Yield and phosphorus uptake of a processing tomato crop grown at different phosphorus levels in a calcareous soil as affected by mycorrhizal inoculation under field conditions

We have evaluated the effectiveness of arbuscular mycorrhizal fungi (AMF) inoculation (+M and −M) at 0, 60, and 120 kg  ha−1 of P fertilizer on crop growth (IEg), plant P nutrition and yield (IEy), and on mycorrhization occurrence in a processing tomato crop. Two experiments were carried out in calcareous soil under field conditions. Phosphorus fertilization had no effect on crop growth and yield. At harvests, +M plants showed higher aerial dry weight, fruit fresh weight, and P concentration. Inoculated plants produced larger inflorescences, higher flower number, and total and marketable fruit number compared with −M plants. At P0 and P60, plants associated with exogenous AMF were able to enhance P recovery, nevertheless factors other than the P uptake improvement concurred to make the inoculation effective. In both years, P fertilization enhanced IEg and IEy, and the application of 60 kg  ha−1 of P in inoculated soil was enough to reach high production level (134 Mg  ha−1). In the first trial, due to earlier root mycorrhization in inoculated and P fertilized soil, higher IEg and IEy were obtained compared with the second experiment. In the latter, during the initial phase, plant growth was more affected by P fertilization than by soil arbuscular mycorrhizal (AM) inoculation. Root mycorrhization by native AM fungi indicates that the intensive management of the investigated agro-system did not depress fungi infectivity; however, it caused the selection of less effective AMF. The application of selected AMF as a biofertilizer may represent an innovative ecosustainable practice for improving the crop profitability for growers while reducing the need for P fertilization.