[902. 



FORESTRY AND IRRIGATION. 



201 



government, illustrating the appliances 

 and methods used in irrigating. 



Professor King has recently been ap- 

 pointed Chief of the new Bureau of 

 Climatology of the Depatment of Agri- 

 culture. Professor Belz, one of his as- 

 sistants here, is to go with him to Wash- 

 ington. Prof. A. R. Whitson will con- 

 duct the experiments next season. 



We had three acres of late potatoes 

 which we were anxious to dig as soon 

 as they were ripe enough. We tested 

 them by digging eighteen hills in an 

 irrigated row and an equal weight from 

 an adjoining unirrigated row, which re- 

 quired fort3^-two hills. I have reason 

 to believe, however, that the average 

 difference in the field was not as large 

 as this. I think the average was about 

 85 bushels per acre for unirrigated and 

 135 bushels for irrigated. The yields 

 from the unirrigated strips were above 

 the average annual yield here. This is 

 the first year of these experiments, and 

 considering the fact that all our crops 

 were planted late on account of unavoid- 

 able delays in the spring, the results se- 

 cured this season should not count for 

 as much as average results of several 

 seasons. 



One of the most interesting instru- 

 ments in use here is the evaporimeter. 

 A circular galvanized iron tank four feet 

 in diameter and three feet deep is sunk 

 nearly to its top in tlie ground. From 

 this tank a tube extends a few feet to 

 one side and rises from an elbow to a 

 small platform, on which is a metal box 

 containing clock-work, which slowly re- 

 volves a vertical roller, on which is 

 fastened a sheet of paper, especially 

 ruled and graduated for the purpose. 

 A lever wath a peculiar pen fastened 

 across one end, and on the other end a 

 small wire, on the lower end of which 

 is a float hanging in the tube, is care- 

 fully balanced so that the pen swings 

 against the side of the roller. Water is 

 filled into the tank until it is nearly full, 

 raising the float in the tube enough to 

 bring the pen to a certain line on the 

 paper. The box is then locked and left 

 for twenty-four hours, when the pen is 

 again adjusted to the same line by add- 

 ing as much water as has been evapo- 

 rated, or taking out if rainfall has ex- 



ceeded evaporation. An irregular line 

 on the paper indicates the amount and 

 rate of evaporation and rainfall during 

 the twenty-four hours. Our irrigations 

 are regulated somewhat b}^ the rainfall 

 thus recorded. It does not matter so 

 much what the evaporation from open 

 water may be, if the soil is thoroughly 

 cultivated evaporation from it may be 

 greatl}' retarded. 



Some simple form of rain gage might 

 be useful to farmers by helping to de- 

 termine when irrigation is desirable. 

 A simple way of determining when soil 

 needs water is to press some of it in the 

 hand. If it packs in the hand so as to 

 retain the impress of the fingers, it is 

 supposed to be sufficiently moist for 

 plant growth ; if not, irrigate. This 

 will do, perhaps, in most cases, but 

 there is so much difference in soils that 

 it will hardly do for a universal rule. 

 There must be sufficient water in the 

 soil so that it will pass by capillarity 

 along the surface of the soil-grains to- 

 ward the little rootlets which are suck- 

 ing it in. In clay soils the particles are 

 so very small that there is much more 

 grain surface for water to adhere to, so 

 that the water-holding capacity of such 

 soils is much greater than sandy soils, 

 in which the soil-grains are large and 

 comparatively few in number. 



But for the same reason plants can use 

 the water to a lower percentage in sandy 

 soil than in clay soil, since in a sandy 

 soil it is spread over a much smaller 

 grain surface, and the water film on 

 each grain w411 be thick enough to move 

 by capillarity, while if divided among 

 all the minute particles of clay soil it 

 would be too thin to move. The per- 

 centage of w^ater necessary for plant 

 growth in clay may be three or four 

 times as great as in light, sandy soil. 

 Both soils would probably appear to be 

 of about the same dryness, the real dif- 

 ference being discoverable by analysis 

 only. Every man should study the pe- 

 culiarities and needs of his own soil and 

 not follow general rules too closely. 



I have just made two new sluice- 

 hose sections, each 80 feet long, with 

 ports for every furrow, with an apron 

 end to lay into the furrow, which will 

 be more convenient. We have 2,400 



