188 THE SYSTEM OF FARM-YARD MANURING. 



The crop produced by a field in a year is always the 

 maximum crop which it can yield under the conditions 

 given : under more favourable external circumstances, 

 that is, with better weather, the field would have fur- 

 nished a greater crop ; under more unfavourable circum- 

 stances, a smaller, always corresponding to the condi- 

 tion of the soil. 



By the production of larger crops, in consequence 

 of favourable weather, the field loses a comparatively 

 greater amount of nutritive substances, and the sub- 

 sequent harvests show a decline ; just as, on the other 

 hand, deficient crops will act upon the yield of subse- 

 quent years, as a fallow year with half-manuVing does, 

 that is, the crops coming after bad years will turn out 

 better, even in ordinary weather. 



The relative proportions of corn and straw, in a crop 

 of cereals, are altered by a continuance of dry or wet 

 weather. Permanent wet, combined with a high tem- 

 perature, favours the development of leaves, stalks and 

 roots ; and as the plant goes on growing, the materials 

 intended for the production of seed are used for the 

 formation of new shoots, and thus the seed crop is 

 diminished. 



Continuous drought, before or during sprouting 

 time, produces the opposite effect ; the store of forma- 

 tive matter accumulated in the roots is used in far 

 greater proportion for the production of seed, and the 

 relation of straw to corn is smaller than it would be in 

 ordinary weather. 



When all these circumstances are taken into account, 

 the consideration of the produce obtained from un- 

 manured fields in the Saxon experiments will leave only 

 a few general points for further investigation. 



The tabular statement of the result shows that each 

 field has a power of production peculiar to itself, and 

 that no two of them have produced the same amount 

 of rye corn and straw, or potatoes, or oats and straw, or 

 clover. 



If we compare the numberless manuring experi- 

 ments of the last few years, in which the crops obtained 



