Balancing water-quality threats from nutrients and production in Australian and New Zealand dairy farms under low profit margins
R. W. McDowell A B G , R. M. Monaghan A , W. Dougherty C , C. J. P. Gourley D , R. Vibart E and M. Shepherd F
+ Author Affiliations
- Author Affiliations
A AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel 9053, New Zealand.
B Agriculture and Life Sciences, Lincoln University, Lincoln 7647, New Zealand.
C DPI Agriculture, NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Woodbridge Road, Menangle, NSW 2568, Australia.
D Agriculture Research, Department of Economic Development, Jobs, Transport and Resources, Ellinbank, Vic. 3821, Australia.
E AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North 4442, New Zealand.
F AgResearch, Ruakura Research Centre, Private Bag 3123, Hamilton 3214, New Zealand.
G Corresponding author. Email: richard.mcdowell@agresearch.co.nz
Animal Production Science 57(7) 1419-1430 https://doi.org/10.1071/AN16646
Submitted: 28 September 2016 Accepted: 10 January 2017 Published: 15 March 2017
Abstract
The loss of nitrogen (N) and phosphorus (P) from dairy-farmed land can impair water quality. Efforts to curtail these losses in Australia and New Zealand (Australasia) have involved a mixture of voluntary and regulatory approaches. In the present paper, we summarise the losses of N and P from Australasian dairy farms, examine the policy drivers used for mitigating losses and evaluate the effectiveness of contrasting approaches to implementing mitigations. Median losses for N and P were 27 and 1.6 kg/ha.year respectively, with a wide range of variation (3–153 kg N/ha.year and 0.3–69 kg P/ha.year) caused by a complex array of climate, soil types, flow paths, nutrient surpluses and land management factors. This complexity, coupled with the variable implementation of measures to mitigate losses, means that many voluntary programs to decrease losses have had uncertain or limited success. Although there is little or no formal regulation in Australia, regulation exists in New Zealand that requires regional authorities to implement the best strategy to improve water quality according to regional-specific characteristics. In testing a generalised approach to mitigation (priority given to those that are easy to implement) in four regions in New Zealand, we found that P could be mitigated quite cheaply, but N reductions required more measures, some of which are costly. Conversely, prioritising on the basis of mitigation cost-effectiveness for a specific nutrient will lead to more rapid reductions in losses of the target nutrient, but with fewer co-benefits for the non-target nutrient or other water pollutants, such as faecal microorganisms and sediment. This information will assist farmers in deciding how to meet a catchment target at least cost.
Additional keywords: mitigations, nitrogen, phosphorus, policy, voluntary measures.
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