The drought-related pressures on the Colorado River system that have been impacting the entire basin and region for 23 years have slackened briefly due to the wet winter in 2023 that included a good snowpack in the mountains, better rainfall throughout the basin, and improved flows into the river. The current water level at Lake Mead on Hoover Dam is 1,068.25 ft. above sea level on 3 January 2024. That level is 160.75 ft below full pool of 1,229.00 ft. (Figure 1).
In mid-December 2023 representatives from each of the seven Colorado River Basin states met in Las Vegas, NV during the annual Colorado River Water Users Association conference. The focus of current discussions among the basin states is to negotiate a new compromise for the guidelines of use under conditions of water shortage. These new guidelines will go into place at the end of 2026. The immediate goal is to draft proposals by March 2024.
The negotiations are incentivized by having the opportunity for the post-2026 guidelines being developed by the basin states themselves as opposed to litigation or legislation. A major concern driving this process among the basin states that basin state representatives should be able to do this better than turning the process over to people and entities that have less direct familiarity with the situation and no real “skin” in the game.
The 1963 decision by the Supreme Court of the United States in of the Arizona v California case directed the federal authority on the management of the Colorado River to the Department of the Interior and the Bureau of Reclamation (BoR). However, the basin states have the chance to negotiate their future management plans on the Colorado River. If they fail to do so in the allotted time, the process will be managed by the federal government.
The basic water budget challenge is based on the following basic statistics:
Some notable progress is being made for conservation of Colorado River water with agreements among lower basin states and tribes that will conserve more than 1.5maf/year through 2026. For example, California water agencies have recently agreed to conserve up to 643,000 acre-feet/year through 2025. The Quechan Indian Tribe has reached an agreement with federal water managers to save up to 39,000 acre-feet/year through 2025. Arizona has agreed to conserve up to 348.00 acre-feet/year through 2026. All these temporary agreements are being supported with federal funding.
With agriculture responsible for 70% of the diversions on the Colorado River, these negotiations are extremely important for the future of agriculture in this region and our capacity to support high population densities that are now common and rapidly growing.
These types of negotiations are certainly challenging in dealing with a limited water supply and a lot of demand. There are many competing interests involved. Yet, we are confident that the representatives we have will be able to work this out and come to a set of functional agreements.
This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Spinach ‘Meerkat’ was seeded, then sprinkler-irrigated to germinate seed Jan 13, 2025 on beds with 84 in. between bed centers and containing 30 lines of seed per bed. All irrigation water was supplied by sprinkler irrigation. Treatments were replicated four times in a randomized complete block design. Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed. Treatments were applied with a CO2 backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles.
Downy mildew (caused by Peronospora farinosa f. sp. spinaciae)was first observed in plots on Mar 5 and final reading was taken on March 6 and March 7, 2025. Spray date for each treatments are listed in excel file with the results.
Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft2areas within each of the four replicate plots per treatment. The number of spinach leaves in a 1-ft2area of bed was approximately 144. The percentage were then changed to 1-10scale, with 1 being 10% infection and 10 being 100% infection.
The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that provided most effective control against the disease include Orondis ultra, Zampro, Stargus, Cevya, Eject .Please see table for other treatments with significant disease suppression/control. No phytotoxicity was observed in any of the treatments in this trial.
Due a lack of effective post-emergence herbicides, most vegetable crops are hand weeded following cultivation to remove in-row weeds. This operation is costly and finding labor to perform the task has become increasingly difficult. Precision micro-sprayers for delivering herbicides have been developed, but lack sufficient speed, accuracy and off-target spray control to be commercially viable. To address this, a high speed, centimeter scale resolution sprayer that can spot apply herbicides to weeds with minimal off-target spray while traveling speeds that are viable for commercial farming operations was developed. The objective of this research was to evaluate the performance of the device in terms of spray delivery accuracy, off-target spray quantity, weed control efficacy and crop safety. The spray assembly comprised 12 custom-built spray modules spaced 1 cm apart. The device was tested with lettuce in the laboratory at a travel speed on 2.0 mph while targeting three weed species at three stages of growth. Results showed that targeting accuracy of spray delivered was ± 2 mm and that the percentage of off-target spray was less than 3%. Weed control efficacy exceeded 95% and there was no observable crop injury. Improvements to the original design were identified and the enhanced sprayer was found to provide sub-centimeter precision. Practical applications of the technologies developed include precision spot spraying of weeds in lettuce, carrot, onion, spring mix and other vegetable crops. A remaining technical challenge for the realization of an automated precision weeding machine is the development of a camera imaging system capable of reliable crop/weed differentiation. Field testing of the precision spot sprayers is also needed.
Click the following link to watch presentation on Centimeter Scale Resolution Spot Sprayer.
https://www.youtube.com/watch?v=XBNGsIu27K0
Devrinol (napropamide), herbicide has been used in cole crop production at preemergence for control of many annual grasses and some broadleaf weeds. With the revision of Dacthal (DCPA) some of our PCAs are turning their attention to this tool for weed control. Like many other preemergence herbicides, it works by inhibiting root growth after weed seeds have germinated. It has sometimes injured lettuce when too much was concentrated near the lettuce seed.
Napropamide is a selective systemic herbicide that according to the label limits the growth of grasses in our area such as Barnyard grass, Junglerice, Wild barley, Annual bluegrass, Canarygrass, Foxtail, Goosegrass, Johnsongrass, Wildoats, Sandbur and Sprangletop.
Broadleaves that we have included in the label are: Lambaquarter, Prickly lettuce, Little Mallow, Redroot pigweed, Common and Horse purslane and Sowthistle.
The PCA study guide for Arizona states that minimum re-cropping intervals of 12 months for cotton, melons and alfalfa, 6 months wheat, 2 for lettuce and 0 for cole crops. We have seen in our trials that head lettuce showed sensitivity to Devrinol when planting too soon.
The following chart from a broccoli trial conducted in 2015 (Tickes/Peña) show the efficacy of napropamide for control of London Rocket and Lambsquarter.
