Temporal and spatial effects of long-term floor management on the bacterial and nematode communities in a Salinas Valley, California grape vineyard

California grape producers traditionally manage vineyard floor vegetation to control weeds and vine vigor, and prevent erosion. The attitude towards vineyard floor management of some has changed from one of preventing disease and weeds to promoting plant and soil-borne microbial diversity. In the final year of a long term vineyard floor management field study, we examined both the bacterial and nematode communities present in the row middles and berms across six different floor management strategies. Samples were assayed for total bacterial and nematode populations in addition to identifying individual members of these communities. An analysis of the culturable bacteria community found weed management and cover cropping practices had no significant quantitative effect on bacterial populations. Qualitatively, however, bacterial populations were altered as a function of cover crop and weed management practices. The grapevine rhizosphere bacterial populations were greater than populations in the row middles bulk soil during the grape root flush in the spring. During harvest and dormancy, bulk soil bacterial populations were greater in the rows than on the berm (P < 0.05). The nematode community in the row middles was significantly affected by both weed management and cover crop practices. In the berm, nematodes were not affected quantitatively or qualitatively under the six management regimes. Moreover, the nematode community of the berm was different from that found in the row. These data suggest changes in the microbial community in the row do not influence the microbial community of the berm where the roots of the vine are concentrated.