Discipline: environment; Keywords: GHG, nitrogen use efficiency, phosphorus, mixed pastures, soil health.
This is a summary of results reported by Dr Craig Galloway (see reference below) of farms where there have been improvements in the carbon balance and other parameters as indicated by data collected between 2013 and 2019. Some of the farms have data for all the years, whereas others only have data for two of the years. All improvements indicated are the most recent data relative to the baseline, which is the first time the assessments were done. The farms are pasture-based dairy farms in the Eastern Cape (Tsitsikamma, Oyster Bay, Humansdorp, Cookhouse, Cradock and Alexandria).
The improvements in soil carbon levels, reduced carbon footprint and improved nutrient use efficiency (which should reduce pollution) are the result of implementing various combinations of sustainable, regenerative farming practices. These include rotational grazing management, which builds soil carbon and reduces the need for supplementary feed; utilizing multispecies pastures, which improve pasture quality and improves soil health; reducing nitrogen fertilizer application rates, which is possible through improved soil health and further improves soil biology, and improved animal selection practices, which increases productivity and feed conversion.
Soil carbon: There are 30 farms where the carbon levels have increased in the 0-15cm profile of the soil from the baseline to their most recent measurement. The average baseline soil total carbon level was 2.2%, whereas the current average total soil carbon levels on these farms is 3.0%, an improvement of 36%.
Carbon footprint: There are 21 farms where the carbon footprint has improved. The improvement was from a baseline of 1.73 kg CO2 e/kg fat and protein corrected milk (FPCM) to a most recent footprint of 1.45 kg CO2 e/kg FPCM, an improvement of 16.2%.
Mineral balance: There are 18 farms where the nitrogen use efficiencies have improved. This implies that the amount of excess nitrogen, which can result in pollution of the atmosphere and water sources, has decreased and as a result these farms have a lower environmental impact than during their baseline year. On the 18 farms the average nitrogen use efficiency has improved from 28% to 36%, an improvement of 29%. The nitrogen fertilizer application rate has also improved from 263 to 201 kg N/ha/year, an improvement of 24%. This improvement should also reflect in the input costs.
In addition, there are 16 farms where the phosphorous use efficiencies have also improved. This implies that the amount of excess phosphorous, which can result in pollution of water sources, has been reduced and as a result these farms have a lower environmental impact than their baseline year. The average phosphorous use efficiency has improved from 33% to 43%, representing an improvement of 30%.
It is clear that implementation of sustainable regenerative principles result in both economic and environmental benefits which dairy farmers who are not currently implementing these practices, should seriously consider.
C. Galloway, 2020. Trace and Save data base, Humansdorp March 2020. See also: The carbon balance on dairy farms. http://traceandsave.com/the-carbon-balance-on-dairy-farms/