Vineyard floor management: Effects on soil carbon and nitrogen dynamics

Disturbance frequency and intensity associated with vineyard floor management practices are lower than in annual cropping systems. Thus, soil carbon and nitrogen dynamics may be distinct in vineyard systems.  This hypothesis was investigated from Fall 2005-Fall 2006 in a Chardonnay vineyard planted in 1997 (Monterey Co.). Vineyard floor treatments included a clean, cultivated treatment and two cover crops [i.e., Trios 102 (Triticale x Triosecale); Merced Rye (Secale cereale)] that had been planted annually for five years prior to the study. Merced Rye had 1.5-2 fold more aboveground biomass than Trios 102 during the growing season, but it was similar just prior to mowing in April. Root biomass (0-10 cm) at peak aboveground biomass was approximately 2.5 times greater in Trios 102 than Merced Rye. Weed biomass was greater in the Trios 102 treatment than in Merced Rye, likely due to Trios 102’s lower aboveground biomass that occurred during the growing season.  Soil respiration and dissolved organic carbon were greatest in Trios 102, followed by Merced Rye, and the cultivated treatment, respectively. This may be linked to greater root biomass in Trios 102 than Merced Rye. In general, both cover crops had greater CO₂ and N₂O efflux, microbial biomass C, ammonium pools, and potential rates of nitrification, nitrogen mineralization, and denitrification than the clean, cultivated soil. The cover crop treatments had similar rates among these factors, despite differences in biomass allocation. Thus, the presence of cover crops enhanced the biological function of the vineyard soils.