Sustainability in pasture-based dairy farming

One of the questions modern farmers face is whether they can farm in an environmentally sustainable, yet profitable, way. Craig Galloway provided the answer in his PhD thesis on the sustainability of pasture-based dairy farms.

Sustainability in pasture- based dairy farming
In his doctoral thesis, Craig Galloway set out to determine whether the goals of reduced environmental impact and profitability could be met simultaneously on pasture-based dairy farms.
Photo: Courtesy of Craig Galloway

The negative environmental impacts of dairy farming are well-established and widely researched. They include loss of biodiversity, eutrophication, ammonia and greenhouse gas (GHG) emissions, and inefficient resource use.

The question is, what practices can be implemented to reduce these impacts while ensuring the long-term profitability of farms? Society wants food at a lower environmental cost, while farmers are challenged with adverse climatic conditions, difficult market conditions and an uncertain political climate.

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 These were some of the questions explored by sustainable agriculture researcher, Dr Craig Galloway, in his recently completed PhD in Conservation Ecology at Stellenbosch University.

The research was conducted using data collected by Trace & Save (traceandsave.com) for the Woodlands Dairy Sustainability Project.

The farms included in the study were all pasture-based dairy farms in the Eastern Cape, between the Storms River in the west and the Great Fish River in the east. This includes the Tsitsikamma, Oyster Bay, Humansdorp, Gamtoos, Alexandria, Cookhouse and Cradock regions.

The Eastern Cape is the largest milk-producing province in South Africa, and the majority of dairy farmers in the study area apply a pasture-based system, making this an ideal location to explore sustainability on dairy farms.

All for sustainability
As part of his research, Galloway conducted a survey on 65 dairy farmers to examine their perceptions of sustainable agriculture. It showed that they had overwhelmingly positive perceptions of the idea.

All respondents agreed with the statement, “Sustainable agriculture methods will ensure long-term success of commercial agriculture in South Africa”.

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All but one agreed with “I want to leave a healthier farm (better soil, water, biodiversity) to future generations”, while all but two agreed with “Sustainable farming practices are needed to protect natural resources”.

However, not all these farmers had adopted the full range of sustainable practices on their farms. The primary reason they gave for not doing so was the time, cost and energy required to implement them.

Measuring impact
To examine whether it was possible to achieve economic sustainability in conjunction with environmental sustainability, Galloway explored some of the environmental impacts of dairy farming.

This involved using two tools developed by Trace & Save: a carbon footprint calculation and a nutrient budget.

Simply put, a carbon footprint is the amount of GHG emissions – a major contributor to global climate change – associated with an activity.

To reduce its environmental impact, dairy farming must reduce the GHG emissions associated with milk production.

A nutrient budget is used to calculate the efficiency with which nutrients, specifically nitrogen (N) and phosphorus (P), have been used on a farm.

Nutrient-use efficiency is calculated by dividing the amount of nutrients removed from the farm by the amount of nutrients imported onto the farm over one year.

The total amount of N and P imported is calculated from the amount of feed, fertiliser and animals brought onto the farm.

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The total amount of N and P removed is calculated from the milk, crops and animals sold. Any inefficiency (more imported than removed) results in an excess of nutrients, which can lead to pollution, especially of freshwater sources.

Environmental impact varied widely among the 43 pasture-based dairy farms studied.

A factor found to be associated with environmental impact was soil health. To assess this, Galloway measured the levels of soil carbon, as carbon contributes to more active soil life, better water-holding capacity and better nutrient retention and cycling in the soil.

The research showed that farms with higher soil carbon levels had lower GHG emissions and higher N-use efficiencies; in other words, a lower environmental impact (see Graphs 1 and 2).

Graph 1

 

Graph 2

TOP (Graphs 1 and 2): The statistically significant relationship between environmental impact (nitrogen- use efficiency, on the left, and greenhouse gas emissions, on the right) and soil health on pasture-based dairy farms. (Note: ECM = energy-corrected milk, a measure that enables farm milk production to be compared on an equal basis.)

 

Economic sustainability
Next, Galloway had to determine whether the farms that had lower environmental impacts were still economically productive.

To do this, Galloway measured the total factor productivity (the efficiency with which inputs are converted into outputs) of each farm, using data envelopment analysis. This provided a measure of farm efficiency, and indicated how profitable the farms were relative to each other.

Graphs 3 and 4 show that when the measures of environmental impact and farm efficiency are compared, the more productive farms had higher N-use efficiencies and lower GHG emissions.

Put simply, the most profitable farms were also those that had the lowest environmental impact.

Graph 3

Graph 4

ABOVE (Graphs 3 and 4): The statistically significant relationship between farm efficiency and environmental impact (nitrogen- use efficiency, on the left, and greenhouse gas emissions, on the right).

The factors that achieve both goals
This important discovery led to a final question: which pasture-based dairy farm systems result in increased productivity and reduced environmental impact?

Here it was found that two aspects are crucial: reducing fertiliser application rates, and feeding less concentrate per litre of milk production, although this should be done while maximising milk production on the available land.

To achieve this requires optimal stocking density, full utilisation of pasture through effective grazing management, and supporting pasture growth with healthy soil rather than fertiliser.

This dynamic is illustrated in the diagram above.

“I believe that as farmers realise that environmental goals are not opposed to economic goals on pasture-based dairy farms, they’ll be willing to put in the effort it takes to produce milk in a more sustainable manner,” says Galloway. – Staff reporter

Email Dr Craig Galloway at [email protected].

Galloway’s PhD research supervisors were: Prof Karen Esler, Dr Heidi Prozesky and Dr Beatrice Conradie.