently available have shown varying levels of susceptibility to the chemicals tested. The majority of the cultivars evaluated have demonstrated low levels of phytotoxicity to the herbicides chlorsulfuron (Glean) and fluroxypyr (Starane and Comet). In general, soft leaf buffalo grasses are varied in their makeup and have demonstrated varying levels of tolerance/susceptibility/adaptation to the conditions they are grown under. Consequently, there is a need to choose the cultivar most suited to the environment it is expected to perform in and the management style it will be exposed to. Future work is required to assess how the structure of the different cultivars impacts on their capacity to tolerate wear, varying shade levels, water use and herbicide tolerance. The development of a growth model may provide the solution.

Quantifying surfactant interaction effects on soil moisture and turf quality

Soil water repellency occurs widely in horticultural and agricultural soils when very dry. The gradual accumulation and breakdown of surface organic matter over time produces wax-like organic acids, which coat soil particles preventing uniform entry of water into the soil. Water repellency is usually managed by regular surfactant applications. Surfactants, literally, are surface active agents (SURFace ACTive AgeNTS). Their mode of action is to reduce the surface tension of water, allowing it to penetrate and wet the soil more easily and completely. This practice improves water use efficiency (by requiring less water to wet the soil and by capturing rainfall and irrigation more effectively and rapidly). It also reduces nutrient losses through run-off erosion or leaching. These nutrients have the potential to pollute the surrounding environment and water courses. This project investigated potential improvements to standard practices (product combination and scheduling) for surfactant use to overcome localised dry spots on water repellent soils and thus improve turf quality and water use efficiency. Weather conditions for the duration of the trial prevented the identification of improved practices in terms of combination and scheduling. However, the findings support previous research that the use of soil surfactants decreased the time for water to infiltrate dry soil samples taken from a previously severely hydrophobic site. Data will be continually collected from this trial site on a private contractual basis, with the hope that improvements to standard practices will be observed during the drier winter months when moisture availability is a limiting factor for turfgrass growth and quality.

Impacts of improved grazing land management on sediment yields, Part 1: Hillslope processes.

Summary Poor land condition resulting from unsustainable grazing practices can reduce enterprise profitability and increase water, sediment and associated nutrient runoff from properties and catchments. This paper presents the results of a 6 year field study that used a series of hillslope flume experiments to evaluate the impact of improved grazing land management (GLM) on hillslope runoff and sediment yields. The study was carried out on a commercial grazing property in a catchment draining to the Burdekin River in northern Australia. During this study average ground cover on hillslopes increased from ~35% to ~75%, although average biomass and litter levels are still relatively low for this landscape type (~60 increasing to 1100 kg of dry matter per hectare). Pasture recovery was greatest on the upper and middle parts of hillslopes. Areas that did not respond to the improved grazing management had <10% cover and were on the lower slopes associated with the location of sodic soil and the initiation of gullies. Comparison of ground cover changes and soil conditions with adjacent properties suggest that grazing management, and not just improved rainfall conditions, were responsible for the improvements in ground cover in this study. The ground cover improvements resulted in progressively lower runoff coefficients for the first event in each wet season, however, runoff coefficients were not reduced at the annual time scale. The hillslope annual sediment yields declined by ~70% on two out of three hillslopes, although where bare patches (with <10% cover) were connected to gullies and streams, annual sediment yields increased in response to higher rainfall in latter years of the study. It appears that bare patches are the primary source areas for both runoff and erosion on these hillslopes. Achieving further reductions in runoff and erosion in these landscapes may require management practices that improve ground cover and biomass in bare areas, particularly when they are located adjacent to concentrated drainage lines.

Modelling the nitrogen-driven trade-off between nitrogen utilisation efficiency and water use efficiency of wheat in eastern Australia.

The nitrogen-driven trade-off between nitrogen utilisation efficiency (yield per unit nitrogen uptake) and water use efficiency (yield per unit evapotranspiration) is widespread and results from well established, multiple effects of nitrogen availability on the water, carbon and nitrogen economy of crops. Here we used a crop model (APSIM) to simulate the yield, evapotranspiration, soil evaporation and nitrogen uptake of wheat, and analysed yield responses to water, nitrogen and climate using a framework analogous to the rate-duration model of determinate growth. The relationship between modelled grain yield (Y) and evapotranspiration (ET) was fitted to a linear-plateau function to derive three parameters: maximum yield (Ymax), the ET break-point when yield reaches its maximum (ET#), and the rate of yield response in the linear phase ([Delta]Y/[Delta]ET). Against this framework, we tested the hypothesis that nitrogen deficit reduces maximum yield by reducing both the rate ([Delta]Y/[Delta]ET) and the range of yield response to evapotranspiration, i.e. ET# - Es, where Es is modelled median soil evaporation. Modelled data reproduced the nitrogen-driven trade-off between nitrogen utilisation efficiency and water use efficiency in a transect from Horsham (36°S) to Emerald (23°S) in eastern Australia. Increasing nitrogen supply from 50 to 250 kg N ha-1 reduced yield per unit nitrogen uptake from 29 to 12 kg grain kg-1 N and increased yield per unit evapotranspiration from 6 to 15 kg grain ha-1 mm-1 at Emerald. The same increment in nitrogen supply reduced yield per unit nitrogen uptake from 30 to 25 kg grain kg-1 N and increased yield per unit evapotranspiration from 6 to 25 kg grain ha-1 mm-1 at Horsham. Maximum yield ranged from 0.9 to 6.4 t ha-1. Consistent with our working hypothesis, reductions in maximum yield with nitrogen deficit were associated with both reduction in the rate of yield response to ET and compression of the range of yield response to ET. Against the notion of managing crops to maximise water use efficiency in low rainfall environments, we emphasise the trade-off between water use efficiency and nitrogen utilisation efficiency, particularly under conditions of high nitrogen-to-grain price ratio. The rate-range framework to characterise the relationship between yield and evapotranspiration is useful to capture this trade-off as the parameters were responsive to both nitrogen supply and climatic factors.

Water use studies and implications for management of subtropical C4 turfgrasses in dryland and irrigated urban open space

A 2000-03 study to improve irrigation efficiency of grassed urban public areas in northern Australia found it would be difficult to grow most species in dry areas without supplementary watering. Sporoboulus virginicus and sand couch, Zoysia macrantha, were relatively drought-tolerant. Managers of sporting fields, parks and gardens could more than halve their current water use by irrigating over a long cycle, irrigating according to seasonal conditions and using grasses with low water use and sound soil management practices that encourage deep rooting. The use of effluent water provides irrigation and fertiliser cost savings and reduced nitrogen and phosphorus discharge to local waterways. Projected savings are $8000/ha/year in water costs for a typical sporting field.

Environment characterization as an aid to wheat improvement: interpreting genotype-environment interactions by modelling water-deficit patterns in North-Eastern Australia.

Genotype-environment interactions (GEI) limit genetic gain for complex traits such as tolerance to drought. Characterization of the crop environment is an important step in understanding GEI. A modelling approach is proposed here to characterize broadly (large geographic area, long-term period) and locally (field experiment) drought-related environmental stresses, which enables breeders to analyse their experimental trials with regard to the broad population of environments that they target. Water-deficit patterns experienced by wheat crops were determined for drought-prone north-eastern Australia, using the APSIM crop model to account for the interactions of crops with their environment (e.g. feedback of plant growth on water depletion). Simulations based on more than 100 years of historical climate data were conducted for representative locations, soils, and management systems, for a check cultivar, Hartog. The three main environment types identified differed in their patterns of simulated water stress around flowering and during grain-filling. Over the entire region, the terminal drought-stress pattern was most common (50% of production environments) followed by a flowering stress (24%), although the frequencies of occurrence of the three types varied greatly across regions, years, and management. This environment classification was applied to 16 trials relevant to late stages testing of a breeding programme. The incorporation of the independently-determined environment types in a statistical analysis assisted interpretation of the GEI for yield among the 18 representative genotypes by reducing the relative effect of GEI compared with genotypic variance, and helped to identify opportunities to improve breeding and germplasm-testing strategies for this region.

Role of Native Fish in Integrated Aquatic Weed and Water Quality Management within the Burdekin Irrigation Area

This report summarises work conducted by the QDPI, in partnership with the South Burdekin Water Board (SBWB) and the Burdekin Shire Council (BSC) between 2001 and 2003. The broad aim of the research was to assess the potential of native fish as biocontrol agents for noxious weeds, as part of an integrated program for managing water quality in the Burdekin Irrigation Area. A series of trials were conducted at, or using water derived from, the Sandy Creek Diversion near Groper Creek (lower Burdekin delta). Trials demonstrated that aquatic weeds play a positive role in trapping transient nutrients, until such time that weed growth becomes self-shading and weed dieback occurs, which releases stored nutrients and adversely affects water quality. Transient nutrient levels (av. TN<0.5mg/L; av. TP<0.1mg/L) found in the irrigation channel during the course of this research were substantially lower than expected, especially considering the intensive agriculture and sewage effluent discharge upstream from the study site. This confirms the need to consider the control of weeds rather than complete weed extermination when formulating management plans. However, even when low nutrient levels are available, there is competitive exploitation of habitat variables in the irrigation area leading to succession and eventual domination by certain weed species. During these trials, we have seen filamentous algae, phytoplankton, hyacinth and curled pondweed each hold competitive advantage at certain points. However without intervention, floating weeds, especially hyacinth, ultimately predominate in the Burdekin delta due to their fast propagation rate and their ability to out-shade submerged plants. We have highlighted the complexity of interactions in these highly disturbed ecosystems in that even if the more prevalent noxious weeds are contained, other weed species will exploit the vacant niche. This complexity places stringent requirements on the type of native fish that can be used as biocontrol agents. Of the seven fish species identified with herbivorous trophic niches, most target plankton or algae and do not have the physical capacity to directly eat the larger macrophytes of the delta. We do find however that following mechanical weed harvesting, inoculative releases of fish can slow the rate of hyacinth recolonisation. This occurs by mechanisms in addition to direct weed consumption, such as disturbing growth surfaces by grazing on attached biofilms. Predation by birds and water rats presents another impediment to the efficacy of large-scale releases of fish. However, alternative uses of fish in water quality management in the Burdekin irrigation area are discussed.

Turf for tough times - keeping grass cover with less water, Proceedings of a seminar held at Redlands Research Station, Cleveland, Queensland, 6 June 2007.

Suitable for gaining some insights into important questions about the management of turf in dry times. Improve your product quality and avoid unnecessary losses. Can varieties help? How important are soils in conserving moisture and how do I measure my soil's condition? How can I make the best use of available water? Can water retaining amendments assist in establishing turf? Is recycled water a good option? Contains research results from turfgrass trials conducted by Queensland Government scientists for Queensland conditions.

Status assessment of water use research in turf growth and maintenance.

The strategic objectives of Turf Australia (formerly the Turf Producers Association (TPA)) relating to water use in turf are to: • Source and collate information to support the case for adequate access to water for the Turf production and maintenance sectors and • Compile information generated into a convincing communication package that can be readily used by the industry in its advocacy programs (to government, regulators, media etc) More specifically, the turfgrass industry needs unbiased scientific evidence of the value of healthy grass in our environment. It needs to promote the use of adequate water even during drought periods to maintain quality turfgrass, which provides many benefits to the broader community including cooling the environment, saving energy and encouraging healthy lifestyles. The many environmental, social and health benefits of living turfgrass have been the subject of numerous investigations beyond the scope of this review. However further research is needed to fully understand the economic returns achievable by the judicious use of water for the maintenance of healthy turfgrass. Consumer education, backed by scientific evidence will highlight the “false economy” in allowing turfgrass to wither and die during conditions which require high level water restrictions. This report presents a review of the literature pertaining to research in the field of turf water use. The purpose of the review was to better understand the scope and nature of existing research results on turf water relations so that knowledge gaps could be identified in achieving the above strategic objectives of the TPA. Research to date has been found to be insufficient to compile a convincing communication package as described. However, identified knowledge gaps can now be addressed through targeted research. Information derived from targeted research will provide valuable material for education of the end user of turfgrass. Recommendations have been developed, based on the results of this desktop review. It was determined that future research in the field of turf irrigation needs to focus on a number of key factors which directly or indirectly affect the relationship between turfgrass and water use. These factors are: • Climate • Cultivar • Quality • Site use requirements • Establishment and management The overarching recommendation is to develop a strategic plan for turfgrass water relations research based around the five determinants of turf water use listed above. This plan should ensure research under these five categories is integrated into a holistic approach by which the consumer can be guided in species and/or cultivar choices as well as best management practices with respect to turfgrass water relations. Worsening drought cycles and limited supply of water for irrigation were the key factors driving every research project reviewed in this report. Subsidence of the most recent (or current) drought conditions in Australia should not be viewed by the turf industry as a reason to withdraw support or funding for research in this area. Drought conditions, limited domestic water availability and urban water restrictions will return in Australia albeit in 5, 10 or 20 years time and the turf industry has an opportunity to prepare for that time.

Increase water use efficiency and productivity, and reduce energy and water usage and costs, of dairy and fodder enterprises, to reduce costs of milk production

Increase water use efficiency and productivity, and reduce energy and water usage and costs, of dairy and fodder enterprises, to reduce costs of milk production.

Increasing Adoption of Irrigation and Water Recycling Technologies in Australia

Retrofitting nurseries to increase water use efficiency and evaluate 4 soil moisture sensors for irrigation scheduling.