During 1990 the emphasis on surveying was placed in the southeastern corner of the state, where damage was found to be most severe in previous years. Estimates of the incidence of and damage caused by the Russian Wheat Aphid (RWA) were made for the entire state. These estimates indicate that small grain producers in the state lost $212,000 due to this pest in 1990.

Yield trials were conducted at the Maricopa Agricultural Center during the 1990 -91 growing season. Barley, Durum and Wheat varieties as well as experimental lines from various seed companies were tested for yield performance. Gustoe and Sunbar 409 barleys, Turbo and Aldura durum wheats; and 911 and Klasic bread wheats were the highest yielding commercial varieties in this yield trial.

Planting date can have a tremendous effect on small grain yield. The purpose of this study is to document the interactions of planting date with current small grain varieties. Field studies were conducted at the Maricopa Agricultural Center over the 198$ 1989, and 1990 growing seasons. Six barley, durum and wheat varieties were compared at four planting dates from November to February. WestBred Gustoe was among the highest yielding barleys and WestBred Turbo was among the highest yielding durum regardless of planting date. The highest yielding wheat was WestBred 911 at the November plantings, Klasic at the December and January plantings, and Topaz and Klasic at the February plantings. The varieties also responded differentially to planting date in terms of plant height, kernel weight, heading and maturity date, but not test weight. This study demonstrates the importance of planting date in choosing a small grain variety.

A 12-inch row spacing is commonly used to evaluate small grain varieties at the Maricopa Agricultural Center and other experiment stations. The objective of this study was to document the interactions of varieties and row spacings. Sir barley, durum, and wheat varieties were planted in the 1989 and 1990 growing seasons at the Maricopa Agricultural Center at four planting dates (November, December, January, February) and 6 and 12-inch row spacings. At the December planting date, which is near optimum, WestBred 881 and Topaz performed best at a 6-inch row spacing while Gustoe, Aldura, Klasic, and WestBred 911 performed best at a 12-inch row spacing. Caution must be exercised when interpreting variety trials planted in 12-inch rows anti, in addition, conducted under growing conditions different from commercial practice.

This experiment was conducted to quantify herbicide carry -over effects on wheat, after plowing the cotton down with conventional and reduced tillage systems. Cotton layby applications of cyanizine, diuron, and prometryne at 1.5 lbs/Ac active ingredient did not result in wheat yields that were significantly different from the untreated checks within any of the tillage systems.

AZSCHED irrigation software was used to schedule irrigation on Aldura wheat on the Safford Agricultural Center with very good results. Irrigations were scheduled at 40%, 50% and 60% calculated soil water depletion throughout the critical part of the growing season. The plots being irrigated at 40% depletion yielded the most and had the highest water use efficiency and showed the least plant stress. Comparing data with previous experiments, it was noted that increased inputs of higher seeding rate and higher nitrogen rate also increased the water use efficiency.

A field experiment was conducted on a Trix clay loam at the Maricopa Agricultural Center to 1) determine the optimum rates of late season N needed to achieve optimum yield and quality of irrigated durum wheat in conjunction with varying rates of early season N, and 2) to evaluate the usefulness of stem NO₃⁻N analysis in predicting the late season N rates which optimize grain production but minimize the potential for nitrate pollution of groundwater. The application of 75, 150 and 300 lbs. N/a during vegetative growth resulted in wheat with highly deficient, slightly deficient and excessive N status at the boot stage as indicated by stem NO₃⁻N analysis. The application of 60 lbs. N/a at heading to highly N-deficient and slightly N-deficient wheat resulted in grain protein levels of 12.7 and 14.3 % respectively but had little effect on grain yield. Applications from 0 to 60 lbs. N /acre at heading to wheat which had previously received excessive N did not affect grain yield but did increase grain protein levels from 15.2 to 17.4 %. The use of stem NO₃⁻N analysis appears to be a useful tool in predicting the minimum N rate to be applied during the early reproductive period to insure acceptable levels of grain protein at harvest in cases where N status during the vegetative period was not highly deficient.

Groundwater contamination by nitrate and other chemicals is a public concern and has subjected agriculture to scrutiny. Field studies were conducted at the Maricopa and Marana Agricultural Centers in 1989 to 1990 to document nitrate leaching potential with border flood irrigation. Calcium nitrate fertilizer was applied at various rates along with potassium bromide, which serves as an additional indicator of nitrate movement. Approximately 8.55 inches of irrigation water was applied at the Maricopa site on a sandy loam soil and 4.0 inches of irrigation water was applied at the Marana site on a clay loam soil. At the Maricopa site, only 64% of the nitrate could be accounted for in the top 6.7 ft. while most of the nitrate was found in the top 4 to 5 ft. at Marana. The water and nitrate moved 3 to 4 times deeper than predicted in the absence of preferential flow.

Durum grain quality is affected by many factors, but water and nitrogen are factors that the grower can control. The purpose of this research was to determine 1) the nitrogen application rate required at pollen shed to maintain adequate grain protein levels if irrigation is excessive or deficient during grain fill and 2) if nitrogen applications during grain fill can elevate grain protein. Field research was conducted at the Maricopa Agricultural Center using the durum varieties Duraking, Minos, and Turbo. The field was treated uniformly until pollen shed when nitrogen was applied at rates of 0, 30, and 60 lbs/acre. During grain fill, the plots were irrigated based on 30, 50, or 70% moisture depletion. In a separate experiment, nitrogen fertilizer was applied at a rate of 30 lbs N/acre at pollen shed only, pollen shed and the first irrigation after pollen shed, and pollen shed and the first and second irrigation after pollen shed. Irrigation had no effect on grain protein level, although increasing nitrogen rates at pollen shed from 0 to 30 and 30 to 60 lbs N/acre increased protein by 1 percentage point. Nitrogen fertilizer application at the first irrigation after pollen shed increased grain protein content from 10.4 to 11.4% and application at the first and second irrigation after pollen shed increased grain protein content further to 11.9% averaged over varieties. Irrigation management during grain fill may not play as large a role in controlling grain protein content as was originally thought except perhaps on heavy soils, and nitrogen fertilizer application during grain fill may not be too late to increase grain protein content.

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