WHEAT. 171 



8 years was 28 bushels; and the average over each of the Produce 

 five subsequent 8-yearly periods was — 34§, 35|, 35f , 28§, {™d maT" 

 and 39£ bushels. Excluding the first 8 years, the average we. 

 produce over the 40 years, 1852-91, was 34£ bushels ; and 

 the average for the whole period of 51 years, 1844-94, was 

 33f bushels per acre per annum. 



On the farmyard manure plot, the first depth of 9 inches Great ac- 

 shows a great accumulation. It is about twice as rich in Cl " n }f^n 



i • i s» 1 1 !••! • oj nitrogen. 



nitrogen as any other plot m the field ; yet this richness is 



not proof against bad seasons, nor are the highest amounts 



of produce in the field obtained on this plot. 



It has been seen that the unmanured plot has declined in Dung in- 

 yield and fertility ; but there can be no doubt that the SwmSL- 

 f armyard manure plot has, on the other hand, increased in ing in soil 

 fertility. Analyses of the surface-soil at different periods c ^ e ^ ol f 

 have shown that it has become about twice as rich in the crop. 

 nitrogen as that of the unmanured plot. It has indeed 

 been shown, that a large amount of the constituents of 

 farmyard manure accumulates within the soil, and that they 

 are very slowly taken up by crops. In fact, notwithstanding 

 this great accumulation within the soil, the wheat crops on 

 the dunged plot seldom, if ever, show over-luxuriance ; and 

 in unfavourable seasons the produce has been comparatively 

 small, largely owing to the encouragement of weeds, and 

 especially of grass, which in wet seasons it has been im- 

 possible effectually to eradicate, and what has been done 

 has not been accomplished without injury to the crop. 



Let us now endeavour to estimate the average annual increased 

 increase of produce on the farmyard manure plot, due to %™f™j n . 

 accumulation, independently of fluctuations due to season, creased /er- 

 as we did the annual decline in yield on the unmanured t ^y in 

 plot due to gradual exhaustion. As in the case of the un- 

 manured plot, so in that of the farmyard manure plot, we 

 have founded an estimate of its standard produce, irrespec- 

 tively of material accumulation, on the yield of the first 8 

 years ; deducting, however, the produce of the first year of 

 all, 1844, as although the yield of the crop of the country at 

 large in that year was high, that of the farmyard manure 

 plot was only 20 bushels. Taking the average of the re- 

 maining 7 years of the 8, we get 29.3 bushels, whilst 3 of 

 the 7 yielded more than 30, and 2 others 29 bushels or more. 

 Adopting then 29.3 bushels as the standard yield, irrespec- 

 tively of material accumulation, the result would be an 

 average annual increase, due to accumulation, of 5| bushels 

 over the 40 years ; whilst the average increase from year to 

 year, if uniform throughout the period, would be a little over 

 £ bushel over the 40 years. 



