P]n/sical and Chemical Fapos. 89 



are obtained from figuies published in Bulletin No. 199, Kansas 

 Experiment Station, and from unpublished data on file in the 

 department of chemistry. Data for samples of the same type, 

 taken as close together as possible, have been selected for 

 comparison. In several cases the sample of the cultivated soil 

 and the uncultivated soil were taken only a few rods apart. 

 In cases where no sample of the cultivated soil is directly 

 comparable with the uncultivated soil on account of location 

 and known history, the average of several cultivated soils is 

 used. This makes a fair comparison. 



It is true that occasionally a sample from a cultivated field 

 shows a higher percentage of nitrogen and organic matter 

 than a sample from the same type in a virgin field. Such cases 

 are noticed in the report of the soils of Shawnee county, pub- 

 lished as Bulletin No. 200, Kansas Experiment Station. In 

 those cases the cultivated soil has received special care and 

 the uncultivated soil represents a very poor phase of the type. 



From the original data presented in Table I the figures in 

 Table II are calculated. "The pounds loss of nitrogen" is the 

 difierence between the amount of nitrogen in the virgin soil 

 and that in the cultivated soil. This difference varies from 

 1200 to 1500 pounds per acre. Soil sample 1032, from Green- 

 wood county, was taken from a field which had been cultivated 

 to corn for thirty years ; the comparison sample of uncultivated 

 soil was taken from a native meadow a few rods away. 

 Sample 1034, Greenwood county, taken in a catalpa grove, 

 shows a higher content of nitrogen and organic matter than 

 any of the virgin soils, except soil sample 1052, taken in a 

 native meadow in Brown county. This shows that, as far as 

 this comparison goes, the soil in the catalpa grove shows no 

 tendency towards depletion of nitrogen or organic matter. 

 The sample of soil taken in a field cultivated to corn and forage 

 crops, next to the catalpa grove, showed a nitrogen content 

 of 3700 and organic matter to the extent of 89,200 pounds per 

 acre in the surface soil, or a difference of 1500 pounds of 

 nitrogen and 36,800 pounds of organic matter in favor of the 

 soil in the catalpa grove. 



What does it mean that an acre of land has lost 1200 pounds 

 of nitrogen in surface soil? To produce one bushel of corn the 

 soil must furnish one pound of nitrogen for the grain and one- 

 half pound for the stalks and cobs. The 1200 pounds of nitro- 



