What is the source of soil carbon ?
The source of soil carbon is plant matter, be it roots, leaves, stems or grain. The largest contribution comes from roots.
Litter from the above-ground plant parts has to be incorporated by either mechanical tillage and/or soil organisms, such as fungi, bacteria and worms. Without tillage, surface litter is broken down mainly by fungi and is incorporated to a shallow depth by worms. With tillage, bacteria are activated, but a large proportion of roots and their associated soil biota are broken apart, exposed and degraded or killed by ultraviolet radiation and desiccation. As well, tillage manages to incorporate only a small proportion of surface litter.
For a very wide range of agricultural plants, roots constitute about 30 per cent of total plant weight, and for many grain crops, the weight of roots is about the same as the weight of grain produced. Hence, as the mass of roots increases, so does productivity.
How is soil carbon increased and preserved in soil ?
The most efficient and effective way of building soil organic matter and soil carbon is to facilitate the growth and in-situ breakdown of roots by creating a root zone environment that is loose, aerobic and moist. Such an environment will enhance root growth and the population of soil organisms in the rhizosphere and, thus, soil carbon. It will also enhance the level of soil nitrogen.
The best means of preserving soil carbon is to create a root zone environment that facilitates both root growth and its preservation, or at least conservation, and this can only happen if there is a form of tillage that loosens soil by severing roots at depth and lifting, opening and dropping soil without inversion or destruction of the structure of the root systems. Such a form of tillage will ensure all the root systems and the by-products of their decomposition, both organic and inorganic, remain in the soil.
How does Deep Seedbed Conditioning increase soil carbon ?
The patented Deep Seedbed Conditioner (DSC) machine was deliberately designed to deepen (to 250 – 300 mm), and loosen root zone soil without inversion or horizontal displacement and to sever roots at this depth without tearing them. It was also designed to minimise draft and soil disturbance. In consequence, the DSC machine has a low energy requirement and its operation can be done at a relatively high speed (equivalent to no-tillage seeding) (Figure 1).
Over many years of field-scale testing the deeper, loose root zone created by DSC soil management has been shown to increase and deepen the root mass of cereals, maize and canola crops by at least 30 per cent (Figure 2), and in consequence, increase soil carbon by 48 per cent (Figure 3a) and increase total soil nitrogen by 34 per cent (Figure 3b). It also produced an average field-scale increase in grain yield of 25 per cent from cereal, maize and canola crops, rainfed and irrigated, over 24 cropping seasons, and a wide range of soils.
How is Deep Seedbed Conditioning able to increase root growth ?
The deeper, loose root zone created by DSC soil management is conserved to the point of being preserved by a pre-seeding pass with the DSC machine. The retained root structures act as reinforcing mesh to minimise, to the point of completely eliminating, any consolidation during and between crops. Such deep, loose root zones allow plant roots to proliferate without restriction and easily access more water and plant nutrients.
Will DSC increase soil carbon more quickly than any other practice ?
The increase in the depth and amount of root growth facilitated by DSC soil management is large, immediate and is replicated each cropping season. The size, immediacy and annual replication of the increase in root growth and soil carbon that has been measured in DSC managed soils is unrivalled amongst published research and observations. Furthermore, its statistical significance has been measured against no-tillage crop establishment, the current industry best practice standard.
Is DSC eligible for the Carbon Farming Initiative ?
Deep Seedbed Conditioning soil management will undoubtedly make carbon farming profitable. Over a 100 ha paddock, the measured increase in organic carbon over that in no-tillage areas in the same paddock was equivalent to 93.3 t / ha / 0.3 m depth of Australian Carbon Credit Units (CCUs). At the February 2022 Australian CCU price of AUD 54.5, this amounts to $ 5,085 / ha.
The practice of DSC soil management is not yet explicitly mentioned in the Australian Government’s Carbon Farming Initiative, but it clearly fits the category of a Sustainable Intensification project, and action is underway to have it officially recognised as such.
Note: Since posting this Blog the Clean Energy Regulator has OFFICIALLY approved DSC as an eligible practice for the Carbon Farming Initiative.
Details of recommended DSC machine manufacturers and field-scale research data supporting all the claims of improved soil conditions and productivity can be found by visiting the website of Maximum Soil and Water Productivity Pty Ltd at https://maxswp.com.au