142 BULLETIN 1059, U. S. DEPARTMENT OF AGRICULTURE. 



drought while the other thrives. Unless, then, it is desired to deal 

 in generalities, and ascribe to one species certain characters which 

 another does not possess, on the basis of general knowledge or pure 

 assumption, it will be necessary in studying competition to go to the 

 whole length prescribed for the determination of the coefficient of 

 availability. 



16. Much the same situation exists with respect to the study of the 

 final character of the forest formation, its height, rate of growth, 

 etc. The critical study of the moisture conditions in relation to 

 ultimate height is of special importance in forestry because ultimate 

 height, in forest management plans, is often taken as a criterion of 

 the quality of the site; that is, its yield possibilities. Are the two 

 things closely related? If the ultimate height is limited by drought 

 conditions which occur only periodically, may not the yield possi- 

 bilities be considerably greater or less than would be indicated by 

 this measure, depending very much on the total water-holding 

 capacity of the soil, etc. ? Obviously such questions as these can be 

 answered only after exhaustive study. This requires the establish- 

 ment of permanent soil-moisture stations, the determination each 

 3^ear of the critical conditions that exist, and the use of the entire 

 system that has been suggested for arriving at a measure of the true 

 conditions. 



Special Equipment for Soil Moisture and Son. Quality Study. 



Soil sieves : 



Standard soil sieves. Per set, about $10. 00 



Soil borers : 



3-foot soil borer, tube, with hammer 9. 00 



6-foot soil borer, tube, with hammer 11. 00 



6-foot soil borer, auger handle hammer 12. 0O 



Soil cans: 



Patent seamless, noncorrosive, tin soil cans — 



4-ounce can, deep style, per gross 3. 50' 



8-ounce can, deep style, per gross 4. 00 



(35 per cent discount on above prices to United States 

 Government. ) 

 Soil sample cans, seamless tin, No. 9178 A — 



Capacity, ounces 4 8 16 



Per dozen $0.22 $0.33 $0.55 



Soil sample cans, aluminum, with screw tops — 



21 inches in diameter by 2^ inches high, unnumbered 9183, 



each . 25 



With can cover numbered. (In ordering, state what numbers 



are desired.) No. 9183 A, each . .30 



Soil sample can, aluminum, with aluminum top. The diameter of 

 these cans is uniform, so that the cover fits the bottom of the can, 



