SOILS. 31 



soluble salts was higher in the poorer soil than in the better soil, but 

 the ditierence was not so great as to make it probable that the unpro- 

 ductiveness was due purel^^ to overconeentration of salts. The sum of 

 the alkalis and nitric acid found ))y chemical methods usually exceeded 

 the total soluble salts indicated by the electrical method. 



kSimilar observations on a humus soil near Hanover Junction showed 

 that plats of this soil planted to onions and treated with land plaster 

 contained 1,043.3 lbs. of alkali per million of dry soil, while untreated 

 plats contained l,026.4i lbs. 



" Samples taken from a wild marsh, where the wild iris grows, showed 682.03 lbs. 

 ])er million, but where the grass was much shorter and where from previous experi- 

 ence the largest amount of alkalis would be expected if poor crops were due to its 

 presence, the analysis showed a little less, or 639.6 lbs. per million of dry soil." 



Determinations of the amount of nitric acid in fallow plats May 2-i 

 and August 22 show that the average amount of nitric acid in the sur- 

 face 4 ft. of soil at the first date was 111.42 ll)s. per acre. At the latter 

 date the nitric acid had increased to 430.11 lbs. One series of these 

 plats was cultivated e\'ery week, the other once in 2 weeks, but it does 

 not appear that the cultivation had any notable influence on nitrification. 



The total gains per acre in nitric acid imder the different treatments 

 were as follows: 



Galiiff of nitric add in soils from Mai/ 34 fo August 23. 



Pounds. 



Cultivated 2 in. deep once per week 315. 49 



Cultivated 2 in. deep once in 2 weeks 307. 44 



Cultivated 3 in. deep once per week 321. 80 



Cultivated 3 in. deep once in 2 weeks 377. 52 



Not cultivated 371. 39 



"It is clear in regard to the fallow plats under consideration that if the porosity of 

 the soil on the plat not cultivated was such as to give the nitrifying germs all of the 

 air they could use to advantage, then no amount of cultivation would have increased 

 the rate of niter forming. Indeed, it might be true that frequent shallow cultivation 

 in a wet season, especially on a heavy soil, might so much reduce the amount of air 

 which could enter the unstirred soil below the mulch as to act as a positive check, 

 the excess of moisture retained acting to exclude the air and thus retard nitrification 

 or even bring about the reverse process. Then, too, with the soil moisture held to a 

 high point smaller amounts of rain would be able to produce leaching and in this 

 way cause a greater loss of the nitrates formed than would be the case in a less nearly 

 saturated soil. It is not inijiossible that these conditions may have operated to lessen 

 the nitrate content in the cultivated fallow plats this season." 



In the experiments on the influence of early tillage in conserving 

 moisture, reported elsewhere (E S. R. , 11, p. 520), the nitric acid was 

 determined April 30, 18 days after the soil had been plowed. The 

 results show that the plowing sensibly increased the nitrogen in that 

 time. Determinations of nitrates were again attempted on May 16. 

 While the results were unsatisfactory, they indicated that the amount 

 of nitric acid had been greatly reduced in that time, due to rains, the 

 loss being greatest on the soil in the most open condition. 



