EXPERIMENT STATION BULLETINS. 



159 



Losses by evaporation, wheu the upper soil is well supplied with moisture, may 

 amount to an inch of water in four days. In our laboratory with little sunshine 

 and no heavy drafts, moisture evaporates from an uncultivated surface 24 inches 

 above standing water at the rate of one inch in 13 days. Reference to TablQ II 

 will show what such a loss means to crop production. 



Cultivation is the means usually employed to prevent evaporation losses. 



The experiments conducted at the Wisconsin Experiment Station and described 

 in their report for 1898, show how different the results of the same series of 

 cultivations upon clay and muck soils.* 



By cultivation is meant any stirring or loosening of the upper layer of the soil, 

 and may be accomplished by means of the plow, harrow, weeder or cultivater. 



Water cannot rise so rapidly through a loose soil as through a compact one. 



Generally the deeper the stirring the more complete the saving of moisture. In 

 a laboratory experiment in which the soil surfaces were 24 inches above stand- 

 ing water one cultivation 1 inch, 2 inches, 3 inches and 4 inches deep respectively, 

 resulted in savings over no cultivation, as shown in Table Ilf. 



In this case it is seen that the deeper the cultivation the greater the saving 

 of water. This will be true for all soils probably. 



Table III. — Showing effectiveness of different depths of a single cultivation during a 



period of 21 days. 



Depth of cultivation. 



inches 



1 inch .. 



2 inches, 



3 inches 



4 inches 



Losses in inches. 



1 inch in 10.89 davs^ 

 1 inch in 21.83 days 

 1 inch in 33.72 days 

 1 inch in 35.85 days 

 1 inch in 39.61 days 



Per cent 



moisture 



saved. 





 50.6 

 67.7— 

 69.6 + 

 72.5 



It is generally believed that the more frequent the cultivations the greater the 

 saving of moisture. Gnerally speaking this is true so far as studied for clays, 

 loams, and possibly for sandy soils. It is not true for all soils. Soils rich in 

 organic matter, such as the muck soils, profit by single cultivation, but so far as 

 studied frequent cultivations do not promote the further saving of moisture.f 



In practice it is found that, with cultivated crops on the soils indicated, fre- 

 quent cultivations with cultivator, harrow or weeder, not over 2 inches deep, prove 

 most satisfactory. 



It is found, too, in practice, that those who are most persistent in frequent 

 shallow cultivating find it profitable practice. 



HAKROWTNG GEAI'^C^ 



The harrowing of grain crops is coming a good deal into favor. Going over 

 the winter wheat field one or more times in spring with a spike-tooth harrow is 

 found to give good results. Some farmers in the west practice harrowing their 

 grains until they are so high as to be apparently considerably broken down by the 

 harrow bars. 



THE DRY EARTH MULCH. 



A layer of dry soil is much more effective in preventing moisture evaporation 

 than a layer of like depth of moist soil, and so it is sought by many, in practice, 

 to develop by frequent cultivations a shallow dry earth mulch or "blanket," using 

 the harrow, weeder, and later, the many-toothed cultivator. 



♦Michigan Farmers' Institute Report (p. 12), 1900-1901. 



tSee Michigan Farmers' Institute Report, 1900-1901, p. 12, and current report (1903-1904). 



