Manure and its biochar affect activities and stoichiometry of soil extracellular enzymes in croplands

Purpose

The influence of organic amendments on the interplay among soil extracellular enzyme activities (EEAs) and their stoichiometry (EES) and nutrient availabilities, key indicators of resource limitations for soil microbes, is poorly understood. This study aims to investigate how manure compost (hereafter “manure”) and its biochar derivative affect EEAs, EES and soil fertility.

Materials and methods

We studied EEAs (BG, β-glucosidase; CBH, cellobiohydrolase; LAP, Leucine aminopeptidase; NAG, β-1,4-N-acetylglucosaminidase and AP, acid phosphatase), EES and soil fertility two years post-application of manure and biochar in central Alberta, Canada.

Results and discussion

Applying manure and its biochar did not affect soil permanganate oxidable carbon (C), total phosphorus (P), and available P and nitroegn (N). Manure application increased NAG activity by 13.9% (75.9 nmol h⁻¹ g⁻¹ soil) relative to the control (66.6 nmol h⁻¹ g⁻¹ soil), whereas biochar application increased LAP activity by 22.1% (64.6 nmol h⁻¹ g⁻¹ soil) compared to the manure treatment (52.9 nmol h⁻¹ g⁻¹ soil), suggesting that manure addition caused microbial C limitation, while biochar addition led to microbial N limitation. However, both manure and biochar treatments did not affect soil NAG, CBH and AP, and enzymatic C:N, C:P, and N:P stoichiometry. Manure and biochar and their interactions with the soil ultimately affect soil physicochemical properties.

Conclusions

Manure and its biochar differentially altered some soil N-cycling EEAs and C and N limitations two years after their applications.