coxTiLXTS. xvn 



CHAPTER III.— cant iitucd. 



required for the growth of plants — Manuring maybe compared to tho 

 application of earth saturated with food — Importance of the uniform 

 distribution of focd in manures; frosli and rotted stall manure ; compost; 

 importance of powdered turf for the preparation of numure — Quantity 

 of food in unmanured fields and their powers of production ; increase of 

 the latter apparently out of proportion to the manure added ; experiments 

 on this point ; explanation ; composition of the soil and its absorptive 

 power compared with the requirements of the plants to be cultivated on 

 it ; surfiice and subsoil plants, the tillage and manuring respectively 

 required by each — Clover sickness ; experiments of Gilbert and Lawes ; 

 their conclusions ; value of them .... page 131 



CHAPTEK IV. 



FARM-YARD MANURE. 



The fertility of a soil depends upon the sum of available food, the continu- 

 ance of the fertility upou the total amoimt of all food in it — Chemical 

 and agricultural exhaustion of the soil — Exhaustion of the soil by culti- 

 vation, laws regidating its progression ; effect of the transformation in 

 the soil of the chemically fixed into physically fixed elements of food ; 

 effect on the progTess of exhaustion by partial restoration of the with- 

 drawn food of plants — Progress of the exhaustion by different cultivated 

 plants — Cultivation of cereals, consequence of removing the grain and 

 leaA'ing the straw in the soil ; intervening clover and potato crops ; 

 effect of leaving in the ground the whole or a portion of these crops ; 

 di-vdsion of soils ; productive power of Avheat fields increased bv accumu- 

 lating in them the materials derived from clover and potato fields : cul- 

 tivation of fodder plants ; their food pai-tly derived from the subsoil ; 

 addition of these increases the productive power of the surface soil — 

 Natural connection between the cultivation of cereals and fodder plants, 

 the influence on the fertility of land — Exhaustion of the soil removed 

 by the restoration of the withdrawn mineral constituents ; the excrement 

 of men and animals contains these ; their restoration depends upon the 

 agricultm-ist ........ 1G.J 



CHAPTER V. 



THE SYSTEM OF FARM-YARD MANURING. 



(Questions to be solved — Experiments of Renning, their significance — 

 Produce of immanured fields — Influence of preceding crops, of the situ- 

 ation, and climatic conditions, on the produce — Each field possesses its 

 own power of production — Large crops, their dependence and continua- 

 tion — Closeness of the food of plants, what is meant thereby — The 

 closeness of the particles of food in the soil is in propoiiion to the pro- 

 duce — Produce of com and straw influenced by the relations of the 

 assimilated food and by the conditions of growth ; action of food sup- 

 plied in manures — Potatoes, oats, and clover crops of the Saxon fields; 



a 



