Cost of fertilizing alfalfa reduced probably 70 per cent.
During the last three years this experiment station has been conducting extensive fertilizer experiments on fruit trees and alfalfa in this valley.
These experiments have been conducted in various orchards and on various farms in all sections of the valley.
During this time very valuable and interesting results have been obtained from the use of commercial fertilizers on alfalfa. It has been found that on some types of soil the yield of alfalfa can be increased from 25 to 500 per cent by the use of either superphosphate or gypsum. It has also been found that no increase in yield of alfalfa has been obtained on these soils by the use of potash, nitrogen or lime when used as fertilizers.
Since superphosphate and gypsum gave such marked increases in the yield of alfalfa the writer decided to determine why this was true. It is well known that superphosphate is a compound of phosphorous, sulphur calcium, oxygen and hydrogen. Oxygen and hydrogen are absolutely worthless in any fertilizer; and for this valley callum also is worthless in fertilizers, as our soils are naturally so well supplied with lime. Phosphorous is a valuable plant food, and many soils throughout the world are deficient in this element. The beneficial results from the use of superphosphate have always been attributed by chemists to the element phosphorous. Sulphur has generally been regarded as a worthless element in commercial fertilizers.
Gypsum or land plaster contains only calcium, sulphur and oxygen. It has already been stated at calcium in fertilizers is worthless for our soils and oxygen is of no value in any fertilizer.
We have noted that superphosphate and gypsum produce similar results in increasing the yield of alfalfa; but gypsum contains absolutely no phosphorous, potash or nitrogen — the three chief plant foods contained in commercial fertilizers. Chemists have therefore concluded that gypsum is only of indirect value — serving a chemical function in making available in the soil supplies of potash and phosphorous already present.