Soil is the foundation of our life on Earth. A few feet of topsoil above rock or clay makes the difference between a green and blue planet and a grey one. Soil provides us with about 95% of the food we consume, and ensures supplies of clean water, as well as storing carbon and nutrients, and providing a buffer against pollution.Soil takes hundreds of years to form from rock, so taking care of what is there was always seen as essential.The advent of artificial fertiliser in the last century promised a new approach, by providing the three essential nutrients – nitrogen, phosphorus and potassium (NPK) – directly to the soil. Farmers embraced it eagerly, with an immediate rise in fertility in some exhausted soils, but indiscriminate use has effectively undercut its value, mining soils for their nutrients and allowing excess fertiliser to run off and poison waterways.Today, the world’s soils are in danger as never before. According to the Status of the World’s Soil Resources report, from 2015, by the ITPS, at least a third of global soil resources are in poor or very poor condition. The FAO estimates we may have as few as 60 harvests left, so depleted in nutrients have our soils become.The causes for this astonishingly rapid decline are complex. Soil erosion – the washing or blowing away of topsoil by rain or wind – is one key threat. Pollution is another, along with acidification, salinization and the loss of organic carbon in soil. Excess nitrogen in soil, from fertilisers, is the main cause of soil acidification and salinization. It also contributes to water pollution.