CONDITIONS AFFECTING GROWTH 13 



during growth is also set free to slowly disintegrate 

 the mineral elements, rendering these soluble and 

 available as plant food. In winter the frost acts 

 upon the hard, compact particles, separating them 

 and making them permeable to air and unlocking 

 new supplies of plant food that would otherwise 

 be unavailable. 



Our upland crops secure a large portion of their 

 nitrogen, as well as other food constituents, from 

 decaying animal and vegetable matter, and it is of 

 very great importance for such plants as melons, 

 which must complete their growth in a compara- 

 tively short period, that as much of this material be 

 made immediately available as possible. The appli- 

 cation of well-rotted barn manure or commercial 

 fertilizers, which act quickly by giving up to the 

 plant the necessary food elements in an available 

 form, is, therefore, especially valuable. 



Drainage is also essential in land that is inclined 

 to be heavy or where the water table is too near 

 the surface, because it serves to promote aeration 

 by removing the surplus water and places the parti- 

 cles of soil in the proper relation to moisture for 

 the reception of the plant roots. Plants of the na- 

 ture of those under discussion will not thrive with 

 wet feet. 



