550 



VARIOUS FERTILITY FACTORS 



from the leaves by rain water. It is not only possible, but even 

 probable, that under some conditions the same plant food may be 

 used twice by the same plant; that is, it may serve an essential 

 need in the growth of the first leaves, then be leached out and car- 

 ried back into the soil, and finally be reabsorbed through the roots 

 and serve the plant again in the newer leaves. While this double 

 use is probably insignificant, the point of special importance is 

 that the analysis of the mature plant may not find all of the plant 

 food which has been absolutely essential for the growth of the 

 plant, as will be seen from the tabular statements. 



Many years ago the Rothamsted Experiment Station harvested 

 a bean crop from different parts of a uniform field at six different 

 stages of growth or development, from May 26 to September 8, 

 and for each period the crop harvested was weighed and analyzed, 

 with the results indicated : 



TABLE 113. COMPOSITION OF THE BEAN CROP AT DIFFERENT PERIODS OF 



GROWTH (ROTHAMSTED INVESTIGATIONS) 



Pounds per Acre 



It will be noted that the dry matter, nitrogen, phosphorus, and 

 sulfur all continue to increase until the full maturity of the plant, 

 the slight apparent decrease for dry matter and sulfur in the crop 



