WHEAT. 167 



Table 47 (p. 168) gives the number of bushels of dressed grain 

 per acre, without manure, and with farmyard manure, in each 

 of the 51 years, 1844 to 1894 inclusive ; also on some of the 

 artificially manured plots, mainly selected to illustrate the 

 effects of exhaustion and of manure-residue. In most cases 

 in this table, and in all in the subsequent tables, the results 

 obtained on the artificially manured plots are only given for 

 the last 43 of the 51 years; as, during the first 8 years, 

 various mineral and nitrogenous manures were applied, but 

 not as a rule the same from year to year on the same plot, 

 as they were subsequently. 



Without Manure every year. 



After a five - course rotation since manuring (turnips, 

 barley, peas, wheat, oats), the first experimental wheat crop 

 was harvested in 1844. The highest yield of the whole 

 series of years without manure was 2'6\ bushels in 1845, 

 and the lowest 4f bushels in 1879. Other yields have 

 been 21| bushels in 1854, 20 in 1857, only 5£ in 1853, and 

 only 8-9 bushels in 1867, 1875, 1876, and 1877. 



The upper part of the table (47) shows that the average Produce of 

 produce without manure over the first 8 years, 1844-51, the unman- 

 was 17-f bushels, which was higher than over either of the 

 subsequent 8 -yearly periods, due doubtless to a greater 

 amount of comparatively recent accumulations from the 

 previous treatment. In the bottom division of the table is 

 given the average produce for each of the subsequent 8- 

 yearly periods, and for the 40 years, 1852 to 1891 inclusive ; 

 also for the whole period of 51 years, 1844-94. It is seen 

 that, without manure, the average annual produce over 

 these 8-yearly periods was — 16|, 13£, 12|, 10|, and 12f 

 bushels ; over the 40 years (1852-91) 13, and over the 51 

 years (1844-94) 13| bushels. 



There can be no doubt that the produce of the unmanured Soil ex- 

 plot has gradually declined ; and, independently of the evi- haustlon - 

 dence of diminishing produce, analyses of the soil at different 

 periods show that there has been a gradual diminution in 

 the amount of nitrogen in it. But owing to the great 

 fluctuations in the amount of produce from year to year 

 dependent on season, it is by no means easy to estimate the 

 decline due to exhaustion of the soil, as distinguished from 

 variations due to the seasons. 



In the first place, it is difficult to say what figure should Former 

 be adopted as the standard produce of the plot by which to c °ff^ l ^ nd 

 compare the yield from year to year. The whole field was 

 manured with farmyard dung in 1839, and then grew tur- 



