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).

The standard procedure for determining nitrogen (N) status in small grains is to sample lower stem tissue for nitrate (NO₃) analysis. The tissues are then submitted to a laboratory for analysis. Sap nitrate (NO₃) can be analyzed in the field, immediately after collecting the sample, using a Cardy meter. Guidelines for sap analysis have not yet been determined. The objectives of this study were to: (i) correlate NO₃-N in dried stem tissue with sap NO₃-N , and (ii) develop sap NO₃ test guidelines for N management in durum and feed barley. In November 1998 one variety of durum (Kronos) and one variety of feed barley (Gustoe) were planted at the Maricopa Agricultural Center. Three N rates (80, 200, and 400 lbs N/acre) were applied in four split applications. Each treatment was replicated five times in a randomized complete block design. Samples were collected from lower stems at the 3-4 leaf 2 node, flag leaf visible, and heading growth stages. Grain yields ranged from 4330 lbs/A to 6794 lbs/A for Kronos and 3220 lbs/A to 4533 lbs/A for Gustoe. Correlation coefficients between stem NO₃-N and sap NO₃-N were 0.76 for Kronos and 0.60 for Gustoe. Sap NO₃-N analysis can be used to determine N status during the season for Kronos. Results for the barley suggest at low concentrations of NO₃ in the lower stem, the Cardy meter may underestimate NO₃ concentrations. This may be due to changes in moisture content in the stem as the season progresses.

Small grain varieties are evaluated each year by industry and University of Arizona personnel. The purpose of these tests is to characterize varieties in terms of yield and other attributes. Variety performance varies greatly from year to year and several site-years are necessary to adequately characterize the yield potential of a variety. The results contained in this report will be combined with results from previous years in a summary available from Arizona Cooperative Extension.

Research has not been conducted in Arizona to determine when to irrigate wheat based on soil water depletion levels. The purpose of this work is to establish the optimum irrigation timing based on depletion of plant available water in the soil. A field experiment was conducted at the Maricopa Agricultural Center testing irrigation of wheat at 35, 50, 65, and 80% depletion of plant available water in the soil for two durum varieties, Kronos and Westbred 881. Grain yields averaged over the two varieties were 6479, 5099, 4283, and 4145 lbs/acre for the 35, 50, 65, and 80% depletion levels, respectively. The results of this study indicate that more frequent irrigations may be required than is typically practiced to optimize wheat grain yields in Arizona. This work will be repeated during the 1999-2000 growing season and the results from both years will be evaluated before general conclusions are drawn.

Malting barley is not a widely planted crop in the Southwest, due to grain protein contents that can sometimes exceed the industry standard of 11.4 %. To achieve < 11.4% grain protein, careful nitrogen (N) management is needed. Tissue testing guidelines for N management for reduced grain protein and acceptable yields have not yet been determined for malting barley in the Southwest. The objectives of this study were to: (i) correlate NO₃-N in dried stem tissue with sap NO₃-N, and (ii) develop stem NO₃-N guidelines for N management in malting barley. In November 1998 two varieties of malting barley, Morex and Crystal, were planted at the Maricopa Agricultural Center. Five N rates (0, 60, 120, 180, and 240 lbs/acre) were applied in four split applications. Each treatment was replicated three times in a randomized complete block design. Samples were collected from lower stems at the 3-4 leaf 2 node, and flag leaf visible growth stages. Grain yields ranged from 1011 lbs/A to 2677 lbs/A for Morex and 827 lbs/A to 2641 lbs/A for Crystal. Grain protein ranged from 6.94 -11.5% (Morex) and 8.48-13.0% (Crystal). Correlation coefficients between stem NO₃-N and sap NO₃-N were 0.83 for Morex and 0.85 for Crystal. For Morex and Crystal, grain protein was within the malting industry grain protein range of 10.5-11.4% and yield was optimized at 180 lbs N/A. Sap NO₃ analysis can be a useful tool for determining N status of malting barley.

Alfalfa producers in the Colorado River region of La Paz County have experienced some shifting trends in markets and production over the last 15 years. Acreage has increased steadily from a low of 25,000 acres in the early 1980's to a high of nearly 50,000 acres in 1999. Average annual alfalfa hay yields in La Paz County have maintained a fairly flat trend ranging from 7.5 to 8.5 tons per acre during this time. Low annual hay yields often resulted from extended cutting schedules and minimal inputs in years of below average hay prices. Alfalfa hay prices were severely depressed during the summer of 1986, from summer of 1991 through winter of 1992, during the summer of 1995, and from winter through summer of 1999. In contrast, La Paz County alfalfa hay producers experienced the strongest markets during the winters of 1989, 1990, 1994, 1997, and 1998. Annual hay tonnage per acre was also high during these years and acreage increases were observed the following spring planting.

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 %).

Three studies were performed in two different geographical areas in Graham County in 1998. A Bt hybrid comparison and a non-Bt hybrid comparison were grown in the Bonita area and a mixed (Bt and non-Bt) study was grown in the Eden area. Results of these three field studies are reported in this paper. Pioneer 33A14 was the leading cultivar in the Bonita Bt study with a yield of 13426 pounds per acre. Pioneer 32J55 had the highest yield in the non-Bt study in Bonita with a yield of 14630 pounds per acre. Novartis N7639 produced the highest yield in the Eden study but with a yield considerably lower than those seen in the Bonita area.

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.

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.