Apatite Stimulates the Deposition of Glomalin-Related Soil Protein in a Lowbush Blueberry Commercial Field

Many wind-sensitive and unproductive soils could benefit from increased glomalin-related soil protein (GRSP), an operationally defined soil protein pool known to improve soil quality and nutrient storage. We expect at least part of this GRSP fraction to originate from fungal biomass. Although P-rich minerals such as apatite are known to increase C allocation from plants to mycorrhizal fungi, there are no studies directly linking apatite with GRSP. We investigated the effect of apatite on GRSP deposition rates in a cultivated field of wild lowbush blueberry ( Vaccinium angustifolium Aiton; Vaccinium myrtilloides Michx.) in the Saguenay‒Lac-Saint-Jean region of Quebec (Canada). A field incubation technique (145 days) using sterilized porous sand bags (50 µm pores) was used to measure in situ easily extractable GRSP (EE-GRSP) deposition rates from bags with ( n = 10) and without ( n = 10) apatite. Half of the bags ( n = 10) were also soaked in Proline® 480 SC (Bayer CropScience, Calgary, Alberta, Canada) (Prothioconazole) to determine if EE-GRSP deposition rates were affected by this commonly applied fungicide. Our results indicated that adding apatite into sand bags significantly increased (+70%) EE-GRSP deposition rates, whereas soaking the bags in fungicide had no significant effect. Although the direct linkage between GRSP and lowbush blueberry plants remains to be detailed, our study reports for the first time GRSP concentrations from lowbush blueberry soils. Implications of these findings are discussed.