This study was initiated in 2003 in response to a push by one of the grain buying companies to produce more durum wheat for export from Arizona. The export market required a minimum of 13% protein and other quality constraints. A nitrogen timing regime was established by the University to provide the crop with this nutrient according to its physiological development. This study had four nitrogen application treatments addressing different ways to provide the crop with its nitrogen needs. This second year of the study showed statistically different yields from the treatments applied and different inferences from the first year of the study. An economic analysis is included to show the profitability of nitrogen applications for this year and an economic summary for the last four years of nitrogen studies on durum wheat.

This study is a follow-up on a study initiated three years ago with an emphasis on the timing of application of nitrogen (N) fertilizer. The times targeted in this study were: at planting, at initiation of growth and at boot stage. A nitrogen starter fertilizer at planting increased yields over 100 pounds of grain per acre for both wheat and barley compared with plots which did not receive the added nitrogen at planting. No difference was seen between applying 46 or 92 pounds of N per acre as a starter fertilizer. Amount of N added at boot stage seemed to increase barley yields slightly but had no effect on wheat yield nor protein content. An economic analysis is included to show the profitability of nitrogen applications.

This two year study is a follow-up to a study started in 1999, looking at phosphorus applications at planting on wheat and barley. Treatments applied were 0, 100, 200 and 400 pounds of 16-20-0 planted through the grain drill with the seed. Phosphorus applied at planting improved yields in most replicates, but because of the cost of the fertilizer, the higher yields were not always the most economically profitable.

This study was initiated in response to a push by one of the grain buying companies to produce more durum wheat for export from Arizona. The export market required a minimum of 13% protein and other quality constraints. A nitrogen timing regime was established by the University to provide the crop with this nutrient according to its physiological development. This study had four nitrogen application treatments addressing different ways to provide the crop with its nitrogen needs. No significant differences were seen in yields but slight differences in percent protein were observed. An economic analysis is included to show the profitability of nitrogen applications.

The 2003 study was a follow up of the 2001 and 2002 studies, but the major differences were the selection of a high quality durum wheat with values significantly higher that those seen in the previous two studies and the untreated check was eliminated and a higher level of phosphorous was applied. Treatments applied were 100, 200, 400 and 600 pounds of 16-20-0 planted with the seed through the grain drill. Phosphorus applied at planting improved yields with increasing application rates. In this study, the highest rate of application of phosphorus produced the highest profit.

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.