GE ~ by A. J. Winkler J. A. Cook W. M. Kliewer L. A. Lider

UNIVERSITY OF CALIFORNIA PRESS Berkeley • Los Angeles • London University of California Press Berkeley and Los Angeles, California University af California Press, Ltd. London, England Revised and enlarged edition, copyright© 1962, 1974 by The Regents of the University of California (Originally published 1962)

ISBN: o-52o-o2591-1 Library of Congress Catalog Card Number: 73-87507 Printed in the United States of America

34567890 6o Clirrutte and Soils of five miles surrounding the city pf Lodi, California. Similarly, the table­ variety Emperor is restricted to a hot, dry district in eastern Fresno, Tulare, and Kern counties. Comparable examples for given varieties, though seldom so restricted, are to be found in most countries that produce table . The centuries of experience and research of European growers and enola­ gists have definitely established the effect of climate on grapes. Climate influences the rates of change in the constituents of the fruit dur­ ing development and the composition at maturity. Moderately cool weather, under which ripening proceeds slowly, is favorable for the pro­ duction of dry table of quality. Cool weather fosters a high degree of acidity, a low pH, and a good color, and in most varieties it brings to the mature fruit optimum development of the aroma and flavor­ ing constituents and the precursors of the bouquet and flavoring sub­ stances of the wines. The combination of specific environmental condi­ tions with the qualities of a given variety has made possible the of , the Clarets and Burgundies of , the of Italy, the Constantias of South Africa, and other renowned wines. If, however, varieties lack special character, even the most favorable climate will not endow the resulting wines with good quality. Table wines from such varieties will be improved-because of a better balance of the sugar, acid, tannin, and flavor of the grapes at maturity-but they will still lack such special qualities as the bouquet and freshness that are characteristic of premium-quality wines. In warm climates the aromatic qualities of the grapes lose delicacy and richness, and the other constituents of the fruit are less well balanced; hence the resulting table wines, even from the best grape varieties, cannot compare with the best wines of cooler regions. In very hot regions, where growth and ripening changes proceed with great rapidity, the taste of most dry wines is harsh and coarse, and the other components are so poorly balanced that usually only common dry table wines can be made. The abundance of heat in some regions, which makes them poorly suited for dry wines, makes them ideal for such dessert wines as port, , and . With abundant heat the varieties

CLIMATIC REGIONS In the investigations of factors affecting wine quality, begun in 1935, it was found that the geographic regions of California (chap. 3) that had l 61 Climate and Soils served well for locating table and raisin grapes did not delineate the effects of climate sharply enough to serve similarly for wine grapes (Amerine and Winkler, 1944). In some instances the geographic regions showed widely varying climatic factors, especially in heat summation, and in other in­ stances there were no differences, in certain factors, between one region and another. For example, the range of heat summation in the Sacramento Valley is almost identical with that in the San Joaquin Valley, whereas there is a wide diversity of heat summations within the North Coast region. Therefore, available climatological data of United States Weather Bureau stations and the stations of the Department of Viticulture and Enology, University of California, were summarized for the areas where grapes are produced successfully for wine making. Then the principal cli­ matic factors of the areas were correlated with the analytical data and quality scores of the matured wines of the areas. The only factor of cliniate that proved to be of predominant importance was temperature. Other factors, such as rainfall, fog, humidity, and duration of sunshine, I may have effects, but these are much more limited than the effect of heat ! i summation. Amount and time of rainfull definitely restrict the production of natural raisins to certain areas. Rainfall, fog, and humidity also influ­ I ence the development of organisms that may have a marked effect on ; production costs and, as in the case of Botrytis cineria (noble rot), may, in certain varieties, be beneficial. Further, these factors of climate influence temperature, but no data show that they have a direct effect on the bal­ ance of the composition of the fruit at maturity, except when the noble rot intervenes. This finding, together with the very marked effect of tem­ perature when expressed as heat summation above 50° F. from April through October, led Professors Amerine and Winkler ( 1944) to use heat summation as a basis for segregating the grape-producing areas of the state into five climatic regions. Heat summation, as used here, means the sum of the mean monthly temperature above 50° F. for the period concerned. The base line is set at 50° F., because there is almost no shoot growth below this temperature. The summation is expressed as degree-days. For example, if the mean for a day is 70° F., the summation is 20 degree-days, and, if the mean for June is 65° F., the summation is 450 degree-days ( 15 degrees times 30 days). The iniportance of heat summation above 50° F. ( 10° C.) as a factor in grape quality has also been indicated by Koblet and Zwicky ( 1965). They found that degree was more closely correlated with heat summation above 50° F. than with total heat summation or hours of sunshine, under the cool condition of Wadenswil. The heat summations for the climatic regions are: I, less than 2,500 degree-days; II, 2,501 to 3,000 degree-days; III, 3,001 to 3,500 degree-days; l

OS : : : : a:CD ~ ~ mmm · •• V"?'.;. V'T'I ..l',1a;-~ f!-~-~o-t..r. · . ' 1{ '\ ..... I 1 ~-~~.,. /,' 1111 ·• ) " ) ·~·s~~~tmNI~ .._ .ht.r·-·..,.~ •,. 1'- ., "'' • •'+j' \ ' llomllb t, lfl!ilr '· · \ ' "~'· ) . .. ,.,,\,\,\...·,~~ ~ '·· ...... / l, ~CI.AR~ .... \ - ) ·. _.. _·-·-·-r-·-· ...... -.~·-1-·-·..r·-~---·- .. - '\. SAil !.IllS GO- .....1111111 . .SAlUEftHAROIIIO ~ i.,, I' ·.,"'\ ~ .../. t, - '• ~A "\ • ~./'·-.."' 1 J l.lllh IARIAAA ff!t.Lr. .... ,'t.. J ~ }~·~_\.... --.~· 11\t= .J' : - _ ,...... - • clflllll'\.. ~.. ~ I/.~~ • •.__.,._,.,---·-·-·-•-•,_,_._..,_ -- - "'\ ;;.::::::..• •,f OtYlftiiVI , , OftAMGi''\,++-1- -= tw-t-...... ~ -""""·-·-·-·-·-·-·-·--·-·-J•N~II~ti I !IMrtRIAI. •• ·=-rn ' ·-·====::.; ~' -·- ...J__...... ~··· ' MEXICO FrcuaE u: 'The climatic regions of California, based on heat summation above ;o~F.

--···· ...... ------·---. ----··- .... ~-A

---...'.)

)·­ -~ IV. 3·)Cl to 4000 degree-days; and V, 4.001 or more degree-days. Some characteristics of the climatic regions in California and their adaptation to important wine-producing localities follow. For further information on the location of the different climatic regions in California see figure 12. Typical and potential wine producing locations and their heat snmmation as degree-days for California along with a few well-known foreign areas are shown in table 3· r--- 6s I Climate and Soils I TABLE 3 (Continued) I I

Station and Heat Station and Heat -I county or country summation county or country summation !

Yakima, Washington z6oo Santa Barbara, Santa San Luis Obispo, San Barbara 2820 Luis Obispo z6zo Los Gatos, Santa Clara z88o I Gilroy, Santa Clara 2630 San Mateo, San Mateo :z88o I Sebastapol, Sonoma 2630 Hollister, San Benito 2890 ! Grants Pass, Oregon :z68o Monte Rosso V d., Sonoma 2C)OO .I Covelo, Mendocino Asti, Italy i 2710 2930 t ! Santiago, Chile 2710N Kelseyville, Lake 2930 Hulville, Sonoma 2720 Santa Rosa, Sonoma 2950 l Petaluma, Sonoma 2740 Sonoma, Sonoma 2950 Dyerville, Humboldt 2750 Bucharest, 296oN Melbourne, Australia 27)0N Placerville, El Dorado 2980 I San Jose, Santa Clara 2760 Novorossisk, Russia 2990* Climatic Region III locations Oakville, Napa poo+ Milan, Italy 3310N Ukiah, Mendocino 3100 Pinnacles, San Benito 333° Upper Lake, Lake 3100 Cuyama, Santa Barbara 334° Paso Robles, San Luis Santa Ana, Orange 3360 Obispo 3100 Tibilis, Russia 337° * Calistoga, Napa 31)0 Jamestown, Tuolumne 3400 King City, Monterey 31)0 Camino, E1 Dorado 3400 Hopland, Mendocino 3150 + Queretaro, Mexico 3400 ++ Astrakhan, Russia v6o * Mokelumne Hill, St. Helena, Napa 3170 Calaveras 3400 Santa Margarita, Livermore, Alameda 3400 San Luis Obispo 3180 Potter Valley, Mendocino 3420 Healdsburg, Sonot;na 3190 Cloverdale, Sonoma 343° Poway, San Diego 3220 Ramona, San Diego 347° Clear Lake Park, Lake p6o Mandeville Island, North Fork, Madera 3260 San Joaquin 3480 Hamadan, Iran p8oD Climatic Region N locations

Martinez, Contra Costa 3500 Gallo V d., Merced 374° Escondido, San Diego 3)10 Nacimento, Upland, San Bernardino 3)20 San Luis Obispo 374° Suisun, Solano 353° Davis, Yolo 3780 Florence, Italy 353°N Vacaville, Solano 3780 7

66 Climate and Soils

TABLE 3 (Continued)

Station and Heat Station and Heat county or country summation · county or country summation

Colfax, Placer 353° Sidney, Australia 378oN Venice, Italy 353° Sacramento, Sacramento 3830 Sao Paulo, Brazil 3540N Delta, Shasta 3850 Turlock, Stanislaus 3000 Clarksburg, Yolo 386o Linden, San Joaquin 3620 Sonora, Tuolumne 388o Mendosa, Argentina 3640 ** San Miguel, Vista, San Diego 3600 San Luis Obispo 3890 Beck, Stanislaus 3676G Aguascalentas, Mexico 39oo++ Pomona, Los Angeles 368o Fontana, San Bernardino 3900 Lodi, San Joaquin 3720 Auburn, Placer 399° Capetown, South Africa 3720N . ,--.. Climatic Region V locations

Ojai, Ventura 4010 Shiraz, Iran 439°D Modesto, Stanislaus 4010 Reedley, Tulare 4410 t Perth, Australia 4020N Merced, Merced 443° Oakdale. Stanislaus 4030 Chico, Butte 445° Split, Yugoslavia f090N Fresno, Fresno 468o Brentwood, Contra Costa 4100 Red Bluff, Tehama 493° Palermo, Italy 4100 Bakersfield, Kern 5080 Stockton, San Joaquin 4100 Algeria, Algers szoot Antioch, Contra Costa 4200 Tehran, Iran 52ION Woodland, Yolo 4210 Terreon, Mexico 59oo++ Peking, China 4290N

SOURCE OF DATA: Climatological Data Reports, U.S. Weather Bureau; ,. Prescott (1965); '"*,Eggenberger {1971 ); t, U.S. Trade Consuls;++, Mr. M. Ibarra; +, Department of Viticulture and Enology Stations; N, Nelson (1968); w, Wynn {1968); n, Development and Resources C01p. Sacramento, California; G, Grape Im­ provement Association.

Region I.-This region contains restricted areas of fertile soils. As a rule, hillside slopes and valley areas of moderate productivity are available for vines. The early maturing premium-quality dry table wine varieties attain their best development here. Heavy-bearing varieties should not be planted. since their production cannot compete with that of warmer districts, with more fertile soils. Region II.-An area of great importance. The valleys can produce most of the premium-quality and good· standard white and red table wines of 67 Climate and Soils California. The less productive slopes and hillsides cannot com­ pete in growing grapes for standard wines, because of lower , but, nevertheless, can produce favorable yields of fine wines. Irrigation is bene­ ficial in the areas of low rainfalL Region III.-Another important region. The lands are generally level or slightly sloping and fertile, except for some that are gravelly or stony and of only moderate depth. The moderately warm climate favors the production of grapes of favorable sugar content-sometimes with low acid, as may occur in warm years. Excellent red wines of later maturing premium quality varieties are the rule here .. White wines of fine· quality may be produced in limited areas on the lighter soils and on slopes with exacting management. Excellent natural sweet wines and good white and red wines can be produced on the more fertile soils. The best of the port varieties of moderate productivity will produce excellent port-type wines. Irrigation is beneficial in the areas of low rainfalL Region N.-The soils in region IV are generally fertile. Most vineyards

FIGURE 13: A wine grape vineyard in region I of the North Coastal area of California in spring. (Courtesy of Wine Institute) 68 Climate and Soils are irrigated and are capable of producing large crops. Some of the soils on the slopes of the east side of the Intermediate Central Valley region and in San Diego County are less fertile and less productive, but their grapes may be of better quality. Natural sweet wines are possible here, but in warm years the fruit of the most acceptable varieties tends to be low in acid. The white and red dessert wines produced here are of good qual­ ity. The white and red table wines are satisfactory if produced from the better, high-acid varieties. . Region V.-This region embraces the Sacrarpento Valley from Sacra­ mento to Redding and the San Joaquin Valley from Merced to Arvin. The soils are the most uniformly fertile· in California. Except for a few vine­ yards near Redding and some in the lower foothills, the region is entirely in the highly productive irrigated interior valleys. Of the regions that can produce wine grapes, this has the hottest climate. Standard red and white table wines of varying qualities can be made from the better high-acid varieties. The white and red dessert wines produced can be very good. Table 4 shows typical effect of heat summation on the color content and total acidity of several varieties of wine grapes in California. The climatic regions into which the grape-producing areas of California have been divided is a basic advance in the development of variety-climatic relationships. The climatic conditions of the present regions merge from one into the other, so the boundaries are not definite. Neither are condi­ tions uniform within a given region. Nevertheless, the figures for heat summation in regions I, II and III provide a valuable indicator of the quality level of the wines of the premium varieties produced in the coastal areas of California. Similarly, heat summation provides a basis for differ­ entiating the interior valleys into regions; some limited areas there have the same heat summation as the warmer coastal regions, but quality levels of the interior valley wines of the same varieties and same climatic regions are not comparable. As reported by Alley et al. ( 1971), the wines of the interior areas tend to be flat, unbalanced, lacking in aroma and finish. These deficiencies are likely owing to factors of climate, such as the heat summation above a given temperature, say 70° F., differences in heat summation during the ripening period, and lower relative humidity. For instance, three region III locations, each with a heat summation of 3,400° day above 50° F., have the following degree-days above 7oo F.: Livermore (coastal area) 15, Jamestown and Mokelume Hill (both. in­ terior areas) 295 and 353, respectively. The average yearly degree-days above ]0° F. for four well known locations-namely, Bakersfield with 1,168, Fresno with 913, Lodi with 311. and St. Helena with 72-when related to the scores of table wines from those areas further indicate the injurious effects of higher and higher temperatures on wine quality. Work­ ing with Tokay over a period of 13 years, Winkler and Williams {1939), 69 Climate and Sails

TABLE4 INFLUENCE OF REGIONAL CONDITIONS ON THE COLOR AND PER CEJ\'T ACIDITY OF GRAPES, CALIFOR"l\'"IA

Region Variety I II III N v Color value by vino-colorimeter

Carignane 100 57 49 Mataro 6) 20 15 Petite Sirah 200 8o 200 40 Total acid, per cent of grapes (as tartaric)

Burger 0 ·49 0.42 Petite Sirah .66 .6o Zinfandel •.)6 ·57

SOURCE OF DATA; Wink]er and Amerine ( 1938) and \\Tinkler ( 1938). found that the heat summation during the ripening period had a marked influence on table grape quality. In years with near 700 degree-days during ripening the fruit was very good, while in years when the heat summation above 50° F. was near 6oo degree-days the fruit scored very poor. These divisions into climatic regions should be considered as general demarcations. Normal year-to:year fluctuations in heat summation may in some years show a borderline area, as shown in table 3, to be in a lower region one year or a higher region of heat summation the next, as the case may be. It is to be hoped that refin~ments will be developed so as to delimit subr~ions within the present regions, thereby ensuring the great­ est potential for quality when the most favorable climatic subregion for a given variety is planted to that variety: Such refinements will largely be the responsibility of local information agencies and alert grower-wine pro-· ducers. This is being done by the agricultural extension service with num­ erous temperature stations in Sonoma County (Mr. R. L. Sission, personal communication), and in Stanislaus County (P. D. La Vine, 1971 ), as well as by a number of growers in various parts of the state. Valuable climatic information can be obtained in several years by comparing the readings of a calibrated weather unit with those of a nearby Standard Weather Bureau Station. The importance of a more restricted climatic area is stressed by the above work, by the well-known relations of area of produc­ tion to quality in Germany, France, and Italy, and by the work of Vagulans ( 1954) in Russia. Seasonal conditions.-In addition to the general effect of climate there I -../ ~------

70 Climate and Soils

.,.I ]: 1"-~

~~' I '1'

FrcuRE 14: A vineyard in the San Joaquin Valley district, with grnpes on tmys for misin production (region V). (Courtesy of California Raisin Ad­ '. ' visory Board) is a seasonal influence that is more or less prnrked according to the posi­ tion of the producing region in the Temperate Zone. Wines of best qual­ ity are usually produced in the hot years of the coolest regions, whereas in the warm regions the cool years produce the higher-quality wines. De­ viations from optimum conditions for maturing of the fruit are greater and most frequent in the coolest regions. Because California's present gmpe acreage is primarily in the warm part of the zone adapted for grape produc­ tion, the belief is prevalent that every year is a " year" in California. If this term simply designates years in which the grapes attain full matur­ ity, such a belief is correct. By general as well as historical- usage, how­ ever, the term "vintage year" -properly designates a year of outstanding 71 Climate and Soils quality. To say that California wines of all years are of outstanding or mperior quality, or even to say that the wines of all years are of equal quality, is not in keeping with the facts. Data on the effects of seasonal conditions on palatability are presented in the discussion of table-grape maturity standards (p. 556).

Sorr.s FOR GRAPES Grapes are adapted to a wide range of soil types. True, one finds a decided preference for certain soil types in nearly every grape-growing district. Nevertheless, when all soils used for growing the various kinds of grapes in the many different grape-producing regions of the world are compared, one finds that they range from gravelly sands to heavy clays, from shallow to very deep, and from low to high fertility. One should avoid heavy clays, very shallow soils, poorly drained soils, and those that contain high concen~ trations of salts of the alkali metals, boron, or other toxic substances. Soils for Vinifera grapes.-Varieties of Vilis vinifera are deep-rooted plants that fully explore the soil to 6 to 10 feet or more if root penetration is not obstructed by hardpan, impervious day substratum, toxic concen­ tration of salts, or a free water table. The largest vines and the heaviest crops are produced on deep, fertile soils. The quality of the fruit is better, although yields are usually lower, on soils of lower fertility or soils limited in depth by hardpan, rocks, or clay substrata. In regions of heavy rainfall, good drainage is essential. Where rainfall is scanty and irrigation is practiced, sub-drainage must allow enough water to escape to prevent the accumulation of injurious concentrations of salts; otherwise, the vines will be short-lived. . Since vinifera grapes grow best in regions that have few or no summe~; rains, enough of the winter rains must be stored in the soil to carry the vines through the summer, or irrigation must be supplied. The first con­ dition-dry farming-requires that the soil be deep and retain moisture. For example, in climatic region I of California, about 16 inches of water is required by the average vineyard of wine grapes each year. Each foot in depth of a loam soil will hold about 3 inches of- available water. Thus, such a soil must be 5 feet or more in depth, or the vines will lack water before the crop is mature. Sandy soils hold less water, and must be cor­ respondingly deeper. Where good irrigation water is available and carefully managed, grapes are being grown successfully on soils less than 2 feet deep. High soil fertility, it is generally agreed, is not so important as soils of such structures that favor extensive root development. On snch soils vine growth is less rank, and the ripening changes start earlier and proceed more slowly. At maturity, therefore, the fruit is firmer, of better balance, and has a rich, more pleasing aroma and flavor. Similar results may be