6 TEXAS AGRICULTURAL EXPERIMENT STATION. 



plant food to a poor soil decreases the consumption of water. Hence, 

 the use of the proper kind of plant food will economize water. For 

 example, the Nebraska Experiment Station found that corn grown on a 

 poor soil used 540 pounds of water for each pound of dry matter pro- 

 duced. When same soil was manured, corn used only 350 pounds water 

 per pound of dry matter produced. 



(e) Variety of plants. Different varieties vary considerably in their 

 requirements for water. 



If we estimate that it requires 300 pounds water to produce 1 pound 

 dry matter, to be evaporated by the plant, the following are the approxi- 

 mate quantities of several crops which would be produced per acre by one 

 inch water (227,000 pounds) used by the crop: 



Cotton, pounds, lint 80 



Corn, bushels 6 



Wheat, bushels 4 



Oats, bushels 9 



Alfalfa, pounds 760 



Hay, pounds 760 



The supply of water is undoubtedly, at various times, the controlling 

 condition of plant growth, and unfavorable moisture conditions often 

 have their effect upon crop production. Methods for decreasing the 

 effect of unfavorable moisture conditions are, therefore, of great advan- 

 tage in practical agriculture. 



WATER AVAILABLE TO CROPS. 



The amount of water at the disposal of the crop will depend upon : 



(1) The quantity of available water in the soil at the beginning of 

 the growing season. 



(2) The amount and distribution of rainfall during the period of 

 crop growth. 



(3) The loss from the soil by evaporation from its surface. 



(4) The loss of the rain water which runs off on the surface of the 

 soil. 



(5) The loss from water which passes through the soil and into the 

 ground water. 



The quantity of available water present in the soil at the beginning 

 of the growing season depends, in turn, upon a, number of conditions. 

 These include: (a) Character of soil, (b) depth of soil, (c) charac- 

 ter and depth of subsoil, (d) rooting habits of the plant, (e) quantity 

 and distribution of the previous rainfall, (f) previous treatment of the 

 soil. 



The character of the soil determines the amount of water it will hold 

 when saturated, its readiness to lose water by evaporation or percola- 

 tion, and the quantity of water which, though present, is held so firmly 

 that plants cannot take it from the soil. 



The depth of the soil, together with the depth of the subsoil, deter- 

 mines the volume of soil from which water may be drawn. It is ob- 

 vious, for example, that when plant roots can occupy eighteen inches of 

 the soil, they have more water at their disposal than when they occupy 



