i6 



Journal of Agricultural Research voi. xiii. no. 



TabXE V. — Total seasonal increases in irrigation-water content of the Willows 



experimental tract 



The averages presented at the bottom of Table IV and in figure 6 show, 

 like those of the Purdy and Tuttle tracts, that but very little water 

 passed below the surface foot of soil. 



Fig. 6. — Graphs of the water content before and after irrigation, moisture equivalent, and pore space o£ 

 clay soils. Each water-content curve is the average of 284 borings. 



RESULTS ON UNIVERSITY FARM, DAVIS 



Among other reasons, the systematic plan of irrigation followed and 

 the length of time covered in the Davis work make it desirable to present 

 separately the results there obtained. No appreciable differences in 

 volume weight were found, notwithstanding textural differences, the 

 average volume weight of several observations being 1.28. Upon this 

 value the calculations given in the following tables are based. The 

 moisture-equivalent determinations as presented in Table VI were made 

 of samples from each of the upper 1 2 feet of soil taken from single bor- 

 ings in three plots,^ D, F, and H. Plots B, C, D, E, F, and G^ are suf- 

 ficiently alike in texture to be placed in one group, although some varia- 



' See Table VII for explanatory note on the ntunbering of the plots. 



' As plot A was given no irrigation water, it is not reported in this paper. 



