INFLUENCE OF IRRIGATION UPON COMPOSITION
I find no report of experiments published by any station in which the influence of irrigation upon alfalfa hay is made a special study, but Bulletin No. 80 of the Utah station contains a great deal of information along this line relative to grain crops, potatoes, and mixed grasses. In summing up the results of the experiments, the following conclusions are
“Heavy irrigations increase the percentage of weight of the heads of plants; light irrigations increase the relative weight of leaves.
“Irrigation modifies definitely the composition of plants and plant parts; the seeds are affected more than any other plant part.
“The percentage of protein in corn kernels was increased from 12.05 to 15.08, as the amount of irrigation decreased; in oat kernels from 14.07 to 20.79; in wheat kernels from 15.26 to 26.72. In all these seeds the fat and nitrogen-free extracts were increased by liberal waterings.
“Increased irrigations increased the starch content and decreased the protein content of potatoes.
“The water in plants is somewhat dependent on the water in the soil.
“The proportion of ear corn to stover increased regularly with the increased application of water.
“The percentage of grain in the wheat crop increased with increased irrigations.
“The yield of wheat increased up to thirty inches of water.
“Crops in an arid district require a greater number of pounds of water for one pound of dry matter than in humid climates.”
The experiments cited do not include alfalfa, yet the results with other crops would indicate that the percentage of protein in alfalfa hay may be less where the crop is grown by irrigation than where it is grown by dry-land farming. The composition of the hay, however, will depend upon the quantity of water supplied to the crop and not upon the method; that is, alfalfa which receives as much natural rainfall as other alfalfa would receive by irrigation, would be similarly affected in composition, and from the experiments with grains reported in the bulletin noted, it would appear that with the application of large quantities of water the percentage of protein is decreased; yet, the yield is increased, and although the feeding value of the crop may be a little less, the quantity may be greater, due to large applications of water.