296 1HE IRRIGATION AGE. 



loose onto his fields in July as soon as he had harvested his winter 

 wheat and removed the crop. The water was allowed to soak down 

 deeply. The field being quite level it soon dried off on top after 

 the water was shut off. The field was quickly plowed and thoroughly 

 worked down by thorough harrowing and again sowed to fall wheat; 

 3899 was a very dry spring, no rain of any account until June 7th. 

 Nearly all winter wheat was a total failure. This field, however, 

 made 4i bushels per acre grown practically by the water that was 

 stored in this soil during the previous July and August; nothing more 

 or less than sub-irrigation. These lessons should certainly be a 

 pointer to those who can get water from these ditches in fall and 

 spring, but usually find themselves short in midsummer. This would 

 certainly apply to such soils as are found in the San Louis valley. 

 When water is plenty, store it in the soil below where it may be drawn 

 upon in time when water is short in the ditches. All there is required 

 to successfully carry this out is to keep the surface soil loose and fine, 

 forming a soil mulch which will prevent the loss of this moisture by 

 evaporation. 



Sub- irrigation of crops can be very successfully practiced in the 

 semi-arid belt without the irrigating ditch, although not so conceded 

 by most who considered themselves posted. To the masses who have 

 spent much time on these semi-arid prairies the idea of raising crops 

 generally without the aid of the great national reservoir and the irri. 

 gating ditch seems ridiculous, but notwithstanding this fact it can be 

 done, and to some extent is now being done, and when the principles 

 involved are generally understood and put to practice, there will not 

 only be successful farming on much of these great prairies now 

 largely given over to stock raising, but in Arizona and many of the 

 arid sections the present supply of water will be found ample to suc- 

 cessfully raise crops on fully two if not three times as mnch land as 

 is now being covered. 



In the more arid portions of the semi-arid prairies it will be ne- 

 cessary to crop the land generally only every other year, giving over 

 each alternate year to summer-culture and the storage of the rain 

 waters, the process of which is very simple. Careful investigation 

 and observation demonstrates very clearly, not only from practical 

 field work but by laboratory experiments, that from two and one-quar- 

 ter to three inches of water are required by the different plants to 

 grow and mature one ton of dry matter. Four tons of dry matter is 

 a very good crop of any kind, thus indicating that from nine to twelve 

 inches of water are necessary to grow a good crop of corn or wheat. 

 Now the fifteen inch annual rainfall goes well into Eastern Colorado 

 centrally on the Eastern line, therefore, if one year is given over to 

 the storage of the rain waters the combined rainfall of two years will 



