08 



THE ROTHAMSTED EXPERIMENTS. 



Nitrogen 

 supplied in 

 dung. 



Root-crops 

 pre-emin- 

 ently de- 

 pendent on 

 manure. 



Value of 

 root-crops 

 in rotation. 



Production 

 of sugar in 

 mangel 

 crop. 



organic manures only becomes comparatively slowly avail- 

 able, yet on that account the more remains in the soil as 

 manure-residue for future crops. 



Finally, the question obviously suggests itself, What is the 

 result when, instead of these artificial manures, a large 

 amount of nitrogen is supplied in farmyard manure, which 

 must always be liberally employed if heavy crops of mangel- 

 wurzel are to be grown ? 



♦ In the first place, larger quantities of nitrogen would 

 generally be applied per acre in farmyard manure than in 

 any of the artificial manures used ; and the results obtained 

 on the farmyard-manure plots point to the conclusion that a 

 much smaller proportion of that supplied would be taken up 

 by the immediate crop than in the case of either nitrate of 

 soda or ammonium-salts, and even less than with rape-cake. 

 But a characteristic of farmyard manure is that it leaves a 

 large but only slowly available residue within the soil. It is 

 the nitrogen of the liquid dejections of the animals that is 

 first rendered available within the soil, then that of the 

 finely comminuted matter which passes, intermixed with 

 some secretions, in the solid excrements, and finally that in 

 the litter. It is in fact to the very large proportion of the 

 constituents of the farmyard manure applied for root-crops 

 which remains available for future crops that an important 

 part of the benefit of the growth of such crops in rotation is 

 to be attributed. Indeed it will be clearly seen from the 

 evidence adduced that the- root-crops, which are assumed to 

 perform the office of restoring the condition of the soil for 

 the growth of the crops alternated with them, are themselves 

 pre - eminently dependent on manure for their successful 

 development. 



It is in fact the great power of utilising the stores within 

 the soil, due in some cases to accumulation, and in others to 

 direct manuring, which these plants possess, growing and 

 gathering nitrogen as they do after the period of its collec- 

 tion by the cereals, and the fact that it is only a very small 

 proportion of their nitrogen and of their mineral matter which 

 is carried off in the increase of the animals and so lost to the 

 land, that constitute a great part of the value of the root- 

 crops in rotation. When, however, roots are consumed for 

 the production of milk, the loss to the manure will be greater 

 than when they are consumed by either store or fattening 

 animals. 



It is a characteristic of the various descriptions of feeding- 

 roots, that they supply a large amount of the non-nitrogenous, 

 respiratory, and fat-forming substance — sugar; indeed about 

 two-thirds of the solid matter of the mangel-root is sugar. 



