58 GARDENING FOR THE SOUTH. 



not only without loss, but with decided benefit, and the 

 ammonia will be retained. 



Another indirect agency of manures is in protecting 

 plants from sudden changes of temperature. There is no 

 doubt that rich soils and those abounding in animal and 

 vegetable remains, are less liable to change their temper- 

 ature with the incumbent atmosphere than those of 

 poorer constituents, for the decomposition of manures 

 gives warmth to the soil. Corn can be grown in high 

 latitudes upon rich land only; upon a poor soil it would 

 perish. 



The last indirect effect of manures upon plants is to 

 improve the texture of the soils in which they grow. 

 Decomposing in the ground, they leave interstices as they 

 become less in bulk, making it more light and porous. 

 The effect of manure in rendering a stiff soil light and 

 friable is very well known. It is equally true that vege- 

 table manures give to sandy soils greater tenacity, 

 enabling them better to retain moisture and ammonia. 



Manures, then, should be adapted to soils and circum- 

 stances. Cohesive and binding manures are most suitable 

 for open sands; those of open texture, for stiff clays; those 

 that readily attract and retain moisture, for dry soils; 

 heating, dry, strawy, and turfy manures, for wet or clayey 

 soils; and those of slow decomposition for hungry gravels. 



Gypsum. — Of this a very small quantity will suffice. 

 One bushel per acre 3 r early is all that is needed. In 

 absorbing ammonia from the manure heap, charcoal dust 

 and leaf-mould are much cheaper. It is the cheapest way 

 of supplying the soil with what sulphur is required. 



Marl, where it can be obtained, may be applied with 

 advantage, especially to sandy soils. It is generally bene- 

 ficial in proportion to the quantity of lime it contains. 



Some marls contain both phosphate of lime and potash 

 in considerable quantities, and hence are of increased 



