Nine alfalfa varieties, most not previously tested under field conditions in Arizona, were planted October 29, 1997, using the same setting on a Great Plains Solid Stand 13 End Wheel drill. Varieties differed in lbs. of seed/acre planted, ranging from 28.0 for CUF 101 to 21.3 for Alto. Seven cuttings were obtained in 1998, a year characterized by much cooler than normal temperatures during April through early July. The variety Alto yielded significantly more hay than CUF 101 in the first cutting and had the highest total yield (10.61 tons hay/acre) in 1998, 4.9% greater than the area standard, CUF 101. Varieties with fall dormancy class ratings of 8 (Alto, WL 525 HQ, and Baralfa 85) had the highest yields during 1998, yielding at least 103% of CUF 101. During 1999, the top yielding varieties were Baralfa 92, Beacon, and Baralfa 85, which all yielded at least 105% of CUF 101. These varieties in addition to Alto yielded 103+% of CUF 101 through the first two years of production.

Fourteen alfalfa varieties with fall dormancy ratings from 6 to 9 were tested in replicated small plot trials on the Kibler farm in Stewart District northwest of Willcox. The leading variety after four years of testing was DeKalb 189 with a dry matter yield over 5 tons per acre on 4 cuttings. This variety was also the leading variety over the four years of the trial with a four year average nearly 7.5 tons per acre. Heat units with temperature thresholds of 77 °F and 40 °F are given for each cutting.

Nine alfalfa varieties, most not previously tested under field conditions in Arizona, were planted October 29, 1997, using the same setting on a Great Plains Solid Stand 13 End Wheel drill. Varieties differed in lbs. of seed/acre planted, ranging from 28.0 for CUF 101 to 21.3 for Alto. Seven cuttings were obtained in1998, a year characterized by much cooler than normal temperatures during April through early July. The variety Alto yielded significantly more hay than CUF 101 in the first cutting and had the highest total yield (10.61 tons hay/acre) in 1998, 4.9% greater than the area standard, CUF 101. Varieties with fall dormancy class ratings of 8 (Alto, WL 525 HQ, and Baralfa 85) had the highest yields during 1998, yielding at least 103% of CUF 101. During the first half of 1999, the top yielding varieties were Baralfa 92, Beacon, and Baralfa 85, which all yielded at least 105% of CUF 101. These three varieties in addition to Alto have had accumulative yields of at least 103% of CUF 101 through the first 1.5 years of production (1998 -June 1999).

Five alfalfa varieties were planted and grown under grower conditions on a field section that had high conductivity, while two varieties were planted and grown on a normal field area. CUF 101, the variety grown in both areas, was the highest yielding variety in both area. Reduction in CUF 101 hay yield due to high conductivity was approximately one ton/acre in the first year of production, with a large amount of this noted in the first cutting. Yield differences between the areas was greatest in the early spring and late fall, with differences not noted in the June cutting. Salado was the second highest yielding variety in the high electroconductivity area, with Sal-T-96 and Leivas Best yielding less than 90% of CUF 101. Sal-T-96 also had the greatest number of weeds, due in part to very slow germination and fewer plants per acre compared with other varieties.

Furadan 4F was applied to alfalfa regrowth stubble following the first harvest of 1998 to examine treatment effects of alfalfa weevils, aphids, resultant plant growth, and threecornered alfalfa hoppers. Furadan 4F reduced larval numbers throughout the period that larvae were present (25 days after treatment). Little effect was noted for adult weevil numbers in field. Aphid numbers were also reduced by the treatment, and alfalfa stems in Furadan 4F plots were significantly taller at 21 days post treatment. Little, if any, effect from the Furadan 4F treatment was noted for adult threecornered alfalfa hopper populations during the five months following application.

A study was conducted in Mohave Valley to examine population dynamics, economic thresholds, and management strategies for potato leafhopper and treehopper (three cornered alfalfa hopper) in desert alfalfa. In 1998, three distinct peaks of adult treehoppers occurred in August, September, and October. Adult potato leafhoppers were detected earlier in the study, with four distinct peaks noted in June, July, August, and September. Spring Furadan alfalfa stubble treatment reduced initial adult treehopper infestation following application by 40-60% and the initial potato leafhopper infestation was reduced by 25-50 %.

Annual grasses such as wild barley and Mexican sprangletop are of economic concern to alfalfa growers in western Arizona. Thus, granular formulations of thiazopyr (Visor 2.5G), trifluralin (Treflan TR-I0), and norflurazon (Zorial 5G) herbicides were evaluated for annual grass control in an established alfalfa field in Mohave County when applied after the first hay cutting in early spring and prior to irrigation. Visor 2.5G was applied in spring 1998 and 1999 at application rates of 0.25, 0.38, and 0.5 lb a.i./acre. Treflan TR-10 was applied at 2.0 lb a.i./acre in early spring or in both early spring and late summer. Visor 2EC was applied at 0.5 lb a.i./acre in spring 1998 but was replaced with Zorial 5G at 2.0 lbs a.i./acre in spring 1999. In 1998, good wild barley control (81%) resulted from a spring application of Visor 2.5G at 0.50 lb a.i./acre. The Visor 2EC formulation at 0.5 lb a.i./acre provided poor weed control (40 %) due to the retention of herbicide on the alfalfa foliage and lack of incorporation into the soil by irrigation. In 1999, fair wild barley control (73 to 79 %) resulted from spring applications of Visor 2.5G at 0.50 lb a.i./acre and Zorial 5G at 2.0 lb a.i./acre. During summer 1998, good Mexican sprangletop control (83-93 %) resulted from Visor 2.5G applied at 0.38 and 0.50 lb a.i./acre and Treflan TR-10 applied in both spring and summer at 2.0 lb a.i./acre. No alfalfa phytotoxicity was observed at the rates applied in this study.

An experiment was conducted in 1998-99 to study the efficacy of spring (April 30, 1998 and March 4, 1999) applications of Zorial 5G (1, 1.5, 2, 2.5, and 3 lb a.i./A), Treflan TRIO (2 lb a.i./A), and Visor 2.SG (0.25 and 0.5 lb a.i./A) on purple nutsedge control in alfalfa. The second half of split Zorial 5G (1+1, 1.5+1.5, and 2 +1 lb a.i./A per year) and Treflan TRIO (2+2 lb a.i./A per year) treatments were made each summer (September 8 and June 22). Purple nutsedge suppression on May 27, 1998 increased linearly as the rate of Zorial 5G applied increased from 1.5 to 3 lb a.i./A. The degree of nutsedge suppression resulting from the initial spring Zorial 5G applications increased with time, reached a maximum on August 4, 1998 (52 to 72 %), and declined later in the fall. Split spring and summer applications of Zorial 5G at annual rates of 2 or 3 lb a.i./A provided good (80-88 %) purple nutsedge suppression in the fall of the first year of this study although the single spring applications of 2 or 3 lb a.i./A provided greater suppression in the spring and early summer. Similar to 1998, there was a slow increase in Zorial 5G efficacy on purple nutsedge during the spring of 1999 with the single spring 1.5 to 3 lb a.i./A Zorial 5G applications resulting in very good control (89-96 %) on June 22, 1999. The annual application rate of 1 lb a.i./A Zorial 5G resulted in only fair purple nutsedge control (at best 75 %) and was significantly worse than the other Zorial treatments. During June, July and August of 1999, there were no significant differences between treatments that received 1.5, 2, 2.5 or 3 lb a.i./A Zorial in a single spring application. In addition, there were no significant differences in purple nutsedge control between treatments that received greater than 1.5 lb a.i./A in a single spring application versus treatments that received split applications of Zorial 5G. Thus, the split 2 lb a.i./A Zorial SG treatment and the two split 3 lb a.i./A treatments were not significantly better than the single spring applications of 2 and 3 lb a.i./A, respectively, during the second year of this study. To date, single applications of Visor 2.5G at 0.25 and 0.5 lb a.i./A and the split Treflan TRIO treatment (2+2 lb a.i./A per year) have provided poor purple nutsedge suppression in 1998 (0-25 %) and 1999 (0-5 %).

Twenty four alfalfa varieties with fall dormancy ratings of 8 or 9 were tested in a replicated small plot trial on a heavy clay loam soil on the Safford Agricultural Center. This was the third year of a new study. CUF JUL only had the heaviest yield in two out of the seven cuttings, but had the highest overall yield for the year at 10.3 tons per acre. Cuf 101 also had the highest average yield over the three years of the study. Heat units with thresholds of 77° F and 40° F are included for each cutting in the study.

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