New culture medium containing ionic concentrations of nutrients similar to concentrations found in the soil solution.

A new growth medium which closely approximates the composition of the soil solution is presented. This soil solution equivalent (SSE) medium contains the following components (millimolar): NO(3), 2.5; NH(4), 2.5; HPO(4), 0.005; Na, 2.5; Ca, 4.0; Mg, 2.0; K, 0.503; Cl, 4.0; SO(4), 5.0; ethylenediamine-di(o-hydroxyphenylacetic acid), 0.02; and MES [2-(N-morpholino)ethanesulfonic acid] (to maintain the pH at 6.0), 10, plus 0.1% arabinose. The advantages of the SSE medium are discussed.