APPENDIX C. 



SHORT APPROXIMATE METHODS OF SOIL EXAMINATION 

 USED AT THE CALIFORNIA EXPERIMENT STATION. 



BY R. H. LOUGHRIDGE. 



THE California Experiment Station has for many years given the 

 farmers of the State the privilege of having their soils examined to as- 

 certain any physical defects, deficiency in plant-food, or the presence 

 of alkali salts. They have quite generally taken advantage of this, and 

 the number of samples of soil sent in each year has been very large. 



A complete analysis of a soil-sample requires fully 15 days; hence 

 the necessity of adopting some quick methods for the determination of 

 the main elements of fertility, viz., humus, lime, potash, and phosphoric 

 acid, that would at the same time give results sufficiently accurate 

 for practical purposes. Similarly for alkali salts in the soil ; the leach- 

 ing-out and analysis of which often occupies more than a week. 



The following methods have been adopted, which shorten the time 

 of examination for the plant-food of a soil to about one hour, except 

 for potash, which requires a much longer time. For alkali salts the 

 time is reduced to two days, and less if a pressure filter be used. 



Humus. The Grandeau method of ammonia extraction requires the 

 removal of the lime and magnesia with weak hydrochloric acid, wash- 

 ing out of the acid and then digestion with weak ammonia ; all of which, 

 with a soil rich in humus, may require many days, though a number of 

 samples may be put through at the same time. 



The method adopted to determine adequacy or inadequacy of the 

 humus (for this is all that is intended in this examination) is completed 

 in less than half an hour. It is based on the color of the humus-extract 

 and avoids the necessity of removal of the lime from the soil. 



The soil is pulverized in a mortar with a rubber pestle, and passed 

 through a half-millimeter sieve. Seven grams of the fine earth is placed 

 in a test tube with 15 or 20 cc. of a ten percent solution of caustic 

 potash and boiled for ten or fifteen seconds, then allowed to settle. 

 The humus is dissolved and the density of the color of the solution is 

 an indication of adequacy or inadequacy. A dense black, non-trans- 



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