24 The Rothamsted Wheat Experiments. 



7. Mixed mineral manure and 4001b. ammonia-salts (= 861b. nitrogen). 

 9. Mixed mineral manure and 5501b. nitrate of soda (== 861b. nitrogen). 



8. Mixed mineral manure and 6001b. ammonia-salts (= 1291b. nitrogen). 



It is only by growing the same crop continuously for many 

 years upon the same land, without any change in the con- 

 ditions of manuring, that the influence of different seasons 

 as so strikingly shown in this table, can be accurately 

 ascertained. It is seen that, in the year 1863, the produce of 

 the unmanured plots was 17| bushels ; whereas, in the worst 

 year, 1879, it was only 4 bushels. Nineteen unmanured 

 crops had been grown previous to 1863, and the yield of that 

 year was equal to the average of the first eight years. The 

 unmanured yield of 1879, only 4 bushels per acre, was about 

 one-third of the average yield of the plot during the whole 

 period of forty years. Contrary to what might be expected, 

 the produce on the land receiving farmyard manure, whilst it 

 falls greatly in yield in a bad season, does not rise as rapidly 

 in yield in a very favourable season. This is well illustrated 

 by the following comparison : Plot 7, receiving mineral 

 manures and ammonia-salts, gave in 1879 a crop practically 

 equivalent to that of the farmyard manure plot (2), 16 

 bushels per acre ; the average produce of the thirty-two 

 years is almost identical in the two cases, one being 32f , and 

 the other 33J bushels per acre. But in the favourable season 

 of 1863, whilst the farmyard manure (plot 2) gave only 

 44 bushels per acre, the artificial manure (plot 7) gave 53f 

 being an excess of nearly 10 bushels per acre. It is therefore 

 evident that, under the most favourable climatic circum- 

 stances, the artificial manure is capable of giving a much 

 larger crop, both of grain and straw, than the farmyard 

 manure. With the heaviest artificial manuring (plot 8), 

 35 1 more bushels per acre of wheat, and upwards of two 

 tons per acre more gross produce (grain and straw), were 

 grown in the most favourable season, as compared with the 

 produce grown by the same manures in the worst season. 



The character of the weather during the best and worst 



