Changes in microbial biomass and activity support ecological intensification of marginal land through cultivation of perennial wheat in organic agriculture

ABSTRACT Ecological intensification of agroecosystems on marginal land through cultivation of perennial wheat may provide greater belowground biomass than cultivation of annual wheat, and thus improve soil organic carbon (SOC) and consequently benefit soil microbial activity. However, little is known about how organically managed hybridised perennial wheat (Triticum aestivum L. × Thinopyrum spp.) stimulates SOC, microbial biomass and activity in marginal soils. Therefore, the effect of three organically managed cropping systems: i) sole perennial wheat; ii) perennial wheat with clover intercrop; and iii) annual wheat; were investigated at three sites in Germany on marginal soils with different textures (silt loam (SL) with impervious soil layer, clay loam (CL) with 30–35% stone content and sandy soil (SS) with low nutrient content). Soil samples, from each cropping system and site, were taken from A- and B-horizons after 3 years of cultivation and were evaluated for SOC, microbial biomass C and N (MBC, MBN), basal respiration, and C-enzyme activities. In CL and SS soils, perennial wheat with clover intercrop increased SOC in the A-horizon compared with annual wheat and sole perennial wheat. Varied effects were observed in the B-horizon, with sole perennial wheat in CL having higher SOC and MBC than the other two cropping systems. SOC storage stock in the B-horizon of perennial wheat was on average 18% higher relative to annual wheat, revealing a considerable C storage potential. Overall, the study showed that perennial wheat cultivation can improve microbial biomass and activity in marginal soils compared with cultivation of annual wheat.