EFFECT OF FALL IRRIGATION ON CROP YIELDS. 



9 



moisture than that of the check plats. On June 27 there were no 

 significant differences in moisture content, all differences being less 

 than their probable errors. It will be noted that the moisture con- 

 tent of the fourth foot was practically the same on each of the three 

 sampling dates. The results of the moisture determinations made 

 in 1914 showed that while the soil of the fall-irrigated plats contained 

 more moisture than that of the check plats early in the season, when 

 all the plats had abundant moisture, the differences decreased as the 

 season advanced and disappeared before the end of June. 



Table VI. — Summary of the results of soil-moisture determinations made in 1914 in the 

 fall-irrigation experiments at the Belle Fourche Experiment Farm. 



Date. 



May 5. . 

 Do. 

 Do. 

 Do. 



June 18 

 Do. 

 Do- 

 Do. 



June 27 

 Do. 

 Do. 

 Do. 



Depth. 



Feet. 

 1 

 2 

 3 

 4 

 1 

 2 

 3 

 4 

 1 

 2 

 3 



Fall-irrigated plats. 



Num- 

 ber of 

 plats 

 aver- 



Moisture 

 content. 



Per cent. 

 28.7±0.4 

 28. 8± .4 

 26. 6± .3 

 21.7±1.0 

 23. 1± .6 

 25. 3± .7 

 26. 5± .6 

 21. 5± .8 

 22. 3± .6 

 25. 8± .4 

 26. 4± .6 

 20. S± .8 



Check plats. 



Num- 

 ber of 

 plats 

 aver- 

 aged. 



Moisture 

 content. 



Per cent. 

 25.1±0.6 



20. 5± .3 



21. 0± .3 



19. 5 ± .7 



21.5± .7 



20. 3± .9 



20. 9± .5 



20. 2± .9 



22. 1± .7 



25. 0± .7 



26. 3± .9 



20. 7± .9 



Difference 



in favor 



of fall 



irrigation. 



Per cent. 

 +3.6±0.7 

 +8.3± .5 

 +5.6± .4 

 +2.2±1.2 

 +1.6± .9 

 +5.0±1.1 

 +5.6± .8 

 + 1.3±1.2 

 + .2± .9 

 + .8± .8 

 + .1±1.1 

 + .1±1.2 



Soil moisture in 1915. — The sampling in 1915 was done on May 24 

 and June 10. All the plats in Series I and II were sampled on the 

 first date and those in Series III and IV on the second. No irriga- 

 tion water was applied to any of the plats in 1915 until July 14, so 

 that the moisture determinations were made five and seven weeks, 

 respectively, before the first irrigation. The samples were taken to 

 a depth of 3 feet. Table VII gives a summary of the results of the 

 moisture determinations, together with the provable errors of the 

 averages of moisture content. v 



Table VII. — Summary of the results of soil-moisture determinations made in 1915 in the 

 fall-irrigation experiments at the Belle Fourche Experiment Farm. 





Depth. 



Fall-irrigated plats . 



Check plats. 





Date. 



Num- 

 ber of 

 plats 

 aver- 

 aged. 



Moisture 

 content. 



Num- 

 ber of 

 plats 

 aver- 

 aged. 



Moisture 

 content. 



Difference 



in favor 



of fall 



irrigation. 



May 24 



Feet. 

 1 

 2 

 3 

 1 

 2 

 3 



7 

 7 

 7 

 7 

 7 

 7 



Per cent. 

 29.2±0.3 

 29. 4± .4 

 28. 1± .2 

 30. 0± .3 

 29. 8± .2 

 27. 9± .3 



7 

 7 

 7 

 7 

 7 

 7 



Per cent. 

 30.4±0.2 

 29. 4± .4 

 26. 0± .9 

 30. 3± .6 

 29. 4± .6 

 27. 6± .7 



Per cent. 

 — 1.2±0.3 



Do 







Do 



+2. 1± .9 



June 10 



— .3± .7 



Do 



+ -4± .6 



Do 



+ .3± .8 







