UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA CIRCULAR 306 May, 192G A GENERAL PURPOSE SOIL AUGER AND ITS USE ON THE FARM STANLEY W. COSBY In any investigation of the soil, particularly one concerned with the production of crops, it is highly important to examine the subsoil zones in which root development occurs and to determine the presence of conditions favorable or unfavorable for plant growth. For such an examination it has been found most desirable to make use of some soil sampling tool (such as the one described herein) that is effective for the purpose, readily used, and easily transported. TYPES OF SOIL AUGERS Several types of soil sampling tools have been designed, among the more important being the "worm" augers, "post-hole" augers, and the "soil tubes." Each of these tools appears best suited for some specific purpose. The soil tube is used primarily by the scientist and investigator who must have accurate and uncontaminated soil samples for laboratory study, while the post-hole auger has been found best suited to sampling certain of the very dry and coarse soils. The worm auger (fig. 1) has proved under a wide range of field conditions to be the best general purpose auger and one that is particularly suited to the farmer's use. In soil survey work by the federal and state governments this auger is used almost exclusively and it has become known as the ' ' Bureau of Soils ' ' type of auger. This auger is being offered for sale at the present time by several manufacturers at prices ranging between seven and twelve dollars. A blacksmith, or anyone handy with tools, can make such an auger from the directions given below. DIRECTIONS FOR MAKING A SOIL AUGER /"PiPE \ ■Bit -Weld A" Pod The side cutting edges and the screw point (A and B in fig. 2) are removed from a li/o-inch carpenter's standard wood bit and the pitch of the worm, between C and D in figure 2, is made slightly steeper. In making the latter change the bit is heated and drawn out on the round point of the anvil, a process that tends to make it somewhat fish-tailed in shape (fig. 3). Finishing touches can be given with a file. The square-tapered, upper end of the bit is then removed and the shank welded to a six-foot length of % or %-inch steel rod. The handle at the top is best made by attaching two 6-inch pieces of 1-inch pipe to the rod with an ordinary Tee-coupling. The auger may be made in two or more sec- tions for greater convenience in carrying it from one place to another by putting in a sleeve- coupling at each joint, as shown in figure 1. This coupling should be strong; the hexagonal wind- mill pump rod connection has been found most satisfactory for this purpose. A short section near the ends of each rod may be slightly flat- Aero motor tened to make it easier to grip with the wrench "i* iSleevi when uncoupling the auger. The threading on the ends of the sections should extend for a sufficient distance to permit jamming the ends together within the coupling. When the auger is thus screwed tightly together it will withstand considerable strain in "backing-out" without uncoupling. It is not advisable to drill a hole through the coupling and the rod for a rivet or pin, as it weakens the rod and is unnecessary if the auger is properly made. HOW TO USE A SOIL AUGER In boring a hole with this type of auger, the surface trash and loose soil should be removed to prevent it from falling into the hole. Twist the auger vertically downward about six inches, place the feet close to the auger on each side and pull straight upward, at the same time giving the auger a quarter turn to the right to break free the core of soil. To remove the soil from the auger, hold it near the point of COC/PUNG r "Pod Tee /Coupling ^m f/6. J. /fssen^c/ balance with the right hand, place the thumb and first finger of the left hand at the tip of the bit and twist the entire anger with the right hand. This will canse the bit to turn through the fingers and drop the soil into the left hand. In particularly dry soils it may be necessary to pour a small amount of water into the hole to moisten the soil and permit the ready removal of the sample. Do not twist the auger too deeply before removal, as in heavy soils it may prove impossible to pull out a deep core. In very tough soils better progress can be made by boring in a half turn of the auger, pulling this up an inch or two to cut it loose, then boring in again, thus filling the worm with soil without having to break it all loose with one effort. /="/<£ 2 - WOOD BIT F/6. 3 - SOIL BIT SOME FARM USES FOR THE SOIL AUGER The soil auger is adapted to a great many uses on the farm. These range from a detailed inspection of land Avhich the farmer contem- plates purchasing or a study of soil conditions for the laying out of his fields and orchards, to the acquisition of soil knowledge on which to base his various cultural methods and irrigation practices. Although the surface of the soil may have a uniform appearance, the subsoil frequently shows marked variation within short distances, either in a vertical or horizontal direction. This is particularly true in the case of our stream-laid soils. In the more recent depositions the vagaries of the depositing streams have produced numerous strips and bodies of soil having wide textural differences ; a very heavy clay sub- soil strata may adjoin a coarse sandy or gravelly remnant of a former channel which has been covered by later depositions. In our old alluvial soils, marked changes in subsoil textures are not so abrupt in a horizontal plane as they are in a vertical direction, the initial differences due to deposition having* been largely obscured by later modifications due to weathering. Generally this period of modification has produced a much heavier-textured subsoil, one that may be very compact and relatively impervious to the penetration of moisture and plant roots. The more extreme developments of these processes have resulted in the formation of the hard cemented subsoil zone, com- monly known as "hardpan." The various subsoil conditions are seldom apparent from surface indications and yet their presence has a profound influence on the production of crops. In purchasing a farm, the intelligent buyer will endeavor to secure extensive information concerning it and to evaluate this in terms of crop-profits. The most reliable and economical method of securing information regarding the soils consists of a systematic series of borings over the entire property in order to determine the soil and subsoil characteristics. Such borings will show the soil variations and may be used subsequently in the construction of a map, or lay-out, to determine the location of the different crops to be planted. This will lead to the crops being situated on those soils which are best suited to their production. On a farm which has already been developed, the soil auger is a valuable aid in cultural practices, particularly in the case of irri- gation. By a study of the moisture conditions both before and after irrigation, information can be secured to determine the time of application of water and the most desirable method to follow. The farmer can ascertain the depths to which the water is penetrating and avoid the undesirable features of too shallow or of too deep a distri- bution, making the application according to the root-depths of his crop. He can vary his applications in different parts of his orchard, or field, according to the local soil variations. By a frequent obser- vation of the moisture in his soil, he can maintain it more nearly at the desirable point than by judging from surface indications, or by a rule-of-thumb schedule. Over-wet soils, high water tables, and the need for artificial drainage can be readily determined with this tool. Many other uses might be suggested, such as studying small areas where failure of crops may be due to some previously undiscovered subsoil condition or moisture variation, or determining the proper location for various farm structures, wells, pits, and other excavations. This type of soil auger is light, easily carried, and rapid and easy in operation, features that are essential if the tool is to be used as extensively and continuously as is necessary in controlling irrigation and interpreting crop responses to soil conditions.