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



the most necessary of the cultural operations, but this is not sub- 

 stantiated either by the experience of many successful farmers or 

 by the records from experimental work. A smooth, deeply plowed, 

 well-harrowed surface looks well and gives the impression of care- 

 fully conducted farm operations, but may prove detrimental in crop 

 production. The smooth, finely pulverized surface is readily sub- 

 jected to blowing, and the loose, unpacked seed bed may be quickly 

 dried by the rather free circulation of air through it. Stubble left 

 on a field may give it an unkempt appearance, but at the same time 

 may be of value in catching snow or in preventing the soil from 

 blowing. There may be a great deal of misdirected labor expended 

 in preparing a seed bed, which defeats the object sought rather than 

 aids in the production of a crop. 



Moisture is generally considered the most important factor in crop 

 production in eastern Colorado. Its conservation is the primary 

 object in cultivation. Experience has shown that on this soil weeds 

 are the greatest robbers of moisture, and their control must always 

 be considered. Stubble, weeds, and uneven ground are the common 

 means of retaining snow and holding a large part of the winter pre- 

 cipitation. In deciding when a field shall be plowed, the question 

 whether a greater amount of moisture will be accumulated by hold- 

 ing the snow that falls than will be dissipated by the growth of weeds 

 must be paramount. It can best be decided by the man on the 

 ground. In answering this question several factors must be consid- 

 ered, namely, the amount of moisture already in the soil that may 

 be lost through weed growth, the probable time before the weeds 

 will be killed by frost, the possibilities of increasing the water in 

 storage in the soil by holding the snow that may come, the danger 

 of soil blowing if the stubble and weeds are removed, and the distri- 

 bution of the farm labor. 



In the following pages the importance of these factors will be 

 considered and the experimental evidence bearing upon them will be 

 given. It is believed that a careful consideration of these data will 

 assist the farmer in determining the best time to plow. 



In order to interpret properly the following data it is necessary to 

 consider the amount and distribution of precipitation during the 

 time these investigations have been in progress. The precipitation 

 records and crop yields of the six years from 1909 to 1914, inclusive, 

 should be studied together if any correlation is to be seen between 

 the distribution of precipitation and the time of plowing. 



PRECIPITATION. 



Table I gives the monthly precipitation for 10 years from 1905 to 

 1914, inclusive, which is the period covered by continuously recorded 

 observations at Akron, Colo., both by the United States Weather 



