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An understanding of the expected variability in irrigated crops under field size, surface irrigation conditions is needed to improve irrigation designs and water management scheduling procedures. The objective of this work is to describe water application uniformity under an efficient level -basin irrigation system and the variability of water use (soil water depletion) for three levels of irrigation and two basin lengths for a wheat crop. High water distribution uniformities with a level -basin irrigation system did not necessarily result in maximum irrigation application efficiencies where variations in soil -water factors were greater on a drier irrigation treatment than medium or wet treatment. Variations in soil water depletion were found for all irrigation treatments with the largest variation (13 %) occurring for the drier treatment. Spatial dependence was exhibited for soil water depletion but not necessarily for seasonal irrigation water applications.

One-irrigation barleys have been selected for performance with a pre-plant irrigation to fill the soil to field capacity to a depth of 5 feet. The barley is then grown with no additional irrigation, which simulates conditions of the North African coast. In this study, two of these barley selections were planted at four planting rates at three dates in Marana to determine optimum seeding rates. A seeding rate of 20 lbs /A resulted in greater yields than 40, 60, or 80 lbs /A when the data were combined for all planting dates.

Additional data to calibrate and refine current guidelines for interpreting soil test values is an ongoing need in Arizona. This includes information for soils testing above and below the level that may currently be considered adequate for optimum plant growth. An experiment was conducted at the Maricopa Agricultural Center during the 1985-86 crop year to evaluate the response of durum wheat to the application of phosphorus (P), potassium (K), magnesium (Mg), or zinc (Zn) on a soil testing adequate or higher for all of these nutrients. Grain yields from plots receiving every combination of three of the four nutrients were compared to yields obtained when all four nutrients were applied. No significant change in grain yield was measured as a result of witholding any one of the nutrients. Current guidelines used to interpret soil test results for wheat production correctly predicted the nutrient status of this soil with respect to P, K, Mg, and Zn.

A four-year experiment was conducted at the Mesa Agricultural Center to study the use of dried sewage sludge from the City of Phoenix as a source of plant nutrients in the commercial production of barley grain. The objective was to compare the effects of sewage sludge and commercial fertilizer on barley growth, grain yield, and quality. Three fertilizer treatments were used: (1) suggested rates of nitrogen (N), phosphorus (P), and potassium (K) in Arizona, (2) dried sewage sludge to supply plant-available N in amounts equal to the suggested rate, and (3) N, P, and K from inorganic fertilizers in amounts equal to those in sewage sludge. Characteristics of barley growth, grain yield, and quality were similar for the three fertilizer treatments. Barley can utilize the fertilizer nutrients in dried sewage sludge in the production of grain as effectively as it can utilize the fertilizer nutrients in inorganic fertilizer.

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Several improved irrigation scheduling methods are available to farmers to reduce the amount of water used while not reducing crop yield. Each scheduling method has its own advantages and disadvantages. Because of the disadvantages, farmers have been slow in adopting some of the newer irrigation scheduling methods. This study compares two improved scheduling methods, the neutron hydro probe and a simplified bookkeeping method using a personal computer, with the irrigation practices normally used by a farm manager to grow wheat. In addition to the traditional parameters of applied water and yield, the time and difficulty associated with each method were evaluated.

The relative ability of barley cultivars to perform outside the environment for which they were selected is not fully known. This study was initiated at Marana in 1985-86 to compare barley cultivars, which were adapted to different input levels, under a line-source sprinkler system that delivered a gradient of water. Higher than average rainfall in February and March provided ample moisture for crop growth, prevented very low water levels and led to the water gradient being applied late in the season when most of the cultivars were in the grain fill stage. We determined that cultivars bred for high level management (Gustoe and Barcott) performed best at the high water levels. Suitable cultivars for minimal water could not be determined since truly low water levels were never attained. Harvest index, the proportion of grain to total plant yield, was greatest for Gustoe at the high water level, but no differences were detected at the low water level. We suspect that one-irrigation barleys, bred to produce grain with a single preplant irrigation, effectively recover water with a deep root system and do not necessarily use less water than other barley cultivars.