214 



THE ROTHAMSTED EXPERIMENTS. 



Effects of 

 manures. 



Wheat and 

 the con- 

 sumption 

 of roots on 

 land. 



the varying conditions, it is important to take the average 

 results of a sufficient number of years to eliminate the influ- 

 ence of the varying seasons. Most of our illustrations will, 

 therefore, be drawn from the average results over the eight 

 years of wheat in the second to the ninth courses ; but some 

 reference will also be made to the averages for the tenth and 

 eleventh courses. 



Let us first compare the average amounts of produce of 

 grain under the three main conditions as to manuring, exclud- 

 ing, however, those obtained on the portion of the unmanured 

 plot where the roots were fed on the land, and where beans 

 or clover were grown in the third year of each course ; as the 

 crops, especially of the barley and of the wheat, were some- 

 what adversely affected by a dell on one side of the plot, 

 the surface-soil being in consequence comparatively shallow. 

 The figures show that, on the three portions, the produce 

 ranged, without manure, from 26 to 28£ bushels ; with super- 

 phosphate, from 28 1 to 31 f; and with the mixed manure, 

 from 30£ to 33£ bushels. Or, taking the amounts of total 

 produce (grain and straw together), the range of amounts is — 

 without manure, from 4407 to 4976 lb. ; with superphosphate, 

 from 4841 to 5658 lb. ; and with the mixed manure, from 

 5808 to 5932 lb. There is, therefore, both in grain and in 

 total produce of the fourth crop of the course, an obvious 

 difference, but certainly less than might have been expected, 

 due to the varying conditions as to manuring in the first 

 year, separated from the fourth by the growth and removal 

 of the intermediate crops. 



Next, comparing the effects on the fourth crop — the wheat 

 — of the removal of the first — the turnips — or the retention 

 of them, or of most of their constituents, on the land, it is 

 seen that without manure, under which conditions there 

 were practically no roots grown, the difference of result from 

 removal or otherwise is quite immaterial, and is probably 

 accidental. With superphosphate alone, and more roots 

 grown, the nitrogen of which was doubtless obtained from 

 previous accumulations within the soil, the removal or the 

 retention on the land of the constituents of the turnips 

 should, therefore, more materially affect the condition of the 

 soil for the growth of the succeeding crops. It was shown 

 that the effect was very marked on the barley which imme- 

 diately succeeded the roots. There was also somewhat less 

 produce, both of clover and of beans, where the roots had 

 been removed ; and now, in the case of the fourth crop — the 

 wheat — there is still distinct effect. Thus, taking the fallow 

 portions, there was an average of 30f bushels of wheat where 

 the roots had been removed, and 31| bushels where they 



