16 PRODUCTIVE FARMING 



Problem. — One hundred pounds of cured corn fodder 

 contain 58 pounds of dry matter, 2.9 pounds of which are 

 from the soil and the remainder from the air. What per 

 cent of the dry matter is from each source ? 



Exercise. — Mineral Matter in Plants. — Burn a piece of 

 very dry wood on a stove shovel in the stove, to save all the 

 ashes on the shovel. If the dry wood be weighed first and 

 the ashes be weighed afterward the exact proportion can 

 be determined. The ash represents nearly all of the mineral 

 matter in the wood. This part comes from the soil and the 

 remainder chiefly from the air. This exercise shows how 

 small a part of the plant's food is from the soil; but this part 

 is very necessary. Our farm crops could not live without 

 the ash or mineral matter which they obtain from the soil. 



Other Needs of the Plant. — ^We have already seen that 

 most plants need light to make use of the food which they 

 get from the air. Light is not necessary for the germination 

 of seeds in the soil. The leaves of the young plant soon seek 

 the light by growing toward the surface of the soil. 



The need of moisture has also been considered. 



Other needs of the plants are a proper amount of warmth 

 and a supply of air. 



Light, heat, moisture, and air are all needed by growing 

 crops. 



Temperatures. — Certain degrees of warmth are necessary 

 for the best growth of plants and the sprouting of seeds. 

 Very few seeds will sprout if colder than 40 degrees F. or 

 warmer than 115°. Wheat will not sprout below 41° and 

 prefers a warmth of 60° or 70°. Corn needs more heat; even 

 48° is too cold for it and soil as warm as 70° or even 90° suits 

 it better. Seeds that sprout in cool soil may be planted in 

 earliest spring time; while those which require more heat 

 must be planted later. 



Air and Oxygen. — Not only must the leaves and stems 

 of plants have free access to air, but the roots of our farm 



