Residue is the Salvation of the Soil

“This system is strongly carbon-positive. It is capable of reversing the carbon-stripping process because it mimics nature’s method of removing CO2 from the atmosphere and putting it back into the soil (called sequestration). No other method of drilling does this as effectively and certainly not conventional tillage or ploughing.”

Malcolm Hopwood interview with Dr John Baker, July 2015

International soil scientist, John Baker, is appalled every time a farmer burns the stubble or crop residues on top of the ground in preparation for sowing another crop. Dr Baker was in Victoria and South Australia in July, and was a guest speaker at the 13th annual Vic No-Till Conference.

He says that from a soil health point of view, burning is “the worst thing that can be done and it happens too frequently in New Zealand and Australia.” “I know there are arguments about weed and pest control in favour of burning, but there are other ways of dealing with these issues and the benefits from accumulating soil organic matter trump weed and pest control every time.”

Crop residues are the salvation of the soil he argues. Dr Baker, who’s based in New Zealand, says residues, whether standing stubble, lying straw or chaff, increase the soil’s water holding capacity and are the food stuff of soil microbes, which, in turn, build soil structure, increase the supply of nutrients and form beneficial symbiotic relationships with plant roots that increase uptake of nutrients.

His message to Australian farmers is “don’t put a match to it or even plough it in, leave it to decompose on the surface of the ground to enrich the soil without disturbing it.”

Dr Baker says, over the last 50 years, crop yields have plateaued or even declined in arable countries like Australia despite advances in other agri-technologies because soil is losing essential organic matter due to conventional tillage (and even minimum tillage) where residue is burnt, baled of buried.

“This soil organic matter is the most influential factor in storing water,” he says. “For example 1 kg of humus stores as much water as 9 kgs of clay.”

“Australian crop yields are more dependent on soil water than any other single factor because high temperatures and sunshine hours remove soil water at such a fast rate. It is therefore crucial for the soils in the driest continent on earth to store as much water as possible,” he comments.

Dr Baker explains that soil water is gained from either irrigation or rainfall and storing it is greatly enhanced by enriching the soil’s organic matter through retaining the crop residues from the previous crop on top of the ground and using low disturbance no-tillage to drill seed and fertiliser directly through this mulch into the soil.

“This system is strongly carbon-positive. It is capable of reversing the carbon-stripping process because it mimics nature’s method of removing CO2 from the atmosphere and putting it back into the soil (called sequestration). No other method of drilling does this as effectively and certainly not conventional tillage or ploughing,” he says.

“Low disturbance no tillage specialises in sequestering carbon and rebuilding the carbon levels of soil.”

Dr Baker points to a ticking clock where, through a decline in the quality of soil, Australian crop yields will fall to lower levels than they are now and the agricultural economy of the country and the quality of life of its people will suffer.

“Countries that depend on Australia to supply them with grain such as wheat will see a noticeable reduction in supply which will have a dramatic effect on the availability of food in a world where the demand for food is expected will double by the year 2050.”

And this when the per-capita supply of arable land globally has decreased by more than 25 percent in the past 22 years, according to Dr Rattan Lal at Ohio State University.”

Dr Baker, who has a MAgrSc in soil science and PhD in agricultural engineering from Massey University, New Zealand, says the mindset of farmers must change from treating straw and stubble as a liability to be disposed of one way or another, to using it as an asset that can enrich the soil. “After all, crop residues comprise up to 50% of the investment that farmers make in growing each crop in the first place. So why waste 50% of that investment?”

His own Cross Slot® no tillage drills are sold in 18 countries and used extensively in the US and Canadian plains, in Australia and the Europe, where they regularly drill through 10+ tonne wheat residues with ease.

The process penetrates through the crop residue on top of the soil and sows seed and fertilise in separate bands beneath it, causing minimal disturbance to the soil, trapping the humidity, preserving the organisms and soil life, largely preventing carbon from escaping and increasing yields.

Dr Baker has twice been nominated for the World Food Prize and the science that underpins the design of his machinery has been endorsed by the United Nations’ Food and Agriculture Organisation (FAO) and USDA.