Wilcox in his “Irrigation Farming”[3] says: “The critical time with alfalfa is the first six weeks of its growth. Flooding during this period is quite certain to give the plants a backset from which they seldom fully recover before the second, and sometimes not before the third year, and it is not often in the arid states that rain falls with sufficient frequency to dispense with the necessity for irrigating the plants while small. By soaking the earth from thirty-six to forty-eight hours before seeding, however, the plants will make vigorous growth until they are ten to twelve inches high, after which they may be irrigated with safety.
[3] “Irrigation Farming,” by Lute Wilcox: 314 pp. Orange Judd Company, New York.
“When alfalfa has become established, a single copious irrigation after each cutting will ordinarily be found sufficient. Irrigation before cutting is undesirable, because it leaves the earth so soft as to interfere with the movement of machinery and loads. It also makes the stalks more sappy, and, while they will retain the leaves better, there is more difficulty to be experienced in the curing at harvest time; and taken all in all, we much prefer to irrigate after each cutting. In Colorado we cut alfalfa three times and often four times in a season, hence the stand gets as many irrigations. Some people irrigate very early in springtime, before the crowns have awakened from their hibernal rest, but this practice is not right. The chill of the water in very early spring is not conducive to quick growth and may often retard the plants in getting an early start. We do not irrigate prior to the first cutting unless the season is particularly dry and the plants seem to actually demand water. We irrigate late in the fall and apply a top-dressing of light barnyard manure, which is found to be of great service in several ways.”
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.