Soil Profiles Identify Series basic soil surveys establish classifying characteristics and indicate selection of most efficient agricultural use

Lloyd N. Brown

Differences in the surface 6’ of soil- made and submitted for correlation on tains the most recent soils. Group I1 in structure, color, texture, reaction, con- a national basis. By this method more soils have a slight clay subsoil, those in tent of salts or humus, mineralogical than one name for the same soil in the Group 111 have a moderate clay subsoil composition-usually have agricultural various states is avoided. For instance, and Group IV soils have a dense clay significance and separate soils into differ- in an early survey a soil was found along subsoil. Soils in Group V have a hard- ent series or identifying units of classi- the Columbia River in Oregon and Wash- pan. Group VI is the smallest group and fication. &early 500 soil series have been ington and was given the name Colum- is made up principally of secondary soils identified in California. bia; subsequently similar soil was found and similar to those in Group IV. Groups Soil series names are place names along the Sacramento River and through VII, VIII, and IX are primary or re- taken from the area where the series is correlation was identified as Columbia. sidual soils formed on hard igneous rock, first found such as Redding, Yolo, The soil series have been divided into hard sedimentary rock, and softly con- Fresno, Hanford, Ramona. When a new nine profile groups. Groups I to V are solidated material. series is found, an official description is Secondary or alluvial soils. Group I con- Concluded on next page

Soil monoliths representing the nine profile groups.

CALIFORNIA AGRICULTURE, MARCH, 1957 11 Soil Sterilized by Irradiation sterilization of soil by exposure to an electron beam offers new tool for research on chemistry and microbiology of soil

A. D. Mclaren and Lola Reshetko

Soil may be sterilized easily by an grams, air-dried and sieved-were ir- zoylarginineamide-BAA-by nonsterile electron beam-of sufficient intensity radiated in sealed polyethylene bags soil proceeded to the extent of 45: i -S.5',; arid energy-without destroying the placed around the rim of a turntable of of the maximum possible release of nitro- urease-enzyme activity. 35 centimeters diameter, which turned gen as ammonia in 80 hours. Thus more Sterile soil is often desired for studies urider a 12 million volt electron beam at ammonia was released than was expected of the chemistry and microbiology of 20 revolutions per minute. The swept by tryptic activity alone, indicating the soil but-unfortunately-the use of heat beam was wide enough to cover com- presence of some arginine decarboxylase or chemicals for sterilization tends to pletely the width of each bag as it passed or arginine dihydrolase activity. No am- change the chemical and nutritional through the radiation field. By this tech- monia was liberated from BAA in irra- properties of soils rather markedly. nique heating was imperceptible to the diated soil. Experience with the irradiation of touch. The bags were turned over after Electron penetration is limited by the foods suggested that heatless steriliza- SO',; of the dose had been received. energy, and for practical reasons this tion of soils-by electron beam radiation Analyses of the irradiated soil samples method of sterilization is only useful for -would leave the soil and its enzymes showed that doses of about two million laboratory and for greenhouse work- essentially unchanged. rep-roentgen equivalent physical. a as with flats-or where the soil penetra- Bacteria. as well as spores, are more unit of energy in radiation dosimetry- tion need be only a few inches. Evidentl! sensitive to electron beam radiation than w i 11 ki 11 all h ac teria and actin om yce tes soil so sterilized is virtually free from are viruses and enzymes. For example, and one million rep will kill all fungi in chemical change and should lend itself to kill bacteria and bacterial spores in soil. At a dose of one-fourth million rep readily to studies with pure cultures of broth only about one-tenth as much radi- the number of viable organisms is re- plant pathogens, riitrogeii fixers. and ation is required as for the inactivation cluced to less than l',, . soil-borne viruses. of urease. 1-rease action converts urea With urea added, the rates of produc- into plant-usable ammonium carbonate. tion of ammonia in slightly alkaline soil A. 11. MrLaren is Associate I'roiessor of Soil Chemistry, University of Cnliforniu, Serkele, . Results of experiments with soil of the and in irradiation sterilized soil were Dublin series show that doses compa- Lola Reshetko was Laborntorv Tec hnirian. nearly constant during the first ten hours llnicersitv of California, Berhele?. when the rable to those required to sterilize broth of incubation. By contrast, autoclaved- above reported study was conducted. are required for killing microorganisms steam sterilized-soil was devoid of ure- The staff of the Applied Radiation Corpora- in soil. ase activity. tion oj Walnut Creek assisted in the experiment Samples of Dublin clay-loam-100 The production of ammonia from ben- in soil sterilization by the electron beam.

SOIL SURVEYS C, the slope; and X,consisting of the fol- SMOG lowing six additional factors: drainage, Continued from precrtling page alkali, nutrient-fertility-level, acidity, Continued froni page 9 A soil profile often can be seen in road erosion. and microrelief. posure to the synthetic smog. E\ en cuts. stream banks. drainage ditches, ex- In addition to establishing the vari- though injury was visible on some of the cavations for pipe lines and other places ous characteristics of soils and their best seedlings, it was apparently not suffi- where a bank of soil is exposed. When agricultural use, the basic information ciently general to account for the pro- such open soil surfaces can not be found represented 1)y soil surveys and ratings nounced dwarfing of the seedlings. it is necessary to bore holes with a soil is used by many public agencies in their Experiments are being continued in an auger to locate a typical profile and then work with soils. The United States effort to determine the effect of natural dig a hole about 3' square arid 5' deep. Bureau of Reclamation uses the infornia- occurring pollutants upon the growth arid The composition and characteristics of tion in setting up irrigability classifica- development of avocado trees. the soil determine its classification by tions of soils; the state engineer wes it 0.C. Taylor is Assistant Horticulturist, 1 rri- series. For purposes of study. mono- in planning irrigation developments; the versity o! California, Rirerside. liths-as shown in the photograph on the United States Soil Conservation Service E. A. Cardiff is Senior Laboratory Terhni- preceding page-are taken from soil pro- uses it in developing their land-use capa- cian, llniversity oi Calitornia, Riverside. files. bility system; and state and county as- J. D. illersereair is Senior Laborator) Tech- Another. and a more involved rating sessors use soil surveys and ratings in nician, University o! Cali\ornia, Ritwside. system-known as the Storie Index-is cetting up classifications for assessment 1. T. Middleton is Plant Pathologist, I'ni- based 011 soil characteristics that govern purposes. cersity of California, Riverside. -- _-__ the soils' potential utilization and pro- The nrithmetiral relationship between the ductive capacity. It is wholly independ- Llord N. Brown is Extension Soils Specialist, 1lnit)ersity of California, Berkeley. destruction of chlorophyll and length oi er- ent of physical and economic factors posure to synthetir smog was reported b) Louis such as climate and accessibility. Soils The soil series profile group system of rlassi- C. Erirkson, Associate Plant Physiologist, I'ni- fication was developed by R. Earl Storie, Pro- versity of Calilornia, Riverside, and R. T. Wed- are rated on four factors: A, the soil pro- jessor of Soils and Plant Nutrition, llnitwsity ding, Assistant Plant Physiologist, Unitersit) file: B, the texture of the surface soil; oi Cali!ornia, Berkeley. of Cali fornia, Riverside.

12 CALIFORNIA AGRICULTURE, MARCH, 1957