The composition of microbial communities responds to soil resource availability, and has been shown to vary with increasing depth in the soil profile. Soil microorganisms partly rely on root-derived carbon (C) for growth and activity. Roots in woody perennial systems like vineyards have a deeper vertical distribution than grasslands and annual agriculture. Thus, we hypothesized that vineyard soil microbial communities along a vertical soil profile would differ from those observed in grassland and annual agricultural systems. In a Pinot noir vineyard, soil pits were excavated to ca. 1.6-2.5 m, and microbial community composition in 'bulk' (i.e., no roots) and 'root' (i.e., roots present) soil was described by phospholipid ester-linked fatty acids (PLFA). Utilization of soil taxonomy aided in understanding relationships between soil microbial communities, soil resources and other physical and chemical characteristics. Soil microbial communities in the Ap horizon were similar to each other, but greater variation in microbial communities was observed among the lower horizons. Soil resources (i.e., total PLFA, or labile C, soil C and nitrogen, and exchangeable potassium) were enriched in the surface horizons and significantly explained the distribution of soil microbial communities with depth. Soil chemical properties represented the secondary gradient explaining the differentiation between microbial communities in the B-horizons from the C-horizons. Relative abundance of Gram-positive bacteria and actinomycetes did not vary with depth, but were enriched in 'root' vs. 'bulk' soils. Fungal biomarkers increased with increasing depth in 'root' soils, differing from previous studies in grasslands and annual agricultural systems. This was dependent on the deep distribution of roots in the vineyard soil profile, suggesting that the distinct pattern in PLFA biomarkers may have been strongly affected by C derived from the grapevine roots. Gram-negative bacteria did not increase in concert with fungal abundance, suggesting that acidic pHs in lower soil horizons may have discouraged their growth. These results emphasize the importance of considering soil morphology and associated soil characteristics when investigating effects of depth and roots on soil microorganisms, and suggest that vineyard management practices and deep grapevine root distribution combine to cultivate a unique microbial community in these soil profiles.

The adoption of precision viticulture requires a detailed knowledge of variation in soil chemical, physical and profile properties. This study evaluates the usefulness of apparent electrical conductivity (EC a ) data within a GIS framework to identify variations in soil chemical and physical properties and moisture content. The work was conducted in a vineyard located in the Carneros Region (Napa Valley, California). The soil was sampled using 44 boreholes to quantify chemical and physical characteristics and 9 open pits to verify the borehole observations. Moisture content was determined using time domain reflectometry (TDR). To characterize soil EC a , three campaigns were undertaken using a soil electrical conductivity meter (EM38). Linear regressions between soil EC a and soil properties were determined. Boreholes and TDR data were interpolated by kriging to characterize the spatial distribution of soil variables. The resulting maps were compared to the results obtained using the best EC a linear regressions. Using EC a measurements, soil properties like extractable Na ? and Mg 2? , clay and sand content were well estimated, while best estimates were obtained for extractable Na ? (r 2 = 0.770) and clay content (r 2 = 0.621). The best estimates for soil moisture content corresponded to moisture in the deeper soil horizons (r 2 = 0.449). The methods described above provided maps of soil properties estimated by EC a in a GIS framework, and could save time and resources during vineyard establishment and management.

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A two-year experiment investigated the effects of compost application rate on soil chemical properties, vine nutrient status, vine performance, and grape juice characteristics in a degraded vineyard soil in northern California. The intent of the research was to identify vineyard management strategies to improve soil fertility and to identify optimal compost application rates. We applied composted steer manure at three rates (11.2, 22.4, 33.6 t/ha) in a randomized complete block design before the 2012 growing season. Pruning and berry weight increased over the control at the highest application rate in both years, while vine yield significantly increased over the control in year two. Polynomial orthogonal contrasts suggest that pruning weight, vine yield and berry weight increased linearly with increasing compost application rate in 2012, and that vine yield and berry weight increased linearly and quadratically with compost application rate in 2013. Measured soil properties increased from compost application, including N, C, pH, exchangeable K, Mg and Ca and available P (Olsen-P), while phosphorus fixation