324 



THE ROTHAMSTED EXPERIMENTS. 



Lastly, it has been clearly illustrated how very much 

 greater is the demand upon the food, especially for nitrogen- 

 ous and for mineral constituents, in the production of milk 

 than in that of fattening increase. 



Constitu- 

 ents of 

 crops re- 

 tained on 

 farms. 



Feeding as 

 a source of 

 manure. 



Food and Manure. 



At the commencement of this Section on the Feeding of 

 Animals, it was shown, by reference to a special example, 

 how large was the proportion of the constituents of the crops 

 grown in a rotation which was retained on the farm for 

 further use — in fact, for consumption by animals, or for litter. 

 It was shown that, in the case selected for illustration, there 

 would be so retained on the farm for such further use, more 

 than two-thirds of the total vegetable substance grown, more 

 than half of the nitrogen of the crops, and about six-sevenths 

 of the total mineral matter ; whilst, of the individual mineral 

 constituents of the crops, less than half of the phosphoric 

 acid, but about four-fifths of the potash, would be retained. 



Of course, in the very varied practice of Agriculture at the 

 present day, there will sometimes be larger, and ■ sometimes 

 smaller, proportions of the various constituents of the crops 

 at once sold off, or retained on the farm ; but the example 

 given may be taken as essentially typical, and as so far con- 

 veying a very useful impression on the subject. But, besides 

 the constituents of the home-grown rotation crops retained 

 upon the farm for food and litter, there will be more or less 

 produce from grass land, whilst modern practices frequently 

 involve the purchase of a considerable quantity of imported 

 food-stuffs. 



Besults relating to the feeding of animals for the produc- 

 tion of meat, and of inilk, have been considered ; and we 

 have now to discuss the subject of feeding as a source of 

 manure. Numerous Eothamsted experiments have shown 

 how small is the proportion of the various constituents con- 

 sumed in food by fattening, or even by growing animals, 

 which is stored up in their increase, and which will therefore 

 be lost to the manure. In the production of milk, however, 

 it has been seen that the loss to the manure is very much 

 greater. 



Of the mineral matters of the food, we know that there 

 need be no loss to the manure beyond that carried off in the 

 animal increase or in milk. Of the non-nitrogenous organic 

 substance of the food, a very large proportion is lost by the 

 respiration of the animals, and a not inconsiderable quantity 

 contributes to the animal increase or milk ; and what remains 

 for manure is of no material value as a direct supply of con- 



