Comparative study on organic composts in blueberry: insights into soil physicochemical properties and heavy metal...

Composts of edible fungal substrates (CEFS) and Chinese herbal residues (CCHR) are potential ecological organic fertilizers, which are sustainable for blueberry cultivation. But how the two composts affect the fertility and the migration or transformation of heavy metals (HMs) in blueberry soil is unknown. In this study, we conducted a field trial by comparing CEFS and CCHR to the special fruit organic fertilizer in the market (SFOF) and potassium sulfate compound fertilizers (PSCF) according to a three-year continuous fertilization experiment in blueberry. We aimed to reveal the effect of different fertilizers on the integrated soil fertility (ISF), nutrients availability, and the heavy metals (HMs) risks in blueberry soil and fruit; simultaneously to clarify the relationships between nutrients input and HMs risks for the blueberry according to RDA analysis. Results showed that the highest integrated soil fertility (ISF) was obtained in the CEFS + PSCF and CCHR, and blueberry was mostly affected by the input of nitrogenous and organic matters, and restricted by heavy metal Cd. CEFS and CCHR demonstrated a better fertility to enhance the ISF by 139.71%-149.31%, improve the effectiveness of soil Nitrogen, Phosphorus. In addition, application of CEFS and CCHR was conductive to reduce the bioavailability of heavy metals as decreasing the HOAc-extractable Cd by 23.94%-39.37%. Correlation analysis revealed that the input of organic matters was positive to the improvement of ISF and the reducing of Cd bioavailability, but excess organic matters would affect blueberry's absorption of Potassium, thus it is necessary to replenish potassium fertilizer in time for blueberry. Our results would provide a theoretical basis for application of CEFS and CCHR in the safety production of blueberry.