DRY FARMING. Martha Stoumen notes for discussion on 6/22/17

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1 DRY FARMING Martha Stoumen notes for discussion on 6/22/17 What is dry farming? Dry farming refers to crop production during a dry season, utilizing the residual moisture in the soil from the rainy season, usually in a region that receives 20 or more of annual rainfall. Dry farming works to conserve soil moisture during long dry periods primarily through a system of tillage, surface protection, and the use of drought-resistant varieties. Very possible (and widely practiced) for perennial crops like grapes and orchards, harder to do with vegetable farming (but some do it!) Grapes can have incredibly long tap root. 6 meters (20 feet) and deeper are not infrequent Why? Ensures no unnecessary water is pulled from the aquifer or nearby rivers. Many growers nowadays use holding ponds that are recharged during winter rains. Even if not completely dry farmed, many growers of premium grapes are pushing the bounds of deficient irrigation with favorable results. For me it s not just about less water use there is a whole slew of practices that are used when one decides to dry farm that I also support. Personally I have found that vines have a natural vine balance (is this b/c most dry farmed vineyards I work with though are old vine?). I am trying to do less in the vineyard always, so not having to hedge or do massive leaf thinning is a plus. Start up costs less initially, although fruit production/revenue is delayed For those wanting to create more of a complete farm ecosystem with composting on site, animal/vineyard integration works better without training wires. Less soil compaction within vineyard rows (generally, not always) due to ability to cross cultivate. Some say wine tastes better when majority of roots are found in lower (deeper) soil horizons with higher mineral content, plus often flavors are more concentrated with dry farming.

2 Establishment vs. Conversion Best to establish as dry farmed vineyard from the get go, but when converting a vineyard to dry farming the below should also be considered: o Rootstocks: St George: St. George seems to avoid drought because of its deep, extensive root system, and does not perform well on shallow soils with limited water. It is a high vigor rootstock with generally low-yield:pruning weight ratios, primarily a function of reduced fruit set. Use of St. George should be avoided with small-clustered or loose-clustered varieties on fertile soils. St. George is susceptible to nematodes and supports relatively high populations of phylloxera. However, there are no examples of failure to phylloxera in the field 110R: Richter 110 is recommended for hillsides or dryfarmed sites where drought is likely. On such sites, it usually out yields St. George and has better yield:pruning weight ratios. Slower to establish but vigorous once established. Good phylloxera resistance, not good nematode resistance. Other less frequently used but high drought tolerant rootstocks: 140Ru (Ruggeri) and 44-53M (Malègue) If considering new site, look where water pools or drains quickly in wet season prior to planting: avoid excess dryness or wetness. Look at current cover, are there shrubs and trees or just grasses? Plant out after wet years. In general: conservative estimate is that at least 15 inches of annual rain are needed to dry farm Plant rootstock and field graft focuses on root growth only in year one. Drop fruit early on (practice in most vineyard establishment, dry farmed or not) Old timers used to plow, not just disk, which some think help root prune, cutting off lateral roots and favoring deep roots Canary Islands cactus trick Soil water-holding capacity important, and will determine spacing: best soils for dry farming are deep clay-loam, silty-loam, or sandy-loam soil with high organic matter content. Minimum 50 sq feet per vine, often more on hillsides.

3 Soil oxygen affects root-growth patterns, microbial activity affects soil oxygen and organic matter Need to have a model not solely based on quantity production (typically in CA I've seen 3 to 4 tons an acre, which is in line for high end production, even for old vines). Young vine dry farmed vineyards not as common, but the one example I know at Dobson Ranch is at 5 tons an acre in a good flowering year for that variety. Practices: Clean cultivation or Permanent Cover Crop One or the other, in between promotes shallow root depths clean cultivation through tillage, and the establishment of a permanent cover crop, diminished root presence in the upper cm of soil. Root pruning and root competition, respectively, are likely the mechanisms involved. Inversely, minimum tillage practices, mulches, plastic covers, and herbicides, all increased grapevine root densities in the upper 20 cm (Grapevine rooting patterns: A comprehensive analysis and review By: D. Smart, E. Schwass, A. Lakso, and L. Morano). Cultivation, traditional in CA: most disk soon after rainy season to create dust mulch. (creates layer over soil capillaries that prevents evaporation) Many dry farmed vineyards are head trained (in order to be able to cross cultivate). Head training is great for vine balance (sun exposure more spread out, great for airflow) Some CA vineyards have been successful with mowing a cover for mulch and cultivating every 6 or so years. Cultivation may be more important in establishment years. Also concerns over competition from cover. Leon Barral experience: o cultivates newly planted vineyards, applies compost on new vineyards o undervine cultivates established vineyards and uses roller/crimper between rows o roller/crimper snaps tops of grass, weeds, etc. without breaking them, which delays growth of weeds, limiting competition with grapes while still helping to retain soil structure o Dormant season: animal inclusion (winter), mulch& compost layering (builds compost within rows) in weak spots of vineyard. o Side note: prunes aggressively (1 bud spur), but leaves more positions to compensate, tries to promote more clusters that are smaller to aid in airflow through bunches (less mildew/rot within bunches).

4 Encourage mycorrhiza growth (AMF). Taken from Mycorrhizal Colonization in Dryland Vineyards of the Willamette Valley, Oregon by R. Paul Schreiner Robert G. Linderman o AMF enhance the growth of numerous plants, including grapevines, by increasing the absorptive surface area between roots and soil o This study measured AMF root colonization at 2 points in growing season, bloom and veraison o AMF colonization of fine (feeder) roots of vines was generally high, averaging 73% and 69% of root length colonized at bloom and veraison, respectively o Bloom: In-row cultivation reduced AMF colonization (so goes against traditional dry farming cultivation practices however soil moisture was higher in cultivated rows AND AMF colonization recovered to the same level as the untilled vineyards by veraison) The proportion of roots colonized by AMF at bloom was negatively correlated to leaf N concentrations and positively correlated to soil and leaf K concentrations The proportion of roots containing arbuscules (the site of nutrient transfer in mycorrhizas) at bloom was positively correlated to soil ph (higher ph = more arbuscules) and leaf K concentrations, but negatively correlated to leaf P and N concentrations o Veraison: foliar application of soluble phosphorus fertilizers reduced arbuscules in roots at veraison AMF colonization of roots was negatively correlated to soil moisture at veraison (drier soils = more colonization). o Takeaway: AMF increases P uptake and is suspected to increase drought tolerance. Raising soil ph, if soils are below a ph of 5.5, and minimizing the use of foliar P fertilizers appear to be the best management strategies to enhance colonization by AMF in Oregon vineyards. CA vineyards often have low (acidic) soil ph as well, so there may be cross-over with this study

5 Future Potential Practices Biochar? Will we see a trend to move away from tillage and towards permaculture type methods? Resources General (with further great links at bottom of article 1): Rootstocks: Soil health: Root growth patterns: review.pdf cover crop versus herbicide.pdf Recharging the CA aquifer: