Subsurface drip irrigated broccoli received experimental combinations of N rate (176 and 268 lb N/ac, and fertigation frequency (daily, weekly, bi-weekly, monthly) at the Maricopa Agricultural Center during winter 1998-99. Marketable broccoli yields were increased slightly with N applications of 268 lb/acre compared to 176 lb/acre. However, neither marketable yield, head diameter, nor petiole nitrate concentrations were significantly affected by fertigation frequency. Nitrogen fertigation frequency does not seem to be a critical management variable for subsurface drip irrigated broccoli grown on medium-textured soils in Arizona.

A field study was designed to determine the effects of cultivar and planting date on growth and yield of strawberries (Fragaria x annanasa D.) in the low desert. The study was conducted at the University of Arizona, Citrus Agricultural Center near Waddell, AZ. Treatments included two strawberry cultivars 'Camarosa' and 'Chandler' and three planting dates of 29 Aug., 7 Oct. and 24 Oct. 1997. There were no significant differences in fruit weight between cultivars . However, fruit number was significantly greater for 'Chandler' strawberries compared to 'Camarosa' and, therefore, fruit size was significantly smaller for 'Chandler' compared to 'Camarosa' berries. Fruit weight and number were significantly greater for both cultivars planted 29 Aug. with nearly 4 times greater production compared to the 7 Oct. and 24 Oct. plantings. Initial results of this study suggest summer planting (late Aug.) of strawberries in the low desert is necessary to produce economically viable yields.

Commercial fresh vegetable production is one of the most rewarding and risky farming activities. The price and yield variations throughout the production year, the special characteristics of fresh vegetable produce (i.e. perishability), and the changing consumer demands are some of the factors contributing to the increased uncertainty faced by vegetable producers. This dissertation combined mathematical programming and econometric techniques to: 1) investigate the optimal production and marketing practices under different price distribution information scenarios, risk aversion levels and marketing outlets and 2) examine growers’ preferences as well the effect of risk aversion levels and growers’ risk perception on the choice of marketing contracts. Specifically, the following three modeling approaches were adopted in order to achieve the dissertation objectives: 1) quadratic programming under a mean-variance framework, 2) discrete choice experiments and 3) a combination of quadratic and integer programming embodied in a meanvariance framework. The findings indicate that optimal production practices and the resulting net returns are substantially influenced not only by the choice of marketing channel but also by growers’ risk aversion levels as well as price knowledge. Furthermore, regarding the choice of marketing contracts, the results highlight the existence of heterogeneity in preferences and illustrate the importance of certification cost, in line with the previous literature. Lastly, the findings indicate that risk aversion and risk preferences do not play a significant role in the choice of contractual agreements by farmers.

Durum growers were surveyed in cooperation with the USDA’s National Agricultural Statistics Service to determine production practices and their effects on yield and protein in the 2006 growing season. The survey was conducted in three regions: West (Yuma and La Paz counties), Central (Maricopa, Pinal, and Pima counties), and East (Cochise and Graham counties). Most of the durum in Arizona is grown in these three regions. We obtained responses from 83 out of an estimated 166 durum growers (50%) representing 46,331 out of 79,000 acres (59%). Durum was grown following cotton (41%), vegetables (27%), lettuce (16%), or other crops. The major varieties were Orita (30%), Kronos (25%), Ocotillo (16%), and Sky (11%). Herbicide was applied on 64% of the acreage. Flood irrigation systems accounted for 69% of the acreage, followed by furrow (17%). The crop was irrigated 6-7 times on average. The predominant soil texture was a sandy clay loam (36%), followed by sandy loam (35%) and clay loam (12%). The average planting date (germination irrigation applied) was December 21 in the Central region, January 4 in the West region and February 7 in the East region. The seed was planted at an average rate of 165 lbs/acre. Phosphorus was applied to only a third of the acreage, but when it was applied, the rate averaged 71 lbs P2O5/acre. Nitrogen rate averaged 224 lbs N/acre. Increased yield was associated with amendment application in the West region; certain varieties, amendment application, seeding rate between 120 and 159 lbs/acre, and nitrogen rate over 200 lbs N/acre in the Central region; and a seeding rate between 140 and 159 lbs/acre in the East region. Increased grain protein was associated with a previous crop of lettuce, lack of phosphorus application, and irrigation number in the West region; and a seeding rate of 140 to 159 lbs/acre and lack of phosphorus application in the East region. This survey documents associations, not cause-and-effect relationships, among durum production practices, yield, and protein.

Durum growers were surveyed in cooperation with the USDA’s National Agricultural Statistics Service to determine production practices and their effects on yield and protein in the 2006 growing season. The survey was conducted in two regions: West (Yuma and La Paz counties) and Central (Maricopa, Pinal, and Pima counties). These two regions represent about 95% of the durum acreage. We obtained responses from 85 out of an estimated 170 durum growers (50%) representing 40,580 out of 70,000 acres (58%). Durum was grown following vegetables (42%), cotton (41%), lettuce (12%), or other crops. The predominant soil texture was a sandy clay loam (47%), followed by sandy loam (30%) and clay loam (16%). Herbicide was applied on 52% of the acreage. The major varieties were Kronos (26%), Ocotillo (20%), Alamo (16%), and Orita (16%). Flood irrigation systems accounted for 87% of the acreage, followed by furrow (11%). The crop was typically irrigated 6 times. The average planting date (irrigation applied) was December 27 in the Central region and January 4 in the West region. The seed was planted at an average rate of 160 lbs/acre. Phosphorus was applied to only a quarter of the acreage, but when it was applied, the rate averaged 65 lbs P2O5/acre. Nitrogen rate averaged 224 lbs N/acre. Increased yield was associated with previous crops other than cotton in the West region, certain varieties, lack of herbicide application, planting in January in the West region and November or December in the Central region, a seeding rate between 100 and 160 lbs N per acre, and an N rate between 200 and 300 lbs N per acre. Increased grain protein was associated with a previous crop of vegetables or lettuce in the West region, lack of herbicide application in the Central region, manure application, clay loam or sandy clay loam soil, December planting in the West region, lack of phosphorus application, and fewer irrigations. This survey documents associations, not cause-and-effect relationships, among durum production practices, yield, and protein.

Durum growers were surveyed in cooperation with the USDA’s National Agricultural Statistics Service to determine production practices and their effects on yield and protein in the 2004 growing season. The survey was conducted in two regions: West (Yuma and La Paz counties) and Central (Maricopa, Pinal, and Pima counties). These two regions represent about 96% of the durum acreage. We obtained responses from 91 out of an estimated 195 durum growers (47%) representing about 38,000 out of 95,500 acres (40%). Durum was grown following cotton (48%), vegetables (43%), or other crops. The predominant soil texture was a sandy loam (36%), followed by clay loam (26%) and sandy clay loam (26%). Herbicide was applied on 67% of the acreage. The major varieties were Kronos (20%), WestBred 881 (18%), Kofa (14%), and Duraking (11%). Border flood irrigation accounted for 77% of the acreage, followed by furrow (11%), and level basin (10%). The crop was typically irrigated 6 to 7 times. The average planting date (irrigation applied) was December 19 in the Central region and January 7 in the West region. The seed was planted at an average rate of 163 lbs/acre. Phosphorus was applied to only a third of the acreage, but when it was applied, the rate averaged 67 lbs P2O5/acre. Nitrogen rate averaged 210 lbs N/acre. Grain yield tended to be higher following crops other than cotton grown on clay loam to sandy clay loam soils. Increased yield was associated with early planting, certain varieties, high N rate, and irrigation frequency. Higher protein content was associated with previous crops other than cotton, border irrigation, early planting, and N rate. This survey documents associations, not cause-and-effect relationships, among durum production practices, yield, and protein.

Durum growers were surveyed in cooperation with the USDA’s National Agricultural Statistics Service to determine production practices and their effects on yield and protein in the 2005 growing season. The survey was conducted in two regions: West (Yuma and La Paz counties) and Central (Maricopa, Pinal, and Pima counties). These two regions represent about 95% of the durum acreage. We obtained responses from 97 out of an estimated 195 durum growers (50%) representing 42,920 out of 75,400 acres (57%). Durum was grown following cotton (38%), lettuce (24%), vegetables (21%), or other crops. The predominant soil texture was a sandy loam (42%), followed by sandy clay loam (31%) and clay loam (21%). Herbicide was applied on 57% of the acreage. The major varieties were Kronos (21%), Alamo (16%), and Orita (16%). Level basin irrigation accounted for 52% of the acreage, followed by border flood (36%), and furrow (12%). The crop was typically irrigated 6 to 7 times. The average planting date (irrigation applied) was December 28 in the Central region and January 14 in the West region. The seed was planted at an average rate of 167 lbs/acre. Phosphorus was applied to only a third of the acreage, but when it was applied, the rate averaged 71 lbs P2O5/acre. Nitrogen rate averaged 213 lbs N/acre. Increased yield was associated with previous crops other than cotton, certain varieties, level basin irrigation, early planting in the Central region, a seeding rate between 140 and 160 lbs N per acre, N rate between 100 and 200 lbs N per acre, and an irrigation number of less than six in the West and seven in the Central Region. Grain protein was associated with varieties. This survey documents associations, not cause-and-effect relationships, among durum production practices, yield, and protein.

Small grain varieties are evaluated each year by University of Arizona personnel at one or more locations. The purpose of these tests is to characterize varieties in terms in terms of yield and other attributes. Variety performance varies greatly from year to year and several site years are necessary to adequate characterize the yield potential of a variety. The results contained in this report will be combined with results from previous years in a summary available from Arizona Cooperative Extension.

Sixteen varieties of barley were tested at the Safford Agricultural Center in 1997. Nebula, a new variety from Western Plant Breeders, was the highest yielding variety in the trial with a yield over 5100 pounds per acre. Nebula also had the highest bushel weight of the varieties tested.

The highest wheat yields in the world are obtained using a growing system called intensive cereal management (ICM). High yielding varieties are planted at high seeding rates, treated with foliar fungicides, plant growth regulators are applied to control lodging, and high nitrogen fertilizer rates are used to obtain high yields. The ICM system adapted to Arizona does not include fungicide treatments due to our lack of leaf diseases. We tested the effect of ICM on yield, grain protein, and other characteristics at three commercial farms in Arizona. ICM resulted in higher protein in one case due to increased nitrogen application and reduced height in another case due to the plant growth regulator. However, in most cases, we were not able to detect an affect of ICM on the crop, and the increased input cost was not paid for by increased crop performance. Intensive cereal management does not appear to hold much promise under our conditions except perhaps in cases where lodging is predictable or yields do not reach their potential.