Dec. 2, 1918 Effect of Farm Manure on Irrigated Field Crops 499 



The facts set forth in Tables I and II may be summarized separately for 

 each of the three stations for the five years 191 3 to 191 7, as follows: 



At Scottsbluff the yield of potatoes, large and small, for the 30 plot- 

 years, has averaged 208 bushels per acre, with a mean annual difference 

 in favor of the manuring of 40 ±7, The yield of marketable potatoes 

 from the same plots has averaged 1 50 bushels per acre, with a mean annual 

 difference in favor of the manuring of 46 ±7. The percentage of the 

 total yield classed as marketable for the 30 plots is 72, while the mean 

 annual difference in percentage marketable in favor of the manuring is 

 8±i.5. 



At Belle Fourche the total yield of potatoes for the 30 plot-years has 

 averaged 131 bushels per acre, while the mean annual difference in favor 

 of manuring is 34 ± 6.4. The yield of marketable potatoes from the same 

 plots has averaged 105 bushels per acre, while the mean annual difference 

 in favor of the manuring is 36 ±6.3. The percentage of the total yield 

 classed as marketable for the 30 plots is 80, while the mean annual differ- 

 ence in percentage marketable in favor of the manuring is 7 ±1.9. 



At Huntley the total yield of potatoes for the 30 plot-years has averaged 

 239 bushels per acre, while the mean annual difference in favor of ma^ 

 nuring is 26db 8.3. The yield of marketable potatoes from the same plots 

 has averaged 221 bushels per acre, while the mean annual difference in 

 favor of the n^anuring is 24 ±8.5. The percentage of the total yield 

 classed as marketable for the 30 plots is 92, while the mean annual differ- 

 ence has been negligible, being in favor of the manured plots by less than 

 I per cent. 



SUGAR BEETS 



The effect of manure on the yields of sugar beets is shown in Table III, 

 which gives the annual yields in tons per acre for the manured and unma- 

 nured plots and the annual differences in yield between the pair of plots 

 that have had similar treatment except for the manuring. The table 

 also shows the mean annual yield of the crop for each rotation for six 

 years and the mean of the annual differences with the probable errors of 

 these means obtained as indicated above in the discussion of Table I. 



In the 12 comparisons shown in Table III the mean yields for the 6- 

 year period all show increases as a result of manuring. Some of these 

 increases are too small to be considered significant, but in 9 cases of the 12 

 the mean of the annual differences exceeds its probable error sufficiently 

 to be regarded as significant. Eliminating the 3 cases of rotation 21 in 

 1 91 2, in which the manure had not been applied, there remain 69 annual 

 comparisons. Of these annual comparisons 62 show increased yields, 

 following the application of manure and only 7 show decreased yields. 



In rotation 21 the manure is applied for the potato crop, which pre- 

 cedes the sugar beets, so that the later crop receives only the second-year 

 effect of the manure. In rotations 21 and 23 manure has been applied 

 to the same plot three times during the 6-year period covered by the table. 



