82 



EXPERIMENTS UPON BARLEY 



seen in the hastened maturity brought about by the phosphoric 

 acid. Not only are Plots 2 and 4, which receive phosphoric 

 acid, in the ear long before Plots 3 and (to a less extent) 

 Plots 1, but they will have begun to yellow for harvest when 

 Plots 3 still show only upright green ears. 



Comparing Plots 2 and 4, we see that a manure supplying 

 phosphoric acid and nitrogen is almost as effective as a complete 

 manure containing also potash and the other alkaline salts. 

 There is a great increase of crop caused by the superphosphate 

 and nitrogen on Plots 2, over the nitrogen alone on Plots 1, 

 and very little further increase for the further addition of potash 

 and other alkaline salts on Plots 4. Where the nitrogenous 

 manure is nitrate of soda or rape cake, the omission of the 



TABLE XXXIII. Ratio of yield of Barley (Grain) without Potash to yield 

 with Potash, for successive 10 -year periods, Ammonium-salts and Nitrate 

 of Soda being the respective sources of Nitrogen. 



potash on Plots 2 compared with Plots 4, receiving a complete 

 manure, shows no effect, whether we make the comparison 

 over the whole period or for successive ten - year periods. 

 With ammonium-salts, however, as the source of nitrogen the 

 omission of potash does eventually diminish the crop ; for the 

 first thirty years the crops on Plots 4 A and 2 A, with and 

 without potash, were equal, but in the fourth decade, as the soil 

 became depleted by the continual removal of potash, the crop 

 on Plot 2 began to fall off, and the diminution is much increased 

 in the following decades. That there is no similar falling-off 

 in the yield of the corresponding plot receiving nitrate of soda, 

 is partly due to the greater root-range induced by the soluble 

 nitrate, and partly to the effect of the soda base of this salt in 

 rendering available to the plant the potash reserves of the soil. 



