EXPERIMENTS WITH ALFALFA AT YUMA 7 
spreading, which is figured at $1 per ton. The farm value for alfalfa 
during these years is placed at $10 per ton, which is probably rather 
conservative. On this basis, and omitting the cost of hauling and 
spreading the fertilizer and the added cost of handling the increased 
yield of hay, the acid phosphate in every case, with the exception 
of the plot receiving 250 pounds in the spring and an additional 
250 pounds in the fall, more than paid for itself the first year. In 
this instance, however, it is not fair to assess the fall application 
against the first year, as the alfalfa received no benefit from it until 
the following year when it increased the yield enough to more than 
make up for a single application of 500 pounds the previous spring. 
The greatest increase in yield came from the heaviest application of 
750 pounds per acre, but the greatest gain for the money invested 
came from the lightest application—250 pounds per acre. Dis- 
regarding the additional cost of labor involved in this increase, each 
dollar invested in acid phosphate returned $6.72 in two years. 
Next to this the most profitable fertilizer application proved to be 
44 per cent acid phosphate at 182 pounds per acre. Figured on a 
similar basis this returned $6.50 for each dollar invested in fertilizer. 
These results indicate that there is little choice in final results be- 
tween the two grades of acid Ebesphale, provided equivalent 
quantities of phosphoric acid are applied. In all cases the value 
of the increases in proportion to the money expended in fertilizers 
was considerably less than this. 
This and the preliminary tests indicate rather clearly that where 
alfalfa is making an unsatisfactory growth on the Yuma project, 
particularly in those sections where the yields have declined, acid 
phosphate can be used to very good advantage. Further experi- 
mentation is needed to determine the most profitable quantity 
and the best time to apply it, but since the otfacts are not very 
lasting it is believed that an application of 250 pounds about the 
1st of March in each alternate year will prove most satisfactory. 
EXPERIENCES OF FARMERS 
Farmers on the Yuma project visiting the experiment station from 
time to time have been impressed with the results obtained from 
oo eae of acid phosphate and have tried it on their own alfalfa 
fields with such satisfactory results in practically all cases that the 
demand for the fertilizer has increased each year. Approximately 
250 tons of 16 per cent acid phosphate was sold to the project farmers 
in 1924. This is the equivalent of 250 pounds per acre on 2,000 
acres, and it probably has had some influence on the average seed 
yields for the project, as Table 1 shows. 
In most cases this fertilizer has been applied by means of a lime 
spreader, but considerable difficulty is encountered in adjusting it 
to spread such small quantities as 300 to 500 pounds per acre. _Wher- 
ever available, the fertilizer distributor will do better work. In case 
neither of these implements is convenient, the acid phosphate is 
spread by hand. In the labor involved the 44 per cent acid phos- 
phate is most economical, but the advantages are in favor of the 
16. ee cent grade in evenness of distribution because of the heavier 
applications required. 
