Summer weeds including established bermudagrass and nutsedge are of economic concern to alfalfa growers in western Arizona. Two replicated evaluations of norflurazon herbicide applications for summer weed control were conducted on established alfalfa fields in La Paz County. Zorial Rapid 80 WP and Evital 5G herbicides were tested for their effectiveness of bermudagrass and nutsedge control when applied following hay harvest but prior to irrigation in early spring. Zorial 80 WP was applied at 2.0 lb a. i. /acre. Evital 5G was applied at single application rates of 1.5, 2.0, and 3.0 lb a. i. /acre in spring and two split applications in spring and summer for a total of 2.0, 3.0, and 4.0 lb a. i. /acre. Norflurazon applications resulted in bleaching and shoot tip death of established bermudagrass 49 days after a single application (DAT), however by 78 DAT bermudagrass regrowth reinfested all plots resulting in zero control. Purple nutsedge control resulting from a single application of Evital 5G at 2.0 lb a.i./acre was 41, 82, and 35% at 35, 63, and 99 DAT, respectively. However, Zorial 80 WP applied at 2.0 lb a. i. /acre provided only 5, 23, and 0% purple nutsedge control at 35, 63, and 99 DAT, respectively. The limited effectiveness of the Zorial 80 WP spray solution for nutsedge control resulted from poor soil incorporation since the liquid was unable to penetrate the dense nutsedge foliage. The Evital 5G norflurazon formulation provided promising purple nutsedge control following one application to established alfalfa since the weight of the granules allowed the herbicide to reach the soil surface where irrigation could move the herbicide down through the soil profile to nutsedge roots. At 99 DAT a second split Evital treatment was applied to control nutsedge regrowth, and hopefully provide season long control. Nutsedge control results following this second split application are pending.

Plant growth regulators were aerially applied on April 26, 1996, to two alfalfa fields, one (Cibola) in its first year of production and the other field (CUF 101) in its third year. The first year field was approximately 50% through the cutting cycle and the third year field was approximately 30% through the cutting cycle when applications were made. No statistical differences were noted in hay tonnage the first cutting after application. Yield increases due to treatments were noted in the second cutting and maximum increases ranged from 277 -461 lbs of hay per acre. No yield or quality differences were noted the third cutting after application. The two fields differed in their response. The lowest rates of plant growth regulators produced higher yields in the first year field, but these treatment rates had greatly lowered hay quality the previous cutting. These effects were not noticed in the third year stand field. Increased hay tonnage was noted in the third year field from the 16 oz/acre rates, but was not evident in the first year field. Hay quality was usually highest in the check the first two cuttings after treatment. It is unknown if the differences noted between the two fields are due to different age of plants, variety and/or stage of growth when treatments were applied.

Some growers feel that nitrogen (N) fixing nodules found on the roots of the alfalfa plant are ineffective in cold soil during the winter and early spring. Thus, starter N fertilizer is commonly applied in late winter to established alfalfa to enhance growth until spring when the soil warms up and alfalfa begins actively fixing atmospheric N₂. Established alfalfa normally does not benefit from applications of N fertilizer since it is a leguminous crop that is capable of fixing its own N from atmospheric N₂. Afield experiment was conducted to determine the effect of N fertilizer applied in winter on alfalfa hay yield at the first cutting in spring. Two treatments consisted of an unfertilized check plot and UAN 32 water run at a rate of 35 lbs. N/acre to three year old 'CVF 101' alfalfa grown on a silt loam soil testing deficient in nitrate-N. Maximum alfalfa hay yield (J ton/acre) was obtained at the first spring cutting without N fertilizer application. However, since the field has a known yield potential of 1.5 ton/acre, factors other than fertility influenced the alfalfa hay yields observed in this study.