Nitrates and the Waikato Region

Question: What does Anchor milk, swimming in our waterways, 'Outdoors with Geoff,’ and dairy farming all have in common?  

Answer: Nitrate.

As already mentioned, Dairy Farming is a backbone industry which has intensified the landuse of much of the Waikato region’s agricultural land. According to the New Zealand Dairy Statistics publication of the 2012/2013 fiscal year, the Waikato region has 1,148,553  (24.0%) of New Zealand’s 4,784,250 strong dairy cow population. 29.9% (3554) of New Zealand’s herds are within the Waikato region – more than the entire South Island. In terms of land, this industry utilises 390,211ha which is 23.3% of the total amount of land used for dairy farming in NZ. Taking this into account, this therefore means that on average, there are 323 cows for every herd in the Waikato, with an average farm size of 110ha. Breaking this down further, this means that for every hectare of land, there are 2.94 dairy cows occupying it. In terms of production, the Waikato region produced 378,529,678kg of milk solids (22.8%) of New Zealand’s total 1,657,722,313kg of milk solids for the 2012/2013 fiscal year. Using the average pay out/kg milk solids for the same financial year ($6.18/kg), this would equate to a total of $2,339,313,410 billion returning to the owner/ operators and sharemilkers through the dairy cooperative system for this fiscal period. These statistics prove that the Waikato region is an important area for dairy farming in New Zealand, as well as portraying the significant economic benefits that the Waikato region receives from this industry.

The issue that is at hand is the interaction that this industry has with the natural environment. More specifically, the interaction between the Antrhoposphere (human activity) and its flow on effects towards the hydrosphere (Waikato water quality), the Paedosphere (soils within the region) and the Biosphere (Organisms within the waterways) are the sections of the earth’s natural ‘system’ that is of importance. In terms of the Anthroposphere, the economic drive of people within the Waikato region to utilise the natural environment and its resources to source an income leads to the usage of fertilizers. These fertilizers (which contain Ammonia) are applied to the pastures in order to provide the soils with more nutrients to encourage faster and stronger grass growth. Within the Paedsophere  (keeping in mind the nitrification equation) this Ammonia is chemically reworked by small bacterium that creates Nitrate. This source of Nitrogen supplies the soils within plentiful nutrients to inspire grass growth. These newly created Nitrates subsequently enter the groundwater table and the waterways of the Waikato region through, overtime, leaching through the soils. Scientists from Lincoln University in New Zealand argue that urine patches from dairy cows are a greater transport mechanism for Nitrates to enter the ground water table. This is due to the high concentration of Nitrogen within the urine, that when deposited, far exceeds the requirements needed to promote growth. This viewpoint is explained by Professor Keith Cameron as follows:

Professor Keith Coleman, Lincoln University. Source: Youtube.

This interaction of Nitrates with the Hydrosphere is the cause of concern in terms of the overall status of the Waikato regions water quality. The local regional authority that is responsible for the management of the areas resources, the Waikato Regional Council (WRC), has highlighted this as huge issue. As has been explained, elevated nitrogen levels within waterways leads to the eutrophication through excessive nutrients, lack of oxygen, and more visibly algal growth, of the water, harming the biota of the hydrological system. In terms of excessive nitrate levels within drinking water for humans, this can cause medical conditions such as  methaemoglobinaemia, a blood disorder which is particularly harmful to bottle fed infants. Hard statistical data on Nitrogen usage and leaching is incomplete in the area, however there is still evidence to show that overall there is no large improvements being made in terms of reversing the trend. This is clearly visible by the two following graphs:

Graph one: Nitrogen usage for Waikato dairy & dry-stock farms. Source: WRC

Graph two: Nitrogen Leaching on Dairy & Drystock farms. Source: WRC. 

Graph one shows the Nitrogen usage in the Waikato Region from 1997 - 2010. Although the usage of Nitrogen on farmland had decreased between 2002-2003, graph two shows that the overall trend in the interim period that has not been reported in in graph one, is that Nitrogen leaching in the form of Nitrates and Nitrite had increased drastically for Dairy farming. In graph two, 2008 has widely been criticized as an outlier year due to the disastrous drought that impacted the region that year.

Graph three: Shows the occurrence of Nitrate in the 110 monitored wells within the region. Source: WRC.

The WCR currently monitors 110 drilled groundwater wells that are interconnected to major rivers such as the Waikato and Waipa Rivers. Graph three, showing the occurrence of nitrate within groundwater, if generalised across the entire affected region, would indicate that over 30% of the regional water network has elevated levels of Nitrate. For community supplies, which is inclusive of drinking water, approximately 12% of the water has elevated Nitrate levels. Interestingly enough, the WRC has not defined the levels in measurement when it indicates 'low,' 'elevated,' or 'excessive,' however, according the Ministry of Health's Drinking-water standards of New Zealand (revised edition 2008), the absolute maximum allowable limit of Nitrates within drinking water is 50mg/l on a short term basis. Exceeding this would make drinking water unsafe. 

The increasing levels of Nitrate within the Waikato Regions waterways is of deep concern. The need for export quality products such as milk is essential to remote nations such as New Zealand in order to sustain our quality of life. However what we also need to take into consideration is if we want to keep the days of old where kids can go down to the local swimming hole for entertainment instead of playing PS4, and for Geoff Thomas to keep producing 'Outdoors with Geoff,'  then the increasing trend of Nitrate levels within the Waikato's waterways needs to reverse. 

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Sources:

Waikato Regional Council - http://www.waikatoregion.govt.nz/

Ministry of Health - drinking-water sandards http://www.moh.govt.nz/notebook/nbbooks.nsf/0/237C397A37EFADA9CC25750600720E08/$file/drinking-water-standards-2008.pdf

Professor Keith Coleman - https://www.youtube.com/watch?v=bf_iUIDzPa4