12 BULLETIN 253, U. S. DEPARTMENT OF AGRICULTURE. 



plowing. The corn was given clean cultivation. The spring-plowed 

 wheat plats averaged 3.8 bushels and the spring-plowed oat plats 1.3 

 bushels per acre more than the fall-plowed plats. 



The heavy rains in August and early September in 1909 prevented 

 thrashing and delayed fall plowing until the latter part of September. 

 By that time the heavy growth of weeds had used the soil moisture 

 resulting from the precipitation of August and September, and plat 

 B plowed up dry and lumpy. No moisture determinations were 

 made at this time, but it is only fair to assume that plat A was equally 

 dry, as it also had produced a heavy growth of weeds. In the spring 

 of 1910 the moisture content of plat A was decidedly greater in the 

 first and second feet and slightly greater in the third foot than it was 

 in plat B. This increase in moisture content was due to the snow 

 held by the stubble on plat A. At harvest time the moisture was 

 exhausted in both plats, but plat A gave a yield of 11.3 bushels and 

 plat B yielded 6.2 bushels. 



The small difference in moisture content in the spring could not 

 account directly for the difference in yields, but the slightly larger 

 amount of moisture in plat A may have caused a quicker growth, 

 which crowded out the weeds. All three crops were better on spring 

 than on fall plowing. The corn, in which weeds were not a factor in 

 determining the yield, showed a difference in favor of spring plowing. 



As the moisture in both plats A and B was exhausted at harvest 

 time, their moisture content was probably the same when plat B was 

 plowed, August 12, 1910. 



The early plowing of plat B prevented weed growth on it, and the 

 greater part of the heavy rains of August and September was stored 

 until the following season. Practically all the water from these rains 

 was used in the fall by a heavy growth of weeds that occupied the 

 plats which were to be spring plowed. Light precipitation during 

 the winter of 1910-11 added very little water to the soil; conse- 

 quently the spring-plowed plats had much less moisture in the spring 

 than the fail-plowed plats. The yield was 4.1 bushels of wheat from 

 plat A and 15.9 bushels from plat B. All the moisture had been used 

 from both plats. Every fall-plowed plat gave a better yield than was 

 obtained from any spring-plowed plat. 



Plat B was plowed on August 16, 1911, immediately after a rain 

 of 1 inch. There were only light rains during August and September, 

 which slightly increased the moisture content of the first foot in plat 

 B but made no change in plat A. The heavy snows of February and 

 March were held by the stubble on plat A. In melting they filled its 

 soil to a depth of at least 5 feet. There was no change below the 

 third foot in the water content of plat B. 



The precipitation of the growing season was so heavy that none of 

 the crops suffered from lack of moisture. The yields from fall plow- 



