with Peter Burton
Functional Fertiliser Ltd
Soil carbon has been given the ‘too hard to measure’ label, and therefore dismissed in the debate on the future of farming. And that’s wrong, because it is fundamental to our survival.
The most valued soils are the deepest blackest soils because they are the most productive. In any farming district land close to river mouths, or deep volcanic soils, are the most sought-after.
Carbon exists in various forms in the soil. Carbon from recently-deposited dung, old leaf and root, is easily lost. However, as digestion proceeds it becomes increasingly tightly held in the soil. Humus, by definition, is what remains after the digestion process is complete and carbon in this form is resistant to loss.
High carbon content soils are sought due to their ability to produce food. They hold more moisture and nutrient, releasing it steadily over time as required by plants, ensuring increased production of higher quality.
Deep black soils are more friable and less prone to compaction, allowing plant roots to penetrate further accessing the moisture and nutrient necessary for strong growth even during periods of dry weather.
The quickest way to sequester carbon is under permanent grazed pasture. Actively growing plants suck in carbon dioxide, release oxygen to the atmosphere with the carbon portion stored in the soil.
During the last 30 years Central Plateau sand soils with little topsoil have developed into highly productive pastoral land producing more than 14 tonne of dry matter per hectare annually.
Animals are an essential component in the cycling of carbon, the building of topsoil, and the development of humus. Without grazing the speed of nutrient cycling slows dramatically, with little carbon sequestered.
It is as the result of decades of intensive grazing that topsoil has been built, food produced, and communities developed – yet many pastoral farmers are now feeling isolated from and rejected by the wider community.
Why, if pastoral farming is the best means of reducing atmospheric carbon dioxide, with nitrous oxide and methane becoming environmentally insignificant, could this have happened?
Could there be another influence? Our view is the consequences of 400,000 tonnes of urea applied annually to our most productive land ought to be examined.
Pasture production in the Waikato has steadily declined from 18 tonneDM/ha prior to the use of nitrogen to 14 tonne today, and in our view excess nitrogen is the likely culprit.
Research by Louis Schipper and his team at Waikato University shows in intensive lowland livestock systems – for example, dairying – soils have lost organic matter by an average of 1 t carbon/ha/yr during the last 20-30 years.
More recent research by Landcare Research shows all irrigated land throughout the country is losing carbon.
It is now argued that to preserve the existing carbon reserves, animals should be removed, and trees planted. The consequences to communities and national income would be catastrophic.
However, there is a home-grown solution that when embraced will position this country once again at the leading edge of sustainable pastoral farming.
It’s been practised by farmers throughout the country for more than 15 years, and the data supporting its effectiveness is not disputed. More importantly, these farmers are enjoying steadily increasing production and lower overall costs.
The soil fertility part of Functional Farming Systems is, to some, surprisingly conventional. Phosphorus, sulphur, and potassium where required are non-negotiable with inputs calculated on historic MAF removal data.
The difference is that nitrogen fertiliser is not a requirement. Pasture yield is often 30% higher with plants more pest and disease resistant.
To maximise the benefits, changes to grazing management are required. Calving and lambing dates are a little later with high-quality supplement, made from genuine summer surplus, used to plug the early-season feed deficit.
Per animal production lifts due to the increased energy content of the feed, nitrate poisoning is unheard of, and animal fertility gains are ongoing.
With Nitrate-N losses to ground water measured at 70 per cent less than those from a conventional high-N operation, the system provides pastoral farmers with the ability to secure their long-term future, leaving their land in a healthier more productive state for those that follow. For more information, call Peter on 0800 843 809.