Managing phosphorus (P) is a global priority for environmental water quality due to P lost from agricultural land through leaching, runoff and subsurface flow. In Western Australia (WA), following decades of P fertiliser application to crops and pastures in low rainfall regions, questions have been raised about this region's contribution to environmental P loss. This study was conducted on the Fitzgerald River catchment in the south Western Australia (WA) with mixed cropping and grazing land uses and a Mediterranean climate with low mean rainfall (~350 mm yr-1). Phosphorus forms were monitored continuously over a three-year period in five separate streams, each draining a defined sub-catchment. The P concentrations in streams consistently exceeded Australian and New Zealand Environment Conservation Council (ANZECC) trigger values throughout the monitoring period. Of the measured total P concentration, ~75% was dissolved P (DRP; <0.45 μm) and 80% of that fraction was in the filterable reactive form (FRP). These water quality measurements and other independent soil investigations at this site, suggest that transport of dissolved P rather than erosion of sediment-bound P was dominant in this environment. Based on extractable soil P (Colwell P) and the P buffering index (PBI), predicted concentrations of dissolved reactive P (DRP) in soil solution in topsoils (0-10 cm) across this catchment, generally exceeded ANZECC's values of 0.07 mg PL-1. The level of exceedance was spatially variable. Streams draining areas with the lowest predicted DRP concentrations also had the lowest measured FRP concentrations. Elsewhere stream water FRP concentrations depended on both DRP concentration and the PBI of the land being drained. Our findings suggest that deployment of practices that physically filter runoff, for example riparian vegetation, would be ineffective in restricting P transport into stream in this environment. This conclusion is consistent with previous findings of the ineffectiveness of riparian buffers on coarse textured sandy soils in higher rainfall areas of southwest WA. A reduction in DRP losses without yield loss could be achieved by following evidence-based fertiliser advice from soil testing to limit losses of legacy P".

A dynamic model of Phosphorus (P) movement through the Peel-Harvey catchment in South Western Australia was developed using system dynamics modelling software. The model was developed to illustrate watershed P flux and to predict future P loss rates under a range of management scenarios. Model input parameters were sourced from extensive surveys of local agricultural practices and regional soil testing data. Model P-routing routines were developed from the known interactions between the various watershed P compartments and fluxes between the various P stores. Phosphorus-retention characteristics of a variety of management practices were determined from local field trials where available and published values where not. The model simulated a 200 year time frame to reflect 100 years to the present day since initial land development, and forecast 100 years into the future. Although the catchment has an annual P-loss target of 70 tonnes per annum (tpa), the measured (and modelled) present-day loss is double this amount (140 tpa) and this is projected to rise to 1300 tpa if current land management practices continue. Broad implementation of neither “biological” BMPs such as perennial pastures and managed riparian zones, or of “chemical” BMPs such as reduced water solubility fertilisers and P-retentive soil amendments, produces reductions in P-loss from present-day levels. Even if broad-scale implementation of the large suite of BMPs tested in this research occurs, catchment P-losses are likely to increase from the present level of 140 tpa to approximately 200 tpa over the next 100 years. This has significant implications for both future land use and subsequent water quality in the catchment as well as questioning the wisdom and perceptions of efficacy of past and future BMP implementation strategies.

Nutrient surpluses, inefficiencies in nutrient use, and inevitable leakage of nutrients from grazed animal production systems are putting growing pressure on Australian inland and coastal water resources. While there are some examples of regulatory policy approaches in Australia which aim to reduce nutrient emissions and improve water quality around important and impaired coastal and inland waters, most policy options involve voluntary schemes, often including financial incentives to both industry organisations and farmers to offset the costs of implementing improved management practices. In contrast, much stronger land management regulations have been implemented in the European Union, USA, and to a lesser extent New Zealand. In the near future, greater societal expectations for water quality, stricter standards from international markets, and increasing costs for purchased nutrients will mean that improving nutrient-use efficiency and reducing nutrient losses will be a necessary part of Australia livestock production systems. This is likely to require somewhat varied and difficult choices to better balance production and environmental goals. Policy responses may include voluntary adoption of appropriate nutrient management practices, caps on nutrient inputs, mandatory nutrient surplus targets, limits to stock numbers per hectare, and re-positioning of higher input farms to more resilient parts of the national landscape. Alternatively, society may have to accept that there are unavoidable trade-offs between water quality standards and livestock productivity, with increasing treatment of polluted water at the community’s expense.

A dynamic model of phosphorus (P) movement through the Peel-Harvey watershed in South Western Australia was developed using STELLA dynamic modelling software. The model was developed to provide a means to illustrate watershed P flux and of predicting future P loss scenarios. Model input parameters were sourced from extensive surveys of local agricultural practices and regional soil testing data. Model P-routing routines were developed from the known interactions between the various watershed P compartments and fluxes between various P stores. The model simulated a 200year time-frame to reflect 100years to the present day since initial land development, and forecast 100years into the future. Although the watershed has an annual P loss target of 70tonnes per annum (tpa), the measured present day loss is double this amount (140tpa) and is projected to rise to 1600tpa if current land management practices continue. This has significant implications for both future land use and subsequent water quality in the watershed.

Escalating fertilizer and feed costs, declining product prices, and increasing regulations to reduce environmental pollution have created new pressures to improve nutrient use in agricultural production. This study provides an overview of factors and processes that impact nitrogen use efficiency (NUE) in dairy production, identifies practices that may bridge gaps between actual-NUE obtained on commercial farms and potential-NUE obtained under experimental conditions, and explores the possibility of using NUE as a performance indicator and policy tool for dairy production. Actual feed-NUE varies from 16% to 36% and is impacted by of a range of dairy practices; manure/fertilizer-NUE varies from 16% to 77% and is very site-specific; and whole-farm NUE varies from 8% to 64% and declines as stocking rates increase. Optimal stocking rate and manure nitrogen (N) crediting can enhance NUE, increase farm profits, and reduce N loss from dairy farms. NUE could be used to further engage dairy producers in collaborative assessments of gaps between their actual N use and the biological potential of N use, to develop performance goals for N use in various production components, and to monitor and evaluate the impacts of alternative feed, manure and fertilizer management practices on N use, profitability, and environmental outcomes.

Dairy farming in Australia continues to intensify. Increased stocking rates have resulted in increased milk production per ha, but have also required greater inputs of purchased feed and fertiliser. The imbalance between nutrient inputs, primarily as feed and fertiliser, and nutrient outputs, in milk and livestock, has resulted in significant nutrient accumulation on dairy farms and, consequently, a greater risk of nutrient loss to the environment. Nutrient budgeting is a technique used to quantify or predict nutrient deficits or surpluses, either at a whole-farm or field scale, in an attempt to improve nutrient use efficiency and reduce nutrient losses from agriculture. A broad range of nutrient budgeting approaches are used internationally, and depending on their purpose, they vary from the very simple to the very complex. Nutrient budgeting has been widely used to assist on-farm nutrient management decisions, in research to identify major nutrient pools, transformations and losses, to enable farmers to access cost-sharing support from governments, and in some countries as a major regulatory tool. The changing nature of Australian dairy operations, the increasing societal pressure on the farming community to reduce nutrient losses to water and air, and the need to provide evidence that farm practices are meeting environmental standards, justifies the need for improved nutrient management practices on Australian dairy farms. This paper describes different types of nutrient budgeting approaches used internationally and assesses the benefits of developing a practical, scientifically rigorous and nationally standardised nutrient budgeting approach for the Australian dairy industry.

The ecology of estuaries on the south coast of Western Australia has been disrupted by increased nutrient and sediment discharge from predominantly rural catchments. A range of conventional management actions are available to reduce nutrient loss at source, and it is important to evaluate possible reductions, and costs, so that limited funds can be targeted to realise the greatest moderation of nutrient loss. A lumped landuse nutrient generation rate model was developed for four catchments (Wilson Inlet, Oyster Harbour, Torbay Inlet and Princess Royal Harbour) near Albany Western Australia and the output compared with existing monitoring data. The nutrient moderating effects of six conventional management actions (perennial pastures; vegetated stream buffers; minimum tillage, effective fertiliser use; stock control and water management; and effluent management) and their associated costs were implemented at different levels in the model. These were used to determine the extent to which these actions could address offsite nutrient pollution, and the cost of doing so. Management actions were implemented in three major scenarios representing the status quo (current nutrient reduction efforts through volunteerism), the highest possible implementation of each action (perhaps indicating mandated change) and the most cost effective set of actions. In each catchment dominated by diffuse nutrient sources, current nutrient reduction efforts amounted to about 10%, whilst the highest possible reductions were of the order of25–30% above this. In the point source dominated catchment current nutrient reduction efforts amounted to about 40%, with an additional 40% possible. The most cost effective scenarios reduced nitrogen more than phosphorus. Under the most cost effective scenarios, it was estimated that the net cost of management actions over 10 years was budget positive, resulting in a net benefit to the land managers involved. This suggests that there are limited economic barriers to the adoption of these conventional management actions, and on this basis current nutrient reduction efforts could be significantly increased. However, predicted reductions from the implementation of conventional management actions may not be sufficient to arrest estuarine decline.

Phosphorus (P) in wastes from piggeries may contribute to the eutrophication of waterways if not disposed of appropriately. Phosphorus leaching, from three soils with different P sorption characteristics (two with low P retention and one with moderate P retention) when treated with piggery effluent (with or without struvite), was investigated using batch and leaching experiments. The leaching of P retained in soil from the application of struvite effluent was determined. In addition, P leaching from lime residues (resulting from the treatment of piggery effluent with lime to remove P) was determined in comparison to superphosphate when applied to the same three soils. Most P was leached from sandy soils with low P retention when effluent with or without struvite was applied. More than 100% of the filterable P applied in struvite effluent was leached in sandy soils with low P retention. Solid, inorganic forms of P (struvite) became soluble and potentially leachable at pH<7 or were sorbed after dissolution if there were sufficient sorption sites. In sandy soils with low P retention, more than 39% of the total filterable P applied in recycled effluent (without struvite) was leached. Soil P increased mainly in surface layers after treatment with effluent. Sandy soils pre-treated with struvite effluent leached 40% of the P retained in the previous application. Phosphorus decreased in surface layers and increased at depth in the soil with moderate P retention after leaching the struvite effluent pre-treated soil with water. The soils capacity to adsorb P and the soil pH were the major soil properties that affected the rate and amount of P leaching, whereas the important characteristics of the effluent were pH, P concentration and the forms of P in the effluent. Phosphorus losses from soils amended with hydrated lime and lime kiln dust residues were much lower than losses from soils amended with superphosphate. Up to 92% of the P applied as superphosphate was leached from sandy soils with low P retention, whereas only up to 60% of the P applied in lime residues was leached. The P source contributing least to P leaching was the lime kiln dust residue. The amount of P leached depended on the water-soluble P content, neutralising value and application rate of the P source, and the pH and P sorption capacity of the soil.

The choice of management practices for the treatment of piggery effluent prior to its disposal to waterways or land is governed by the desire to simultaneously minimise the cost of treatment whilst minimising pollution of the environment. Laboratory experiments were conducted to compare the removal of total and total filterable phosphorus (P) (<0.45 mum) from ortho-phosphate solutions or piggery effluent by hydrated lime or lime kiln dust alone, or from recycled piggery effluent by lime and physico-chemical treatment methods. In addition, the ability of lime to remove P from recycled piggery effluent at an intensive piggery was assessed.Most P in lime treated effluent was present in the >0.45 mum fraction because of the presence of unsettled flocs of P impregnated lime. The efficiency of total P removal by hydrated lime and lime kiln dust decreased as effluent quality declined. The efficiency of removal of total filterable P by hydrated lime or lime kiln dust was not affected by effluent quality. Hydrated lime was more efficient in removing P from effluent or ortho-phosphate solutions, but lime kiln dust was more cost effective. More than 95% of total P was removed from recycled piggery effluent when physico-chemical treatment followed settling with or without lime. The physico-chemical treatment decreased total P mainly by decreasing the number of suspended particles in the effluent and by precipitating some total filterable P as iron, aluminium or calcium compounds.

In order to manage phosphorus (P) losses from soils to waterbodies, knowledge of the mechanisms through which P is retained or released from the soil is essential. Sandy soils of the Peel-Harvey catchment (Western Australia) were subjected to a range of environmental and management factors in the laboratory and field in order to gain an understanding of the mechanisms that affect the magnitude of P losses. Sandy soils accumulated P, despite having little sorption capacity, and this accumulation could be monitored by measuring an acid-extractable fraction. The potential, short-term P loss could be estimated by determination of water-soluble soil solution P prior to winter rains. An annual cycle of the change in arbitrarily defined soil-P pools is discussed in relation to environmental and management factors. Laboratory experiments indicated that P rundown and potential annual P loss in the absence of P fertilizers could be estimated using bicarbonate extractable P. Phosphorus losses were decreased by the application of fertilizers with a low content of water-soluble P. The low ability of sandy soils of the Peel-Harvey coastal catchment to retain P, when compared to other Western Australian soils, is because of low contents of clay minerals and iron and aluminium hydrous oxides.

Nutrient loss from rural point sources and urban environments need to be minimised as part of strategies to overcome declining water quality on the Swan Coastal Plain and in the Peel-Harvey estuary in Western Australia. This paper discusses the management of nutrient losses from domestic effluent, urban stormwater runoff, domestic gardens and public open space, intensive animal industries and intensive irrigated agriculture. Measures to minimise nutrient losses from these sources are outlined, using cooperative, technological and regulatory approaches.

Eutrophication problems in waterbodies in south-western Australia are primarily caused by inputs of nutrients from diffuse sources within the agricultural catchments of these waterbodies. To reduce the algal growth and seagrass decline caused by these inputs, it is essential to modify land management to minimise nutrient losses. Permanent reduction in nutrient losses from agricultural catchments should involve voluntary changes in farm management practices based on improved land management. Specifically, these include on-farm nutrient management such as soil testing, fertilizer management, the use of perennial plants, and water and erosion control measures to reduce nutrient loss from rural land. This paper describes the management of nutrient loss from the catchment of Oyster Harbour on the south coast of Western Australia using a co-operative approach.

The effect of sesquioxidic gravels (>2 mm size fraction) on phosphorus sorption by two gravelly lateritic soils was investigated by phosphorus sorption experiments, X-ray diffraction, autoradiography and electron microscopy.In one soil the abundance and size of gravels decreased downslope. As the gravel content of both soils increased (13-61%), the proportion of large (>8 mm) gravels increased (0-70%). Phosphorus sorption increased in the order: (>2 mm fraction) < (whole soils) < (<2 mm fraction). Phosphorus sorption on lateritic gravels (>2 mm) decreased with increasing gravel size and increased with increasing time. Phosphorus sorption by whole soils decreased with increasing gravel content. Phosphorus sorption by the >2 mm fraction was principally by the external surfaces of the gravels. The estimation of phosphorus application rates for lateritic soils depended on the amount of phosphorus required by the plant and the gravel content of the soil. The former is the important factor at low soil gravel contents whereas the latter becomes more important as the gravel content increases. The implications for fertilizer management on the soil with consistent relationships between landscape position, gravel content and subsequent P sorption properties of whole soils are discussed.

The consequences of previous as well as current environmental conditions and management practices on the potential for phosphorus (P) to be lost by drainage from sandy soils in the short term (< 1 year) were studied in the laboratory and the field. The potential for P losses by drainage was estimated by measuring soil solution P levels and rapidly released P. Rapidly released P was measured by determining the concentration of dissolved inorganic P contained in filtered (<0.45 pm) soil solutions after incubating soil at saturation for 15 min at ambient temperature. In the laboratory, sandy soils were incubated with ordinary superphosphate, coastal superphosphate (a granulated mixture of equal parts of superphospate, rock phosphate and elemental sulfur) or lime-superphosphate (a lime-reverted superphosphate with 18% kiln dust) and sequentially desorbed with deionized water. The effects of the extent of leaching, fertilizer type, application rate and the time of contact with the soil on soil solution P levels were investigated. The influence of annual pasture death and summer rainfall on rapidly released P in soils that had been pre-treated by leaching were also investigated. Phosphorus concentrations decreased logarithmically in the successive supernatants of the sequentially desorbed soils. More P was desorbed from soils incubated with superphosphate and lime-superphosphate than soil incubated with coastal superphosphate. At each level of pre-leaching, the P concentrations in the soil solution increased with increasing time. The level, to which the P concentration in the soil solution increased at each time, decreased with increased extent of pre-leaching. The addition of P fertilizers increased the concentration of P in the soil solution. The concentrations increased with increasing application rate and were much higher for superphosphate than for coastal superphosphate; however, there was little effect of contact time on soil solution P levels. Rapidly released P levels after leaching increased during a period of no further leaching. Additional moisture or plant material during this period of no further leaching increased the rate and extent to which rapidly released P increased. Monitoring of rapidly released P in the 0-2, 2-5, 5-10 and 10-20 cm layers of field plots, with and without applications of superphosphate, showed that sampling depth, water flow path, fertilizer management, rainfall pattern and background P levels would affect the estimate of short-term P losses. Rapidly released P in the 0-2 cm layer varied markedly with time and was higher (P < 0.05) than that in lower soil layers. Rapidly released P increased after the winter and spring rains diminished and then decreased after the rains commenced again at the end of the summer. A possible annual cycle of P in sandy soils in a mediterranean climate is postulated by considering the laboratory and field data in combination.

Long-term phosphorus (P) losses and gains in sandy soils continuously fertilized with either ordinary superphosphate or coastal superphosphate (a granulated mixture of superphosphate, rock phosphate and elemental sulfur) or previously fertilized with superphosphate were investigated under leaching conditions in columns in the laboratory. The soils were subjected to 10 consecutive cycles designed to simulate the mediterranean weather conditions in the Harvey region of the Coastal Plain of Western Australia. Each cycle consisted of a wet phase during which the equivalent of 850 mm of rainfall was leached through the soil and a drier phase during which the soil was incubated in the presence of moisture equivalent to summer rainfall (150 mm). Dissolved inorganic P in the leachate was used as a measure of P loss. A sequential fractionation procedure (a resin extraction followed by 0.5 M sodium bicarbonate, 0.1 M sodium hydroxide and 0.1 M sulfuric acid extractions) and total inorganic and organic P were used to measure changes in P levels in the soils. Phosphorus losses from the previously fertilized soils decreased logarithmically with increasing number of cycles. Total inorganic P and resin-extractable P were able to explain >94% of the variation in P losses. Addition of either fertilizer increased the amount of P leached from the soil and 10-40% more P was leached by adding superphosphate rather than coastal superphosphate. The percentage of the cumulative P lost by leaching decreased with increasing application rate of both fertilizers when expressed as a percentage of the cumulative water plus citrate-soluble P added. Addition of either fertilizer increased the amount of acid-extractable P, but coastal superphosphate had a much greater effect than superphosphate. Leaching losses of P were influenced by fertilizer solubility in the short term (< 1 year). In the long term, however, the water plus citrate-insoluble P in the fertilizers also contributed to P losses by leaching.

Piggery effluent may contribute to the eutrophication of waterways, if it is not treated before disposal, because of high levels of phosphorus. Limes and red muds (a residue from bauxite refining) were used to remove phosphorus from piggery effluent (41 mg litre(-1) total P). Lime-based amendments were more effective than the red muds at removing phosphorus when compared at the same liquid: solid ratios. Based on laboratory data, the cost of treating effluent increased rapidly as the final required phosphorus concentration decreased to less than 4 mg litre(-1). Kiln dust was the cheapest amendment tested down to 2 mg litre(-1). Hydrated lime was able to clarify and flocculate the effluent to 1 mg litre(-1) within 60 min. The re-useability of all limes may be determined by a simple pH test. Red mud could be used to remove phosphorus when its pH was lowered to 6.0-6.5 and it is used at liquid:solid ratios <20:1.