SOILS 



1851 



possible proportion of soil moisture. This 

 depth will vary with different types of 

 soil. Professor Thorn, soil physicist of 

 the Washington State Experiment Station, 

 working with the ordinary "volcanic ash'* 

 soil of the Palouse regions, found the fol- 

 lowing effect of mulches of different 

 depths upon the loss of soil moisture from 

 the soil during the month of August, 

 1912: 



Table YI 



Effect of Depth of Mulch Upon Evapora- 

 tion of Soil Moisture 



Moisture loss, 

 Depth of calculated as 

 mulch. to acre-inches. 

 No mulcii 1.66 



1 inch 1.42 



2 inches 1.15 



3 inches 1.02 



4 inches 1.01 



5 inches 98 



These results show that while mulches 

 deeper than three inches save slightly 

 more moisture, the saving is too little to 

 compensate for the additional loss of 

 plant food supply. Similar results have 

 been reported from measurements made 

 by the United States irrigation investiga- 

 tions on irrigated lands in California, 

 where it was found that a three-inch 

 mulch saved 72 per cent of the total pos- 

 sible saving and that increasing the depth 

 of the mulch to ten inches only resulted 

 in a saving of 88 per cent of the total pos- 

 sible amount. For all ordinary soils and 

 conditions, therefore, a three-inch mulch 

 is the most efficient depth. 



R. W. Thatcher, 

 Director Washington Experiment Station. 



EAPIDITY OF RISE OF CAPILLARY 



MOISTURE IN DIFFERENT TYPES 



OF SOIL 



The rate at which water rises through 

 soil by capillary action depends upon the 

 size of the soil particles and the propor- 

 tion of humus which the soil contains. 

 In an experiment conducted by Prof. C. 

 C. Thorn, soil physicist of the experiment 

 station at Pullman, Washington, the fol- 

 lowing results were obtained. The dif- 

 ferent soils were placed in large galvan-' 

 ized iron tanks in the open field, all 

 equally compacted, and a constant supply 

 of water fed to each at a depth of two 

 feet below the surface. The amount of 

 water, expressed both in pounds and in 



the equivalent acre-inches, which came up 

 through the soils and evaporated away 

 into the air during the month of August, 

 1912, is shown in the following table: 



Table VII 



Rate of Capillary Rise of Water in Soil, 

 as Shown by Evaporation 



Losses 



Kind of Loss Ifoss, as 



Soil in lbs. acre-ins 



Sand 33.3 2 19 



Loam 26.2 1.66 



Clay 24.0 1.53 



Humus 18.4 1.17 



R. W. Thatcher, 



Director Washington Experiment Station. 



PROBLEMS m SOIL FERTILITY M 

 IfESTERJf WASHINOTOlSr 



From all over Western Washington far- 

 mers are constantly inguiring "What fer- 

 tilizer shall I put on my soil to make it 

 grow vegetables, grasses, or fruit?" or 

 "Will you please analyze my soil and tell 

 me what element it lacks, or what element 

 it contains?" These inquiries show a very 

 general need for information as to how 

 food elements exist in the soil and how 

 fertility may he developed within the soil. 



All agricultural plants require for their 

 growth thirteen elements, all of which are 

 found in greater or less quantity in every 

 soil that will grow plants at all. Of these 

 elements the only ones apt to he deficient 

 in any soil are nitrogen, potash, phos- 

 phoric acid, and sometimes lime. Phys- 

 ically, all soils consist of broken down 

 rock and decaying organic matter (the 

 remains of leaves, stems, roots, manure, 

 etc.). The plant must derive its potash, 

 phosphoric acid and lime from the broken 

 down rock of the soil. The nitrogen 

 needed by the plant is secured from the 

 decaying organic matter of the soil, ex- 

 cept in the case of leguminous plants, 

 which are able to secure some of the free 

 nitrogen of the air through the action of 

 certain bacteria on their roots. 



How do the plants take up these ele- 

 ments? Pour water through a bucket of 

 good soil; it will come through discolored. 

 Chemical analysis will show that the 

 water has dissolved certain compounds 

 of potash, of phosphorus, and of nitrogen 

 (as well as compounds of other elements) 

 from the soil. This solution of compounds 



