Reducing nutrient discharge from agriculture through the implementation of BMPs – how far can we go?

Algal blooms in south west Western Australia are a symptomatic response to excess nutrient input. Whilst a range of Best Management Practices (BMPs) are available to address the causes of nutrient pollution, most investment has been directed towards symptoms. In order to treat nutrient pollution causes effectively it is important to evaluate possible nutrient reductions and costs, and to determine whether accrued benefits can influence BMP adoption. Models were developed for catchments near Albany (south coast of Western Australia), and for the Peel-Harvey catchment (70 km south of Perth) to estimate costs and benefits of implementing conventional BMPs in scenarios representing the current nutrient reduction effort, the maximum feasible and the most cost effective suite of BMPs. For catchments without ready access to Alkaloam™ (a nutrient-retentive soil amendment), model estimates indicate that current nutrient reductions are around 10%, with a further 20-30% possible. Those with access to Alkaloam™ could reduce phosphorus by a further 25%. Over a 10 year period, the net cost of BMPs was budget positive, resulting in a net benefit to land managers. Economic barriers to the adoption of these BMPs appear limited and bring the current low adoption levels into question. The maximum possible reductions using available BMPs may not be sufficient to arrest water quality decline and to achieve water quality targets

SSPND –Support System for Phosphorus and Nitrogen Decisions – modeling of management practices can guide the way ahead

Algal blooms in rivers and estuarine waters in south west Western Australia are a symptomatic response to excess nutrient input. Whilst a range of Best Management Practices (BMPs) are available to reduce the causes of phosphorus (P) and nitrogen (N) pollution, most investment has been directed towards symptoms. In order to treat nutrient pollution causes effectively, possible nutrient reductions and the likely adoption costs of a range of BMPs require evaluation. Catchment-scale evaluation of implementation scenarios offers insights not possible through long term on-ground implementation and performance monitoring, and assists community groups and government to respond to pollution issues through adhoc funding or programs. The Support System for Phosphorus and Nitrogen Decisions (SSPND) is a risk based tool used in south west Western Australia to estimate costs and benefits of implementing conventional BMPs. It is an adaptation of a P indicators approach which combines source factors, transfer factors, and delivery factors. Model estimates for the Geographe Bay and Peel- Harvey catchments indicate that the net effect of catchment nutrient management to date has been to reduce P loss by 5-10%. SSPND indicates that a further 50% reduction is possible, with approximately half coming from P fixing soil amendments applied to sandy soils in these catchments. For N the picture is similar, but the major management options are riparian fencing and planting, with reduced applications of fertiliser and the use of non-legume species such as perennial pastures being significant also. For the Geographe Bay catchments, a 20yr plan of targeted investment could see significant reductions of nutrient in the Geographe Bay catchment, over 40% for P and 30% for N. However even over a 20-yr timeframe, and with an investment of over $20M, the resulting nutrient load reductions are unlikely to meet water quality targets in most catchments. SSPND provides a range of outputs which assist in the development of management plans for nutrient reduction, and can be used to target nutrient BMP implementation on the basis of water quality, cost/benefit or nutrient reduction. It is currently providing direction in the development of the Geographe Bay Water Quality Improvement Plan

An audit of the uptake of agricultural nutrient management practices in the Peel-Harvey catchment

Recent funding through the Coastal Catchments Initiative aims to significantly reduce the discharge of nutrients to the waterways of the eutrophic Peel-Harvey catchment. A range of projects within this initiative have been developed, which include activities designed to develop, test and implement point and non-point source best management practices (BMP) for the control of nutrient export, and to audit the current levels of adoption of these practices. Landholders who manage approximately 30% of the catchment area have been interviewed under major BMP themes of fertiliser management, soil amendment, perennial pastures, riparian and water management, revegetation, irrigation management and effluent management. The BMP audit indicates that whilst some management actions are in place, there is significant scope for further works, and therefore gains to be made in improved water quality

Farm gate nutrient balances in south west Western Australia – An overview

Farm-gate nutrient budgets can be used to identify the efficiency of nutrient use within and between individual enterprises and catchments, and may be used to represent a component of the risk that particular landuses represent to water quality. Over the past 5 years, more than 400 farm-gate nutrient balance audits have been conducted across a range of catchments and landuses in southwest Western Australia (WA). Values for nutrient use efficiency and surpluses across landuses and catchments are reported. Patterns of nitrogen and phosphorus signatures closely reflect one another across landuses, though nitrogen input, output and surplus values are consistently higher than those for phosphorus. High intensity landuses with high levels of input per hectare, such as annual horticulture and dairy systems, also show higher outputs than extensive landuses such as broadacre grazing and cropping systems. However, surpluses per hectare are also higher than for other landuses. Cropping systems were found to be less variable and more efficient in nutrient use than other animal based landuses. Annual horticulture displayed interesting disparity with other data by having relatively high N efficiency concurrent with low P efficiency, defying the trend of N and P signatures reflecting one another closely. The general surpluses and efficiencies for different landuses were also reflected in catchment nutrient use efficiencies, based on the landuse makeup in those catchments. Catchments dominated by animal based landuses such dairy and other grazing systems tended to have higher nutrient surplus and lower efficiency than catchments dominated by plant based cropping systems

A Comparison of Agricultural and Urban influences on Water Quality in South West WA

In Western Australia, a number of coastal rivers and estuaries have suffered from eutrophication since the 1960’s. Often the focus of the threat to water quality in these areas has been agriculture because of its extensive nature and widespread use of highly soluble fertilisers. Over recent years a focus on nutrient inputs, outputs and nutrient balance in a number of projects provides an opportunity to compare the relative nutrient threats from the agricultural and urban sectors, placed in the context of increasing urbanisation and development. These disparate data sets also allow a comparison of nutrient inputs in each sector in the form of fertiliser and non-fertiliser sources, and show how these translate into whole of catchment nutrient inputs, transformations and exports to waterways. These sets of data also provide some insight into the adoption of management practices in each sector, and the relative threats to water quality from each sector on the basis of its location in a catchment

On the measurement and modelling of high pressure flows in poppet valves under steady-state and transient conditions

Flow coefficients of intake valves and port combinations were determined experimentally for a compressed nitrogen engine under steady-state and dynamic flow conditions for inlet pressures up to 3.2 MPa. Variable valve timing was combined with an indexed parked piston cylinder unit for testing valve flows at different cylinder volumes whilst maintaining realistic in-cylinder transient pressure profiles by simply using a fixed area outlet orifice. A one-dimensional modelling approach describing three-dimensional valve flow characteristics has been developed by the use of variable flow coefficients that take into account the propagation of flow jets and their boundaries as a function of downstream/upstream pressure ratios. The results obtained for the dynamic flow cases were compared with steadystate results for the cylinder to inlet port pressure ratios ranges from 0.18 to 0.83. The deviation of flow coefficients for both cases is discussed using pulsatile flow theory. The key findings include: 1. For a given valve lift, the steady-state flow coefficients fall by up to 21 percent with increasing cylinder/manifold pressure ratios within the measured range given above; 2. Transient flow coefficients deviated from those measured for the steady-state flow as the valve lift increases beyond a critical value of approximately 0.5 mm. The deviation can be due to the insufficient time of the development of steady state boundary layers, which can be quantified by the instantaneous Womersley number defined by using the transient hydraulic diameter. We show that it is possible to predict deviations of the transient valve flow from the steady-state measurements alone

Peripheral Visual Reaction Time Is Faster in Deaf Adults and British Sign Language Interpreters than in Hearing Adults

Following auditory deprivation, the remaining sense of vision has shown selective enhancement in visual cognition, especially in the area of near peripheral vision. Visual acuity is poor in the far periphery and may be an area where sound confers the greatest advantage in hearing persons. Experience with a visuospatial language such as British Sign Language (BSL) makes additional demands on the visual system. To test the different and separable effects of deafness and use of a visuo-spatial language on far peripheral visual processing, we investigated visual reaction times (RTs) and response accuracy to visual stimuli, between 30◦ and 85◦ along the four cardinal and four inter-cardinal meridians. We used three luminances of static, briefly illuminated stimuli in visually normal adults. The cohort tested included profoundly congenitally deaf adults (N = 17), hearing fluent BSL users (N = 8) and hearing non-signing adults (N = 18). All participants were tested using a peripheral forced choice paradigm designed previously to test deaf and hearing children (Codina et al., 2011a). Deaf adults demonstrated significantly faster RTs to all far peripheral stimuli and exceeded the abilities of both signing and non-signing hearing adults. Deaf adults were significantly faster than BSL interpreters, who in turn were significantly faster than hearing non-signing adults. The differences in RT demonstrated between groups were consistent across all visual field meridians and were not localized to any one region of the visual field. There were no differences found between any groups in accuracy of detecting these static stimuli at any retinal location. Early onset auditory deprivation appears to lead to a response time visual advantage in far peripheral responses to briefly presented, static LED stimuli, especially in the right visual field. Fluency in BSL facilitates faster visuo-motor responses in the peripheral visual field, but to a lesser extent than congenital, profound deafness