The use of sustainable soil management practices is becoming common in wine growing regions around the world in response to an increased awareness of the value of soil health to maintain environmental quality, crop yield, and grape quality. In spite of this, little information is available on the meaning of soil health within a viticultural context, the effects of soil management practices on soil health and the consequences for grape quality and the expression of the terroir. In this review we discuss interrelated dynamic physical, chemical, and biological properties associated with soil health and how they could be important in the expression of the terroir. We focus on the use of cover crops and compost application, two practices commonly used in vineyard soils, and how they affect these physical, chemical and biological aspects of soil health, grape quality and the expression of the terroir. Finally, we discuss research gaps, and best management practices to reduce possible tradeoffs associated with these practices such as the emission of greenhouse gasses.

Lithology is a principle state factor of soil formation, interacting with climate, organisms, topography and time to define pedogenesis. A lithosequence of extrusive igneous lithologies (rhyolite obsidian, dacite, andesite and basalt) was identified in the Clear Lake Volcanic Field in the Coast Range of northern California to determine the effects of lithology on pedogenesis, clay mineralogy and soil physiochemical properties. Based on regional landscape erosion rates (0.2-0.5 mm yr −1 ), the soil residence times for the investigated pedons (~150 cm deep) were of the order of 3000 to 7500 years indicating that the soils developed under the relatively stable Holocene mesic/xeric climate regime. Soils from all lithologies developed to a similar Xeralf taxonomy with remarkably consistent physiochemical properties. Although total (Fe t ) and dithionite-citrate extractable (Fe d ) iron concentrations diverged across lithologies, the degree of weathering as assessed by the Fe d /Fe t ratio was similar across the lithosequence. In spite of large differences in silica content of the parent materials, the clay mineralogical assemblage of all lithologies was dominated by kaolin minerals (kaolinite and/or halloysite). All pedons displayed an increase in halloysite and the degree of halloysite hydration with increasing depth, except the basalt pedon, which was dominated by kaolinite with only trace halloysite. We attribute this lack of halloysite in the basalt pedon to the lower silica activities associated with this silica-poor lithology. There was a lack of nanocrystalline minerals across all lithologies as inferred from selective dissolution. The dominance of crystalline materials is a function of the xeric soil moisture regime whereby summer soil profile desiccation promotes dehydration and crystallization of metastable nanocrystalline precursors. Further, the pronounced summer dry period results in dehydration of halloysite (1.0 nm) to halloysite (0.7 nm; also referred to as meta halloysite in some literature), together with transformation to kaolinite, in the upper soil profile. In spite of the relatively young soil residence times of these soils (Holocene age), the effects of lithology persisted only in differences in Fe oxide concentrations (Fe d ), as well as a lack of significant halloysite in basalt pedons. The overwhelming effect of climate in these highly weatherable parent materials narrowed the trajectory of pedogenesis, resulting in soils from contrasting lithologies converging on kaolin mineralogy, a lack of nanocrystalline constituents, and similar soil physiochemical properties.

Core Ideas Phosphorous fertility was evaluated in weathered volcanic soil in winegrape production. Seasonal Hedley P fractionations, P sorption, microbial biomass carbon, and DOC were investigated. Application of compost, alone or with TSP, reduced sorption and increased MBC. Labile Pi responded significantly to fertilization despite advanced pedogenesis. Significant labile Pi response in weathered soil may be due to low‐Fe lithology. Phosphorus dynamics and management strategies were investigated in a strongly weathered rhyolitic soil in the northern Coast Ranges of California. Recent conversion of upland, native oak (Quercus spp.) woodland ecosystems to winegrape production has led to a P deficiency in these soils. We investigated the growing season behavior of Hedley phosphorus fractions, the P sorption index (PSI), microbial biomass C (MBC), and dissolved organic C (DOC) in response to a single P application from three sources: composted steer manure (CSM), triple superphosphate (TSP), and mixed compost and triple superphosphate (MIX). Phosphorous sources, equal in P application rate (39 kg ha−1), were applied in the winter of 2012, and soils were sampled in spring, summer, and fall. Labile inorganic P (Pi) (resin Pi + NaHCO3 Pi), Fe/Al‐Pi (NaOH Pi), and total P were significantly (p < 0.01) increased by P application, regardless of source. Calcium‐Pi (HCl Pi), DOC, MBC, and pH were increased, and PSI was reduced, by compost addition. Net extractable Fe/Al‐Pi increased during the study period. Moderately labile organic P (Po) (NaOH Po) declined, independent of fertilization, reflecting background soil P cycling. Calcium‐Pi totals were low (mean 9 mg kg−1 for untreated plots), and other indicators of chemical weathering were high, suggesting an advanced stage of pedogenesis with respect to Walker–Syers P availability. In spite of advanced pedogenesis, labile Pi increased significantly from fertilization and remained elevated throughout the growing season. Results of this study inform P management in highly weathered, P‐fixing soils experiencing P deficiencies.

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

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