4 BULLETIN" 253, U. S. DEPAETMENT OF AGRICULTURE. 



Rains in August and early September invariably produce a growth 

 of weeds, which usually exhaust the available soil moisture, a ton of 

 Russian thistles using 65 per cent as much water as would be used 

 in producing a ton of unthrashed wheat. 1 The loss of moisture which 

 has penetrated to a greater depth than 3 inches after the weeds are 

 dead in the fall and before growth starts in the spring is almost negli- 

 gible, either from land fall plowed or from that covered with stubble. 

 Light precipitation evaporates, unless it falls as snow which is blown 

 into drifts until a considerable quantity has accumulated. As 10 

 inches of light snow is the equivalent of only 1 inch of rain and 1 inch 

 of rain penetrates the surface soil to a depth of 6 inches, it will be 

 readily seen that snows of 1 to 5 inches supply a very small amount 

 of moisture, the greater part of which will be lost by evaporation. 



While the normal precipitation of the six months from October to 

 March, inclusive, is only 25 per cent of the normal annual, the highest 

 recorded precipitation for any month, with one exception, is 5.45 

 inches in March, 1905. In five years of the ten recorded the precipi- 

 tation in March has been less than 0.5 inch. The precipitation in the 

 winter months has varied almost as much, in some years there being 

 only snow flurries, while in others the snowfall sometimes ' totals 20 

 inches in a month. There has been a wider variation in the precipita- 

 tion of the fall and winter, when moisture should be stored, than in the 

 growing months. 



Early fall rains will be used by weeds unless the land is cultivated. 

 Heavy winter snows may occur, but they are likely to blow off the 

 fields unless there is either stubble or an uneven surface to hold them. 

 The time and method of cultivation, then, should be planned to pre- 

 vent weed growth and still leave the soil or stubble in such a condi- 

 tion that it will hold the maximum of snow. The period when labor 

 is available will also be an important factor in determining the time 

 of plowing. When labor is scarce, cultivation other than plowing, 

 which will kill weeds and can be done rapidly, may be resorted to. 

 If this cultivation leaves the stubble on the surface or leaves the sur- 

 face rough enough to hold snow, it may have even greater value than 

 plowing. Disking or listing in the fall are the methods most com- 

 monly used. 



EXPERIMENTAL WORK. 



The experiments in crop-rotation and cultivation methods at 

 Akron afford an opportunity for a number of comparisons between 

 fall plowing and spring plowing. In this paper only the time of plow- 

 ing after small grain will be discussed. 



The practice has been to plow as early as practicable after harvest. 

 The soil is then packed with a disk set straight and weighted. This 



i See Briggs, L. J., and Shantz, H. L., Bulletin 284 of the Bureau of Plant Industry, entitled "The Water 

 Requirement of Plants. I.— Investigations in the Great Plains in 1910 and 1911." 



