12 



2. Effect of Residues on Sugar-Beet. 



The Eothamsted experiments furnish many striking 

 instances of the substantial effects produced on subsequent 

 crops by the residues of previous applications of manure. 

 Let me call your attention to one instructive instance which 

 was not mentioned by Messrs. Lawes and Gilbert in their 

 recent paper. In the field devoted to roots, the same manures 

 had been applied annually for eighteen years, the first 

 fifteen years to swedes, and the last three years to sugar-beet. 

 Then came an interval of two years in which no nitrogenous 

 manures were applied, but during which sugar-beet was grown 

 as before. In the table opposite we have the average 

 produce of the sugar-beet during three years with manure, 

 and in the second year after the manuring had ceased. 



While the manures were applied each year, both nitrate 

 of soda and rape cake gave a somewhat larger produce than 

 farmyard manure ; but when the manures ceased to be 

 applied, the plot which had received farmyard manure gave 

 by far the largest produce indeed, the crop obtained from 

 the residue of this manure was practically equal to that 

 previously obtained when the manure was annually applied. 



The yield of the plots which had received the other nitro- 

 genous manures is very instructive ; there is in all cases a 

 considerable excess of produce due to the previous manuring. 

 This excess is much the greatest where rape cake had been 

 applied. The organic matter of which this manure is com- 

 posed decomposes rather slowly in the soil, and there is thus 

 a residue left after the first season to benefit future crops. 

 The results also show a very distinct effect produced by the 

 previous applications of ammonia salts and nitrate of soda ; 

 and, in the case of the latter, the excess of crop due to its 

 action amounts to over 4 tons per acre. To what are we to 

 attribute this apparent effect of residues of ammonia salts and 

 nitrate of soda ? There can, I think, be little doubt that the 

 subsequent effect of these salts is in this case due to the 

 ploughing in of the leaves of the sugar-beet during the three 

 preceding years : the roots were in all cases carted off the 

 land. The table shows that over 6 tons of leaves had thus 

 been returned to the soil each year on the nitrate of soda 



