At a commercial tree nursery near Evans, western Louisiana, 5m pine seedlings are packed on to 12 vast circular irrigation tables, each as wide as a football field. Last September, many of these young trees were sprayed with what looked like muddy water.
The substance was in fact a liquid extract teeming with hundreds of species of wild soil fungi. Brad Ouseman, the nursery manager, is confident he will see results from this fungal inoculation, which is intended to improve yields and reduce the need for artificial fertilisers.