1080 



EXPERIMENT STATION RECORD. 



relations of bacteriological procosHOS to soil fertility, and the conditions affecting the 

 development of soil bacteria, with descriptions ^)l the method of making a bacterio- 

 logical analysis of soils and the results of a number of such analyses of Delaware 

 soils. 



The results reported include data relating not only to the number of bacteria in 

 different types of soil at different depths, but also their ammonifying and acidifying 

 efficiency, the first representing "the number of parts of ammonia jiroduced in 10 

 days in a standard pe[)tone broth medium culture, kept at 20° C, comi)ared with 

 the amount present in the blank inoculated medium, kept under the same conditiims, 

 and taken as unity;" the second representing "the amount of normal acid produced 

 in a 10-day 2 per cent cane sugar broth culture compared with that present in the 

 blank taken as unity." The principal results are summarized in the following table: 



TJic rehitio)! of flw numher of bacteria in iJie soil to aiimioiiifyimj and acidifying efficiency. 



Sou. 



Total num- 

 ber of bac- 

 teria per 

 gram of dry 

 soil. 



Total 

 ammoni- 

 fying efti- 

 cienev. 



Total 

 acidify- 

 ing c'fR- 

 eiencv. 



Experiment station garden: 



First analysis 



Second analysis 



Murray soil, Viola 



Killen soil, Felton 



Detrich .soil. Chestnut Hill. 



3,130,000 



1,294,000 



250, 000 



540, 000 



4,040,000 



13. 75 

 2. 48 

 2.13 

 S. 90 



20. 08 



2.22 



1.81 



.69 



.58 

 8.57 



"The above table shows that while zymotic efficiency is generally proportionate 

 to the total number of bacteria present in a soil, it is not exactly proportionate; 

 that is, zymotic efficiency may increase at a much greater rate than the numbers. 

 In other words, it is not only numbers of bacteria but also kinds which determine 

 the efficiency of a soil; or, again, a high bacterial jiotential is quite as important as 

 high numbers. 



"The kinds of bacteria in a soil seem to be an extremely fortuitous matter. There 

 is a possibility that the future will develop some practical means of introducing 

 favorable bacterial forms into the soil and thus of raising bacterial potential. 



"It will then become merely a question of increasing numbers to attain the highest 

 possible efficiencies. 



" Numbers can be increased by the introduction of sufficient humus into the soil 

 to form food for the bacteria and by stimulating their growth by active tillage. 



"Deep plowing means that a thicker zone of soil will be brought under bacterial 

 action. More frequent cultivation means better comminution, better a?ration, and a 

 better conservation of moisture. These are all necessary conditions for bacterial 

 development." 



Soil moisture investigations for the season of 1903, J. D. Tinsley and J. J. 

 Vernon [Ncn^ Mexico Sla. Bui. 4S, ji/k 15). — This is an account of a continuation 

 with wheat in place of corn of investigations which have been carried on at the sta- 

 tion for a number of years (E. S. E., 15, p. 343). The principal objects in view in 

 the experiments here reported were to study "(1) the effects of different numbers of 

 irrigations on the yield of wheat, especially the effect of frequent irrigations from the 

 time of heading until the crop began to ripen; (2) the relation between the number 

 of irrigations, the amount of moisture in the soil, and the yield; (3) the distribution 

 of the soil moisture in depth, percolation; (4) the relation between the amount of 

 water applied and the soil moisture." 



The plan of experiment and the general methods of i^rocedure were the same as in 

 previous investigations. The results obtained are summarized as follows: 



"(1) Too much water causes growing wheat to turn yellow, retards rii)ening a few 

 days, and causes a decreased yield of grain. 



