Soil microbial biomass as affected by groundcover management in a Fraser fir (Abies fraseri [Pursh] Poir) plantation after 1 year

Abstract

We investigated soil microbial biomass response to incorporating a non-leguminous [perennial ryegrass (Lolium perenne)] and two leguminous [Dutch white clover (Trifolium repens) and alfalfa (Medicago sativa)] cover crops into a newly established Fraser fir (Abies fraseri) plantation. Groundcover treatments consisted of growing each cover crop in the interspaces of the plantation, mowing the aboveground biomass every 3 weeks, and leaving the plant residues on the ground to decompose. Conventionally managed plots were used as a control. Soil total C, total N, and microbial biomass carbon (SMB-C) and nitrogen (SMB-N) were assessed at the 0–15-, 15–30-, and 30–35-cm soil depths. Soil total C was unaffected by groundcovers at any depths, whereas soil total N was significantly (P = 0.031) higher in the cover crop treatments than in the conventional system at the top soil layer. Groundcovers increased SMB-C and SMB-N by 20–50% and 35–80%, respectively, in the top soil layer relative to the control. These results suggest that groundcovers could potentially improve soil fertility and be a good strategy for sustainable fir tree production.