EFFECT OF ALFALFA ON YIELDS OF FIELD CROPS. 
plats of 40 bushels per acre, while the alfalfa has increased the yield 
by 100 bushels per acre over that of the check plats. At Belle 
Fourche and at Huntley the beneficial effects of manure have been 
at least significant. The alfalfa has not produced increased yields 
at Belle Fourche, though it has done so at Huntley. 
Table II. — Comparison of the effect of farm manure and of alfalfa on subsequent yields 
of Irish potatoes in crop rotations under irrigation at the Scottsbluff, Belle Fourch^ 
and Huntley Field Stations. 
Yield of potatoes per acre. 
Factors compared. 
Scottsbluff. 
Belle Fourche. 
Huntley. 
Manure. 
Alfalfa. 
Manure. 
Alfalfa. 
Manure. 
Alfalfa. 
Total crop: 
Yield (mean of check and treated 
plats) , . .bushels . . 
Mean annual difference do 
Marketable potatoes: 
Yield do 
Mean annual difference in yield. do 
208 
40±7 
150 
46±7 
72 
8±1.5 
236 
100±7 
192 
101 ±7 
76 
12±1.3 
131 
34±6.4 
105 
36±6.3 
80 
7±1.9 
135 
-4±6 
107 
-4±5.6 
81 
.5±2.2 
239 
26±8.3 
221 
24±8.5 
92 
258 
50±12.6 
241 
55±11.4 
93 
Mean annual difference in percentage . . 
1±.55 
OATS. 
The effect of alfalfa on the subsequent yield of oats is shown in 
Table III for six pairs of rotations at Scottsbluff and Belle Fourche 
and for four pairs at Huntley. The oats crop follows directly after 
alfalfa in only one rotation (No. 42) at each station. In all the other 
rotations the oats occur as the second crop after alfalfa, being preced- 
ed by potatoes in three cases (Nos. 44, 60, and 61), by wheat in one 
case (No. 48), and by corn in one (No. 62). Because of this position 
in the rotation the oats did not come on plats that had been in alfalfa 
until 1914 except in the case of rotation No. 42. Thus, 16 compari- 
sons are made in Table III, of which 12 show increases in the mean 
yield of the crops following alfalfa and 4 show decreases. But if 
we accept as a test of significance of the mean that it shall be at 
least three times as large as its probable error, then only 5 of the 16 
comparisons show definite benefits from the alfalfa, and in one case, 
(rotation No. 42, at Belle Fourche) there is a consistent reduction 
in yield following alfalfa. 
While these results do not show a strikingly beneficial effect from 
the use of alfalfa in the rotation, it is to be observed that these oat 
crops have been grown on soil that was virgin at the beginning of the 
experiment and of relatively high productivity, as shown by the 
mean yields of all the plats included in the experiment. It has been 
noted also in connection with these experiments that the plant 
growth has been more vigorous on the plats of oats following alfalfa, 
as is shown in the yields of straw. These notes, together with the 
facts concerning the grain yields for each of the three stations, are 
summarized below. 
