220 



THE KOTHAMSTED EXPEKIMENTS. 



Manurial 

 treatment. 



No man- 

 ure. 



With 



superphos- 

 phate. 



Mixed 

 manures. 



continuously, as above described. It shows the amounts, sep- 

 arately in the roots, leaves, and total produce, of the turnips ; 

 in the grain, straw, and total produce, of the barley, and of 

 the wheat; in the corn, straw, and total produce, of the beans; 

 and in the clover. It will be seen that the arrangement and 

 headings of the columns are exactly the same as in the tables 

 of produce already considered ; and that, for each description 

 of crop, or part of the crop, the first line shows the amounts 

 obtained under rotation, the second those in the crop grown 

 continuously, and the third the difference between the two. 



The Dry Matter in the Turnip Crops. — Eeferring first to 

 the upper division of the table, relating to the Swedish 

 turnips, it should be stated that results for the crops grown 

 continuously are not available for the same eight years as 

 those grown in rotation ; but for each of the three conditions 

 as to manuring, the average for 19 years of growth is taken. 

 So far as manuring is concerned, the unmanured and the 

 ■superphosphate conditions were the same for the rotation and 

 for the continuous crops. But, in the case of the mixed 

 manure, the rotation plots received a larger amount of nitro- 

 gen for the roots ; in fact, enough to carry the four crops of 

 the course. The continuous plot, on the other hand, received 

 a less amount each year ; but, unlike the rotation plots, with 

 no intermediate crops to use up any available residue from 

 the previous application. 



The figures show that — without manure — the difference in 

 the amounts of dry matter produced in rotation and in con- 

 tinuous growth are immaterial. The utter failure in both 

 cases without manure is confirmatory of the absolute depend- 

 ence of this valuable rotation crop on supplies within the 

 soil itself, either from accumulations or from direct manuring. 



The less produce of the continuous than of the rotation 

 crops with superphosphate is also quite consistent with the 

 supposition that, under such conditions, the crop greatly 

 exhausts the available nitrogen of the soil, and especially of 

 the surface-soil. 



With the mixed mineral and nitrogenous manure, again, 

 there is also considerably less production of dry substance 

 when the crop is grown continuously than when it is grown 

 in rotation. The result is, however, due partly to the larger 

 amount of nitrogen directly supplied by manure to the rota- 

 tion crops as above referred to, but partly to the fact that 

 when the same description of root-crop, with the same char- 

 acter and range of roots, is grown year after year on the 

 same land, the surface-soil becomes close, and a somewhat 

 impervious pan is formed below ; conditions which are very 

 unfavourable for a crop which pre-eminently requires a good 



