Barley lines have been developed for one-irrigation conditions. The purpose of these studies is to provide information required to develop recommendations for nitrogen fertilizer practices for one - irrigation barley. A total of nine field studies were conducted at the Marana and Maricopa Agricultural Centers testing six nitrogen rates ranging from 0 to 200 lbs N/A under a variety of conditions. The optimum nitrogen fertilizer rate ranged from 0 to 40 lbs N /A. No relationship was established between optimum nitrogen fertilizer rate and preplant soil nitrate, previous crop, planting date, or number of irrigations (1 vs. 2). Based on the results of this and other studies, a nitrogen rate of 40 to 50 lbs N/A is usually adequate for one-irrigation barley, and nitrogen rates greater than 80 to 100 lbs N/A is considered excessive.

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.