Dairying and its environmental impact

In addition to the over-application of nutrients from water-soluble and non-bio-friendly fertilisers, it is nitrous oxide (N2O) emissions with high global warming potential and close association with dairying that should be our focus in terms of greenhouse gas emissions.

I wonder if we are given entirely the right messages about the other two greenhouse gases – carbon dioxide (CO2) and methane (CH4). While there are many contributors to CO2 in the environment, CO2 is a molecule necessary for photosynthesis.

Its removal from the atmosphere is, however, significantly reduced by the extensive removal of forests in South East Asia, Brazil, Central America, and Central Africa. The reduction of atmospheric CO2 is also lessened by the reduction of the photosynthetic capacity and photosynthetic rate of pastures by overgrazing and by limiting the dry matter production on farms. And we wonder why CO2 levels are increasing.

Methane necessary

Methane is rapidly broken down in the atmosphere by hydroxyl radicals photo-oxidising CH4 to CO2. Moist air above pastures can photo-oxidise 100 times more CH4 than what is able to be produced by the soil or animals grazing that area. Methane is also a necessary requirement of methanotrophic bacteria in the soil which take up and oxidise CH4 from the atmosphere.

While the government is currently spending millions of dollars a year on research and projects to counter agricultural emissions to reduce GHG emissions, methane emissions for example can be slashed by up to 99 per cent by simply adding seaweed (Asparagopsis taxiformis) to the cow’s diet. This highlights the importance of diet in mitigating GHG emissions, something that is not given the recognition and funding it deserves.

The emissions of NO2 can also be significantly reduced by reducing the nitrate-nitrogen/crude protein content of pasture and increasing its energy level (sugar/carbohydrate content), providing the rumen microbes with the energy required to convert the ingested feed into milk, meat and fibre.

Supplement reliance

While grass-fed animals are by far the cheapest form of pastoral agriculture, we are developing an increasing reliance on high-cost supplements because we’re not presenting the cow with high- energy pastures with the appropriate nutrient content.

As a consequence, only 20 per cent of the protein in the herbage is utilised while 80 per cent converts to ammonia which is subsequently emitted as N2O into the atmosphere and as N-rich urine into the groundwater and waterways. The N conversion efficiency (Kg MS per kg N leached) is very poor. This is something we could easily fix by simply ensuring the soil and plant has a good nutrient balance, including having good levels of the key sugar-making elements.

The bottom line is we need to protect our environment and ‘clean green image’, our tourism and recreational industry, and ensure our farmers are profitable with secure markets producing quality food products.

There are effective ways to achieve this but do we have the industrial and political will to implement effective change? Will vested interest groups continue to compromise the profitability and the environmental footprint of dairy farmers by selling them nutrients they do not need and in water-soluble and non-bio-friendly forms? Will we continue to try and address the symptoms of our high environmental footprint rather than the cause?


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