106 



THIRD ANNUAL SESSIONS 



plant food into an available state. During tlie growing season when a 

 crop is being produced the moisture in the soil is so utilized as to be 

 of small value in hastening the bacterial activities which bring about a 

 state of solubility in the plant foods. With the early seeding necessary 

 in dry farming, the soil temperature is not high enough to encourage 

 nitrate forming activities before the plant roots are claiming a large por- 

 tion of the moisture. 



Plant Foods. 



"It appears to be necessary to so manage dry land soils that oppor- 

 tunity is occasionally afforded for the plant food organisms to work 

 under conditions of sufficient moisture during a certain period of the 

 warm weather. The moisture is essential in the growth of the crops, 

 but apparently no more so than is the plant food activities in the soil. 

 Heavy rains may come during the early spring and replenish the mois- 

 ture supply, but since the nitrates forming organisms appear to act very 

 slowly under conditiions of low temperature, we ought not expect high 

 yields though the spring moisture may be ample, if we have not provided 

 an opportunity for the flant foods in the soil to become available the 

 previous season. 

 Bacteriology of Soil. 



"There is a large and very important field awa'ting the investigator 

 who will take up soil bacteriology in the great plains country. 



Summer Follow. 



"From the figures presented on the foregoing discussion it would 

 seem that the practice of summer fallowing more properly belongs to 

 dry land agriculture than to the agriculture of humid or irrigated regions. 

 It meets the requirements demanded by the organisms which make plant 

 food available in the soil without the loss from' leaching which is noted 

 in humid areas. I do not wish to be understood as recommending the 

 adoption of the practice by our dry farmers generally, unless tests which 

 shall be conducted with the various inter-tilled crops show that they will 

 not meet the requirements. It is the purpose to refer briefly to some 

 summer fallow substitutes in the last part of this discussion. 



Water Conservation. 



"Moisture and nitrate determlnatitons have been miade on summer 

 fallowed soils handled in various ways. The average percentage of mois- 

 ture maintained in a summer fallow that was kept cultivated during the 

 season was 16.84 against 14.91 in an uncultivated fallow, with 34.5 parts 

 per million of nitrates while an uncultivated fallow contained 15.1 parts 

 per million. The yields from these two plots were 20 bushels per acr^.^ 

 after the cultivated fallow, and sixteen bushels per acre after the 

 uncultivated fallow. 



Weeds Waste Moisture. 



"These figures show the necessity of keeping a piece of fallow land 

 properly cultivated in order that the moisture will be conserved to be 



