Wednesday, 5 August 2020
Regenerating New Zealand pastoral agriculture
I have worked in agricultural research and development in the area of nutrient cycles (soil/plant/animal) for over 40 years and in that time have also seen cycles of interest both from farmers and non-farmers in the way farming in New Zealand should be conducted. From biodynamic to organic, ecological to biological, conventional to industrial, all have their proponents and their detractors. The latest one that has fired people’s imaginations is regenerative agriculture.
The concept and genesis of regenerative agriculture
According to Regeneration International’s website, regenerative agriculture (RA) “not only does no harm” to the land but improves it, using technologies that regenerate and revitalise the soil and environment. This is said to lead to healthy soil, capable of producing high-quality, nutrient-dense food while simultaneously improving rather than degrading land, and ultimately leading to productive farms and healthy communities and economies.
Encompassing the principles of permaculture, organic, biodynamic and biological farm practices, this evocative discourse would strike a chord with any thinking person and is laudable.
The push for RA in New Zealand is predicated on the assumption that the current practice of agriculture here is somehow broken and has degraded our soils to the extent that they need significant regeneration. The push is baffling, seemingly more directed at pastoral farming, rather than arable or commercial vegetable production, where some of the concerns about soil degradation may be more relevant.
Like many things, Covid-19 included, this concept of the need for regeneration has been imported from overseas. Farmers on the American Great Plains learned that continual deep ploughing and removal of the dryland grasses caused huge losses of topsoil, by wind erosion, which had turned to dust when the droughts of the 1930s hit.
Soil degradation is no laughing matter, with continuous cultivation for arable cropping still occurring in many countries today, including New Zealand. The resultant loss of soil organic matter and mechanical intervention results in decreased soil structure, moisture retention and increased nutrient loss and compaction. American scientists have warned that there are only 60 harvests left globally if the degradation is not reversed, while in 2014, United Kingdom scientists warned there were only 100 harvests left in UK-farmed soils.
In my experience, our farmers are constantly evolving their farming systems as new science, new technology and new genetic material (plant and animal) becomes available to them. Despite the political, social and climatic changes, they continue to produce quality food in an environmentally and economically sustainable way.
Grazed pasture is the biggest agricultural land use here and while our pastoral farmers do not necessarily do everything perfectly, just how does our current conventional system compare with the concept of RA?
Principles of regenerative agriculture
There are five core principles of RA; minimising soil disturbance, maximising crop diversity, keeping the soil covered, maintaining living-root systems year-round, and integrating livestock.
1. Minimise soil disturbance
Disturbing soil has profound effects on the soil microbial community because not only does this disrupt their habitat, it also leads to loss of carbon from organic matter that the soil biology uses for energy.
Permanent pastures are at the heart of our animal grazing systems and as such, most of the farm area for most of the time is not cultivated. Some summer and winter forage crops are sown to ensure animals are fed well either over the dry summer or cold winter periods, followed by pasture renewal. Soil disturbance here can be minimised by using direct drilling and minimum tillage.
A comparison of an arable soil and a 38-year grazed and fertilised pasture soil at the Winchmore Research Centre in Canterbury showed that the microbial biomass carbon and organic carbon was 45% less in the arable soil.
2. Maximise crop diversity
One of the often-repeated claims of alternative approaches to pastoral agriculture is that the conventional system only uses a ryegrass monoculture. Anyone who has walked through permanent grazed pastures will observe that in fact they consist of a large variety of grasses, legume and other species. Farmers have learnt that the classic ryegrass/white clover pasture does not universally flourish in the jumble of different soils and climates that are part of pastoral farming in New Zealand, having long planted lucerne, plantain, chicory and other specialist crops as part of their system to feed their stock.
The RA proponents claim that there should be between 15 to 30 different species (as claimed occurs in nature, although no natural grassland in the world has this number of species evenly intermixed) sown together to provide diversity both for animal nutrition and to ‘feed’ the soil microbiome. Sowing multiple species together may work well for the first year in terms of maximising the diversity of species but climate, management and grazing behaviour will conspire to favour the more adaptive and aggressive species so that fewer species will prevail and will be separated rather than evenly mixed, based on which of the microclimates within a paddock favours them.
3. Keep the soil covered
A permanent pasture sward is the basis of New Zealand pastoral agriculture, albeit with a limited amount of other specialist forage crops and pasture renewal. Provided that minimum tillage practices are employed, this means soil is covered with living plants almost all year round.
4. Maintain living root year-round
Maintaining living roots in soils not only helps hold topsoil in place against wind and water erosion, but also the root exudates from plants help form soil structure and provide an energy and nutrient source for soil micro-organisms. In permanent pastures this is a given. The pastures exist year-round and year-on-year their root systems are in a constant cycle of growth and renewal – from initiation to death and decay.
5. Integrate livestock
The RA concept of adaptive multi-paddock grazing is what conventional farmers call rotational grazing, adopted in the 1960s and 70s when scientists and farmers demonstrated the productive benefits of the practice. The only difference between the two seems to be that under RA more residual herbage is left after grazing.
Proponents claim that this practice adds large quantities of organic matter (OM) to soils. However, pastoral soils under long-term conventional grazing also accumulate large quantities of OM, with 30-60t OM/ha in the top 18.5cm in semi-arid Central Otago soils and up to 175-300t OM/ha in the volcanic soils of Taranaki, Waikato and the Central Plateau. This has accumulated over decades through the processes of litter return, root turnover and dung deposition by grazing animals. In one recent review, soil carbon increased by 13.7t C/ha on recent conversion from woody vegetation to long-term grazed pasture.
Opinions and facts
The major differences between RA and conventional pastoral agriculture appear to revolve around fertiliser and agchem use, the number and diversity of species and grazing management.
Claims that the RA concepts will lead to healthier soils, higher productivity and better environmental outcomes are yet to be proven in New Zealand pastoral systems. In order to be true to the principles of RA any farmer converting, in my opinion, will be required to de-intensify their farm, which will have ramifications for economic viability unless the consumer is prepared to pay large premiums for any credence attributes they believe the produce will have. Studies have shown that while deintensification may reduce greenhouse gas emissions and energy requirements, sustainable intensification is input efficient (amount of food produced per kg of input) with less land area required and acidification and eutrophication potential all lower than extensive production systems. There are many ways to farm and we should always examine the merits of new ideas and concepts to improve current practices.
There are some obvious synergies between RA and pastoral farming but imposing ‘systems’ based on belief and/or values, however well-meaning, rather than robust science, could result in unintended environmental consequences. It could also have a negative impact on the profitability of individual farm businesses and the national economy. As Senator Patrick Moynihan famously said, “Everyone is entitled to their own opinion but not their own facts.”