■id 



MASS. EXPERIMENT STATION BULLETIN 232 



before planting save in the case of grass and clover, where it was applied 

 MS a top dressing. On the nitrate of potash plots the amount of nitrate 

 of soda was reduced to compensate for nitrogen applied in the potash 

 carrier. 



The testimony of two adjacent experimental fields indicates that crop 

 yields were not limited by lack of nitrogen and phosphorus. The large 

 amount of nitrate of soda applied may conceivably have served to decrease 

 need for applied potash, in which case response to the use of fertilizer 

 potash was of a diflerent magnitude from tliat which otiierwise might have 

 been secured. 



The weighted per centum yields of all crops grown on potash treated 

 plots during the progress of the test, excluding only corn stover and the 

 straw of grains and of soy beans, are as follows (the yields on the no- 

 potash plots taken as 100): Series I, 112.4 per cent; Series 2, 110.6 per 

 cent; Series 3, 110.2 per cent; Series 4, 134.9 per cent; Series 5, 131.2 per 

 ctuf. Variation between series, as indicated by the average response to 

 potash of all potasli-treated plots within the series, is high. The cause 

 (A tliis variation is now under investigation. F'or the present we must 

 a.ssume that each check, in each series, is truly representative of the plots 

 concerned. This assumption, naturally, cannot be proven. 



Varying Response of Different Crops to the Use of Fertilizer Pota&h 



The four crops grown a sufficiently large number of times to make 

 results of value — namely, corn, soy beans, potatoes, and grass and clover — 

 show a widely varying response to the use of potash. The following 

 tiible summarizes the data, respectively for Series 1, 2 and 3 on which 

 potash gave but a small response for most of the crops, and for Series 4 

 i'nd 5 where the response was larger than tlie average for all crops. 



Response of Different Crops to the Use of Fertilizer Potash 

 No Potash = 100 



Potash gave a significant increase in yield of potatoes on all series, 

 differing markedly from soy beans whicli not only did not respond at all 

 on Series 1, 2 and 3, but which gave response in but a single year, on a 

 single series (4), for the rest of the field. Tlie yields of both potatoes 

 and soy beans were at least fair, as will later l)e shown. The inability 

 ()1 the potato to forage for its potash, and the very great ability of the soy 

 l)ean to make use of the natural supply of the soil, are both plainly 

 e\ iileiit. 



Corn failed to give consistent increase in grain except on the last two 



