Irrigation management practices that reduce water use with acceptable impacts on yield are important strategies to cope with diminished water supplies and generate new sources of water to transfer for other agricultural uses, and urban and environmental demands. This study was intended to assess the effects of moderate water deficits, with the goal of maintaining robust alfalfa (Medicago sativa L.) yields, while conserving on-farm water. Data collection and analysis were conducted at four commercial fields over an 18-month period in the Palo Verde Valley, California, from 2018–2020. A range of deficit irrigation strategies, applying 12.5–33% less irrigation water than farmers’ normal irrigation practices was evaluated, by eliminating one to three irrigation events during selected summer periods. The cumulative actual evapotranspiration measured using the residual of energy balance method across the experimental sites, ranged between 2,031 mm and 2.202 mm, over a 517-day period. An average of 1.7 and 1.0 Mg ha⁻¹ dry matter yield reduction was observed under 33% and 22% less applied water, respectively, when compared to the farmers’ normal irrigation practice in silty loam soils. The mean dry matter yield decline varied from 0.4 to 0.9 Mg ha⁻¹ in a clay soil and from 0.3 to 1.0 Mg ha⁻¹ in a sandy loam soil, when irrigation water supply was reduced to 12.5% and 25% of normal irrigation levels, respectively. A wide range of conserved water (83 to 314 mm) was achieved following the deficit irrigation strategies. Salinity assessment indicated that salt buildup could be managed with subsequent normal irrigation practices, following deficit irrigations. Continuous soil moisture sensing verified that soil moisture was moderately depleted under deficit irrigation regimes, suggesting that farmers might confidently refill the soil profile following normal practices. Stand density was not affected by these moderate water deficits. The proposed deficit irrigation strategies could provide a reliable amount of water and sustain the economic viability of alfalfa production. However, data from multiple seasons are required to fully understand the effectiveness as a water conservation tool and the long-term impacts on the resilience of agricultural systems.

We measured the gas exchange parameters of six onion varieties in two photoperiodic regimes. The photoperiods simulated early (long-day) and late (short-day) onion growing seasons of the high desert regions near Lancaster, California. We used six locally grown onion varieties: RedBull (RB), RedWing (RW), Hybrid Cometa (HC), Granero (YG), Hybrid Valero (HV) and Hybrid SR (HS). For both photoperiod regimes, daylength and temperature were changed weekly to represent the natural progression of field growing conditions. The results show that the onion plants grown under short-daylength (SD) and higher temperature regimes exhibited higher leaf photosynthetic rates and stomatal conductance than onion seedlings grown under the long-day (LD) regime. Onion plants also had different functional leaf traits depending on crop growth environment during the onset of bulbing. The higher photosynthetic rate of the short-day plants coincided with bulb initiation. Onion photosynthesis and stomatal conductance increased at bulb initiation, apparently to provide carbohydrates for growth and storage in the bulb.

The objective of the study was to evaluate the efficacy of various new and standard insecticides against sweetpotato whitefly (SWF) on upland cotton under desert growing conditions. Cotton was direct seeded on 13 Apr 2015 at the University of California Desert Research and Extension Center, Holtville, CA, into single row beds on 40-inch centers. Stand establishment was achieved with furrow irrigation; used thereafter. Plots were two beds wide by 50-ft long and bordered by one nontreated bed. Five replications of each treatment were arranged in an RCB design. Insecticide names, formulations, and rates of treatment for each compound are provided in the tables. The applications were made on 26 Jun and 10 Jul 2015 with a Lee Spider Spray Trac operated at 30 psi delivering 16.9 gpa. A broadcast application was delivered through 4 TJ-60 11003VS nozzles covering four beds. The adjuvant, Hasten Modified Vegetable Oil (Wilbur-Ellis Company, Fresno, CA) at 16 fl oz per acre was added to each spray mixture for all foliar spray treatments. Populations of whitefly adults, eggs, and nymphs were evaluated on 24 Jun, 2 day pretreatment (2-PT); 7 Jul, pretreatment (PT) sample taken just prior to spray applications; 29 Jun, 3-d after treatment 1 (3-DAT1); 2 Jul, 6-DAT1; 10 Jul, 14-DAT1; 13 Jul, 3-DAT2; 17 Jul, 7-DAT2; 24 Jul, 14-DAT2. Adult populations were estimated by taking leaf turn samples and recording direct counts on the undersides of leaves. Leaves selected for adult counts were fifth main stem node leaves below the plant terminus from five randomly selected plants per plot and reported as adults per leaf. Immature (eggs and nymphs) densities were estimated by extracting a single fifth main stem node leaf from five randomly selected plants per plot. Extracted leaves were bagged, labeled, and taken into the laboratory where densities of eggs and nymphs were counted on the abaxial surface of a 2 cm ² leaf disks from the lower, left-hand quadrant of each sample leaf using a binocular dissecting microscope. Immature densities were tallied from the five 2-cm ² leaf disks on each sample date and reported as eggs or nymphs per 10 cm ² . Harvest data of seed cotton per 0.001 acres were collected on 30 Sep 2015 (one row of 13.1 ft was hand-picked in each plot) and the seed cotton weights for each plot were recorded. Data sets were analyzed using two-way ANOVA and means separated by a protected LSD ( P < 0.05).