Scientist’s Dire Warning About Destruction of Soil
Scientist’s Dire Warning About Destruction of Soil
May 19, 2014.
An international soil scientist is calling on the government to focus attention on the most important issue facing the world, soil quality.
Dr John Baker says, while the issues of global warming and water and air quality are frequently debated, soil quality is ignored.
He says 90 percent of our food comes from annually-sown crops growing in soil and, in the next 20-30 years, nations have to find a way of producing more food from the same amount of soil.
“Soil feeds us. It’s as simple as that,” Dr Baker says. “Yet we are pre-occupied with another report on Climate Change while people are going hungry and we haven’t addressed the urgent need to feed another 50 percent of our population by 2050.”
“The government and its ministries can provide leadership on this by recognising how we’ve been raping our soils for years and introduce measures to restore the essential nutrients.”
Dr Baker, who has a MAgrSc in soil science and Ph.D in agricultural engineering from Massey University, says, for generations, the world has been stripping the soil of carbon and organic matter and giving nothing back.
“Every time we cultivate the soil we oxidise some of its carbon and discharge it into the atmosphere as carbon dioxide. We have never made a serious attempt to replace this soil carbon that we’ve removed,” he comments.
“This source of carbon dioxide contributes up to 20 percent of the total carbon dioxide entering the atmosphere each year. Politicians get on the global warming bandwagon but never address one of the main causes that can be reversed.”
Dr Baker explains that carbon dioxide can’t be seen because it’s a colourless, odourless gas. They can see plenty of dust during ploughing and people presume it will settle somewhere in time. But sadly amongst the dust is carbon dioxide that disappears into the atmosphere unnoticed he says.
“The end result is that the organic matter and carbon levels in all of the world’s arable soils have declined cumulatively over the long period that’s elapsed since man began tilling the soil,” he comments.
“Most of the world’s arable soils that, may have had 6-16 percent of organic matter before ploughing, now have 0-1 percent as a result of tillage operations.
“That low level of organic matter won’t support the soil biology which lives on organic matter.”
By soil biology Dr Baker means the microbes and other soil organisms like earthworms that teem in healthy soil. These soil microbes hold the soil particles together and stop it eroding through the exudates they secrete.
They all play a significant part in maintaining healthy soil but they’re being destroyed. Surface microbes decompose crop residue into compounds and elements, especially carbon, that are taken into the soil by earthworms and other soil biology, other microbes fight and destroy common plant pathogens and diseases, mycorrhizal fungi form symbiotic relationships with plant roots that increase the amount of nutrients and water taken up by these roots and still other small animals eat soil organic matter and deposit their excreta as nutrient rich casts.
Dr Baker says the list is numerous but the key question is whether the cumulative stripping of soil organic matter can be reversed.
He acknowledges that spreading lots of organic manure on the ground certainly helps but the world’s arable soils are far too extensive for this to be a total solution.
Even blowing tractor exhaust into the ground doesn’t create a long term benefit because only five percent of the total carbon released into the atmosphere during tillage comes from the tractor exhaust in the first place.
He says plants themselves play an important part in the regeneration of the soil. The sown plants gather carbon dioxide from the atmosphere and combine this with rainfall and the sun’s energy in a process known as photosynthesis.
“The amount of carbon gathered by photosynthesis is massive and it’s nature’s way of recycling carbon,” Dr Baker explains.
“When farmers harvest a food crop like wheat about half of the plant’s carbon is removed as food which is acceptable but the other half remains available for recycling in the form of cut straw, stubble and other forms of crop residue.”
It is this stage of the process that is crucial to regenerating the soil and reversing the rape of its nutrients which will, in turn, lead to increased food production that will feed the world.
Dr Baker is adamant that low disturbance no tillage is the answer.
He emphasises that the residue or vegetation referred to should remain on top of the soil and not worked into it because the carbon gained from the buried organic matter is more than offset by the carbon lost during the working-in process.
A low-disturbance no-tillage drill sows seeds directly into undisturbed soil. It penetrates through the residue to create seed slots. It sows the seed while dropping fertiliser in a separate band at the same time, covers the slot, traps the humidity, preserves the micro-organisms and soil life and prevents most of the carbon from escaping into the atmosphere.
Compared to traditional methods, the crops grow faster and yields can increase by up to 50 percent. This technology also means that failures are greatly reduced when moisture is retained because the no-tillage drill only minimally disturbs the soil.
“The key fact is that such machines exist. Anything less will simply perpetuate the continued rape of our soils and will eventually lead to famine in some areas of the world with marginal food supplies,” he says.
In calling on the government to focus attention on preserving and restoring the quality of soil, Dr Baker says scientific research should monitor soils already undergoing true low-disturbance not-tillage regimes – some for more than 10 years – to estimate how long it will take to get the world’s arable soils back into full health and production.
Some have already achieved that status he says.
Dr Baker, who was a finalist in the 2013 World Food Prize, has recently appeared on BBC radio talking about how healthy soil can feed the world.