Farming under the Lake Taupo nitrogen cap - Can native plantings help? Roger MacGibbon
Lake Taupo has a problem! Lake Taupo has very high water quality, BUT: Monitoring has shown a steady increase in nitrogen concentrations in the lake water since 1974 This has lead to an increase in lake algal growth and nuisance weed growth The lake experienced its first toxic algal blooms in 2001 Predictions are that water quality will continue to deteriorate but could be reversible if action is taken now.
Where does the Lake Taupo nitrogen come from? Source Atmospheric deposition Load of N (tonnes/year) % of Total N Load Effective yield (kg N/ha/yr) 272 20 4.4 Undeveloped land 311 23 2.0 Tongariro power development Pine on unimproved land Pine on unimproved pasture Pine on improved pasture 87 6 122 9 2.0 12 1 2.7 3 8 <1 4.2 6.0 N fixing scrub 7 <1 12 Dairy pasture 68 5 29 Non dairy pasture 442 33 8.6 Urban run off 16 1 8.0 Sewage 17 1 Total 1357 1362
Manageable nitrogen sources to Lake Taupo Source Pine on improved pasture Load of N (tonnes/year) % of Total N Load N reaching the lake (kg N/ha/yr) N leaching from the land surface (kg N/ha/yr) 3 8 1 4.2 6.0 8 12 N fixing scrub 7 1 12 24 Dairy pasture 68 12 29 58 Non dairy pasture 442 80 8.6 17 Urban run off 16 3 8.0 16 Sewage 17 3 Total 553 558
Situation summary: 92% of the manageable N entering the lake comes from farm land. There are only 6 dairy farms in the catchment (contributing 12% of the manageable N) The average age of water entering the lake is about 45 years old in some catchments with some as old as 180 years (ie. some of the water fell as rain as early as 1830!). 45 year old water pre dates most of the intensification of agriculture around Lake Taupo. In other words, the worst is yet to reach the lake.
What is being done about the problem? 1. Nitrogen cap In 2007 Waikato Regional Council imposed rules that cap the amount of N that can be lost (leached) from farms in the Lake Taupo catchment at levels experienced on each farm in the years 2001 2004. This rule is intended to prevent any further increases in N leached from farms into groundwater, and therefore cap the loads reaching the lake (after the time lag has been caught up with). This was viewed by many farmers as a cap on productivity, profitability and farm capital value. Farmers now require a consent to continue farming and must have their farms benchmarked and monitored to gain consent
What is being done about the problem? 2. Lake Taupo Protection Trust established and given a target of 20% further reduction in N by 2020. Given $72.5 million to reduce the N load to the lake by 20% (153 tonnes/annum) They are doing this by: Buying farms, imposing covenants, reselling the land. Purchasing N from Taupo landowners
What is being done about the problem? 3. Set up a nitrogen trading scheme within the catchment Landowners and LTPT can buy and sell N Prices have been as high as $650 / kg N, now trading around $400 to $420.
What are the options for landowners? 1. Sell property to low N use businesses i.e. pine forestry companies 2. Improve the efficiency of N usage on farm (ie. reduce the waste) 3. Optimise land use: focus high N use practices (livestock farming) on the most productive land (where the returns per ha will be highest) and low N use practices on less productive and/or environmentally sensitive land (ie. native timber stands / biodiversity to steep slopes) 4. Optimise natural on farm N extraction systems (eg. wetlands)
Native trees as a land use option for farmers in the Lake Taupo catchment Native trees have considerable long term potential to generate good returns from sustainable native timber production and carbon sequestration, but The major barrier to the establishment of more native trees on farms is the cost. At $15,000 plus per hectare the planting of medium to large areas in natives is unaffordable. The value and affordability of native trees would look better if : natives could generate nitrogen benefits for farmers the cost of establishment could be reduced substantially
Nitrogen benefits: For every hectare planted in native trees and shrubs a reduction of 14 15 kg N/ year in N leached is achieved which can be transferred to more productive areas of the farm. Or, if this N was traded, it could be worth $5600 /ha on the current market.
1. Trials to reduce the cost of establishing native trees and shrubs on marginal farmland Overall objective: to investigate ways to reduce the cost of native plant establishment on Taupo farmland, by: Comparing the cost and performance of open ground grown seedlings with planter bag and root trainer seedlings. Exploring and trialling alternative native plant establishment strategies such as direct seeding, and growing natives under an exotic canopy.
Planting trial site Waihaha, west Lake Taupo
Planting trial site Waihaha, west Lake Taupo
Planting trial site Waihaha, west Lake Taupo
Layout of the replication blocks for the 2009 and 2010 plantings
2009 planting survival rates (12 months after planting)
2009 mean height increment (12 months after planting)
2010 planting survival rates (2 months after planting)
Comparison of establishment costs interim results after two years of planting (prices exclude GST) Open ground PB3 container Root-trainer container Site preparation $0.10 $0.10 $0.10 Plant purchase $1.00 $2.50 $1.25 Plant transport $0.10 $0.50 $0.15 Plant placement $0.19 $0.50 $0.22 Planting $1.50 $1.50 $1.50 Maintenance?????? Blanking?????? Total cost / plant $2.79 $5.10 $3.22 Total cost / ha 1 $6975.00 (45% less) Note 1: Calculated at 2500 plants per ha., plants at 2 metre spacings $12,750.00 $8050.00 (37% less)
2. Evaluation of the potential of wetlands to reduce the nitrogen load entering central North Island lakes Every hectare of functional wetland restored could extract as much as 323 kg N/year. 475 ha of restored wetlands would achieve all of the Trust s 20% N reduction target. If this method of N extraction was recognised, it could be used elsewhere on the farm or traded at $129,200 / ha!
Optimising wetland performance
Comparison of the nitrogen removal potential of restored wetlands TOTAL NITROGEN Restored natural Restored seepage Constructed wetland Floating wetland N removal efficiency (kg/ha) 289 323 368 714 N extraction efficiency Up to 50% Up to 90% Up to 60% Unknown Cost effectiveness ($/kg) $60 $20 $79 $437 Catchment interception * HIGH LOW VERY HIGH MODERATE * Potential to intercept a large proportion of the nutrient load generated in a catchment
Thank you