IRRIGATED FARMING IN TWIN FALLS COUNTY, IDAHO 39 
8.2 tons; (2) to rotation 21 increased the yield of potatoes 48 bushels 
per acre and that of sugar beets 6.1 tons per acre; (3) to rotation 
25 increased the average yield of potatoes 67 bushels per acre, that 
of oats 14 bushels; and (4) to rotation 31 increased the average 
yield of potatoes 52 bushels per acre, that of oats 17 bushels, and that 
of sugar beets 7 tons. 
Combined effect of rotation of crops, alfalfa, and manure on crop 
yields—The combined influence of rotating crops, adding alfalfa to 
the rotation, and the application of 12 tons of manure per acre once 
in the rotation period is indicated by a comparison of the yields 
obtained when the respective crops were grown continuously on the 
same land with the yields obtained in rotation 61. This comparison 
shows these three factors increased the yield of potatoes 229 Backer 
per acre, that of oats 33 bushels, and that of sugar beets 11 tons. 
That is, these three factors increased the yield of potatoes 388 per 
cent, that of oats 82 per cent, and that of sugar beets 136 per cent. 
Effect of manure on the yield of sugar beets in the district studied — 
Table 19 is presented to show that high yields (at least of sugar 
beets) can be obtained in the district studied by a liberal use of 
barnyard manure. This table shows the yields of sugar beets grown 
on four well-manured tracts of land located near the sugar factory 
at Twin Falls, Idaho. The footnotes following the table show the 
quantities of manure applied. 
The following points deserve attention: (1) That beets were grown 
continuously on the 10-acre tract for eight years, on the two 6-acre 
tracts for six and seven years, and on the 20-acre tract for six years; 
(2) that the lowest yield obtained during these years was 14 tons 
er acre; and (3) that the average yields of the four tracts ranged 
rom 17 to 20 tons per acre. For the four years of the survey (1919— 
1922) the average yield of these four tracts of beets was 18.8 tons 
per acre; for the same period, the average yield of beets on all of 
the farms studied was 12.2 tons per acre. Probably not all of this 
difference should be credited to the influence of the manure applied, 
for the men who grew these four tracts of beets were far more 
skilled in the art af sugar-beet culture than most beet growers and 
there may have been some difference in the grade of land used. 
TaBLE 19.—Yield in short tons per acre of sugar beets grown continuously on heavily 
manured land, near the sugar factory, Twin Falls, Idaho 
| 
Year 10 acres 1 | 6 acres ? | 6 acres 3 | 20 acres 4 
TATG SS Se eS a ee eae ee ee BU. a crn eR A eg oe Reel a EST 
ogee eee ene eeetee ewan OT ee 1G a] Aen rss 16:5 6 
Lait lS SS a ee 18 20 22° | 14 
USL oe Se a ee ee 20 21 18 20 
ES ce Soe SS Sp ea eae ae ee 14 16 22 15 
De pe bn 2. UE oc et Se ee ee 17 19. 5 16 16. 5 
LAL es ee eee ee eee 21 21 22.5 21 
1G RRS oS 5k Dae ee Se Be oe ee ee a oe ee eee 20 24 26 22 
PARC AG Ona eh eee ea ee Fe se ee i Se 17.4 20. 2 20. 4 | 18.1 
1 pare applied at the rate of 15 tons per acre each year except two years when only 5 tons per acre were 
applied. 
2 Manure applied at the rate of 15 tons per acre. 
3 Manure applied at the rate of 12 loads (90 bushels per load) per acre each year. 
4 Manure applied at the rate of 10 tons per acre. 
The tons of manure applied in each case were estimated, and the water content of the manure doubtless 
varied widely. For these reasons, no close comparison can be made as to the quantities of plant food that 
were applied to these four tracts of land. 
