ROOT-CROPS. 



39 



annum on the different divisions of the farmyard manure 

 plot over the three years of the direct application of the 

 manures, and over the succeeding two years of manure- and 

 crop-residue. It was as follows : — 



TABLE 11. 



Thus there was an average of little more than 2\ tons of 

 roots per acre per annum less over the two years of unex- 

 hausted residue of the farmyard manure than over the three 

 years of its direct application. There was also less leaf over 

 the two years of residue. It is seen, however, that on the 

 divisions of the farmyard-manure plot, where artificial nitro- 

 genous manures were used in addition, there was an average 

 of from 7 to 8 tons of roots less over the two years of residue 

 than previously. There was also considerable reduction in 

 the produce of leaf. Still the greater produce over the two 

 years of residue-action, where the nitrogenous manures had 

 been previously used in addition than where the farmyard 

 manure had been used alone, show considerable effect from 

 the residue either of the artificial nitrogenous manures them- 

 selves, or from their increased crop-residue ; and so far as 

 there is any direct effect from the manure-residue of the pre- 

 viously applied nitrate or ammonium-salts, it is probably 

 chiefly due to nitrates being drawn up again from the sub- 

 soil. Even in the case of the rape-cake, the residue-effect is 

 also doubtless largely due to crop-residue, but to a consider- 

 able degree to manure-residue also — a portion of the nitro- 

 genous matter of such organic manures becoming very slowly 

 available in the soil. 



To sum up on this point : In the case of the nitrate and Manure- 

 ammonium-salts, the effect of residue will be in the least pro- ^^f „. 

 portion due to manure-residue, and in the greatest to crop- residue. 

 residue. With such manures as rape-cake, the effect will be 

 due in a large proportion to manure-residue, and also largely to 



