Skin of the Earth

Crop fields and housing

Using every inch. How do we keep people fed as populations explode and good farmland dwindles?

22 March 2018 by Julia Horton

It might be easy to dismiss the earth beneath our feet as just so much dirt. But without it humankind would not exist.

As former US president Franklin D Roosevelt once said:

"The nation that destroys its soil destroys itself."

He was speaking in the 1930s after years of severe drought and relentless winds turned states across America into the 'dust bowl'. The notorious disaster wiped out crops and livestock and forced countless families across America to abandon their farms.

More food, less land

Nearly a century on and the climate remains a huge threat to agriculture and survival around the world. But now exploding populations are challenging the world to keep more people fed using less - and less good quality - land. The problem is perhaps most stark in China, where millions of people have been leaving the countryside to move into rapidly growing cities spreading onto former farmland. The vast influx is creating serious environmental challenges "from soil erosion to increased use of contaminated land" as food production expands in growing urban areas.

A planetary 'skin'

NERC experts stress that it is not just soil that matters, it's what they call the Earth's critical zone. This is the vital area from the bedrock up to the tree tops. Likened to a 'planetary skin' on which human life depends, it contains, along with soil, vital rocks, air, water and organisms.

In the right balance they collectively sustain life by providing clean air and water, food and renewable energy.

NERC scientists and colleagues at the National Natural Science Foundation of China are working together on a joint £10 million project entitled the Critical Zone Observatory programme. It was set up to find out how to produce enough food to meet demand in a sustainable way.

Too much of a good thing

One of the problems has been high use of chemical fertiliser. Professor Tim Daniell, chair in soil microbiology at the University of Sheffield and research leader in soil ecology at Scotland's James Hutton Institute, is working on a solution using animal manure in Ningbo, one of the fastest growing cities in the Yangtze Delta.

Tim said:

We use fertilisers to replace nutrients in the soil as they are used by plants for growth, but in China they often apply too much fertiliser because it has been subsidised by the government there and there have been some issues with farmers not being fully aware of the possible risks.

Too much fertiliser can increase nitrogen in the soil to toxic levels. Producing fertiliser in factories requires a lot of energy and also creates greenhouse gases. If too much fertiliser is used, it can leach into rivers where it pollutes the water, or create more greenhouse gas emissions.

Is pig poo the answer?

The project Tim is working on involves trialling organic fertiliser from pig slurry as a more sustainable alternative to chemical fertilisers for growing wheat, rice and vegetables.

Ploughing back animal waste into fields creates a cycle of food production from plant to animal and back again, which is more efficient. But it is not without it's problems either; it could transfer potentially harmful bacteria from animals to humans and there are other things to consider too. Tim said:

While it might be sensible to use an organic fertiliser like pig slurry because you're not wasting that resource, the risks might include adding contaminants which you don't want in a crop, such as heavy metals like zinc or pharmaceuticals from drug treatments given to livestock. These can build up and might become harmful to people eating food produced from treated crops. They could also drive antibiotic resistance. The question is, if you did that for 100 years would you be creating a problem? We're trying to find a balance between opportunity and risk.

It is too early for any results, yet since the work began about a year ago, but the need for answers is clear. Tim concluded:

I think working out how to provide food sustainably as populations rise is the major challenge facing our society today.

Digging up the facts on soil

  • It takes an estimated 500 years to produce about an inch of topsoil, which is the most productive layer of earth.
  • A handful of soil contains more microorganisms than there are people on the planet.
  • Soil can provide all the nutrients which plants need to grow. Fertiliser is added to replace those nutrients as they are used up by plants.
  • Soil consists of 45% minerals, 25% water, 25% air and 5% organic matter.
  • Roughly 10% of the world's carbon dioxide emissions are stored in the soil.

Decades of NERC research has led to ways farmers can increase the number of pollinators on their intensively farmed land to increase yields, income and biodiversity.

Benefits include UK schemes that created 11,000 hectares of habitat for pollinators with low‐cost seed mixes providing wildflower food for pollinators. These interventions have been shown to increase the number of different types of pollinators, and farms that take part see between seven and nine times as many of them overall.

Keeping up with demand

It is predicted that 60% more food will be needed worldwide by 2050 to feed the expanding global population. The government has announced £90 million of new funding to help businesses, researchers and industry to transform food production. Find out more at the GOV.UK website - external link.

The formation of this programme was supported by UK Research & Innovation China.