Residue is the Salvation of the Soil

Residue is the Salvation of the Soil

July 13, 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 says from a soil health point of view, burning is “the stupidest thing that can be done and it happens too frequently in New Zealand and Australia.”

While Dr Baker acknowledges there are arguments in support of burning to control weed and pests, there are other alternatives “and the benefits from accumulating soil organic matter trump weed and pest control every time.”

Instead crop residues are the salvation of the soil he argues. Dr Baker 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 to increase the uptake of nutrients.

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

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

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, crop yields will fall to lower levels than they are now and the agricultural economy of Australia, in particular, 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 to double by the year 2050.”

“And this when the per-capita supply of arable land globally is diminishing. It 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 Ph.D in agricultural engineering from Massey University, says the mindset of farmers must change from treating straw and stubble as a liability to be disposed of one way or the other to using it as an asset that can enrich the soil.

“After all crop residues comprise up to 50 percent of the investment that farmers make in growing each crop in the first place so why waste 50 percent 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, the UK and Europe where they regularly drill through 10+ plus tonne of 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.

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