Reducing N & P Enrichment of Rotorua Lakes
Eutrophication of Rotorua lakes is caused in part by farming operations in the catchment. Modelling studies have estimated that 70% of nitrogen and 40% of phosphate loading is of farm origin. Environment Bay of Plenty is introducing legislation to limit the nutrient load from both urban and rural areas, and this will have a major impact on farming.
Stakeholders are working towards win-win management solutions that will allow farming to continue profitably but will substantially reduce N & P runoff into waterways and help clean up the lakes.
In 2004, the Rotorua Lakes and Land Trust (RLLT) was formed by Rotorua/Taupo Federated Farmers and Te Arawa Federation of Maori Authorities. It is supported by Environment of Bay of Plenty, the Lakes Water Quality Society Inc and the New Zealand Landcare Trust. RLLT Trustees include Richard Vallance, who is currently the General Manager of Ngati Whakaue Tribal Lands Incorporation, and Giff McFadden, Chairman of Rotorua/Taupo Federated Farmers dairy farmer from Reporoa.
MAFs Sustainable Farming Fund is supporting ongoing research in the area, which is being carried out by NIWA and AgResearch. The overall aim is to provide farmers with a suite of management options that can be tailored to meet their needs.
Richard Vallance & Gifford McFadden
As representatives of major landholders they have the view that local and central government should not throw babies out with bath water into the lake. Shutting down farming operations and ruining peoples livelihoods is not a rational option.
Rick Vallance says that they are looking to science to provide a range of solutions, which could include modifying feed and/or the operation of the animals gut, using N inhibitors, runoff water filtering systems, and so on.
We think that there are huge gaps in the understanding of ways of increasing the microbial activity in soils so that they will better utilise all the nitrogen, and of breeding plants with better developed root systems. Those two things combined might well prevent leaching, he says.
We have been doing it in an amateur fashion and we think it is time to put in the resources needed to solve the problem. It doesnt apply just to land around her or other sensitive lakes or rivers in the Waikato or on the Canterbury plains, we think it applies everywhere including on hill country. We think that if we learn how to develop topsoils better and condition them and get them deeper and healthier with deeper rooted plants we will achieve land stability as well, and that is a major target for hill country.
So we think this whole topsoil development area is part of the answer and we think it is an indictment on a country depends on topsoil to have paid so little attention to it.
Vallance believes that mitigation options currently being investigated are part of the solution, and although it is still early days there are slightly more innovative options than shooting farmers or stealing their farms.
Policymakers, he says, have become quite disconnected from the primary sector and while they may acknowledge that the economy is dependant on agriculture they have forgotten that agriculture is dependant on topsoil.
The obvious steps to reduce nutrient runoff have already been taken. On Wharenui station around 350ha has been retired into plantings or natural revegetation. A similar area of native bush has been put into reserves. Waterways have been fenced and bridges put in so that stock have no access to waterways.
In addition, a large amount of effort has been put into a land use optimisation study by Scion. Says Vallance: The Octopus study is aimed at helping us totally re-think land use from the perspective of economics, topography, soil types and so on. We are looking at sustainable nutrient export, amenity planting, and the potential long-term uses of the land for the next 100 years.
Alongside that we are looking at what soil research can offer, and perhaps strategies like planting the less productive slopes in trees but maintaining the best, highly productive areas in pasture.
Watercress harvesting trial James Sukias, NIWA
One of several technologies being tested is using aquatic plants to take up nutrient out of streamwater. Watercress grows naturally in watercourses in the area and is a source of food for stock and humans. James Sukias of NIWA says that watercress is considered a luxury feeder and if nutrients are available it will take up more than it requires for normal growth.
Watercress has recently been planted in two sets of four troughs with two different flow rates. A netting roof has been placed over the compound to provide additional protection for the plants. Preliminary results indicate that even with low biomass (ie. the plants are still small) they are removing nitrate from the water. As they grow larger, and particularly in summer when the plants are growing more actively, they are expected to remove more.
Some unknowns with harvesting watercress are the presence and uptake of contaminants such as arsenic, which concentrates on the below-water plant tissues. Pathogenic bacteria and water snails that are an intermediate host for liver fluke may also be a problem, depending on how the watercress is harvested and used.
One way of harvesting the watercress might be to put a grill over the top so that stock can graze the upper foliage only.
Stakeholders are working towards win-win management solutions that will allow farming to continue profitably but will substantially reduce N & P runoff into waterways and help clean up the lakes.
In 2004, the Rotorua Lakes and Land Trust (RLLT) was formed by Rotorua/Taupo Federated Farmers and Te Arawa Federation of Maori Authorities. It is supported by Environment of Bay of Plenty, the Lakes Water Quality Society Inc and the New Zealand Landcare Trust. RLLT Trustees include Richard Vallance, who is currently the General Manager of Ngati Whakaue Tribal Lands Incorporation, and Giff McFadden, Chairman of Rotorua/Taupo Federated Farmers dairy farmer from Reporoa.
MAFs Sustainable Farming Fund is supporting ongoing research in the area, which is being carried out by NIWA and AgResearch. The overall aim is to provide farmers with a suite of management options that can be tailored to meet their needs.
Richard Vallance & Gifford McFadden
As representatives of major landholders they have the view that local and central government should not throw babies out with bath water into the lake. Shutting down farming operations and ruining peoples livelihoods is not a rational option.
Rick Vallance says that they are looking to science to provide a range of solutions, which could include modifying feed and/or the operation of the animals gut, using N inhibitors, runoff water filtering systems, and so on.
We think that there are huge gaps in the understanding of ways of increasing the microbial activity in soils so that they will better utilise all the nitrogen, and of breeding plants with better developed root systems. Those two things combined might well prevent leaching, he says.
We have been doing it in an amateur fashion and we think it is time to put in the resources needed to solve the problem. It doesnt apply just to land around her or other sensitive lakes or rivers in the Waikato or on the Canterbury plains, we think it applies everywhere including on hill country. We think that if we learn how to develop topsoils better and condition them and get them deeper and healthier with deeper rooted plants we will achieve land stability as well, and that is a major target for hill country.
So we think this whole topsoil development area is part of the answer and we think it is an indictment on a country depends on topsoil to have paid so little attention to it.
Vallance believes that mitigation options currently being investigated are part of the solution, and although it is still early days there are slightly more innovative options than shooting farmers or stealing their farms.
Policymakers, he says, have become quite disconnected from the primary sector and while they may acknowledge that the economy is dependant on agriculture they have forgotten that agriculture is dependant on topsoil.
The obvious steps to reduce nutrient runoff have already been taken. On Wharenui station around 350ha has been retired into plantings or natural revegetation. A similar area of native bush has been put into reserves. Waterways have been fenced and bridges put in so that stock have no access to waterways.
In addition, a large amount of effort has been put into a land use optimisation study by Scion. Says Vallance: The Octopus study is aimed at helping us totally re-think land use from the perspective of economics, topography, soil types and so on. We are looking at sustainable nutrient export, amenity planting, and the potential long-term uses of the land for the next 100 years.
Alongside that we are looking at what soil research can offer, and perhaps strategies like planting the less productive slopes in trees but maintaining the best, highly productive areas in pasture.
Watercress harvesting trial James Sukias, NIWA
One of several technologies being tested is using aquatic plants to take up nutrient out of streamwater. Watercress grows naturally in watercourses in the area and is a source of food for stock and humans. James Sukias of NIWA says that watercress is considered a luxury feeder and if nutrients are available it will take up more than it requires for normal growth.
Watercress has recently been planted in two sets of four troughs with two different flow rates. A netting roof has been placed over the compound to provide additional protection for the plants. Preliminary results indicate that even with low biomass (ie. the plants are still small) they are removing nitrate from the water. As they grow larger, and particularly in summer when the plants are growing more actively, they are expected to remove more.
Some unknowns with harvesting watercress are the presence and uptake of contaminants such as arsenic, which concentrates on the below-water plant tissues. Pathogenic bacteria and water snails that are an intermediate host for liver fluke may also be a problem, depending on how the watercress is harvested and used.
One way of harvesting the watercress might be to put a grill over the top so that stock can graze the upper foliage only.