Dr Jacqueline Rowarth: Is regenerative agriculture really the way forward?

Photo / FIle

Comment: The claims that regenerative agriculture can create nutrient dense food, develop healthy soils, mitigate climate change and reduce impact on waterways need examining, writes Dr Jacqueline Rowarth.

Regenerative agriculture is being presented globally as the way to create nutrient dense food, develop healthy soils, mitigate climate change and reduce impact on waterways. By avoiding synthetic chemicals life will be better.

Pictures of enthusiastic farmers standing in fields of sunflowers are the demonstration that life is good.

While there are undoubtedly benefits that can be achieved through different approaches to production, including regenerative agriculture, the effectiveness of a change often reflects renewed interest by the farmer, and the determination to make a difference.

Whether any one approach can do all that is being promoted by regenerative agriculture advocates deserves examination.

Nutrient dense food, for example, applies to the difference between what leaves the farm, orchard or market garden and what is purchased at the fast food outlet or from the snack aisle at the supermarket.

There is as yet little consistent, scientifically examined data that indicates a significant difference between foods produced on farm (or orchard or market garden) under different production systems.

Dr Jacqueline Rowarth. Photo / Supplied

What makes the difference between organic and conventionally grown fruit and vegetables is cultivar, season and geographical location.

There is evidence to suggest that increased carbon dioxide in the air has allowed plants to increase their carbohydrate content without increasing mineral nutrient content. This applies to all plants whatever the production system. The change is not significant within the context of modern diets.

There is a difference between organically raised meat and milk in comparison with that from grain-fed barn or feedlot animals. The difference reflects access to pasture, which is the norm in New Zealand, whatever the production approach.

Healthy soils are usually associated with the presence of organic matter and soil organisms, which require oxygen and moisture.

Healthy is an emotive term but encompasses many aspects of function which facilitate plant growth and organic matter turnover.

New Zealand researchers and scientists have been investigating soils and pastures for well over a hundred years. Sears and Evans, working at DSIR Grasslands in the 1950s, examined organic matter and the influence of soil fertility on pasture growth.

Pasture management (set stocking or rotational grazing) was also examined, with the benefits of rotational grazing to maintain pasture quality advocated from the 1940s.

Listen to Jamie Mackay interview Dr Jacqueline Rowarth on The Country below

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When pastures are maintained at high quality, animal performance is optimum, and pasture debris (litter) is also high quality. This means high quality food for the soil organisms and rapid turnover of organic matter in the soil when conditions are warm and moist.

It is now recognised that turnover rather than quantity leads to soil benefits – aggregation, friability, structure, drainage, porosity, infiltration - all those factors beloved of soil scientists.

The organic matter turnover also results in release of nutrients in an accessible form – ideally use by more soil organisms or uptake by plants, but also to rainwater leaching.

And carbon dioxide is released to the atmosphere during the process of turnover – the organisms respire. This respiration is part of the balance that means pastures are not a carbon sink unless organic matter is increasing.

Organic matter can be increased relatively easily by increasing inputs, such as increasing grass growth by applying nitrogen and other nutrients, or by overcoming a limitation to grass growth such as drought by applying irrigation.

Decreasing stock numbers whilst maintaining nutrients and water will also increase the potential for organic matter increase, but only if inputs are maintained.

Regenerative agriculture involves Adaptive Pasture Management (called rotational grazing in New Zealand) but allowing the pasture to grow longer and leaving more pasture after grazing than New Zealand research recommends.

The result is a decrease in pasture quality, a decrease in efficiency of production, a decrease in organic matter as soil organisms adjust and then a decrease in turnover.

Professor Tony Parsons, now retired from Massey University, has shown that greenhouse gas and nitrate loss per unit of milk or meat produced will be increased under this scenario in comparison with the New Zealand optimised system.

This means more impact on the environment for a given amount of production. Reducing production means less food.

Farmers who understand their soil, climate, animals and markets, supported by the rural professionals and their processing and marketing companies, have chosen different paths towards sustainability; in some countries overseas, their efforts are supported with subsidies.

People in democracies are allowed to have different views, but farmers making decisions about their businesses usually expect to have evidence upon which to make their decisions.

The conventional New Zealand system is built on decades of New Zealand specific research, developing systems, breeding pasture plants, and identifying the most accurate ways of analysing soil so that the appropriate balance of nutrients can be added.

Ongoing analysis and trials continue to make improvements, and New Zealand soils have far more organic matter in them already than regenerative agriculture has achieved on the impoverished soils where the concept was born.

Success along that path towards sustainability depends upon the ability of the farmer, and New Zealand farmers have done well. It is good farming that makes the difference, not what you call it.

- Dr Jacqueline Rowarth CNZM CRSNZ HFNZIAHS has an Agricultural Science degree from Massey University, with honours in Environmental Agriculture. Her PhD in Soil Science examined phosphate cycling in grazed, hill-country pasture and her research has focussed on nitrogen and carbon in the soil-plant-atmosphere. The analysis and conclusions above are her own. jsrowarth@gmail.com