represent the most important of the soils of the many agricultural regions of the State. These have been arranged in vertical positions in the soil museum of Budd Hall and are being examined as rapidly as possible from a chemical, physical, and biological standpoint. The results will be presented in a special report.

Distribution of Humus in Soil Columns from Each Agricultural Region. The agricultural regions of the State comprise the Sacramento and San Joaquin valleys, forming together the central Great Valley, the Foothills lying on the western slope of the Sierra Nevada, the many Coast Range valleys and low hills among the mountain ranges along the western side of the State, the Southern California valleys and the low hills, the Desert Plain which is being brought under cultivation by the development and use of irrigation water, and the Northeastern Lavabed valleys. A large portion of the State is too mountainous and rugged for tillage and is partly timbered with forests of redwood, pine, and other trees suitable for lumber. The redwood forests form a region of the Coast Range of mountains.

As the object of this investigation was chiefly to ascertain the extent to which humus was found in the lower depths of the soils, the soil columns were only taken from those regions whose soils are many feet in depth. The number of columns obtained was 110 from thirtyseven counties, each column intended to represent a characteristic type of land in its particular region. There are of course very many small valleys and minor soil regions that have not been included in this investigation, some of which may be taken up later and reported when the results of the chemical and physical examination of these soil columns are given to the press. The analyses of the first foot of the soils. of many of these regions have already been published in the reports of this station. It is believed that the results presented in this investigation represent very well the humus conditions that prevail in the soils. in general throughout the State.

The humus and nitrogen determinations given in the following pages were made successively by Messrs. F. E. Johnson, M. E. Holter, and F. H. Wilson.

Soil Columns of the Sacramento Valley.

The valley of the Sacramento River, lying between the two great mountain ranges-Sierra Nevada on the east and Coast Range on the west-and which unite on the north, covers an area of 6,200 square miles. The valley is widest on the south where it unites with the San Joaquin Valley. Within its area are four or five general and highly distinct soil regions, or types, each of which is represented by one or more soil columns in our collection, or eighteen in all.

Alluvial Lands. These border the Sacramento River and are timbered with sycamore, white oak, and ash. The soil is a dark loam with little or no change to the depth of twelve feet, as shown in the soil columns, and even deeper. Three columns were taken from the following localities: Near Cottonwood, Shasta County, by W. S. Guilford; Glenn post office, in Glenn County, east of Willows; and near Perkins, Sacramento County, by Professor George Roberts, now of the Kentucky Agricultural College. To these was added a column of the alluvium of Chico Creek, taken from the Bidwell place, at Chico, Butte County.

Clay Loams of the Valley. These reach south from near Red Bluff and occupy the central part of the Sacramento Valley. As typical of this class of soils, seven columns were obtained from the following localities: Three miles west of Tehama, Tehama County; Willows, Glenn County; J. W. Walton's place a few miles south of Yuba City, Sutter County; Woodland, Yolo County; the University Farm, Davis, Yolo County; Live Oak, Sutter County, and from near Elmira, Solano County. In each case a depth of 12 feet was reached except at Live Oak, where at 9 feet the presence of water prevented a deeper sampling. Black Adobe Clay Soils. There are several regions of these black clays within the eastern, western, and southern parts of the Sacramento Valley. One of these reaches from southwest of Yuba City northward, passing west of Gridley and beyond Biggs. A column was taken from this belt, a few miles southwest of Yuba City, the surface soil of which contained 39 per cent of clay. Below this upper foot the color changed from black to gray. Another column was taken by F. E. Johnson from near Biggs. This contained 50 per cent of clay in its upper foot and the black color changed to gray below the third foot.

A region of black clay lies three miles east of Willows, Glenn County, whose surface foot contains 47.46 per cent clay, and the black color extends through five feet. A column of this was taken to the depth of twelve feet. Another column was taken from a body of intensely clayey and black land lying south of Dixon. It contains 61.75 per cent of clay.

Red Mesa and "Bedrock Lands." These form a wide border along the eastern and northern sides of the valley, and are characterized by usually shallow soils underlaid by either heavy compact red clays, or by cemented beds of gravel and grit, forming a hardpan or bedrock at depths of from two to five feet below the surface. Because of the shallowness of these lands, this region is represented by but three columns; one from near Sheridan, Placer County, representing the lands on the eastern side of the valley; another from the bluff of Oak Creek, southwest from Red Bluff, and one half mile west of the Corning road; and still another taken by F. E. Johnson near Acampo, San Joaquin County.

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HUMUS AND HUMUS-NITROGEN IN SOILS OF THE SACRAMENTO VALLEY.

It would naturally be supposed that because of their deep color the black clay adobe soils would contain more humus than any other soil, but the above results show that such is not the case, for the alluvial soils are richer, and even the gray loams have nearly as much as the black adobe in the first foot and are a little richer in the rest of the column. The color of a soil, then, is no certain guide as to the relative amount of humus it contains.

Among the individual columns the richest of the alluvial group are those from Glenn and Chico, the former in the upper three feet and the latter in the entire column; there is .52 per cent in the twelfth foot of the Chico column.

The richest of the clay loam group is that from Davis, the average in the upper three feet being 1.16 per cent and an average of .755 for the entire column; the twelfth foot contains .69 per cent. The columns from Tehama, Waltons, and Willows are next in their respective percentages, Waltons being the richest in the upper three feet.

The black adobe east of Willows is the richest of the four that form the composite column, and contains an average of 1.27 per cent in the upper three feet.

Soil Columns of the San Joaquin Valley.

San Joaquin Valley, with an area of one thousand square miles, possesses many large and distinct soil types or regions, each of which is represented in our soil collection in columns of ten or twelve feet each.

Twenty-four localities in eight counties were selected from which to obtain columns of soil as nearly typical as possible of each region, and fifteen of the columns were taken to depths of ten or twelve feet, the others being limited in depth either by hardpan, coarse gravel or other obstruction which prevented the penetration of the soil auger; sometimes the water table at depths of less than ten feet produced such mushy conditions in the soil as to prevent its being removed by the

auger.

Rich Alluvial Lands and Tule Marshes. The rivers of the San Joaquin Valley are usually bordered by narrow bottom lands, the Merced and Kings rivers being exceptions where they enter the valley plains. A column of eight feet depth was taken by F. E. Johnson from the lands of Kings River near Kings River post office, and is the only representative of such lands from this valley. The surface soils of other streams have, however, been examined from time to time and their humus content ascertained.

The tule marshes cover a very large region at the junction of the San Joaquin and Sacramento rivers and are divided up into islands by many sloughs. The soil of these islands is shallow and peaty though rich, and water appears at but a few feet below the surface. There are localities, however, where a deep soil may be found, and from one of these a column of twelve feet was obtained for us by W. W. Mackie of the United States Bureau of Soils. It was taken from a few miles northwest of Stockton, and is an excellent representative of these lands.

Black Adobe Clay Lands. A large area of black adobe land occupies an area in San Joaquin County extending from two miles north of Calaveras River south to French Camp slough and from the tules or marshes of San Joaquin River eastward toward the hills, and is timbered with oaks. The character of the soil is shown in a column twelve feet in depth taken three miles southeast of Stockton.

The region continues southward in a narrow belt along the base of the hills into Kern County, being known in Tulare County as "dry bog," because of its tendency to break up into small fragments when dry. It is here underlaid by a reddish clay loam from which it is sometimes separated by a whitish calcareous or siliceous lime and magnesian bed of varying thickness. Two columns of this black clay adobe were secured from near Porterville, one of which appears in the table of analyses.

On the west side of the valley another narrow black adobe belt reaches along the base of the hills from west of Tracy into Merced County on the south. It is represented by a column of ten feet taken three miles west of Tracy.

Reddish Clay Lands. A prominent and wide region of lands of this character occupies a large part of the eastern side of the valley; it is narrow on the north in San Joaquin, Stanislaus, Merced, and Madera counties, and on the south in Tulare and Kern, but quite wide in Fresno County. It is the southern extension of the belt of "bedrock" lands of the Sacramento Valley. It is largely characterized by a rocky hardpan of cemented gravel and grit, with thicknesses of an inch to as much as twelve inches, and even more, and occurring at depths of from two to six or eight feet below the surface; when it occurs near the surface, the

hardpan, because of its irregular bedding, gives rise to a rolling or hogwallow feature. An excellent soil underlies the hardpan, however, and when the latter is broken up by dynamite good results in tree growth are usually obtained.

Columns of this land were obtained from a few miles east of Fresno; from the Kearney Park; from Lindsay in Tulare County; and from two miles southwest of Farmington, San Joaquin County, sent by H. Mueller.

Delta Plains of Kings and Kern Rivers. There are two tracts of this class of lowlands which are made of fine sediment brought down from the Sierra Nevada; the Coast Range on the west contributing little or nothing to these deltas, as its streams mainly flow westward to the Pacific.

The Mussel Slough region bordering Tulare Lake received its sediment from Kings, Kaweah, and Tule rivers and covers a very large area. It is timbered with oaks, and the nature of its soils are shown in columns twelve feet deep, taken respectively from near Corcoran and Armona.

The Kern River delta further south, with an area of about 290 square miles, is also timbered with oaks. It is represented in the soil collection by a column taken three miles southwest of Bakersfield. Water was reached in the seventh foot.

Gray Sandy Loams and Sandy Soils. The greater part of the San Joaquin Valley is covered with gray sandy and sandy loam soils on the east side of the valley and with gray clay loams on the west side. On the east side, the slope of the valley to the central trough is wider than on the west, and the numerous and rapidly flowing streams have brought from the Sierra much sand and gravel, which comprises from 85 to 95 per cent of the composition of the gray soils. Notwithstanding their very sandy nature these lands are usually deep and very highly productive under adequate rainfall or irrigation. Calcareous hardpans are found in some localities in irregular sheets and at various depths, but their injurious effects can be obviated in orchards by blasting; a good soil underlies them. Columns of these lands were obtained from Modesto, Stanislaus County; from three miles west of Tulare; and from a few miles north of Exeter, both in Tulare County; and from near Livingston, Merced County.

Gray Clay Loam Lands. The lands on the west side of the valley are quite level and contain more clay than those of the east side. There are but few streams on the west side, and these have their source but a short distance within the Coast Range, whose drainage is almost entirely westward. These west-side lands, therefore, must have been deposited from the waters coming from the Sierra Nevada after they had dropped