38 



Journal of Agricultural Research 



Vol. III. No. I 



Table XXII. — Water requircnicnl of alfalfa, Sudan grass, and millet grown during 

 the late sum7ncr aiid autumn at Akron, Colo., in igi2, -without additional fertilizer — 

 Continued 



The effect of fertilizer added to the previous crop on the water require- 

 ment of the next crop is shown in the following measurements : 



Water 

 Crop requirement 



Alfalfa, following fertilized Bluestem wheat 473 ±13 



Alfalfa, following unfertilized Kubanka wheat S85±ii 



Alfalfa, following fertilized Grindelia, following imfertilized 



Bluestem wheat 564±i6 



The water requirement of alfalfa following unfertilized Kubanka wheat 

 was higher than that following the fertilized Bluestem, and although 

 this difference is not very marked (19 ±3 per cent) when the probable 

 error is considered, it is sufficient to show a slight effect of two consecu- 

 tive crops without fertilizer in increasing the water requirement. Two 

 pots of alfalfa following Grhidelia squarrosa had a water requirement 

 equal to that of the unfertilized set. Grindelia was started in pots which 

 had already produced a crop of Marvel Bluestem wheat in 191 1 without 

 fertilizer. Therefore alfalfa was the third crop from the same soil mass, 

 and although the pots growing Grindelia were fertilized, the succeeding 

 alfalfa crop gave a water requirement in accord with that following 

 unfertilized wheat. 



