190 THE EFFECTS OF 



though barley is more exhausting than oats, yet, upon 

 strong land, in a less perfect state of culture, the latter 

 produces proportionably larger crops, consequently ab- 

 sorbs more nutriment ; and, for this reason, they may 

 be both stated at 25 per cent. 



" The exhaustion by these crops is proportionably re- 

 paired, and the land is restored to its former nutritive 

 powers, in three ways, namely — 



" By the application of putrescent manure ; according 

 to its quantity and quality. 



"By the ground being left a certain time under pasture ; 

 according to the number of stock which it can support. 



'' By the operation of a summer fallow ; according to 

 the manner in which it is performed." 



Von Thaer considers the exhaustion by grain crops in 

 the following relative proportions : — Wheat 4 degrees, 

 rye SJ, barley 2J, oats ly^^, per bushel of product ; that 

 upon poor soils, whose original fecundity is 40, according 

 to the scale given in the preceding chapter, a fallow adds 

 10 degrees to its fertility, pasture 20, and 8 tons of ma- 

 nure, of ordinary quality, 50 degrees — so that the manure 

 and fallow, or manure and pasture, add 60 or 70 degrees, 

 and are more than sufficient to double what the crop would 

 have been without them. Without them, a crop of rye 

 would have yielded but five bushels per acre ; with them, 

 the yield would be 7^ to 10 bushels. A fallow is bene- 

 ficial, not only on account of the fertilizing properties it 

 may draw from the atmosphere, and by the influence of 

 working the land, but from the weeds and vegetable mat- 

 ters which it buries in the soil. Pasture is fertilized by 

 the droppings of the stock, and the rich sward it gives to 

 the plough and to the tilled crop. 



In the two following tables, the journal, which is about 

 two thirds of an English acre, is the measure of land ex- 

 perimented upon. The schiffel is more than a bushel 

 and a half, Winchester measure. These tables are pre- 

 dicated upon accurate experiments, and show the aug- 

 mentation or diminution of fertility, caused by the crops, 

 the manures, the pasture, and the fallow. 



