56 PRODUCTIVE FARMING 



in solution in the soil water. It is a valuable substance in 

 soil. It furnishes the important plant-food, calcium. Lime- 

 stone crumbles or dissolves easily and helps to make avail- 

 able other plant-foods in the soil. The lime aids in the decay 

 of vegetable matter and in the formation of nitrates from 

 decaying vegetable matter. It improves the physical con- 

 dition of soil; its presence helps to make heavy clay soil loose 

 and more easily worked and to facilitate the passage of 

 water and air through it. In small quantities it improves 

 sandy soil by causing the particles to adhere more closely to 

 each other, and consequently, to hold moisture better. It 

 prevents harm from acids and certain other poisonous com- 

 pounds in soil. It lessens the injury from certain plant 

 diseases that are transmitted through the soil. Soil contain- 

 ing an abundance of lime is usually of good character. It is 

 easy to work and should be well adapted to grains and fruits. 



While lime is very valuable in the soil, h is possible for 

 it to become harmful. Too much of it in sandy soil or grav- 

 elly soil is more harmful than in clay soils. It may cause 

 other plant-foods to be liberated faster than they can be 

 used by the crop, and they will be wasted. It may cause the 

 vegetable matter or humus to decay too fast; it may reduce 

 the yield of certain crops, as cranberries, and watermelons 

 which prefer acid soil. 



A loam is a soil consisting of a mixture of sand and clay 

 and containing humus. If two-thirds of the mixture is sand 

 it is called a sandy loam. If one-half of the soil is clay it is 

 called a heavy clay loam. Soils between these two extremes 

 are called loams or medium loams. When gravel or coarse 

 sand and lime are present in considerable amounts, we have 

 gravelly or limy loam. Loam soil is the best for most farm 

 purposes. Sand, clay, and humus are improved as they 

 become mixed together. 



Medium loams are the best soils for farming if there is 

 a large amount of humus present. The farmer says, "they 



