Thorough Tillage System ror Plains or Colorado. 31 
13. Roots of all cultivated plants make their best growth when the 
following conditions are supplied: 
soil well supplied with plant food. 
14. The earth mulch prevents excessive evaporation and thus con¬ 
serves moisture. 
15. Deep plowing furnishes a soil reservoir of good depth to store 
moisture and summer culture conserves it. 
16. Crops require more moisture to mature them under semi-arid 
than under humid conditions. 
17. Our field crops rank from the lowest to highest in amount of 
moisture required to mature them as follows: Corn, potatoes, wheat, barley, 
field peas, oats, alfalfa and red clover. 
18. Ten inches of rain furnishes enough moisture to mature more 
than twice that number of bushels of wheat per acre. 
19. The amount of rainfall, together with the selection of drouth 
resistant crops, must be considered under any system of soil culture—under 
semi-arid conditions. 
20. The total area of land which can be successfully farmed within 
Colorado’s semi-arid belt is yet to be determined.. 
