436 [Assembly 



for the growth of certain kinds of plants ; they are seen growing 

 spontaneously in one season, in another they are not seen at alL 

 And so also of fruit : and this is the case where there is neither 

 too much nor too little rain. The wind being unfavorable is 

 probably the chief cause. Fertilizers must operate in two ways^ 

 to wit : By attraction from the air, and by furnishing matter to bo 

 attracted by the plant from their substance while undergoing dis- 

 solution. 



Minerals, lime, gypsum, &c., and ashes, operate chiefly by at- 

 traction. And the vegetable and animal manures, by surrounding 

 the plant with their elements, and while being dissolved ; and 

 also by attraction from the air during fermentation and dissolution. 

 Fermentation and subsequent dissolution cannot go on without 

 the presence of air, warmth and moisture. Therefore manures 

 must be at or near the surface of the soil, where they will have 

 air, warmth and moisture ; and where they may attract most from 

 the air. A soil most suitable for the growth of a particular kind 

 of plant, is one composed of substances having the greatest at- 

 traction for the elements of which the plant is being formed. 



It may now be said, if the plant draws its substance chiefly 

 from the air, why is the soil impoverished by continued cropping? 

 We answer : it appears to be caused by disturbing it too frequently 

 and leaving it bare too much. It requires covering and rest ; and 

 why does it want rest ? The animal is the receptacle of vegetable 

 life ; they bolh require intervals of rest, because they were so 

 constituted by their Maker. He commanded the Jcavs, while in 

 a land of great fertility, to let it have intervals of rest. 



We have also abundant evidence of the sustaining and renova- 

 ting effect of rest to the soil, especially if covered. It requires to 

 be covered the greater part of the time. 



The native soil of the prairie and the forest is covered and pre- 

 served in its fertility. Meadows and pastures are greatly benefit- 

 ed by having a good covering of grass through the winter. 



A soil that has been impoverished by too frequent stirring and 

 exposure is renovated and improved by being covered for two oi 

 three years. 



