362 



THE IRRIGATION AGE. 



depth evaporated, while from the tanks that received 

 a depth of 11.3 inches, 9.5 inches, or 84 per cent, was lost 

 by the time the experiment was terminated in Septem- 

 ber. The losses in several tanks are shown by the table 

 below : 



Amount of irri- Amount 



gation water applied of evaporation 

 No. of tank. over the surface, over the surface. 



1 and 2 0.0 



3 and 4 3.8 



5 and 6 5.7 



7 and 17 7.0 



18 and 19 9.5 



20 and 21 11.3 



0.5 

 3.1 

 5.4 

 6.5 

 8.5 

 9.5 



Duration of 

 experiment. 



92 



92 



92 



92 



92 



92 



A similar test was made in the orchards of south- 

 ern California during the present month with tanks 



year? afro the citrus orchards of southern California 

 were watered by means of shallow furrows. At that time 

 no deep furrows were used. Now more than half the 

 orchard ists use a smaller number of furrows and make 

 these deeper. This change has resulted in maintaining 

 a drier surface, in deeper application of water, and in 

 deeper root development. In light irrigation it is be- 

 coming common to make bxit one deep furrow, in which 

 the soil may be loosened to a depth of fifteen inches 

 midway between the tree rows, and immediately after ir- 

 rigation this deep furrow is filled with dry soil. By this 

 method there is practically no loss by evaporation. By 

 the use of shallow furrows, spaced two and a half feet 

 apart, the surface is moistened, evaporation is excessive, 



Weiser Bridge, acioss Snake River, Weiser, Washington County, Idaho. 



holding 1.200 pounds of soil and the results corroborate 

 the test of the previous year. 



HOW TO LESSEN THE WASTE FKOM EVAPORATION. 



Less Frequent Waterings. In a brief paper like 

 this the several practical ways of checking evaporation 

 can only be suggested. Climatic conditions, crops, soils, 

 quantity; of available water, and other factors exert a 

 controlling influence. In the performance of all labor 

 toward this end, the main principle to be kept con- 

 stantly in mind is that the rate of evaporation from 

 the surface of soil is in direct proportion to the amount 

 of moisture which it contains. Keep the surface of a 

 field moist by continued or frequent irrigation and the 

 greater part of the water will pass from the soil into the 

 air. On the other hand, keep the surface dry, or wet it 

 only at long intervals and cultivate often and thoroughly 

 and the greater part will be retained. The first sugges- 

 tion I have to offer, therefore, is to irrigate all deep- 

 rooted plants less frequently and apply, if need be, larger 

 quantities of water at each irrigation. 



A smaller number of deeper furrows. A dozen 



and the fibrous rootlets are lured to the surface layer of 

 soil, only to be withered and killed by the succeeding 

 drouth. 



Cultivate After Each Irrigation. Whereved the 

 nature of the crop will permit of cultivation, no time 

 should be lost in pulverizing the surface when it is suf- 

 ficiently dry. Keeping always in mind the fact that a 

 moist surface soil in hot weather will daily lose a large 

 amount of water by evaporation, the soone'r a field can be 

 cultivated after being irrigated the more water will 

 be retained. This practice need not be confined ex- 

 clusively to orchards, root crops, vegetables and corn. 

 A thprough harrowing at the right time does not injure 

 alfalfa and the yield from grain fields can frequently be 

 increased by a like practice. 



Deeper Soil Mulches. The belief is cvirrent that 

 a dry, well pulverized soil mulch, two inches in depth, 

 will protect the moisture beneath from 'evaporating 

 and that it would be a useless expenditure of time and 

 labor to increase this mulch beyond four inches. -This 

 belief does not hold true for the warmer regions of Cali- 





