Influence of vesicular-arbuscular mycorrhizae on celery transplant growth and phosphorus-use efficiency

Elevated phosphorus (P) levels present in Everglades Agricultural Area (EAA) stormwater runoff are an environmental concern for adjoining wetlands in South Florida. A regulatory program requires EAA growers to adopt best management practices that reduce P in farm drainage water. Given the prevailing regulatory climate, P fertilization practices are under scrutiny, and a premium is placed on identifying management practices that improve crop P-use efficiency. By enhancing root P uptake, vesicular-arbuscular mycorrhizae (VAM) can potentially reduce P inputs to celery (Apium graveolens L.) without compromising crop yields. The initial objective of this study was to determine whether celery infection by Glomus intraradices was feasible. Subsequent objectives included the assessment of plant growth response to VAM inoculation during the transplant production phase and quantification of VAM effects on P-use efficiency in celery. Pre-germinated celery seeds were direct-seeded into flats containing VAM-amended potting mix at concentrations of 0, 200, 500, and 1000 chlamydospores (30-mL mix)-1, for treatments V-0, V-200, V-500, and V-1000, respectively. Following 90 days growth, root colonization under low VAM amendments (V-200) ranged from 87.1% (Experiment #1) to 92.7% (Experiment #2), far exceeding the non-inoculated control (V-0; 0 to 3.7%). Relative to V-0, celery plants infected with VAM averaged 21.7 to 57.0% greater shoot dry matter, were 22.9 to 42.7% taller, supported 9.5 to 15.5% more petioles, and shoots had 8.6 to 23.0% greater P concentrations. Overall P-use efficiency, represented by top-growth P uptake, was 33.0 to 94.2% greater than the control. Under high VAM (V-1000) amendments, P uptake exceeded V-0 by 61.7 to 102.5%. Time-trend analyses indicate that shoot dry matter accumulation and P uptake trends over the 90-day growing period generally ranked as follows: V-1000 > (V-500 = V-200) > V-0. These results document successful VAM colonization in celery. Additionally, VAM confers improved growth performance and P-use efficiencies during celery transplant growth.