Asda has teamed up with LEAF to produce a booklet designed to help farmers improve their soil health.

Simply Sustainable Soils sets out six steps for farmers to improve the performance, health and sustainability of their land.

It covers physical health, drainage, compaction, ­nutrient balance and exchange, soil PH and nutrients, and biological health.

Asda saw the farmers it worked with as partners, said Chris Brown, head of sustainable sourcing. "The challenge of stewardship of natural resources has to be met by co-operation."