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Sustainable agriculture often suffers from a case of lots of theory but not much relevant data to back up how it has worked practically. Trace & Save would like to change that by sharing case studies of how farms have become more sustainable over time through the implementation of good management practices. The farms included in these case studies are pasture-based dairy farms in the South Africa.

Note: This is an updated version of a previous case study, Carbon footprint and productivity case study, which explored carbon footprint data. The reason for the updated version is that we have now collected data from more farms, therefore the data is more robust. This case study also takes a slightly different angle, focussing on how farmers can reduce their carbon footprint.

Dairy cows

Why carbon footprints?

Greenhouse gas emissions, climate change and carbon footprints are global buzzwords. Very simply, excessive greenhouse gas emissions lead to climate change. Climate change is a threat due to the more regular occurrence of extreme weather events (especially drought and flooding), increasing global temperatures (which has many associated issues), shifting climate regions (which means agriculture must adapt), and many others.

A carbon footprint is a simple measure of the amount of greenhouse gas emissions emitted by an entity over a year. The most significant greenhouse gases emitted by farmers are carbon dioxide, nitrous oxide and methane. Doing a carbon footprint for a farm therefore provides an idea of the extent to which the farm is contributing to greenhouse gas emissions, and therefore climate change. From the research I did for my PhD, I showed that the carbon footprint of a farm is correlated to the farm’s profitability1. Simply put, farms which have a lower carbon footprint make more money. This was also shown in the previous case study (Carbon footprint and productivity case study). So having a lower footprint is win-win for farmers and for the environment.

How a carbon footprint works?

A carbon footprint is a yearly assessment which translates all these emissions into carbon dioxide equivalents. This provides a consistent, comparable measure. On dairy farms, the total amount of greenhouse gas emissions, measured in carbon dioxide equivalents, is calculated relative to milk production. The milk production is measured in kilograms of fat-protein corrected milk, which also allows for consistent comparison between farms. For a full description of Trace & Save’s carbon footprint, see Galloway et al. 2018b2.

Aim of this case study

The aim of this case study is to examine how other farm productivity measures are associated with the farm’s carbon footprint. Thereby we can identify what measures and practices are important when aiming to reduce the carbon footprint on a dairy farm. It is very much an updated, simplified version of what was published in Galloway et al. 2018a1.

Case study area

This case study pools all the carbon footprint data in the Trace & Save research database. This includes footprints on farms in the Eastern Cape from 2012 to 2019, and farms in the Western Cape and Kwa-Zulu Natal from 2018 to 2019. For the sake of completeness and comparability, farms which do not include heifers in their yearly data are not included in this case study. There is a total of 182 yearly carbon footprint assessments on 62 farms.

Results

Carbon footprint overview

The average carbon footprint for all 182 observations was 1.58 (range: 1.09 – 3.47) kg CO2e/kg FPCM. I have divided the farms into three relatively equal groups. This provides an indication of what carbon footprint is relatively low, moderate and high on the farms which Trace & Save works on. Table 1 shows this data. Farms with low carbon footprints (i.e. less than 1.40 kg CO2e/kg FPCM) have an average footprint of 1.28 kg CO2e/kg FPCM.

Table 1: Average carbon footprint and number of farms per tercile

Table 1 Carbon footprint case study

Carbon footprint and productivity measures

One of the noticeable results from Table 2 is that, although the carbon footprint is negatively correlated with all three measures of milk production – i.e. the more milk produced per hectare, per cow and per 100 kg liveweight the lower the carbon footprint – the bottom third of carbon footprint observations have lower litres per hectare and litres per cow than the middle third. They do have higher milk production per 100 kg liveweight though. Milk production per 100 kg liveweight is also the most highly negatively correlated to the carbon footprint data.

Concentrates and non-pasture roughage fed in grams per litre (an indicator of feed-conversion efficiency) are positively correlated with the carbon footprint. The more bought-in feed is required to produce a litre of milk, the higher the carbon footprint.

Neither of the fertiliser efficiency figures are correlated to the carbon footprint. The nitrogen applied per hectare is lowest on the top third group of farms, but these are less-intensive farms, as shown by the low milk production per hectare. In terms of nitrogen conversion to pasture, the bottom third has the best efficiency, but there is not much of a difference between the three groups.

Table 2: Average productivity measures per carbon footprint tercile, and correlation of productivity measures to carbon footprint (CF)

Table 2 Carbon footprint case study

Discussion

It has been identified that a carbon footprint of greater than 1.6 kg CO2e/kg FPCM is relatively high, as then a farm would be in the bottom third of all data. This is not bad when compared to the global average carbon footprint for milk production, which was 2.40 kg CO2e/kg FPCM in 20153.

Feed conversion

It is obvious that efficient milk production is imperative to farm productivity. The question is how best to measure efficiency. An increase in milk production per hectare, cow and 100 kg liveweight are associated with a lower carbon footprint. But production per 100 kg liveweight is the most important. Farmers should focus on feed-conversion and cow efficiency, not just aim for the highest production per cow and per hectare – this usually requires excessive inputs (especially concentrates), which is why it results in a higher footprint for the middle third of farms.

Further evidence of this emphasis on feed conversion is that concentrates, and roughage fed per litre are positively correlated to the carbon footprint. Farmers that rely on bought-in feed to produce milk are less efficient and have a higher carbon footprint. The bottom and middle thirds are quite similar, but on farms with the highest footprints, there is an obvious association with poorer feed conversion.

Stocking rate

An important dynamic that largely influences all these factors discussed is stocking rate. I did not include stocking rate in the productivity measures, because it can make it seem as though there is a perfect stocking rate. Unfortunately this is not the case. Stocking rate is something that needs to be figured out on a farm-to-farm basis, and on a year-to-year basis. The ideal stocking rate is the one where each cow on the farm eats their fill in pasture, and all the pasture is utilised effectively. This will lead to optimal milk production from the least amount of bought-in feed. Therefore it is interesting that the farms in the bottom third of carbon footprints, have a lower milk production per hectare than those in the middle third. This can be seen as less efficient, and wasted opportunity to carry more cows and produce more milk, but that extra milk production comes at a cost – it is less efficient.

Fertiliser

The lack of association between the carbon footprint and fertiliser efficiency identifies an area where there is huge opportunity. That it takes more than 16 kg of nitrogen to grow a ton of pasture on average across all the farms is unacceptable. The figure which I have challenged farmers to get below is 10 kg N/ton pasture. There are many farmers who are already achieving this.

Case study: Improving nitrogen fertiliser efficiency

Conclusion

Farmers need to maximise pasture intake. Being able to do so means that farmers need to grow sufficient, good quality pasture. This needs to be done without using excessive amounts of fertiliser though, as this just leads to higher greenhouse gas emissions. Excessive fertiliser also has multiple other negative impacts.

A focus needs to be placed on soil health – this is how farmers can reduce their carbon footprint and make more money. Healthy soils require less fertiliser, while growing more and better-quality grass. Another aspect that needs to be focussed on is correct stocking rates. It does not help to do everything right when it comes to soil health, pasture and grazing management, but then having too many cows on the farms and still needing to buy in tons of feed to get them to produce enough milk.

References

  1. Galloway C, Conradie B, Prozesky H, Esler K. 2018a. Are private and social goals aligned in pasture-based dairy production? Journal of Cleaner Production. 175:402-408.
  2. Galloway C, Conradie B, Prozesky H, Esler K. 2018b. Opportunities to improve sustainability on commercial pasture-based dairy farms by assessing environmental impact. Agricultural systems. 166:1-9.
  3. FAO and GDP. 2018. Climate change and the global dairy cattle sector – The role of the dairy sector in a low-carbon future. Rome. 36 pp. Licence: CC BY-NC-SA- 3.0 IGO. (https://dairysustainabilityframework.org/wp-content/uploads/2019/01/Climate-Change-and-the-Global-Dairy-Cattle-Sector.pdf – Accessed 16 December 2019)
Craig Galloway
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