Alfalfa has the highest water requirement of any crop grown in Arizona, and any strategies that conserve water growing this crop could have a large impact on water availability in the state. The purpose of this study is to determine yield and profitability of sub-optimal irrigation strategies in alfalfa. An irrigation study was conducted at the University of Arizona Maricopa Agricultural Center on a sandy clay loam soil. The following irrigation treatments are included in this study: 1) One irrigation per cutting, 2) Two irrigations per cutting, 3) Summer (August) irrigation termination, 4) Winter (December, January, February) irrigation termination, and 5) Summer and Winter irrigation termination. The Winter irrigation termination treatments were initiated in December 2009 and data is not available yet for these treatments. The amount of water applied from January through November 2009 was 69.7 inches (one irrigation per cut), 80.5 inches (two irrigations per cut), and 78.6 (Summer irrigation termination). The annual hay yields were 12.5 tons/acre (one irrigation per cut), 13.7 tons/acre (two irrigations per cut), and 12.9 tons/acre (Summer irrigation termination). Sub-optimal irrigation increased the forage quality by decreasing fiber (ADF and NDF) and increasing protein content. Sub-optimal irrigation did not reduce stand density. The water use efficiency of applied water (plus rainfall) was not affected by irrigation treatment.

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This study is part of an ongoing effort on evaluate alfalfa cultivar performance at various locations in Arizona. Forage yields of 25 alfalfa cultivars and experimentals were measured at the Maricopa and Yuma -Mesa Agricultural Centers. During the time period reported, many of the newer cultivars were more productive than the popular cultivar CUF 101 . Selection of alfalfa cultivars should be based upon fall dormancy, pest resistance, seed cost, and yield potential.

Ten alfalfa varieties ranging from very non -dormant to moderately dormant were tested. No statistically significant differences were seen. The highest yielding variety yielded more than seven tons per acre, considerably better than the county average of 5.5 tons per acre.

Little Malva (Malva porviflora L.) is an important weed that is resistant to herbicides that will selectively control most other broadleaf weeds in alfalfa. Oxyfluorfen (Goal) has been placed under an Experimental Use Permit for alfalfa. In 1987, this herbicide was evaluated for the selective control of malva in alfalfa in the Avra Valley west of Tucson. Oxyfluorfen stunted both the malva and the alfalfa. However, the alfalfa was stunted to a lesser degree, and had begun to recover three weeks after the application of oxyfluorfen. The malva did not recover, and the alfalfa was relieved from weed competition three weeks after treatment.

Improving the germination salt tolerance of alfalfa will help this crop endure both increasingly saline irrigation water and salt build -up in the soil. Seven previous cycles of selection for salt tolerance at germination plus the parental line, Mesa-Sirsa, were evaluated for percentage germination under various levels of NaCI solutions. Germination improved linearly from the earliest to the latest cycle of selection. Germination salt tolerance can be improved through recurrent selection techniques.

Deposition of salts from irrigation water is an increasing concern for Arizona farmers and agronomists. Selection for salt tolerance during the seedling stage has been undertaken over the past three years. Yield tests were conducted in greenhouses and a significant increase in dry matter production was shown in the selected material.

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There has been limited research on the rooting patterns of alfalfa. This information would be important in developing new germplasm sources that are more water efficient, salt tolerant and drought tolerant. Ten alfalfa varieties were evaluated for possible genetic control of rooting traits. Seedlings were grown hydroponically in a growth chamber. The cultivars evaluated showed a significant statistical difference for width of lateral root system and number of lateral roots. The variation in seedling rooting patterns is sufficient to warrant a selection program for improved lateral rooting patterns.