288 NATDEE AND PROPERTIES OF SOILS 



Table LXV 



yields to the acre of crops, and composition of soil and 



water extract of soil. rothamsted experiment 



station farm. england. 



Teeatment 



YlELB TO 



THE Acre 



(POUNDS) 



Complete Analy- 

 sis 



Water Extract 





P.O. 



KjO 



% 



PA 



p. p. M. 



p. p. M. 



Untreated 



N — KoO 



1276 

 2985 

 3972 

 5087 

 6184 



.099 

 .102 

 .173 

 .182 

 .176 



.183 

 .257 

 .248 

 .326 

 .167 



.525 



.808 



3.900 



4.025 



4.463 



3.40 

 30.33 



N + PA 



N-K30-PA- 

 Farm manure .... 



3.88 

 24.03 

 26.45 



151. Summaary. — 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. 



