PERMEABLE SOIL IS IMPORTANT 51 



in the best possible manner, the following conditions and lequiie- 

 ments must be met: 



(a) Sufficient moistm^e must be present in the soil. 



(b) The plant must have air from which to secm^e oxygen and 



carbon dioxide. 



(c) Favorable temperature must prevail. 



(d) The soil must be in good tilth. 



(e) The plant must be able to secure sufficient nitrogen and 



mineral elements from the soil. 



(/) The plant must have sufficient sunlight. 



It is to be observed that in this period the plant demands three 

 other requirements and conditions in addition to those required 

 during germination; viz., carbon dioxide, plant-food elements 

 and simlight. 



Temperattire in Relation to Crop Growth, — The air temperature 

 at which plants grow the best varies with different farm crops. 

 The best for small grains is between 77 and 88 degrees P.; for 

 cucumbers and melons, between 88 and 99 degrees; for corn and 

 hemp, between 99 and 110 degrees. 



The lowest air temperatures at which crops can make some 

 growth are as follows: for small grains, between 32 and 41 degrees 

 F.; for corn, between 41 and 51 degrees; for tobacco, between 51 

 and 60 degrees; and for melons and cucumbers, between 60 and 

 65 degrees. 



Permeable Soil Is Important (Good Tilth). — ^If the soil covering 

 a seed should become hard and very compact, the stem may not, 

 or may with difficulty, succeed in breaking through. If the soil 

 around and below it also becomes too hard and compact, the roots 

 are checked in their development — a, stunted plant is the result. 



If, on the other hand, the soil is in a condition to permit the 

 stem to push itself through to the surface with ease, and the roots 

 to penetrate the soil without hindrance, the seedling soon estab- 

 lishes itself as a vigorous plant. A permeable soil, therefore, is 

 an important condition, not only when the plant is very small 

 but throughout its growing period. 



Much attention, therefore, should be given to the preparation 

 of the most favorable condition that will enable a young plant 

 to establish itself in the soil in the quickest and best possible 

 manner. This attention is to be conffiaed largely to the develop- 

 ment of good tilth, or in other words, to the preparation of a good 

 seed bed. The smaller the seed to be sown, the better the seed- 

 bed preparation should be (Figs. 20 and 21). 



