160 
ELEMENTARY AGRICULTURE 
layer of soil particles over the surface to check the 
evaporation of water. Berries and vegetables may be 
mulched with straw, leaves, or cotton seed hulls. The 
soil mulch is good and very economical. 
Fig. 118.—A tile drain will last for years and enables the farmer to till all of 
his land. 
“Farm Soils Need Organic Matter.”—In short, 
“humus is the key which unlocks the store house of soil 
fertility.” Decayed organic matter performs an impor¬ 
tant work by binding together particles in loose, sandy 
soils and by making heavy soils open and porous. Humus 
