Phosphorus Fertilization and Fungal Inoculations Affected the Physiology, Phosphorus Uptake and Growth of Spring Wheat Under Rainfed Conditions on the Canadian Prairies

<jats:title>Abstract</jats:title><jats:p>Some fungal species have been shown to improve plant growth under drought conditions and to increase plant phosphorus (<jats:styled-content style="fixed-case">P</jats:styled-content>) uptake from the soil. How moisture limitation, <jats:styled-content style="fixed-case">P</jats:styled-content> availability and fungal inoculation interact to affect plant physiology and growth is, however, poorly understood. Here, we studied the combined effects of fungal (arbuscular mycorrhizal fungi (<jats:styled-content style="fixed-case">AMF</jats:styled-content>) or <jats:italic><jats:styled-content style="fixed-case">P</jats:styled-content>enicillium</jats:italic> spp.) inoculations and phosphorus (<jats:styled-content style="fixed-case">P</jats:styled-content>) fertilization (0, 45 and 90 kg ha<jats:sup>−1</jats:sup>) on the net rate of photosynthesis, water‐use efficiency, <jats:styled-content style="fixed-case">P</jats:styled-content> uptake and growth of spring wheat (<jats:italic>Triticum aestivum</jats:italic> var. Superb) under field conditions at two locations (<jats:styled-content style="fixed-case">C</jats:styled-content>astor and <jats:styled-content style="fixed-case">V</jats:styled-content>egreville) in <jats:styled-content style="fixed-case">A</jats:styled-content>lberta, <jats:styled-content style="fixed-case">C</jats:styled-content>anada. Both fungal inoculation and P application increased the rate of photosynthesis. Under the same <jats:styled-content style="fixed-case">P</jats:styled-content> level, <jats:styled-content style="fixed-case">AMF</jats:styled-content> inoculation had a greater positive effect on the rate of photosynthesis than <jats:italic><jats:styled-content style="fixed-case">P</jats:styled-content>enicillium</jats:italic> inoculation. The <jats:styled-content style="fixed-case">AMF</jats:styled-content> inoculation increased the instantaneous water‐use efficiency (<jats:styled-content style="fixed-case">WUE</jats:styled-content>i) of plants at <jats:styled-content style="fixed-case">C</jats:styled-content>astor, but not at <jats:styled-content style="fixed-case">V</jats:styled-content>egreville. Leaf carbon isotope discrimination (<jats:styled-content style="fixed-case">CID</jats:styled-content>, Δ<jats:sup>13</jats:sup><jats:styled-content style="fixed-case">C</jats:styled-content>) increased with the rate of P application but was not affected by fungal inoculations. Phosphorus concentrations of stem and seed increased with both fungal inoculation and P application irrespective of location, with <jats:styled-content style="fixed-case">AMF</jats:styled-content> inoculation showing the largest effects. The interaction between P addition and fungal inoculation was significant for stem P concentration in Vegreville. Both fungal inoculation and P application increased the leaf area index (<jats:styled-content style="fixed-case">LAI</jats:styled-content>), biomass production and grain yield at both locations. Under the same P level, <jats:styled-content style="fixed-case">AMF</jats:styled-content> inoculation had a greater positive effect on <jats:styled-content style="fixed-case">LAI</jats:styled-content>, biomass production and grain yields than <jats:italic><jats:styled-content style="fixed-case">P</jats:styled-content>enicillium</jats:italic> inoculation. Morphological characters such as spike length and kernels/spike were also improved by fungal inoculation and P application at both locations. We conclude that the studied sites were deficient in P availability, and both fungal inoculation and P application improved P uptake and crop productivity, while the effect of fungal inoculation on water‐use efficiency was site specific.</jats:p>