A recent E-coli outbreak is thought to have been caused by contaminated salad leaves. There have been over 200 confirmed cases of food poisoning across the UK caused by e-coli bacteria found in manure, with nearly half those affected admitted to hospital. So how does the bacteria get into the salad, and what are farmers doing to prevent it?

As part of our week looking at salads, we visit Evesham Vale Growers in Worcestershire, where they grow 500 acres of spring onions outside and some 70 acres of premium tomatoes in glasshouses. Alongside salad production, they grow crops including maize and wheat to feed anaerobic digesters for gas and electricity, and there's a solar farm. Some of the gas and electricity is used to heat and light the glasshouses - insulating them somewhat from fluctuating energy prices.

The Soil Association, which campaigns for sustainable and organic food and farming, has published it's list of demands in the run up to the election. It wants the next Government to 'grow green jobs' by backing sustainable British farming and protect the NHS by supporting healthy and sustainable food.

Presented by Anna Hill Produced for BBC Audio in Bristol by Heather Simons