88 Kansas Academy of Science. 



soil than the seed used thirty or forty years ago no student of 

 agriculture will deny. Instruments of tillage have also been 

 improved. The better the soil is cultivated, other things being 

 equal, the greater its crop-producing power. In spite of these 

 two factors which should have increased the average crop 

 production per acre, we have a decrease. 



The chemical department of the Agricultural Experiment 

 Station has made a chemical analysis of about 250 samples of 

 Kansas soil taken from thirteen different counties. These 

 samples are analyzed for total nitrogen, phosphorus, potas- 

 sium, calcium, organic and inorganic carbon. Studies in 

 physiological botany have shown that plants also require iron, 

 magnesium and sulphur from the soil. But agricultural ex- 

 perience as well as chemical analysis of soils have shown that 

 soils are well supplied with these elements, and for that reason 

 they are not included in our chemical analysis. 



A study of the figures obtained in the chemical analysis of 

 these Kansas soils shows that the elements nitrogen and carbon 

 have disappeared from cultivated soils in proportionately 

 larger quantities than the other essential elements. The oppor- 

 tunity for making this comparison does not always present 

 itself. Generally a sample is taken to represent a soil type. 

 If the field which best represents this type is . in cultivation 

 it may not be possible to get a sample of the same soil type 

 from a native meadow or pasture. A few such opportunities 

 have presented themselves, and the data obtained in the 

 analysis of such samples form the basis of the discussion in 

 this paper. 



The soil sample is taken in three strata. Surface (0-7 

 inches), subsurface (7-20 inches), and subsoil (20-40 inches). 

 Both nitrogen and carbon occur in a greater per cent in the 

 surface stratum. They are a part of the organic matter or 

 that portion of the soil which has come from decomposed plant 

 substances. The carbon is assumed to constitute half of the 

 organic matter. The ratio nitrogen to carbon is about 1 to 11. 

 An acre of soil seven inches deep is assumed to weigh 2,000,000 

 pounds. If the percentage composition is known, the amount 

 of any element per acre can be computed. The amount of car- 

 bon is multiplied by two to represent the organic matter. 



In the accompanying table are given the pounds of nitrogen 

 and organic matter per acre in the surface soil. These data 



