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Home , Castilleja neglecta, Garrya congdonii, Serpentine soil

'S SERPENTINE

by Art Kruckeberg

Serpentine Rock

Traditional teaching in geology tells us that rocks Californians boast of their world-class tallest and can be divided into three major categories—igneous, oldest trees, highest mountain and deepest valley; but metamorphic, and sedimentary. The igneous rocks, that "book of records" can claim another first for the formed by cooling from molten rock called magma, state. California, a state with the richest geological are broadly classified as mafic or silicic depending tapestry on the continent, also has the largest exposures mainly on the amount of magnesium and or silica of serpentine rock in North America. Indeed, this present. Serpentine is called an because unique and colorful rock, so abundantly distributed of the presence of unusually large amounts of around the state, is California's state rock. For magnesium and iron. Igneous rocks, particularly those botanists, the most dramatic attribute of serpentine is that originate within the earth's crust, above the its highly selective, demanding influence on life. mantle, contain small but significant amounts of The unique flora growing on serpentine in California illustrates the ecological truism that though regional controls overall plant distribution, regional Views of the classic serpentine areas at New Idria in San Benito County. The upper photo was taken in 1932, the lower in 1960 geology controls local plant diversity. Geology is used of the same view; no evident change in 28 years. Photos here in its broad sense to include land forms, rocks courtesy of the U.S. Forest Service and Dr. James Griffin. and . Geologists of the early days in California were aware of serpentine to a greater extent than the early botanists. An 1826 geological map of area plots serpentine outcrops. The map, a work of naturalists with the H.M.S. Blossom, located serpentine on Tiburon Peninsula and Angel Island. The first major geological survey of California by Whitney in 1865 recorded serpentine too; yet the survey failed to connect serpentine with the barren- ness of the vast landscape in their visit to New Idria in San Benito County, the most spectacular serpentine occurrence in the state. As the state began to extract resources, serpentine became more widely recognized. Mercury, , , and magnesite were found in or adjacent to serpentine out- crops. In a 1918 report on quicksilver (mercury ore) deposits of the state, a photo of the New Idria land- scape is captioned: "Serpentine surface near New Idria . . . showing characteristic sparseness of timber and brush growth." Serpentine rock was named for the likeness of the rock to the mottled pattern of a snake's skin. In Greek, the word "serpent" translates to ophidion, from which the species name is derived for the serpentine endemic grass, Calamagrostis ophitidis. The Greek physician Dioscorides apparently recommended ground serpen- tine rock for the prevention of snake bite, surely a rather extreme remedy. The word, serpentine, has come to be used both for the rock and for the soils derived from the rock. _o Jug_Q" _ ------di. calcium, sodium, and potassium, along with small DEL MOP T amounts of iron and magnesium. Serpentine, however, has only minute amounts of calcium, sodium and potassium, but unusually large amounts of nickel, , and chromium. SHASTA LASSEN Deep in the mantle of the earth, the igneous precur- sor of serpentine, , is composed largely of two , hard, greenish magnesium silicate HUMBOLDT , and pyroxene, both of which contain large

• percentages of iron. Peridotite has nearly the same TRINITY : chemical composition as serpentine, namely a high magnesium and iron content. Thus peridotite and I \\II T MAMA serpentine are both included in the category of ultramafic rocks. As presently understood, serpentine

ARA , is a metamorphic product of peridotite in which water MENOOCINO molecules are chemically incorporated into the rock ( I matrix by a recrystallization process. Serpentinization ) % PLACE is still poorly understood; however, it is known that

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Distribution of serpentine outcrops (black areas) in California and southwestern Oregon, by county. Note especially the north- south trend of the outcrops and their restriction to the Coast Ranges and to the Sierra Nevada foothill country. Map , courtesy of the California Division of Mines and Geology. -•-•"'"jxtC O 12 Digger pine and sparse serpentine chaparral, New Idria serpentine barrens. Photo courtesy Dr. James Griffin. it can take place at temperatures less than 500°C down mafic rocks, peridotite and serpentine, are transported to ambient temperatures, as long as water is present. to the earth's surface. In this theory giant plates of the This metamorphic process produces the following earth's crust float over the hot plastic mantle of the serpentine minerals depending on the temperature: earth. Mafic and ultramafic material forms oceanic chrysolite and lizardite (low temperature) or antigorite plates which migrate toward continental plates where (high temperature). Serpentinization is a unique one crustal plate descends beneath another where they recrystallization process in that only water is added and are recycled in the magma core. Occasionally a part the original ratios of the elements remain similar in of the rides up over the leading edge of the metamorphic serpentine as in parental peridotite. the continental plate exposing the ultramafic rock in In spring waters associated with serpentinizing perido- the form of peridotite and serpentine. This conver- tites we find calcium-rich waters with pH of 11.5 that gence and overlapping of oceanic crust and mantle is indicate that calcium is expelled during the process of common in mountain-building zones and is part of the serpentinization, but this represents less than 1% of formation of most mountain belts. the total rock. What is crucial for the weathered prod- The serpentine masses in California were probably uct of ultramafics, the , is the very low amounts first exposed at the surface during the middle Mesozoic of calcium and potassium, so essential for plant (ca. 150 million years ago) as seen in the sedimentary growth, and the excessive and potentially- toxic record; some exposures may be as late as the last Ice amounts of magnesium, nickel, and cobalt. Many Ages (Pleistocene). Western California under the influ- exposures of these rocks on the earth's surfaccconsist ence of plate movements, as for example in the San of a mixture of peridotite and serpentine though there Andreas fault, has been the site for redistribution of is generally more serpentine. Because of their similar the serpentine exposures and in many cases on-going unusual chemical composition, these rock types yield tectonic activity has been so intense that soil has not similar unusual soils, and similar limitations to . been able to develop on the surface of some exposures. Geologists have debated over the poorly understood On the other hand some of the serpentines of the complex of ultramafic rocks for years. In recent years Klamath mountains and the Sierra foothill belt have the revolutionary new plate tectonic theory has pro- deep, well-developed soil profiles where they have not vided clues and perhaps answers as to how the ultra- been deformed by recent tectonic activity. Distribution of Serpentine every kind of terrain and exposure in northwestern California from arid to mesic, from the low elevations From Oregon south to Santa Barbara and Tulare at Gasquet in Del Norte County to the summits of the counties, eleven hundred square miles of serpentine higher peaks at Mt. Eddy, Preston Peak and Scott and related rocks are distributed in numerous masses Mountain. Any west-east traverse of this complex with discontinuous and northwest-trending orienta- mountain system provides the traveller with views of tion. There are gaps in its distribution with essentially great expanses of sparse forest or chaparral clinging no outcrops in southern California (a tiny outcrop in soils to the and serpentines. Serpentine out- the Santa Ana Mountains), none in the high Sierra or crops are numerous on the east and west slopes of the their eastern flanks, and none in the Great Valley or Yolla Bolly Mountains and all the way from arid desert areas. Serpentine is a familiar sight in the South lowlands, bordering the Sacramento Valley across the and North Coast ranges, the Klamath-Siskiyou coun- summits of peaks like Dubakella, Snow, and Red try and the lower western slopes of the Sierra. mountains to the redwood belt where islands of serpen- A quick tour of California from north to south tine intrude into the forest. highlights the most important areas of serpentine or Serpentine occurs in many places in the North Coast ultramafic rock occurrence. The Weed sheet of the Ranges, including Lake, Tehama, Mendocino, and state geologic maps covering the Klamath-Siskiyou Trinity counties, and supports some of the most unique area in northern California shows the most massive flora tolerant to the substrate. A procession of nearly and extensive outcrops in the state. There is nearly unbroken sequences of outcrops occurs from the Oregon border down to the Lake County side of the Mayacamas Mountains, the country east of Middle- "The Cedars," Cupressus sargentii on massive serpentine town, and around Clear Lake. outcrop, upper east Austin Creek, Sonoma County. Photos by the author unless otherwise noted. Although we think of the Sierra Nevada as a great granitic island perched over desert and the Great Valley, serpentine intrudes into many places along the western flanks of the range. Many a foothill of the Sierra contains serpentine, though much of it is covered in northern Plumas County by more recent lava flows from Mt. Lassen. Outstanding serpentine localities in the Sierra Nevada include the rich displays in the Feather River country, and the Coulterville- Bagby area of Tuolumne County near Chinese Camp. Major outcrops continue to the southeast in Tulare and Fresno counties. North of San Francisco there are several well known serpentine areas including those in northern Napa County around Mount St. Helena; in Sonoma Coun- ty, the Cedars area of upper Austin Creek, and Occi- dental; and in Marin County outstanding are the sites on Tiburon Peninsula, particularly at Ring Mountain, on Angel Island and in State Park. Notable outcrops in and around San Francisco include the Presidio, and sites in the Oakland-Berkeley Hills, in San Jose, and in the Crystal Springs Reservoir area in San Mateo County. To the south and southwest the Santa Lucia Moun- tains and the Diablo Range have serpentine outcrops; however, the most impressive ones are in the Inner South Coast Ranges of San Benito County, particular- ly the New Idria barrens and San Benito Peak. There are well-known serpentine exposures near the coast in San Luis Obispo County at the Cuesta Ridge and in the hills of San Luis Obispo. And to the south the last significant serpentine outcrops occur in the Figueroa mountain area of the San Rafael Mountains in Santa Barbara County. 14 1 20

react to weathering primarily by going into solution. Deeper serpentine soils are punky, pigmented residuals of iron oxides released during intense weathering of serpentine rock. Often soils derived from other rock types will wash down and cover serpentine rock, pro- viding a mistaken impression of a thick serpentine soil or of vegetative growth on serpentine soil and rock. Considerable research has been done on the inability of serpentine soils to supply adequate nutrients for normal plant growth. Several University of Califor- nia scientists, Hans Jenny, James Vlamis, Perry Stout, C.M. Johnson and Richard B. Walker, all attributed the infertility of serpentine soil for plants to an im- balance between calcium and magnesium. Levels of , phosphate and potassium (NPK), and the essential micronutrient molybdenum are low in most serpentine soils, while some can contain toxic amounts of nickel. When grown on serpentine soils, cultivated plants are depressed in growth and exhibit other defi- ciency symptoms corrected only with massive, repeated Serpentine chaparral between Paskenta and Covelo, Tehama additions of gypsum (CaSO 4) and NPK. County. Quercus durata, Ceanothus jepsonii and Digger pine So inhospitable a medium for plant growth has not predominate. stopped colonization of serpentine by some of the California flora. Species from many different plant Serpentine Soil—A Demanding Medium families are able to tolerate the unusual chemical and for Plant Growth physical qualities of these soils. Explanations for the mechanisms that provide this inherited tolerance of Hans Jenny, California's great soil scientist and con- serpentine plants are only partially satisfactory. We servationist, reminds us that a given is the now know that serpentine tolerant species are able to outcome of many variables — geology (parent rock or extract calcium and other essential elements in low other substrates), climate, topography, organisms— supply in the soil better than plants not found on all acting and interacting through time. In such a for- serpentines. Hans Jenny reminds us that the complex mulation, serpentine rock and granite in adjacent sites relationships between plants and soil involves the inter- will produce different soils, for the only variable is the play of many factors. For the network of factors that rock type. Soil is thus the most direct manifestation foster serpentine vegetation, Jenny has coined the term of geological influence on plant life. "serpentine syndrome," reminding us of the many Except for serpentine sites with nothing but bare linked strands of plant-soil interactions. In this con- rock, most outcrops have a soil mantle of exceptional cept the exceptional chemical composition of serpen- physical and chemical properties, developed by tine soil (low calcium, high magnesium, heavy metals, weathering and other soil-forming processes. Soils over etc.) sets in motion a biological response that results serpentine rock strongly reflect the chemical nature of in a low turnover of nitrogen and phosphorus. The the parent material. High values for magnesium, low low nutrient status and the cation imbalances result amounts of calcium, plus the prevalence of heavy in a sparse plant cover and in turn a high heat budget metals, iron, chromium and nickel, are as much a part at ground level. High temperature effects and moisture of the soil as the parent material. Conversion of rock stress further check plant growth and survival. Since to soil merely reduces the absolute values of these- serpentine soils are usually derived from rock outcrops elements. The only new chemical component in serpen- on steep or irregular topography, the habitats are often tine soil is a product common to most rock Weather- of unstable talus, adding a further stressful challenge ing, a kind of mineral composed of aluminum, to plants. oxygen, and silica molecules. Colloidal clay particles play an important role for plants of binding and releas- ing nutrients in the soil. Only minor amounts of clay Plant Responses to Serpentine are formed in serpentine soil from minor amounts of aluminum oxide released from the magnesium-rich, Plants have a characteristic growth form on serpen- aluminum-poor serpentine rock. Serpentine soils are tine soils. Woody plants are either stunted or compact, thus thin because of a lack of clay and because they and herbaceous species are often dwarfed. Leaves are •

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••••?•40611 X'‘. • lak • ,•• • ■••,. • ' t:r. ••";,, k4 ;h s.% i• .4, Vii, t1 . T .7, A serpentine landscape in Lake County, near Middletown. reduced in size, tough and narrow, with a glaucous distribution, and that these different responses are "bloom" or pubescence, and frequently are purplish usually inherited. Such differentiation within a species in color (anthocyanous). was elegantly demonstrated in California by the Plants seem to accommodate to the exceptional Carnegie Institution of Washington group at Stanford chemistry of serpentines either by rejecting undesirable when species like Achillea lanulosa, Potentilla glandu- elements, or by accumulating them harmlessly in cer- losa and Zauschneria spp. were found to have more tain tissues. This individualistic reaction to serpentine or less distinct races in their distributions from sea- is nicely illustrated in a recent study on Streptanthus level to high altitudes. Later on, I found that serpen- species, in the mustard family. One serpentine tine soil, like climate, has a selective effect on popula- endemic, S. polygaloides, was found to be a hyper- tions within an "indifferent" species. Races within a accumulator; that is, it can take up amounts of nickel species had evolved that were either tolerant or intol- in excess of 1000 parts per million. Yet other serpen- erant to serpentine. While many herbaceous species of tine endemic species of Streptanthus are not hyper- an indifferent (bodenvag) nature probably have genetic accumulators. differences in their ability to tolerate serpentine, not Plants can be categorized in terms of degree of all species demonstrate genetic differences. Some fidelity or restriction to serpentine soils. The narrow woody species do not evolve into genetically different endemics, which grow only on serpentine, are perhaps races; for example, Dr. Jim Griffin could find no such the most intriguing. In a second group "indicator" racial character for Digger pine (Pinus sabiniana). It species are those that may occur on other soil types is just possible that some indifferent species may have elsewhere but are locally or regionally faithful to what Dr. Herbert Baker, Professor of Botany at the serpentine. A third category, the indifferent species, University of California, Berkeley, calls a "general- are those that occur both on and off serpentine, purpose genotype," a wide range of growth response sometimes called "soil wandering" (or bodenvag, in with little genetic variation. German). In setting up these three discrete groups I am compelled to confess to a misgiving about preci- sion, so well stated by G. Ledyard Stebbins: "The only Serpentine Vegetation 'law' that holds without exception in biology is that exceptions exist for every 'law'." Often, ecologists are preoccupied with total plant It is known that species have different responses to cover and less concerned about the kinds of plants different environments throughout their range of making up that vegetation, a kind of reversal of the 16 121 old adage about not seeing the forest for the trees. It and leather oak (Quercus durata), which are unmis- is hard to avoid taking some note of the species that takable "indicator species" because of their typical make up a serpentine landscape, for, so often, the restriction to, and numerical dominance on, serpen- dominant species are serpentine endemics. In Califor- tine soils. Serpentine chaparral may be associated with nia, serpentine soils effect changes in four major types foothill woodland Digger pine (Pinus sabiniana) or of vegetation: conifer, oak woodland, , and montane coniferous forest Jeffrey pine (Pinus jef- chaparral. When serpentine crops out in any of these freyi), yellow pine (P. ponderosa), knobcone pine (P. vegetation types, the effect is usually dramatic. attenuata), Douglas-fir (Pseudotsuga menziesii) as an Number and quality of trees per acre is reduced, and understory. The thousands of hectares of serpentine species distribution is different from that in the sur- chaparral in the North Coast Ranges are easily distin- rounding non-serpentine forest. In the North Coast guished from the oak- on hills of non- Ranges, a high-yield mixed conifer forest gives way serpentine origin. to open stands of jeffrey pine and incense cedar. A classic study of Robert Whittaker on vegetation Elsewhere, conifer forests on normal soils may be of the Siskiyous provides critical comparisons of vege- replaced by chaparral on serpentine soils often with tation types on contrasting rock types, from ultramafic serpentine indicator or endemic such as Quer- to acid igneous. Whittaker found that the gradient cus durata, Ceanothus jepsonii and congdonii. from wet to dry on any particular kind of rock effects In other situations, typical mesic forest is replaced by changes in vegetation. For serpentine, mesic forest of Digger pine, cypress, and chaparral woodland with Port Orford cedar (Chamaecyparis lawsoniana) and Sargent cypress, Cupressus sargentii and MacNab's western white pine (Pinus monticola) nearest water or cypress, C. macnabiana essentially restricted to serpen- in ravines shifts to xeric chaparral at the dry ridgetop, tine soil. The finest displays of Sargent cypress on usually with indicator shrubs like tanbark oak (Litho- serpentine are in the upper east Austin Creek area of carpus densiflorus var. echinoides), huckleberry oak northern Sonoma County, where the pure stands are (Quercus vaccinifolia), dwarf silk-tassel (Garrya buxi- locally known as "The Cedars." Oak woodland on folia) and shrubby California bay (Umbellularia nearby non-serpentine soils is replaced by chaparral, californica). usually dominated by serpentine species. The Gray's study of vegetation along a sequence of country around Middletown, parts of Napa and Lake changing rock types tells of the sharp break in com- counties, exemplifies well this mosaic of contrasting munity structure and composition. Gray looked at the vegetation types. On serpentine, grassland becomes elevational gradient and vegetation change on Snow sparse, with a substantial component of indicator or Mountain in Lake County. Chaparral woodland on endemic species. The grasslands on the serpentine out- serpentine at lower elevations abruptly gives way to crops at Jasper Ridge, part of the Stanford Univer- montane coniferous forest on non-serpentine soils at sity reserve system, and on Tiburon Peninsula in Mahn higher elevations. The sharp break between the vegeta- County provide good examples. The serpentine tion types is mirrored by the changes in species com- grassland on Tiburon Peninsula boasts three local position. Along the Snow Mountain transect, the com- endemics, Streptanthus niger, Calochortus tiburonen- mon woody plants on serpentine soils are Digger pine, sis and neglecta. buck brush (Ceanothus cuneatus), leather oak, and A good source of descriptions of vegetation on chamise; on nearby non-serpentine substrates, com- serpentine is the indispensable guide to California mon woody species are yellow pine, canyon oak (Quer- vegetation by Barbour and Major (Terrestrial Vegeta- cus chrysolepis), hoary manzanita (A rctostaphylos tion of California). I paraphrase their description of canescens), sugar pine (Pinus lambertiana) and white serpentine chaparral as follows. Serpentine chaparral fir (Abies concolor). is an open, low type associated with serpentine soils from San Luis Obispo County northward through the Ed.'s note: The author would like to acknowledge the Coast Ranges and foothills of the northern Sierra .contribution of Dr. R. Coleman of Stanford Univer- Nevada. The shrubs are characterized by apparent sity to the section on geology in this article. The se- "xeromorphism" (plant parts adapted to drought cond article in the series will deal with the variety of stress) and dwarfed stature resulting from reduced pro- plants, some narrowly endemic, found on serpentine; ductivity and growth. . . . The dominant shrubs are the possible origins of our serpentine flora; and the chamise (Adenostoma fasciculatum) and toyon status of conservation of serpentine plant life. Readers (Heteromeles arbutifolia), but noteworthy are several may be interested to know that the California Native localized endemic shrub species, white-leaf manzanita Plant Society recently provided Dr. Kruckeberg with (Arctostaphylos viscida), Jepson's ceanothus a grant to assist in the preparation of his monograph, (Ceanothus jepsonii), Sargent cypress (Cupressus California Serpentine Plants, soon to be published by sargentii), Congdon's silk-tassel (Garrya congdonii), the University of California Press. 123 Correcting Serpentine Soils Trenching In Gypsum Pr )vides Promising Results

three feet deep was dug. This was deemed an adequate space for root than the soil and plant tissue By Pat Summers development. Four treatments were analysis. Treatments one and two Contributing Editor used. First a control, which was had similar but substantially less igh magnesium soils have not trench only, and no gypsum. The growth than treatments three and been a vineyard problem un- gyp applications were 1.15 tons per four, which were quite similar to -F1- til recently. Viticulture text acre, 11.5 tons per acre, and 115 each other. Although measurements books address magnesium deficien- tons per acre. The amounts are were not taken to quantify this cy, but the black sticky serpentine given in tons per acre, but because growth difference, photographs soils, so high in magnesium, were only the vine rows were actually indicate the very dramatic contrast. simply avoided by vineyardists until treated, the total amount applied is This points out a dilemma with the recent vineyard expansion suggested only about a third that amount for use of plant and soil analyses which a need to at least consider the each acre, and is concentrated in do not correlate well with differ- possibility of correction. the vine growth area. That would ences in plant growth," Meyer said. In 1978 a University of Califor- make the heaviest application 115 The pruning weight data and nia team started work with Andy tons per vineyard acre. The gypsum crop yields were more telling. In Cangemi at Pope Valley Vineyards, application was made Dec. 4, 1978. 1981 the pruning weight for control Napa County, Calif., to see if it was The gypsum was applied by was 48.3 grams per vine. The 1.15 possible to rectify a high magnesium pouring it along the outlined rows. tons per acre was less, 41.0, for problem. The experiment is not yet A trencher moved down the vine- 11.4 tons per acre it increased to finished, but signs indicate this may yard row, and as the dirt was 79.0 and the 115 tons per acre was be a problem with a solution. excavated, it was turned over with 219.4 grams per acre. The Aug. 31, Pope Valley Vineyards has a po- the gypsum and laid beside the row. 1984, harvest underscored the rest. tential for about 2,000 planted vine- Later a dozer pushed it back into The control harvested at 23.7 yard acres. Only 700 acres have been the trench, thus mixing the gypsum degrees Brix yielded 3.6 tons. The developed so far. When it came time and dirt mechanically. The vineyard 1.15 tons per acre at 23.8 degrees B to develop one 250-acre block it was was planted the following spring. gave 3.3, the 11.5 tons per acre at evident there was a problem. The results so far show that all 24.0 degrees B gave 3.7 and the 115 A good sized "road" of serpen- treatments produced results. Ac- tons per acre yield at 23.0 degrees B tine soil wandered down through cording to Bowers, just trenching was near double, 5.8 tons. the block. Though the total alone improved the apparent vigor Figures for 1984 were not yet involved soil measured only 21/2 of the plant. As Meyer wrote in a available, but the 1983 figures acres, it cut a swath covering about paper prepared for the Napa Coun- showed that the total acids varied 125 rows by 50 vines, like a river ty Viticulture Technical group, from a low of .66 for control to .70 through the block. Left uncor- "The results of both the soil and for 11.5 tons per acre. The pH rected, it would have made manage- plant tissue samples agree very ranged from a low of 3.68 for the ment of the block a major head- closely in that the first three 115 tons per acre to a high of 3.70 ache. Cangemi could have chosen treatments are similar but quite for the control. to isolate and plant around it, or different than treatment four." farm an uneven vineyard. The soil showed significant im- Of course the purpose of the University of California soil scien- provement with the highest applica- exercise was to see if it could be tists agreed to run a test at the vine- tion. Soil samples revealed that pH made to work at all and it does yard. Roland D. Meyer, soils spe- changed very little. The ECe was in- look like it can. A question to be cialist in plant nutrition headed up creased by the 115 tons per acre answered is what happens when and the group which included William E. rate. Exchangeable calcium and if those roots escape the trenched Wildman, specialist, magnesium as well as the calcium to area. Another problem, 115 tons Arnand Kasimatis, viticulture spe- magnesium ratio changed very little per acre is a lot of material to be cialist and Keith Bowers, farm ad- from the previous year. The greater applied. Would 50 work? Would 25 visor for Napa County. solubility of magnesium relative to work? Cangemi is working to see if The soils were analyzed. The sur- calcium gives rise to the wider ratios 15 and 20 tons per acre, applied by face pH was near neutral and rose contained in the saturated extract. a plow trencher, less labor intensive to a pH of 8 at the 30 to 36-inch The magnitude of the change in method, on both sides of an depth. While normal soils have a sodium concentration between treat- established vine, will work. He ratio of one part magnesium to four ments was large, but levels were in indicated that at this time the parts calcium, this soil measured the general, relatively small as compared method shows promise. reverse, the magnesium was 3.9 to to calcium and magnesium. 6.3 and the calcium one. "The results of both the soil and Meyer outlined a field trial that, plant tissue samples agree very using gypsum, might reverse the closely in that the first three calcium/magnesium balance. Gyp- treatments are similar but quite sum has been used for this purpose, different than treatment four. in the past, but never in exactly this "Observations of plant growth manner. Meyer's new concept was I/4 were, however, somewhat different to apply gypsum only to the vine row. A trench two feet wide and by Management of Vineyard Soils with Adverse Chemical Characteristics: Alkalinity, Salinity, Sodicity and High Chloride

'American Vineyard / March 1997 By Stan Grant, Viticulturist

ome soils have chemical characteristics that adversely affect vine growth and production. Four such soils Occurrence in California that occur in the San Joaquin Valley are alkaline, saline, The occurrence of alkali soils is mainly a function S of parent material from which they formed. Their sodic and high chloride soils (table 1). Management of these soils in vineyards may be difficult and expensive. . persistence is mainly a function of climate. Alkali soils Alkaline soils are soils of high pH (pH > 7.5 to 8). These persist where rainfall is insufficient to leach carbon- soils normally contain large quantities of carbonates which ates. The Cajon, Calhi, Chino, Hilmar, Panoche and buffer the soil's pH, that is, they act to maintain high soil pH. San Emigido series include areas of alkaline soils. Salinity refers to soil's total salt concentration. A saline Saline, sodic and high chloride soils occur mainly soil has a high salt concentration. The principle ions that in areas of poor drainage, areas irrigated by saline contribute to are calcium, magnesium, sodium, water (water SAR greater than 8.0), and areas affected sulfate, bicarbonate and chloride. These ions are charged and by salt water intrusion ( e.g., western portions of the have the ability to conduct electricity. This ability allows them Sacramento - San Joaquin Delta). that to be easily measured. A saline soil with an electrical conduc- include areas of saline, sodic and high chloride soils tivity (EC.) greater than 4.0 mmhos/cm or ds/m will greatly include the Cajon, Chino, Columbia, Dinuba, Foster, affect mature vines, although some yield reduction will occur Fresno, Hesperia, Hilmar, Marguerite, Orestimba, • at EC's as low as 2.0 mmhos/cm. Soils with an EC. > 1.6 Pachappa, Pescadero, and Solano. mmhos/cm will affect young grapevines. Effects on Vines and Soils Alkaline soils cause slow vine growth primarily Table 1. Definitions for 4 adverse soil due to the reduced availability of mineral nutrients. chemical conditions Zinc deficiency is most commonly associated with alkaline soils in California. Iron deficiency also occurs Soil Condition Definition and is common in southern San Joaquin County, north- Alkaline pH> 7.5 to 8.0 east of French Camp. Phosphorous, manganese and copper may also be low in alkaline soils. Saline Ec> 2.5 to 4.0 mmhos/cm The effects of high soil salinity are stunted growth, Sodic ESP> 10% particularly growth of foliage and reduced fruit yield. High Sodium Na>30 meq/1 or 690 ppm These effects are due to the decreased ability of vines High Chloride Cl> 10 meq/I or 350 ppm to acquire water (i.e. osmotic effects) and ion toxicities (i.e. specific ion effects). Soil sodicity causes soil aggregates to breakdown High soil sodium (Na), regardless of calcium or and disperse causing surface crusts to form. As a result, magnesium, can cause reduced vine growth and pro- water movement into and within the soil is restricted. ductivity. The concentration at which vines become In addition to effects on soils, high soil sodium can affected is about 30 meq/1 or 690 ppm. (These are the cause toxicity in grapevines. This occurs most com- same sodium concentrations given in different units). monly during hot weather while vines are transpiring High soil chloride (Cl). will also cause reduced large amounts of water. Sodium is taken up with the vine growth and productivity. Soils with concentra- . and it moves as far as possible within the tions greater than 10 meq/1 or 350 ppm are excessively vines - to the margins of the leaves. At the margins the high in chloride. sodium accumulates and causes death of leaf tissue. These conditions - alkalinity, high salinity, high This normally occurs when leaf sodium concentrations • sodicity and high chloride - may occur alone. How- are greater than 0.25%. ever, it is more common for them to occur in combina- High soil chloride causes vine foliage to become tion. Saline - alkaline and saline - sodic soils are dark green. Chloride moves with soil water and accu- examples. mulates in leaves in a manner similar to sodium. Table 2. Amount of sulfur required to lower the pH of an alkaline soil to 6.5

Chloride will cause marginal leaf bum • Initial soil pH Definition to Clay when leaf concentrations are greater than 0.50%. Young vines are much more sensi- 7.5 400 - 600 800 - 1000 tive to the toxic effects of high soil 80 1000 - 1500 1500 - 2000 salinity, sodium and chloride than ma- 8.5 1500 - 2000 2500 - 3000 ture vines because they have much less biomass in which to distribute ions and to lower soil pH is influenced by the Requirement (LR) developed therefore, ions accumulate to toxic lev- initial soil pH, texture, and carbonate by the USDA. els much more rapidly. concentration (table 2). The higher the Ecatc , Management: initial pH the greater quantity of amend- LR = ment needed. 5EC-EC Soil Modification Acidifying fertilizers (e.g., urea and The most commonly used approach ammonium) and acids injected to pre- for managing these problem soils is soil ECW = EC of the irrigation water. vent chemical clogging of drip emitters EC. = target soil EC for the root zone. modification, usually by applying soil also act to lower the pH of alkaline soils, amendments, to make the soil environ- but only in the soil volume wetted by the The value of EC. is selected from ment suitable for growth. emitters. Anhydrous and aqua ammonia table 3. Obviously a small yield reduc- The pH of alkali soils may be low- fertilizers will increase a soil's pH. tion is desirable and therefore, the tar- ered with sulfur, sulfuric acid, or other Reducing soils' salts, sodium and get EC, is usually between 1.5 and 2.0. acidifying agents applied to the soil. chloride requires adequate drainage, Adequate drainage is essential for leach- Ideally, the amendments should be in- leaching and maintenance of soil mois- ing to be effective. corporated as deeply as needed to affect ture with water low in salts, sodium and Prior to leaching, sodic soils nor- the alkaline portion of the soil. In some chloride. Leaching is accomplished by mally receive an application of an instances this is not possible, but the applying water in excess of what is amendment that displaces sodium from amendment may be incorporated into required for vine use during each grow- the soil directly, acidifies the soil, or the upper portion of the root zone. ing season. The amount of excess water does both. The amendment is incorpo- The amount of amendment required (in percent) required for leaching can rated as deeply as possible or as deeply be calculated using the formula for as needed. Table 3. Target ECse for Calculating leaching requirement and association grape yield reductions Target ECse Yield Reduction (mmhos/cm) (96%)

1.5 0 2.0 5 2.5 10 3.0 15 3.5 20 4.0 25

Table 4. Soil amendments for lowering soil sodium and their effectiveness relative to sulfur Tons equal to 1 Iblacre to replace 1 Amendment ton sulfur meq/1 sodium Sulfur 1.00 320 Gypsum 5.38 1720 Potassium thiosulfate 5.87 1880 Ammonium polysulfide 1.59 510

American Vineyard / March 1997

Gypsum is frequently used to amend adapted to high chloride soils. Own tices including the use of tolerant sodic soils. It serves as a source of rooted vines are poorly adapted to high rootstocks, soil amendments and calcium. Soils retain calcium more chloride soils. thoughtfully applied irrigations. The readily than they do sodium. This char- Rootstock Summary: combination of tolerant rootstocks and careful irrigation management may be acteristic of calcium allows it to displace 1. 140Ru is well adapted to alkaline sodium from the soil. Application rates and saline soils. sufficient when these adverse chemical conditions are very mild. Both practices of gypsum are usually between 1 and 4 2. 101-14 is well adapted to saline are a part of normal vineyard operations, tons/acre and are rarely greater than 10 and high chloride soils, but poorly and, therefore, require little additional tons/acre. The amount of gypsum re- adapted to alkaline soils. quired to replace soil sodium can be expense. Drainage improvement prior 3. 420 is well adapted to alkaline to planting may be needed, which estimated with a laboratory test called soils, but poorly adapted to saline soils. adds greatly to development costs. the Gypsum Requirement. Gypsum may 420A is a low vigor rootstock and may be either applied directly to the soil or not be appropriate for production-ori- More severe soil chemical condi- with irrigation water. ented vineyards in the San Joaquin tions require soil amendments. Soil If sodic soil contains high levels of Valley. amendments have to be reapplied when carbonates, calcium is already present 4. Salt Creek and Schwarzmann their effects diminish and chemical con- ditions worsen. Soil testing at regular in the soil and may be released from the (and probably 99R) are well adapted to intervals will reveal if and when reap- carbonates with the addition of sulfur or saline, high sodium and high chloride plication is necessary. Management of other acidifying amendments. Sulfur is soils. more effective than gypsum in reduc- 5. Avoid own rooted vines and extreme conditions may not be practi- cal or economically feasible. ing soil sodium (table 4). An agricul- Freedom for use in saline, high sodium tural laboratory can determine if car- and high chloride soils. Vines growing in soil with adverse bonates are present in the soil. chemical characteristics are frequently Amendments that both displace so- Summary smaller than normal. Spacing vines dium directly and acidify the soil in- Management of alkaline, saline, sodic closer in the row will compensate for clude potassium thiosulfate and ammo- and high chloride vineyard soils nor- smaller vine size and maximize fruit nium polysulfide. mally involves multiple viticulture prac- production. cD) Management: Table 5. Rootstock adaptation for 4 adverse soil Tolerant Rootstocks chemical conditions Tolerant rootstocks are another im- portant component of managing alka- Soil Condition Well Adapted Poorly Adapted line, saline, sodic, and high chloride soils. Tolerant rootstocks will rarely Alkaline 5BB, 420A, 140Ru 3309- 44-53, 101-14 substitute for modification of these prob- lem soils, but they lower the amount of Saline Salt Creek, Dogridge Own roots, Freedom, amendments required. To my knowledge, no studies on 101-14, 140Ru, 1616 420A, SO4 rootstock tolerance to soil alkalinity have been reported in the . Sodic Salt Creek, Schwarzmann Own roots, Freedom However, in France many soils contain high levels of lime and vines grown in High Chloride Salt Creek, Schwarzmann, Own roots these soils frequently suffer from iron SO4, 5BB, 99R, deficiency. Given that lime is another St. George, 101-14 name for calcium carbonate, it seems highly probable that these soils are al- kaline. Rootstocks that have been shown to tolerate high lime soils in France include 5BB, 420A, and 140Ru. Roostocks that do poorly in these soils include 3309, 44-53 and 101-14. Salt Creek, Dodgeridge, 101-14 and 140Ru are tolerant of saline soils. In southern France, 1616 is used success- fully on saline soils. Own rooted vines and vines on Freedom, 420, and SO4 poorly adapt to saline soils. Rootstocks are practically the same. Salt Creek, Schwarzmann, SO4, 5BB, 99R, St. George and 101-14 are well Ag Basics Soil Compaction:

A & L Midwest Ag Labs ture present. higher the organic matter, the less the Information Capsule No. 141* The soil's bulk density will also be soil will compact. The soil aggregate will changed from compaction. Bulk density be coarser, which will allow for better Soil compaction is a problem that movement of moisture through larger is often overlooked when attempting to pore spaces. Also, the density of organic Figure 1 identify causes of reduced production. matter is less than the soil, which means Bulk Density Effects on it will not compact as easily. Figure 2 Compaction is simply the arrangement Soil Compaction of soil particles to create a density that is indicates the inverse relationship be- high enough to limit root growth, soil 2.00 tween and bulk BULK moisture, and aeration. A compacted 1.75 density. DENSITY condition can be naturally occurring; gm/cm however, management is the cause of 1.50 Soil Symptoms most compaction. Larger equipment, 1.25 Soil symptoms can be seen in the tillage, and early planting are thought to field when compaction occurs. The fol- be reasons for soil compaction. Rotation 1.00 lowing conditions can be indications of Loose Tight without perennial crops could also add compaction: Coarse Textured (sandy , ) to compaction. It should be noted that Fine Textured ( !owns, clays) • Surface crusting is the deteriora- the use of anhydrous ammonia has not j tion of soil structure on the soil surface. been linked with increasing soil com- This can often occur from too much soil paction. can be defined as the weight of a unit preparation. Crop emergence will be a Compaction can have many ef- volume of dry soil that includes both the problem. fects on the soil. The soil structure is an solids and pore spaces. Bulk density will • Erosion may become more se- equilibrium of solids such as sands, , generally increase as soils become com- vere. Since infiltration is reduced, there clays, and organic matter along with pacted. will be greater soil runoff. Erosion will liquids and gases. The soil is comprised The amount of organic matter a increase compaction since the organic of 50% solids, and 50% air and water soil contains will affect the soil's capa- matter decreases as the becomes pore spaces. Compaction will cause the bility to be compacted. Generally, the exposed. aggregates to be realigned, and the pore spaces are reduced. The larger pore spaces will be reduced first into smaller pores; however, the equilibrium of air Figure 2 and water is disrupted and most of the air Relationship Between Bulk Density and Organic Matter is removed from the pore spaces and the water is retained. This leads to slower water infiltration, poor drainage, and Organic aeration. These factors will limit root growth and nutrient uptake. Matter (%) Soils that are made up of equal mixtures of sands, silts, and clays can compact easier than a more uniform soil made up of one type of particle. Figure 1 indicates the potential of compaction on two different soil types. 1.1 1.2 1.3 1.4 1.5 1.6 The moisture in the soil has the greatest influence on compaction. When field capacity is reached, compaction Bulk Density (gm/cm 3) will occur at its maximum. Soil particles are easily arranged when there is mois- . 1w3 Ag Basics A Review

• Standing water is also a symptom will also be a symptom of compaction. ure compaction in the field. This is the of compaction. The porosity is decreased This also is due to poor aeration and measurement of pressure required to from compaction, which reduces infil- reduced nutrient uptake when soils are move the tip of a shaft through the soil at tration. Infiltration can be reduced by up wet and cool. This uneven growth will a constant rate. The moisture content of to 16 times when these pore spaces are often continue through the season. Fig- the soil will have an effect on compac- compacted. ure 3 indicates the difference in plant tion readings. As the in- • Herbicide problems can also height at various rates of compaction. creases, the amount of pressure required occur when a soil is compacted. The Purple color in corn plants is also a to move through the soil will be re- movement of the herbicide into the soil symptom of compaction. Poor internal duced. Figure 4 indicates the lower can be slowed since porosity is reduced. drainage will reduce production of sug- amount of pressure required as the soil There can also be higher rates of carry- ars in the plant. When this occurs, the moisture increases at various bulk densi- over with herbicides that rely on micro- plant will begin to produce a more promi- ties. bial activity for breakdown. The effi- nent red pigment. Certain hybrids may To determine the actual amount of ciency of the microbes under compacted tend to show this symptom more often. compaction with a penetrometer, addi- conditions is reduced considerably. Rooting patterns are also affected tional analyses such as soil moisture and bulk density must be performed. How- ever, a penetrometer can be used to compare areas in a field that would be Figure 3 similar in soil moisture and bulk density Plant Height of Corn Reduced from Compaction for compaction. Crops may be affected differently in terms of root restriction and 128 — crop yield. Figure 5 shows an approxi- Average 121- mate reduction curve for most fibrous Plant 114 — root crops such as corn and small grains. Height (in.) 107 — 100 — However, this will shift, depending on the rooting nature of various crops. Compaction can reduce crop yields

Compacted Moderately Not as shown in Figure 6. Corn yields were Compacted Compacted reduced significantly in compacted ar- eas in comparison with noncompactgd fields.

by compaction. Often, a fibrous root Continued on page 4 Plant Symptoms system will grow horizontally along a The condition of the plants will compacted layer. This root system will Figure 4 show the effects of compaction and soil generally be shallower, and moisture Effects of Moisture and Bulk symptoms described earlier. There are stress can be a problem under dry condi- Density on Compaction many plant symptoms of compaction. tions. Lodging can also be a symptom High These can be seen in both the above- when compaction is present. The uptake Low ground portion and root system. of the potassium will often be reduced in Slow emergence will often occur compacted soils. Research has shown Pressure when soils are compacted. The surface an increased rate of lodging as the potas- crust will stress the young seedlings and sium decreases in relationship to the delay emergence. The soils may also be nitrogen level. Low High wet and cool due to poor internal drain- Measuring soil compaction can be Low High age from compaction. This will lead to very difficult since there are many para- Bulk Density disease associated with the . meters that will affect the compaction. A Uneven growth early in the season soil penetrometer can be used to meas- Figure 5 Soil Compact ion Root Penetration in Relationship to Soil Compaction Continued from page 3

Solutions to Compaction Problems 100 - Root Soil compaction can be minimized once the causes of compaction have Penetration (%) 80 - been determined. The following are ways 60 - to minimize compaction: 40 - • The types of tillage equipment and number of passes should be exam- 20 - ined for sources of potential compac- tion. I • Disc harrows along with large 100 200 300 400 500 600 tractors and combines will cause com- paction. Penetrometer Resistance PSI • Flotation tires will allow for the compacted area to spread horizontally instead of vertically, and can be broken up much easier. Figure 6 • Freezing and thawing will break Corn Yields and Compaction up compaction on the surface. How- ever, there would be very little effect on 220- deep subsoil compaction. Subsoil ing can 180- Yield be used to correct these deeper layers, (bu/Ac.) 140- 100- although for the best results the ground 40— should be fairly dry. The addition of organic matter can II. III hi also reduce compaction, so crop rota- Compacted Moderately Not tion is essential. Compacted Compacted * Reprinted with permission.

SPECIAL NOTICE TO OUR READERS Recently, there have been changes in the responsibilities within the technical support groups of Unocal Chemicals Division, Nitrogen group. Dr. Dale Rush, who initiated the Solution Sheet New Series, and was technical editor and frequent author, has been assigned to Unocal's new product development program. The responsibilities of the Solution Sheet content and technical editing have been taken over by Dr. Steven Petrie of Agronomy Services, and Mr. Jim Saake, Manager of Domestic Marketing. Any correspondence regarding the Solution Sheet should continue to be directed towards Patrice Moore, editor.

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Stephen Krebs, Prog. Coord. Viticulture & Wine Technology Napa Valley College Napa CA 94558 150