238 THE FARMER OF TO-MORROW 



Here we find the concentration of the phos- 

 phate element of plant food producing the 

 best growth when it is only 8 parts per million. 

 At 56 parts the slowly declining line takes a 

 sharp drop, until at 80 the "crop" produced in 

 these solutions was less than one-fifth that of 

 8, although the available plant food was pres- 

 ent in ten times the quantity. 



The results of these experiments seem to 

 establish one point beyond doubt that Nature 

 herself has provided a definite ratio at which 

 she liberates the mineral food of plants, and 

 that this ratio is fixed. Furthermore, if 

 the above experiments are worth anything 

 they prove that the plant has adapted itself to 

 this fixed ratio, in much the same way as man 

 has adapted himself to three meals a day, and 

 that any attempt on the part of the experi- 

 menter to vary this ratio, even within very 

 narrow limits, is disastrous to the plant, results 

 in "crop failure." 



These facts seem to verify themselves in 

 the laboratory. Do the same conditions ac- 

 tually prevail in farming? Does the soil pre- 

 sent the same peculiarities as a laboratory test 

 solution? 



Naturally, in an hypothesis so much at 



