90 EXPERIMENTS UPON BARLEY 



root-crop receives a nitrogenous dressing of rape cake and 

 ammonium-salts; all this nitrogen is returned to the soil 

 in the root-crop which precedes the barley. It will be seen 

 that on these five plots the growth of barley is proportional 

 to the amount of nitrogen which may be supposed to be 

 available ; all except Plot 1 receive heavy mineral dressings 

 containing both phosphoric acid and potash, yet in the 

 absence of nitrogen these minerals on Plot 2 are not able 

 to raise the crop above, nor even up to the level of the wholly 

 unmanured Plot 1. 



The weight per bushel increases with each addition of 

 nitrogen ; up to a certain point the proportion of grain to straw, 

 and the weight of 1000 grains also increases, but on Plot 5, 

 with the highest nitrogen, these characters begin to show a 

 decline. The percentage of nitrogen in the barleys increases 

 with the supply in the soil, but only becomes at all above the 

 average with the highest sample from Plot 5. The valuation 

 rises with the supply of nitrogen in the soil up to a certain 

 point, but shows a slight decline for the last sample from 

 Plot 5. 



Summarising these results, we see that a good weight per 

 bushel and a large berry cannot be obtained without a 

 sufficient supply of nitrogen in the soil, but when a certain 

 point has been reached further excess of nitrogen in the soil 

 results in coarseness and an excessive proportion of nitrogen 

 in the grain, deteriorating the quality. A fair supply of 

 phosphates is also necessary to ensure early and complete 

 maturation. In the Agdell field, Plot 4 represents the best 

 soil conditions to obtain high quality in the barley ; on Plot 5 

 this optimum point has been passed, and the land has become 

 too rich in nitrogen compounds. 



The barley grown in rotation is on the whole much superior 

 to that grown continuously, mainly because its supply of 

 nitrogen is derived from the nitrification of nitrogenous residues 

 in the soil, i.e., from what a farmer would call "condition," and 

 not from nitrogenous manure directly applied. 



