Expert spills dirt on declining soil quality

Soil provides us with much of our food.

An international soil scientist claims that, too often, New Zealanders treat "soil like dirt" when it should be revered because "our lives depend on it".

John Baker, noting this year has been declared International Year of Soils by the UN General Assembly, said human life exists because of soil yet all most people do is walk on it, dirty their shoes or dig it up and put buildings and roads on it.

"Soil is a living entity," Dr Baker said. "It provides us with up to 90 per cent of our food. There are more living organisms in a cupful of healthy soil than people on the planet."

"The UN General Assembly has declared 2015 as the International Year of Soils," he said. "If we stopped being complacent we could lead the world in conservation agriculture but it requires recognition and an innovative approach from our politicians before it's too late. The clock is ticking on how many harvests New Zealand has left."

He said figures provided by the UN Food and Agriculture Organisation (FAO) and the UK Farmers Weekly suggest the quality of soil is rapidly diminishing, and FAO predicts the world, on average, has just 60 more years of growing crops left.

Dr Baker said New Zealand's rotation of arable crops and pasture land "gives us more time", but many arable farmers around the world are still "unknowingly but progressively destroying the soils".

"Eventually crop yields will decline to the point where the world's ability to feed its ever-increasing population will be compromised," he said. "Crunch point is expected to be about 2050 by which time there will be famine in some developing countries." Twice nominated for the World Food Prize, Dr Baker doubts the issue is being taken seriously in some quarters.

"Because soil isn't sexy, is not on our radar and is metaphorically beneath us, it's taken for granted by many farmers and ignored by politicians and city dwellers.

"On the other hand there are notable farmers here who value their soil and have stopped ploughing it. Instead, they use low disturbance, no tillage to establish crops and pastures and, in the process, are rebuilding their soil organic matter levels and increasing yields."

Ploughing kills off earthworms and micro-organisms which are an integral element of healthy soil, Dr Baker said.