THE DRY FARMING CONGRESS. 



105 



water in this plot was nearly six times as great as in the plot cropped 

 in 1907, and explains the yield of 20 bushels per acre, fi've times as great 

 as on the other plot. 



Water Conservation. 



"Again determinations made at the end of a season when summer 

 fallowing was practiced, and carried to a depth of nine feet showed that 

 this soil contained on an average of 11 per cent, moisture for this depth, 

 with 19 per cent, in surface foot and 8.5 in the ninth foot. This shows 

 something as to the possibilities of accumulating moi'sture in a soil as 

 a result of a season of summer fallow. From these figures it is evident 

 that the moisture accumulated in a soil during a season of summer fal- 

 low is an important factor in the production of the crops on the succeed- 

 ing year, and further indicates that high yields ought not to be expected 

 where some provisions are not made for accumulating a certain degree 

 of moisture in the soil. 



Plant Foods. 



"Another equally important influence exerted by the uncropped con-, 

 dition is in bringing the plant food in the soil into a soluble state so that 

 plant roots may be able to utilize it. Fortunately for mankind, nature 

 has locked up her supply of those elements in the soil from which man 

 must get his food and certain conditions have to be established before 

 the food supply will be released. The investigations taken up were along 

 the lines of available nitrogen or nitrates as throughout the western 

 country where ash elements are commonly present in abundance. It is 

 the supply of available nitrogen that governs the crop possibilities to a 

 considerable degree. 



Summer Fallow Adds Nitrogen. 



"Nitrate determinations made in 1908 on soil that had produced a 

 spring wheat crop continuously for the past three years, showed a sea- 

 sonal average of 9.5 parts of nitrate in every million parts of soil, with 

 a range of from 8.3 to 13.7 parts. Determinations made on like soil grow 

 ing a similar crop the same season, after .a 1907 summer fallow showed 

 an average for the season of 34.5 parts per million or nitrate with a range 

 of from 15.1 to 39.3. At the end of the summer fallow season the soil 

 contained 40.8 parts per million of nitrate. These figures show the tre- 

 mendous advantage in relation to the availability of plant food in the 

 soil, resulting from a season of summer fallowing. The effect of this 

 advantage appeared in the crop harvested. The yields of 4 and 20 bushels 

 per acre as reported for the continuously cropped and summer fallowed 

 areas under the moisture discussion places practical emphasis on the 

 advantage of having the plant food brought into the proper condition 

 in the soil. 



Moisture and Nitrates. 



"Considering these two points, moisture and nitrates, in their rela- 

 tion to crop production, it appears that moisture is essential in bringing 



