Comment: Soil scientist Dr Jacqueline Rowarth explores the belief that organic production systems are better for the environment than conventional systems.

New Zealand has relatively little land in organic production systems in comparison with other developed countries. Although this has led to suggestions that adoption should be encouraged, it is important to recognise the nature of our soils (innately phosphorus deficient), the lack of housed animals which could provide nutrient-containing manure, and the lack of subsidies that have supported adoption in the EU.

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This article explores the belief that organic production systems are better for the environment than conventional systems. Whether this is or isn't the case depends upon the food being produced and the environment and soil. It also depends upon the base unit for the calculation – land area or unit of food.

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The Facts

• Organic production systems generally have less impact on the environment than conventional systems when measured on a per hectare basis.

• Organic production systems generally have more impact on the environment than conventional systems when measured on a per Kg of food basis.

• Higher costs of organic food are generally associated with lower yields per unit of land, higher requirement for manual labour, and the greater expense of the natural pesticides and fertilisers allowed.

• Lower yields per unit of land mean that to create the same amount of food as a conventional system, organic production systems require more land than conventional production systems.

• The greatest impact that humans are having on biodiversity (the number of species per unit of area) is through agricultural expansion.

The Concern

The use of synthetic chemicals in food production has been associated with negative environmental impacts. Spray broad spectrum insecticides at the wrong time, and beneficial insects will suffer as well as the pests. Use broad spectrum herbicides and diversity of plants will be reduced, insect forage sources will be limited and bird food might also be restricted.

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Use of fertiliser nitrogen (from whatever source) favours high producing forage plants over less productive species, and applying fertilisers in the wrong form, in the wrong place at the wrong time can result in impact on waterways.

Developments in targeted chemicals (that is, affecting only specific insects, fungi and plants) and precision agriculture have assisted in limiting the effect of anything applied to the target pest or crop.

A recent media article promoting the success of the Netherlands in food production highlighted the importance of measurement and management.

Tomatoes grown organically (no insecticides or fungicides were needed) in glasshouses heated with renewable thermal energy and fed with a nutrient solution (which would rule out organic certification in some countries) were promoted as the future for world food production.

However, tomatoes are not a protein crop, and the Netherlands as a whole has a nitrogen balance of 199kg/ha loss (OECD figure). New Zealand, where animal protein is the main export, has a nitrogen balance of 60kg/ha loss (OECD figure).

Dr Jacqueline Rowarth. Photo / Supplied
Dr Jacqueline Rowarth. Photo / Supplied

The Comparisons

Current estimates are that synthetic nitrogen fertiliser feeds 45-50 per cent of the global population.

Suggestions that organic production systems (where synthetic nitrogen fertiliser is banned) can feed the world have been discredited in the scientific literature.

The fundamental problems are lack of animal manure to provide organic nutrients and the overall yield difference between an organic and conventional system. Estimates of the yield gap range from 20-40 per cent, but can be 0-100 per cent depending on the season, pest attack and the crop under consideration.

Comparisons are dependent on the 'before and after': a poor-performing conventional system might be worse in terms of production and environment than a top-performing organic system.

Good farmers and growers make the difference. In terms of profitability, the premium associated for organic meat and milk sometimes offsets the drop in production, but again, there are many variations.

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

The Calculations

Organic production systems tend to be less intensively managed (fewer inputs) than conventional production systems. This assists with a reduction in greenhouse gases and nutrient loss per hectare in some situations. It also enhances the maintenance of biodiversity.

However, the decrease in yield associated with organic production systems means that any inputs, which include natural products and increased cultivation for crops, are spread over a smaller output. This means that greenhouse gases and nutrient loss per kg of food tend to be higher for organic food than conventionally produced food.

Biodiversity

Although biodiversity tends to be greater in organic production systems than those that are managed conventionally, the biggest difference in biodiversity is between land in production (whatever the system) and native land.

Research has indicated that the greatest negative impact on biodiversity globally is expansion of food production to feed the ever-increasing human population, not the production system involved.

Reassurance

Science and technology continue to make advances for managing food production.

The protein equivalent of the Netherlands tomatoes, for instance, could be insects such as crickets. Although consumers haven't yet embraced the concept of 'cricket bars', advances are being made all the time, including with on-farm and in-orchard management of inputs.

We are feeding more people to a better state of nutrition than at any stage in the past.

Unintended consequences of environmental impact are now being addressed and a one-sized production system will not fit everywhere.

- Dr Jacqueline Rowarth CNZM CRSNZ HFNZIAHS has a PhD in Soil Science and has held various academic and government positions across the environment, agriculture and business spectrum. She has worked on organic and conventional farms in the UK and New Zealand.