In order to improve the sustainability of agriculture it is imperative that the P-use efficiency of temperate cereal crops be improved. This can be achieved both by agronomic and genetic approaches. While many studies have demonstrated genotypic variation in P-use efficiency in a number of cereal species the robustness of this genetic variation with variation in environment is rarely considered. In this paper we describe an experiment in which we compare the P-nutrition of winter and spring barley genotypes grown in a field trial with contrasting cultivation treatments (conventional vs. minimum tillage) which have been developed over a number of years. We demonstrate that while there is significant variation between genotypes in their P nutrition that this variation is not comparable between cultivation treatments and only one winter barley genotype (cv. Gleam) has beneficial P-use efficiency traits in both cultivation systems. These data suggest that it may be possible to identify a genetic component to variation in P nutrition in barley but that a large interaction with environmental variables may limit the usefulness of any genes or markers discovered for improving P-use efficiency to the conditions under which the screening was performed.