288 NATURE AND PROPERTIES OF SOILS 



Table LXV 



YIELDS TO THE ACRE OP CROPS, AND COMPOSITION OF SOIL AND 



WATER EXTRACT OP SOIL. ROTHAMSTED EXPERIMENT 



STATION FARM. ENGLAND. 



151. Summary. — The solution as it exists in a normal 

 soil is highly dynamic. Its concentration and composition 

 are fundamentally governed by rate of solution, by absorp- 

 tion, and by the amounts of the various solutes in the solution 

 itself. Many factors are active in preventing a condition of 

 equilibrium between these three phases. Those of especial 

 importance are season and crop. Temperature, moisture con- 

 tent, and leaching are subfactors of season. Tillage of all 

 kinds and the addition of manures, lime, and fertilizers are 

 practical means of modifying the soil solution moie to ade- 

 quately meet the needs of the crop. In fact, all of the com- 

 mon practices so successfully used in economic soil manage- 

 ment attain their end through a modification and control of 

 the soil solution. 



