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Papers by Selva Selvarajah
From the regional councils' perspective the Resource Management Act (RMA) provides greater re... more From the regional councils' perspective the Resource Management Act (RMA) provides greater regulatory control over water quality and quantity management. Air and soil quality management is based on contaminant discharges. The regional councils can also manage land for the purpose of soil conservation. Despite the relative significance to water management, soil-plant systems continue to play a major role in environmental management in New Zealand. Coupled with cultural needs and relatively higher assimilative capacity, soil-plant systems have led to land being the preferred discharge medium over water. Despite their relatively limited treatment capacity, constructed wetlands are also preferred over direct discharges to water. Market access for food products, climatic and soil conditions, land value and sensitive groundwater aquifers are important limiting factors. Soil-plant systems are also vital in mitigating against non-point source discharges. Riparian strips are known to min...
There is a widely held view among the technocrats and policy makers that in New Zealand the point... more There is a widely held view among the technocrats and policy makers that in New Zealand the point source discharges are no longer an issue and that they have been managed properly. The reality is the contrary. Many local authority sewage discharges arc still of third world discharge quality and many consented discharges to water will still require lengthy mixing zones. The paper uses several consent applications as examples to demonstrate how consent process could he used successfully in dealing with complex land and water discharges of effluent.
This paper reports on Environment Waikato's investigations into seepage from dairy farm effluent ... more This paper reports on Environment Waikato's investigations into seepage from dairy farm effluent treatment ponds. Seepage was measured at three different pond sites near Matamata, and intact pond floor cores were analysed for bulk density and clay content.
Water quality issues related to dairy farming The following dairy farming activities are likely t... more Water quality issues related to dairy farming The following dairy farming activities are likely to cause adverse effects on water quality: Stock access to waterways Poor nutrient management
Economic contribution of farming to Gross Domestic Product (GDP) in New Zealand remains significa... more Economic contribution of farming to Gross Domestic Product (GDP) in New Zealand remains significant. It may be argued farming component is only 13% of the GDP in 2013. However, the farming input to total NZ export earnings is 1/3, which is nearly 50% of the export earnings derived from the exports of goods alone. Farm production, particularly dairy has been increasing more rapidly in the past decade. For example, increasing dairy production is attributed to increased productivity per cow and increased expansion. Concerns had been raised by water users and environmental advocates about growing dairy expansions and the subsequent increasing pressure on water resources. Much of the concerns have been about degrading water quality, particularly increasing nutrient levels in waterways. The paper takes the view that while nutrient monitoring is critical and useful to monitor potential adverse effects on waterways, long-term biological health monitoring of the waterways is also vital to ca...
Journal of environmental quality
Soil depletion and degradation have been increasingly recognized as important environmental issue... more Soil depletion and degradation have been increasingly recognized as important environmental issues in many parts of the world. Over the last decade a number of political and legislative measures have been introduced to encourage and enforce sustainable soil management in New Zealand. Application of the new legislation has highlighted gaps in our knowledge of soil quality and a lack of scientific methods to assess and monitor soil quality. This paper describes the legislative measures and outlines the sdentific response to the needs of regulatory agencies responsible for maintaining environmental quality. The research recommended a set of indicators to assess soil quality. Each soil quality attribute has an associated "target range" defining the acceptable value for the attribute. The paper also discusses the communication of results to end-users, including the development of a computerized assessment tool. The legislative measures and scientific response have fostered a cl...
Conference: Nutrient Management in Farmed LandscapeAt: Farmed Landscape Research Centre, Massey University, Palmerston North, New Zealand, 2020
The Resource Management Act (RMA) has been New Zealand's key environmental legislation since its ... more The Resource Management Act (RMA) has been New Zealand's key environmental legislation since its enactment in 1991. It accorded wide ranging functions and powers to the regional councils and the Minister for the Environment to manage natural and physical resources. Freshwater is one of the critical natural resources locally and globally hence its sustainable management is critical. Since 1991, much of the freshwater management has been by the regional councils under their regional rules whose performances have been monitored by the Officer of the Auditor-General (OAG) on several occasions involving selected regions with recognitions for performance and recommendations for improvements. Since 1991, whilst freshwater quality has been reported as improving in some polluted catchments, the overall trend has been declining water quality and increasing water allocation/use owing to intensifying urban and rural activities. Being much more effective and powerful than the regional councils in managing freshwater sustainably, how did the central government perform in the past 28 years? In the absence of a similar regional councils' audit by the OAG, there has been little or no reporting of the central government performance in the freshwater management. In this policy research paper, the author who has been implementing the RMA since its enactment provides his perspective of the central government management of the freshwater resources since 1991.
New Zealand Land Treatment Collective 2021 Annual Conference, 2021
It is commonly known among the land treatment experts that optimally managed cut & carry systems ... more It is commonly known among the land treatment experts that optimally managed cut & carry systems are the best wastewater treatment systems environmentally, economically and culturally. However, most such systems require discharge permits for sewage and industrial wastewater discharges under the Resource Management Act (RMA) from the regional authorities. The critical factors encountered in the consent application, consent process and compliance performance management are the determination and regulation of suitable wastewater nitrogen (N) loading and the regulation and management of potentially leachable N in cut & carry land treatment systems. The use of models that are not fit for purpose to determine wastewater-N loading, N leaching and groundwater nitrate contamination, may result in excessive regulation of the cut & carry systems with exorbitant pre-treatment of irrigated wastewater or the demise of the cut & carry system altogether by resorting to direct discharge to water. At the 2019 Land Treatment Collective conference I discouraged the use of models that are not fit for regulatory purposes and proposed the use of plant-N uptake to determine wastewater-N loading and to minimise nitrogen leaching. This technical paper assesses the feasibility of using plant-N removal as a critical factor to determine and regulate wastewater-N loading rate for sewage and industrial wastewater discharge consenting and compliance performance monitoring purposes. I have concluded that annual potential plant-N removals rates (APPNRR) derived from the past agronomic field trials could be used conservatively to set wastewater-N and plant-N removal limits and managing cut & carry systems under optimal conditions to minimise nitrogen leaching.
New Zealand Land Treatment Collective 2019 Annual Conference, 2019
To avoid direct discharges to water and to minimise adverse effects on mauri of water and surface... more To avoid direct discharges to water and to minimise adverse effects on mauri of water and surface and marine water quality, most regional councils promote land treatment systems to treat municipal and industrial effluent. Under the Resource Management Act (RMA) 1991, virtually all regional councils using varying regional rules require consents to discharge municipal and industrial effluent to land. This paper focuses on the management of nitrogen (N) as a contaminant because it is one of the key components of the municipal and industrial effluent and has been a key water contaminant in New Zealand. In the first decade since the regional council formation in 1989, in the absence of appropriate nutrient/effluent models, regional authorities set effluent-N irrigation loading rates without N leaching limits and with some requiring groundwater nitrate monitoring. In the past decade, nutrient model such as Overseer® has been used extensively to set effluent-N loading and leaching rates. Consequently, much of the compliance/performance monitoring of N leaching from land treatment of effluent has been performed by using nutrient models such as Overseer®. This paper assesses three decades of consenting, monitoring and the science of the land treatment systems in New Zealand for effectiveness in the context of N contamination management and provides way forward where appropriate.
There is wide concern that intensive farming practices are likely to provide non-point sources of... more There is wide concern that intensive farming practices are likely to provide non-point sources of ground water NO3-N pollution. Similarly, land based disposal of industrial effluent provides numerous point sources of ground water NO3-N. This study uses ground water NO3-N data (including consents monitoring data) collected by Environment Waikato to investigate both non-point and point sources of NO3-N pollution in the Waikato region. Elevated ground water NO3-N levels are found in the north Waikato (south of Pukekohe), Coromandel coastal settlements, Tokoroa, Upper Piako catchment (Hauraki District), and Hamilton Basin. The full extent of ground water NO3-N pollution in the Waikato region will not be known until extensive ground water monitoring is completed. Monitoring wells in an intensively farmed area between Hamilton and Cambridge reveal NO3-N concentrations above 10 mg L-1. The effects of non-point sources of NO3-N are found predominantly in shallow bores (<30 metres) with water levels within several metres of ground surface. The major mechanisms that control NO3-N fluctuation in shallow aquifers are water recharge and ground water outflow to adjacent streams. Rapid increases in NO3-N levels are attributed to accumulation of soil NO3-N during dry periods, combined with the NO3-N flushing effect of infiltrating rainwater. It has been estimated that NO3-N leaching from intensively farmed areas contributes at least 60 kg NO3-N ha-1 y-1 to shallow aquifers in the Hamilton Basin. During a period of declining ground water levels, the apparent NO3-N decrease from these shallow aquifers equals 280 g NO3-N d-1. Regardless of intensive land use, certain shallow aquifers contain little or no NO3-N. This may be attributed to reducing soil and water conditions prevailing in these areas (e.g. Lower Piako catchment). Under these conditions there is little or no dissolved oxygen present, and NO3-N is reduced by Fe 2+. Consequently, ground water containing elevated levels of Fe 2+ (>0.2 mg L-1) has very low NO3-N levels. A significant part of the intensively farmed area in the Waikato region falls into this category. Nitrogen loading rates at industrial waste disposal sites are several fold greater than N loading due to non-point sources. A case study of one such industrial disposal site is presented, where dairy factory waste water disposal onto land has markedly increased ground water NO3-N pollution. At individual bores, NO3-N levels have increased over the last decade from background levels (e.g. <1 mg L-1) to more than 70 mg L-1. The high N and hydraulic loading from this point source contribute at least 13 t NO3-N y-1 to the adjacent Mangaone Stream. Proposals for the disposal of industrial waste water onto land will require an appropriate N management strategy. These N management strategies must demonstrate that applied-N is unlikely to adversely affect ground water quality in the region.
From the regional councils' perspective the Resource Management Act (RMA) provides greater re... more From the regional councils' perspective the Resource Management Act (RMA) provides greater regulatory control over water quality and quantity management. Air and soil quality management is based on contaminant discharges. The regional councils can also manage land for the purpose of soil conservation. Despite the relative significance to water management, soil-plant systems continue to play a major role in environmental management in New Zealand. Coupled with cultural needs and relatively higher assimilative capacity, soil-plant systems have led to land being the preferred discharge medium over water. Despite their relatively limited treatment capacity, constructed wetlands are also preferred over direct discharges to water. Market access for food products, climatic and soil conditions, land value and sensitive groundwater aquifers are important limiting factors. Soil-plant systems are also vital in mitigating against non-point source discharges. Riparian strips are known to min...
There is a widely held view among the technocrats and policy makers that in New Zealand the point... more There is a widely held view among the technocrats and policy makers that in New Zealand the point source discharges are no longer an issue and that they have been managed properly. The reality is the contrary. Many local authority sewage discharges arc still of third world discharge quality and many consented discharges to water will still require lengthy mixing zones. The paper uses several consent applications as examples to demonstrate how consent process could he used successfully in dealing with complex land and water discharges of effluent.
This paper reports on Environment Waikato's investigations into seepage from dairy farm effluent ... more This paper reports on Environment Waikato's investigations into seepage from dairy farm effluent treatment ponds. Seepage was measured at three different pond sites near Matamata, and intact pond floor cores were analysed for bulk density and clay content.
Water quality issues related to dairy farming The following dairy farming activities are likely t... more Water quality issues related to dairy farming The following dairy farming activities are likely to cause adverse effects on water quality: Stock access to waterways Poor nutrient management
Economic contribution of farming to Gross Domestic Product (GDP) in New Zealand remains significa... more Economic contribution of farming to Gross Domestic Product (GDP) in New Zealand remains significant. It may be argued farming component is only 13% of the GDP in 2013. However, the farming input to total NZ export earnings is 1/3, which is nearly 50% of the export earnings derived from the exports of goods alone. Farm production, particularly dairy has been increasing more rapidly in the past decade. For example, increasing dairy production is attributed to increased productivity per cow and increased expansion. Concerns had been raised by water users and environmental advocates about growing dairy expansions and the subsequent increasing pressure on water resources. Much of the concerns have been about degrading water quality, particularly increasing nutrient levels in waterways. The paper takes the view that while nutrient monitoring is critical and useful to monitor potential adverse effects on waterways, long-term biological health monitoring of the waterways is also vital to ca...
Journal of environmental quality
Soil depletion and degradation have been increasingly recognized as important environmental issue... more Soil depletion and degradation have been increasingly recognized as important environmental issues in many parts of the world. Over the last decade a number of political and legislative measures have been introduced to encourage and enforce sustainable soil management in New Zealand. Application of the new legislation has highlighted gaps in our knowledge of soil quality and a lack of scientific methods to assess and monitor soil quality. This paper describes the legislative measures and outlines the sdentific response to the needs of regulatory agencies responsible for maintaining environmental quality. The research recommended a set of indicators to assess soil quality. Each soil quality attribute has an associated "target range" defining the acceptable value for the attribute. The paper also discusses the communication of results to end-users, including the development of a computerized assessment tool. The legislative measures and scientific response have fostered a cl...
Conference: Nutrient Management in Farmed LandscapeAt: Farmed Landscape Research Centre, Massey University, Palmerston North, New Zealand, 2020
The Resource Management Act (RMA) has been New Zealand's key environmental legislation since its ... more The Resource Management Act (RMA) has been New Zealand's key environmental legislation since its enactment in 1991. It accorded wide ranging functions and powers to the regional councils and the Minister for the Environment to manage natural and physical resources. Freshwater is one of the critical natural resources locally and globally hence its sustainable management is critical. Since 1991, much of the freshwater management has been by the regional councils under their regional rules whose performances have been monitored by the Officer of the Auditor-General (OAG) on several occasions involving selected regions with recognitions for performance and recommendations for improvements. Since 1991, whilst freshwater quality has been reported as improving in some polluted catchments, the overall trend has been declining water quality and increasing water allocation/use owing to intensifying urban and rural activities. Being much more effective and powerful than the regional councils in managing freshwater sustainably, how did the central government perform in the past 28 years? In the absence of a similar regional councils' audit by the OAG, there has been little or no reporting of the central government performance in the freshwater management. In this policy research paper, the author who has been implementing the RMA since its enactment provides his perspective of the central government management of the freshwater resources since 1991.
New Zealand Land Treatment Collective 2021 Annual Conference, 2021
It is commonly known among the land treatment experts that optimally managed cut & carry systems ... more It is commonly known among the land treatment experts that optimally managed cut & carry systems are the best wastewater treatment systems environmentally, economically and culturally. However, most such systems require discharge permits for sewage and industrial wastewater discharges under the Resource Management Act (RMA) from the regional authorities. The critical factors encountered in the consent application, consent process and compliance performance management are the determination and regulation of suitable wastewater nitrogen (N) loading and the regulation and management of potentially leachable N in cut & carry land treatment systems. The use of models that are not fit for purpose to determine wastewater-N loading, N leaching and groundwater nitrate contamination, may result in excessive regulation of the cut & carry systems with exorbitant pre-treatment of irrigated wastewater or the demise of the cut & carry system altogether by resorting to direct discharge to water. At the 2019 Land Treatment Collective conference I discouraged the use of models that are not fit for regulatory purposes and proposed the use of plant-N uptake to determine wastewater-N loading and to minimise nitrogen leaching. This technical paper assesses the feasibility of using plant-N removal as a critical factor to determine and regulate wastewater-N loading rate for sewage and industrial wastewater discharge consenting and compliance performance monitoring purposes. I have concluded that annual potential plant-N removals rates (APPNRR) derived from the past agronomic field trials could be used conservatively to set wastewater-N and plant-N removal limits and managing cut & carry systems under optimal conditions to minimise nitrogen leaching.
New Zealand Land Treatment Collective 2019 Annual Conference, 2019
To avoid direct discharges to water and to minimise adverse effects on mauri of water and surface... more To avoid direct discharges to water and to minimise adverse effects on mauri of water and surface and marine water quality, most regional councils promote land treatment systems to treat municipal and industrial effluent. Under the Resource Management Act (RMA) 1991, virtually all regional councils using varying regional rules require consents to discharge municipal and industrial effluent to land. This paper focuses on the management of nitrogen (N) as a contaminant because it is one of the key components of the municipal and industrial effluent and has been a key water contaminant in New Zealand. In the first decade since the regional council formation in 1989, in the absence of appropriate nutrient/effluent models, regional authorities set effluent-N irrigation loading rates without N leaching limits and with some requiring groundwater nitrate monitoring. In the past decade, nutrient model such as Overseer® has been used extensively to set effluent-N loading and leaching rates. Consequently, much of the compliance/performance monitoring of N leaching from land treatment of effluent has been performed by using nutrient models such as Overseer®. This paper assesses three decades of consenting, monitoring and the science of the land treatment systems in New Zealand for effectiveness in the context of N contamination management and provides way forward where appropriate.
There is wide concern that intensive farming practices are likely to provide non-point sources of... more There is wide concern that intensive farming practices are likely to provide non-point sources of ground water NO3-N pollution. Similarly, land based disposal of industrial effluent provides numerous point sources of ground water NO3-N. This study uses ground water NO3-N data (including consents monitoring data) collected by Environment Waikato to investigate both non-point and point sources of NO3-N pollution in the Waikato region. Elevated ground water NO3-N levels are found in the north Waikato (south of Pukekohe), Coromandel coastal settlements, Tokoroa, Upper Piako catchment (Hauraki District), and Hamilton Basin. The full extent of ground water NO3-N pollution in the Waikato region will not be known until extensive ground water monitoring is completed. Monitoring wells in an intensively farmed area between Hamilton and Cambridge reveal NO3-N concentrations above 10 mg L-1. The effects of non-point sources of NO3-N are found predominantly in shallow bores (<30 metres) with water levels within several metres of ground surface. The major mechanisms that control NO3-N fluctuation in shallow aquifers are water recharge and ground water outflow to adjacent streams. Rapid increases in NO3-N levels are attributed to accumulation of soil NO3-N during dry periods, combined with the NO3-N flushing effect of infiltrating rainwater. It has been estimated that NO3-N leaching from intensively farmed areas contributes at least 60 kg NO3-N ha-1 y-1 to shallow aquifers in the Hamilton Basin. During a period of declining ground water levels, the apparent NO3-N decrease from these shallow aquifers equals 280 g NO3-N d-1. Regardless of intensive land use, certain shallow aquifers contain little or no NO3-N. This may be attributed to reducing soil and water conditions prevailing in these areas (e.g. Lower Piako catchment). Under these conditions there is little or no dissolved oxygen present, and NO3-N is reduced by Fe 2+. Consequently, ground water containing elevated levels of Fe 2+ (>0.2 mg L-1) has very low NO3-N levels. A significant part of the intensively farmed area in the Waikato region falls into this category. Nitrogen loading rates at industrial waste disposal sites are several fold greater than N loading due to non-point sources. A case study of one such industrial disposal site is presented, where dairy factory waste water disposal onto land has markedly increased ground water NO3-N pollution. At individual bores, NO3-N levels have increased over the last decade from background levels (e.g. <1 mg L-1) to more than 70 mg L-1. The high N and hydraulic loading from this point source contribute at least 13 t NO3-N y-1 to the adjacent Mangaone Stream. Proposals for the disposal of industrial waste water onto land will require an appropriate N management strategy. These N management strategies must demonstrate that applied-N is unlikely to adversely affect ground water quality in the region.
Queenstown-Lakes District, New Zealand is one of the fastest growing districts in New Zealand. It... more Queenstown-Lakes District, New Zealand is one of the fastest growing districts in New Zealand. It has some of the most pristine alpine lakes and rivers. With its ever increasing resident and tourist population coupled with its sensitive receiving environment, human wastewater discharge has to be managed carefully. While the district has three major human wastewater treatment facilities which cover much of the district, in excess of 28% of the dwellings’ discharges are via septic tanks and developer catered treatment systems. Townships such as Kingston, Glenorchy and Cardrona are in need of wastewater reticulation to avoid any short and long-term water contamination issues and any new septic tank discharge restrictions arising from the Otago Regional Council (ORC) plan changes. The paper discusses in detail population dynamics, human wastewater issues and approaches to manage wastewater effectively.
Economic contribution of farming to Gross Domestic Product (GDP) in New Zealand remains significa... more Economic contribution of farming to Gross Domestic Product (GDP) in New Zealand remains significant. It may be argued farming component is only 13% of the GDP in 2013. However, the farming input to total NZ export earnings is 1/3, which is nearly 50% of the export earnings derived from the exports of goods alone.
Farm production, particularly dairy has been increasing more rapidly in the past decade. For example, increasing dairy production is attributed to increased productivity per cow and increased expansion. Concerns had been raised by water users and environmental advocates about growing dairy expansions and the subsequent increasing pressure on water resources.
Much of the concerns have been about degrading water quality, particularly increasing nutrient levels in waterways. The paper takes the view that while nutrient monitoring is critical and useful to monitor potential adverse effects on waterways, long-term biological health monitoring of the waterways is also vital to capture actual adverse effects on freshwater habitats.
The paper analyses long-term water quality, including biological status of the rivers and lakes in New Zealand using regional and national monitoring reports results to gauge the actual impacts of farming on water quality. The overall analyses indicated that there had been compelling evidence on deteriorating nutrient levels in waterways in many agricultural catchments. Based on the sparse scientifically rigorous trend analyses such deterioration has not yet, however, fully or correspondingly manifested into significant habitat damage.
The paper nevertheless takes the view that environmental impacts, both potential and actual, have to be managed promptly and effectively. It analyses the effectiveness of a range of tools in the Resource Management Act to manage the impacts of farming on water quality.
The paper analyses a range of treatment options available to treat farm dairy effluent from the U... more The paper analyses a range of treatment options available to treat farm dairy effluent from the Uruguayan dairy farmers' perspective.
The paper analyses a range of treatment options and their efficiencies to treat farm dairy efflue... more The paper analyses a range of treatment options and their efficiencies to treat farm dairy effluent in New Zealand.
Treatment ponds have been used on dairy farms in the Waikato Region New Zealand to either treat t... more Treatment ponds have been used on dairy farms in the Waikato Region New Zealand to either treat the effluent and discharge into waterways or to irrigate onto pasture. This study assessed leakage from several treatment ponds and causes for it.
The describes how effluent discharges are regulated in the Otago Region, New Zealand where there ... more The describes how effluent discharges are regulated in the Otago Region, New Zealand where there are many sensitive rivers and lakes.
A comprehensive paper on non-point and point source of nitrogen and effects on groundwater nitrat... more A comprehensive paper on non-point and point source of nitrogen and effects on groundwater nitrate levels in an intensive farming region Waiakto in New Zealand. The also paper uses a set of shallow aquifer nitrate level data to model and estimate nitrate leaching under non-point source discharge scenario.
This paper assesses a range issues associated with the nitrogen management in the dairy pasture s... more This paper assesses a range issues associated with the nitrogen management in the dairy pasture system in New Zealand and identifies methods to minimise the impacts of nitrogen on water quality.
Often field studies on nitrate pollution are held with a narrow perspective. Many studies conside... more Often field studies on nitrate pollution are held with a narrow perspective. Many studies considered leaching losses of nitrate using a range of field techniques without consideration to groundwater nitrate measurement. Others investigated the extent of nitrate pollution in groundwater without measuring nitrate leaching losses. This field study measured leaching losses of nitrate from paddocks applied with different rate of fertiliser-N and measured the extent of nitrate pollution in the shallow aquifer beneath those respective paddocks.
Wastewater treatment by land has been popular in New Zealand with the interest of avoiding or min... more Wastewater treatment by land has been popular in New Zealand with the interest of avoiding or minimising treated industrial, farm and municipal wastewater discharges to water. There are also added financial benefits whereby crops, pasture or forestry growth could be boosted by wastewater application to land. However, the concept of land treatment has several threats which require overcoming for the successful utilisation of the land treatment systems.
New Zealand's new environmental legislation which was enacted in 1991is referred to as Resource M... more New Zealand's new environmental legislation which was enacted in 1991is referred to as Resource Management Act. Under this act regional authorities (16 regional councils) are given powers to manage water and air and land for the purpose of managing water quality. This paper analyses in detail how soil-plant systems could play a role in the management of the environment.
While there are only approximately 400 dairy farms in the Otago Region, New Zealand, most of the ... more While there are only approximately 400 dairy farms in the Otago Region, New Zealand, most of the farms are high producing farms by New Zealand standard resulting in Otago Region being the fifth largest milk solid producer. By the requirement of the regional farm dairy effluent regulation, all dairy farms are required to apply their farm dairy effluent onto pasture under certain specifications. All farms are visited and inspected by the regional authority annually and in addition any complaints from the community regarding any illegal effluent discharges are also promptly visited and investigated. This paper illustrates how stringent enforcement of the regional farm dairy effluent regulations can yield impressive compliance results.
Farm dairy effluent discharges to land and water are regulated in New Zealand by the Regional Aut... more Farm dairy effluent discharges to land and water are regulated in New Zealand by the Regional Authorities (Councils). This paper covers how regulation was implemented in the dairy farming region, Waikato in the 1990s.
When urea granules are surface applied to soils as a result of urea hydrolysis and ammonia build-... more When urea granules are surface applied to soils as a result of urea hydrolysis and ammonia build-up in soil there may be ammonia volatilised from soils. This paper studied the relationships between different soil characteristics and the extent of ammonia volatilisation for a range of selected soil types in New Zealand.
Farm dairy effluent is irrigated onto pasture in New Zealand to avoid treated effluent discharges... more Farm dairy effluent is irrigated onto pasture in New Zealand to avoid treated effluent discharges to water and to utilise effluent for productive purpose. However, if not applied at the appropriate rate there may be ground water contamination as a result of nitrate leaching. This paper was a pioneer paper in New Zealand which attempted to model and determine a sustainable nitrogen loading rate for farm dairy effluent irrigation for a range of soils and aquifers.
Effluent water and sludge samples from a number of dairy and piggery units were collected. These ... more Effluent water and sludge samples from a number of dairy and piggery units were collected. These samples were analysed for the free-ionic and the organic-complexed copper (Cu). A glass house experiment was conducted to examine the transformation of Cu in soils and the uptake of Cu by pasture. Three Cu sources were used which included fast-release copper sulphate (CuSO4), slow-release copper oxide (CuO), and sludge Cu. The pasture samples were analysed for Cu concentration. The transformation of Cu in soils was monitored by analysing the soil samples for various fractions of Cu.
The potential for ammonia (NH3), loss from granular urea applied to soil can be influenced by var... more The potential for ammonia (NH3), loss from granular urea applied to soil can be influenced by various soil, environmental and agronomic factors. Two field experiments were conducted to investigate the soil factors influencing the volatilisation potentials of a wide range of undisturbed New Zealand soils. Sample blocks of surface soil (0-7 cm depth) were transported from various parts of New Zealand to the experimental site (Lincoln University, Canterbury) and buried at ground level in enclosures configured for active trapping of volatilised NH3. Urea granules were broadcast (@ 100 kg N ha -1 ) and volatilised NH3 was measured in the field laboratory.
The number of nitrifiers (NH4 - oxidizers and NO2 -oxidizers), total heterotrophs, amount of ammo... more The number of nitrifiers (NH4 - oxidizers and NO2 -oxidizers), total heterotrophs, amount of ammonium nitrogen (NH4-N) and nitrate nitrogen (NO3-N) were determined in a Red Yellow Podzolic soil with gravels (pH 4.2), under a coconut-pasture association in Sri Lanka to understand the distribution of inorganic nitrogen in coconut-growing soils and to study the effect of pasture on nitrification.
