Dormant Season Alfalfa Water Balance on the NIIPby Brian Boman,
Abstract: Non-growing season water balance parameters were measured for alfalfa under high-elevation desert conditions of the Navajo Indian Irrigation Project in northwest New Mexico. The lysimeters were in a loamy sand soil and constructed from plywood frames covered with plastic sheeting. The drainage lysimeters were 1.8 m in length, width, and depth and buried with the tops about 5 cm below the ground surface. Drainage water was removed by applying vacuum to ceramic candles or perforated drainage tubing in the lysimeter bottoms. Irrigation water was supplied by a sprinkler system as required. Alfalfa, with oats as a cover crop, was planted in the lysimeters in the summer of 1979. During the growing season, irrigation was applied to maintain well-watered conditions. In the dormant season, irrigation water was not applied and leachate from rainfall was periodically pumped from the lysimeters. Non-growing season water loss was calculated as precipitation—drainage—soil moisture change. The non-growing season was defined as the period from the first killing freeze in the fall to the beginning of spring growth in the next year (average temperature of 10C°). The lysimeter site recorded rainfall of 119 mm, 66 mm, 82 mm, and 144 mm for the 1979/80, 1990/81, 1981/82, and 1982/83 winter seasons, respectively. Non-growing season water loss for the 5 lysimeters averaged 114 mm, 146 mm, 147 mm, and 173 mm for the four seasons, with an average daily rate of 0.8 mm day-1. Non-growing season water use amounted to 15% of the measured growing season FT.
Subject Headings: Seasonal variations | Measuring instruments | Vegetation | Irrigation | Water balance | Irrigation water | Surface drainage | Water loss | North America | United States | New Mexico
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