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 (DW), fruit fresh weight (FW), 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 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 eco-sustainable practice for improving the crop profitability for growers while reducing the need for P fertilization.