Irrigating Alfalfa.
I am making parallel ridges for alfalfa, sending a full head of water down to the end of the field between each ridge. Should I calculate the lands to be mowed one at a time in even swaths? The mower being 5-foot cut, would you count on cutting a 4 1/2 or 5-foot swath? This soil is sandy, water percolating rapidly. The fall is 8 feet to the mile. How wide, then, would you advise making the ridges to suit the mower, and to flood economically, using from 2 to 4 cubic feet per second? The length of the lands is across 40 acres.
Growing alfalfa in long parallel checks, to be flooded between the levees, is the way in which much alfalfa is being put in at the present time where the land has such a slope as you indicate. It is calculated, however, to seed the levees as well as the check bottoms, and to run the mowers across the levees, thus leaving no waste land and mowing across the whole field and not between the levees as you propose. For that purpose these levees are made low, not over a foot in height, calculating that they will settle to about six or eight inches, which is sufficient to hold the water and direct its flow gently down the slope. There is, however, a limit to the distance over which water can be evenly distributed in this way, the difference being dependent upon the character of the soil, slope, etc. A length of nine hundred feet is sometimes found too great for an even distribution, and, for this reason, supply ditches at shorter intervals are introduced.
Unirrigated Alfalfa.
In what part of the State does alfalfa grow best without irrigation?
Obviously the parts which have the greatest rainfall in connection with retentive soil and plenty of summer heat. Alfalfa grows best without irrigation on "sub-irrigated" land where the ground water is sufficiently deep to allow a deep rooting of the plant in free soil and yet not too far down to be readily reached by the deep-running roots. Good results can be obtained with anywhere from four to ten or twelve feet of soil above water. On shallower soils the plant is apt to be short-lived through root troubles. Unirrigated alfalfa is also reduced by the incursions of gophers which flooding at least once a year will destroy.
Alfalfa and Overflow.
How long can alfalfa stand water without being drowned out? I have a piece of alfalfa on which the water will stand for considerable time in the winter time.
Alfalfa while dormant will endure submergence for several weeks. We do not know exactly how long, but evidently for a considerable period, providing temperatures are too low to invite growth. On the other hand, growing alfalfa is quickly and seriously injured by overflow.
No Nurse-Crop for Alfalfa.