QUALITY OF CIJOP 83 



show the ratio the yield of Plot 2 (without ])()t;isli) Ijoiv to iliat 

 of Plot 4 (with potash), during each decade. 



Thus the yield on Plot 2 A (annnoniuni-salls and suimt- 

 phosphate), which for the first thirty years was practically ccjual 

 to that on Plot 4 A (ammonium-salts, superphosphate and 

 potash), fell off by 10 per cent, in the fourth decade and '2'.) per 

 cent, in the fifth ; whereas the corresponding yield on Plot 2 X 

 (nitrate of soda, and superphosphate), is as good as that of 4 N 

 (nitrate of soda, superphosphate and potash) up to the end. 



Potash plays a less important part than phosphoric acid 

 in the manuring of barley. Very little increase of crop has 

 resulted from its use on the Rothamsted soil, and the oidy 

 indication of the supply in the soil giving out has been seen in 

 the last twenty years on the plot receiving superphosphate and 

 ammonium-salts. Of course the Rothamsted soil starts with 

 a very large original store of potash. 



Speaking generally, we find that barley is nuich more 

 dependent on a supply of mineral manures than is wheat, a 

 free supply of phosphoric acid in particular beinu- essential to 

 its proper development. 



D. Character of the Crop as affected Jnj M<nnn''ni(j. 

 Table XXXIV. shows some of the characteristics of the 

 barley crop during the last fourteen years compared with the 

 average market valuations put upon the sami)les by .Mr J-'ew, 

 of Cambridge, who has examined them from year to year. 

 The current market price prevailing at the time of the 

 valuation is taken as 100, and the value j)Ut on each saniph- 

 is calculated on that basis. The first thing that becomes 

 apparent on inspecting the table is that it is impossible to grow 

 high-class barley by simply starving the plant. In each of tlir 

 series it will be seen that the barley showing the higiiesi 

 average value, the best wei'jht per bushel, the largest grains. 

 and the smallest j)roportion of tail corn i> that gn.wn on IMots 

 4, where a complete manure containing both nitrogen and 

 minerals is supplied. It does not, however, follow that any 



