- Author: Richard Smith
- Author: Michael D Cahn
- Posted by: Gale Perez
Richard Smith is the Vegetable Crop Production and Weed Science Farm Advisor and Michael Cahn is the Irrigation and Water Resources Farm Advisor. Both are with the University of California Cooperative Extension in Monterey County.
Cultural practices for producing lettuce are changing with the development of new technologies and with the advent of new economic pressures. The shortage of labor has spurred development and adoption of technologies that make crop production less labor intensive. The most noticeable and dramatic of these technologies is the development of automated thinners and weeders. These machines are now routinely used in lettuce and other vegetable production (see: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=46608).
Equally important are technologies and practices that make irrigation less labor intensive. The use of permanent solid set sprinkler systems, where lateral pipes are positioned on an unplanted “guest bed,” as well at the use of single-use drip tape both increase the efficiency of labor for irrigation. Permanent solid-set sprinklers allow growers to cultivate and fertilize crops without needing to remove pipe from the field. Single-use drip tape can be shallowly buried and used to germinate many vegetable crops without the need to install sprinklers. After harvest the tape can be removed using specialized extraction equipment and brought to a recycling facility.
Single-use drip for germination of vegetables works well on many soil types where the water can move laterally to wet seedlines six inches or so to the side of the tape (Photo 1). This is a different mode of wetting the soil than sprinkler irrigation where water moves downward into the soil. Kerb (pronamide) is the principal lettuce herbicide and is quite water soluble. This characteristic of Kerb can result in it being moved too deep in light textured soil with heavy irrigations; this can result in poor weed control if Kerb is moved below the depth where weed seeds are germinating (e.g. the top 0.5 inch). In drip germinated lettuce, water moves upwards and laterally which facilitates keeping Kerb in the upper 0.5 inch of soil where it remains more active on germinating weeds.
In the first weed evaluation Kerb at both rates significantly reduced the number of purslane plants for each application method compared to the untreated control. There was no difference in the yield in any of the treatments in the sprinkler incorporated treatment, but there was an indication of slight yield reduction in the 5.0 pint/A rate in the drip applied Kerb treatment. These results indicate that injecting Kerb into the drip system during germination of the crop can provide good weed control in lettuce.
These studies help adapt the use of Kerb for a new irrigation technology and helps growers manage weeds better. It is especially important to have low to moderate weed pressure in fields when relying on autoweeders to conduct later weeding operations. Low weed populations help the automated technologies work more efficiently. All of this is to the good to help growers manage costs and to adjust to new realities with less labor to grow labor-intensive crops.
- Author: Denise Godbout-Avant
Whenever a drought happens in California, most of us look for ways to conserve water in our gardens and home. However, with droughts becoming the norm, rather than the exception, practicing water sustainability needs to become a way of life.
How can we conserve water in our daily lives? Our gardens are a good place to start, since about half of urban water is used for outdoor irrigation. The following are some suggestions which can have an impact on the amount of water you use in your gardens.
Practice water-wise garden irrigation by changing sprayers to drip system whenever possible, since sprayers decreases the amount of water going to your plants due to evaporation. Water according to the season, reducing or eliminating watering during the cooler, wet winter months – investing in a water timer with a rain sensor can help with this. Water early in the morning or late in the day when temperatures are cooler. Check your irrigation system regularly to check for leaks, repairing or replacing as needed.
Plant water-wise plants that need little water once established. The above link will provide you with many suggestions. Another wonderful source of plant information is the UC Davis Arboretum All-Stars: https://arboretum.ucdavis.edu/arboretum-all-stars
There are ways to reduce our water use in our homes also, including having a water-efficient washing machine, dishwasher, shower and toilet, and not letting the faucet run while shaving, brushing our teeth, or washing our hands.
These are a few of the many ways we can make being water-wise a way of life in our gardens and homes. Every drop of water counts!
To learn more about our water and ways to use it wisely, join the UCCE Stanislaus County Master Gardeners on Tuesday, June 29th at 6:00pm on Zoom for our talk “Water-wise Tips for Your Garden and Home.” You can sign up at: http://ucanr.edu/water-wise/2021
- Author: Allison Rowe and Ben Faber
How to irrigate is probably the most common question in irrigated agriculture, even with 10,000 years of cultivation knowledge to guide us. The complexities of irrigation and the unique situation for each grower makes this question so difficult. Not enough water, and plants have diminished growth or the propensity for disease and disorder 1. Too much water leads to root disease and nutrient problems 2. So, it can't be too much or too little, but just right. There are times when citrus can handle a little more water stress than other times, which can lead to water savings 3, especially in a drought year or in areas where water costs are crucial. Salinity further compounds the question of irrigation where striking a balance determines the health of your tree. Staying in tune with your orchard and using appropriate methods to measure water need, water use, environmental water demand, and soil water-holding capacity will help inform irrigation management decisions.
There are all kinds of ways of estimating tree water need 4 , a valuable piece of information for irrigation decision making. An inexpensive and often overlooked method of estimating tree water requirements is grower observation in the orchard to assess leaf color, leaf size, the look of the leaves, and canopy fullness. Pure observation and knowledge of your trees yields a lot of valuable information regarding irrigation management. Beyond observation, a direct measure of the tree with a porometer, pressure gauge (bomb), sap flow meter, dendrometer or other device gives an absolute or relative number of tree performance. Technological advances, such as telemetry and imaging with drones or satellites, holds promise, but are still being perfected for general irrigation use. In general, technological devices yield informative data, but tend to be expensive, delicate, and require manual monitoring to account for tree-to-tree variation in the orchard.
Soil moisture sensors can be an effective method of evaluating water use by the tree. The most basic way to measure soil moisture is with a human powered shovel or soil tube 5. While it requires an operator who knows what they are doing, the technique is easily learned and repeatable. A human and shovel can move around an orchard checking out different suspicious spots that are not easily done with fixed-in-place sensors. Installation of soil moisture sensors systems range in cost and capabilities, yet provide specific data on water use. Integrating certain systems into communication relay systems allow for the monitoring of multiple sites at once. Some sensors can measure soil salinity, as well as soil moisture, to give a sense of whether the water in the soil will be useable by the tree. If soil moisture sensors are used, correct placement of where roots are taking up water is imperative to get an accurate assessment of water uptake. Overall, it is critical to keep the entire orchard in mind and understand that fixed sensors only take a specific location's reading.
Another great technique to inform irrigation scheduling is an estimate of the demand that drives water use. An evapotranspiration estimate either by CIMIS, a private weather station with ET-calculation or atmometer gives not only an amount to apply but also when to apply that amount based on the water holding capacity of the soil and the rooting depth of the crop. Soil moisture holding volume can be complicated, but can be estimated from the NRCS table in the previous paragraph5 or from tables in the Web Soil Survey 7.
Simply running an irrigation system for a specific amount of time and probing for depth of water penetration and extent of wetted area is the best way to get an estimate of soil moisture holding capacity. This knowledge is needed in order to decide whether the active rooting volume is getting wetted sufficiently or too much is being applied. Emitters are rated by gallons per hour, but that 1 gph, 5 gph, 20 gph emitter output might differ according to water pressure that can vary over an irrigation period. On the flip side, monitoring soil moisture depletion over time can give an approximation of how depletion compares to ET estimates. Soil moisture depletion can be measured by soil moisture sensors or by shovel and feel. This estimate of applied water compared to output and ET only needs to be done once at a given growth stage of the orchard. If the orchards is young, it will need to be done each year as the trees fill out. An estimate of canopy growth can also be used to better approximate young orchard ET.
All of these methods suppose that a grower has the capability to irrigate when, where and for how long they need to. If water delivery is on a fixed schedule and the amount of water can be controlled it is valuable to understand specific water needs. Knowing the rated applied amount of an emitter is important, but that amount shouldn't be assumed, especially considering natural wear and tear, damage from harvest, poor filtration, clogging, or damage by wildlife. Maintenance to insure good distribution uniformity is critical to the operation and the correct application of water to trees and for the maintenance of tree health. Low-pressure systems are wonderful but they should be evaluated on a yearly basis and tuned up in preparation for every irrigation season. Many growing areas have mobile irrigation labs that will evaluate system performance and make recommendations for improvement.
All said, knowing the orchard and evaluating tree health will inform irrigation management decisions. Applying technology where technology is appropriate will help. Using it to help advise irrigation decisions is valuable, but new tools will not always be the answer.
It's important to know what is being applied.
Trust but verify.
Drought Tips & Video: https://www.youtube.com/watch?v=LKSQRuHAnYA ; https://anrcatalog.ucanr.edu/pdf/8549.pdf
- Author: Ben Faber
Sand media filters are commonly used in agricultural microirrigation systems. They have the advantages of simplicity and large capacities and are favored by many farmers and designers over other filtration hardware when there is a lot of organic matter in the water. The Irrigation Training and Research Center (ITRC) at Cal Poly San Luis looked at sand filters to see if it were possible to use lower-than-accepted backflush pressure and thereby reduce the total pressure required for irrigation systems. By lowering backflush pressure it would be possible to design a system that could run at an overall lower pressure and hence cost. The various components of microirrigation systems run at lower pressures than the backflush pressures recommended for most sand media filters.
The conclusions are:
There are substantial pressure differences amongst different models and designs during backflush and filtration
The main pressure loss is at the backflush valves
If designed right large backflush flow rates can be accomplished at low backflush pressures (this is critical for proper detritus removal).
There are substantial differences among underdrains of various models which affects pressure requirements
No large intimal high pressure was necessary to break up the media bed, a common practice.
Different underdrain designs create different patterns of cleaning the media.
There were substantial differences among models in the amount of sand discharged from the system at backflow rate of 190 GPM. Sand discharge should actually be avoided since it's an indication of preferential flow and poor cleaning.
These are some new ideas, and even though they are meant to reduce pressure and energy use, they are also good management suggestions.
If this strikes your fancy, read more at http://www.itrc.org/reports/mediafilters.htm
- Author: Dennis Pittenger
[From the August 2015 issue of the UC IPM Green Bulletin]
A. Landscape irrigation accounts for only about 9% of total statewide developed water use, but the percentage varies widely among communities. Water applied to landscapes is estimated to account for about 50% of residential water consumption statewide, but the amount varies from about 30% in some coastal communities to 60% or more in many inland suburban communities.
Q. Does a landscape have to be re-planted with specific drought resistant, native, or California- Friendly plants to save significant amounts of water?
A. No. Field research studies indicate that traditionally used landscape trees, shrubs, and groundcovers have considerable drought resistance and perform acceptably with about 40% to 60% of the water required to maintain the average lawn in good condition. This is comparable to the water required by so-called drought resistant, California Friendly, and native plants to perform acceptably in landscapes. The common perception is that plants traditionally grown in landscapes are not drought resistant, so they are usually over watered.
Q. How much water can be saved by removing a lawn?
A. Water savings depends on how effectively the lawn has been irrigated, the type of turfgrass removed, which plants and how many will replace it, and how effectively the water applied to new plants is managed. If a lawn is removed and plant material is changed but the irrigation system and water management practices are not improved, then little water savings will be realized. If the lawn has been over watered and irrigation was poorly managed, then maximum water savings are possible by removing the lawn. However, in such situations keeping the lawn and simply improving irrigation management and improving or replacing an inefficient irrigation system will also generate substantial water savings without the trouble, cost, and the loss of aesthetics and functions that occur when removing the lawn.
A. As with lawns, it depends on the amount of water currently being applied. Plantings that have been maintained with high soil moisture content can usually maintain acceptable performance with a 20-40% reduction in irrigation by extending the interval between thorough irrigations as described above. Additional 10- 20% irrigation reductions to theses plantings or to plantings that have already been irrigated below optimum will usually allow plants to remain functional, but they will grow less, possibly wilt and drop some leaves. It is important to gradually reduce water over a few to several week period by extending the interval between irrigations and applying enough water to wet most of the root system at each watering.
A few deep, root-zone wetting irrigations spaced 3 to 6 weeks apart from spring through fall can be enough to keep most trees and shrubs alive when water is in short supply. Many tree and shrub species will drop leaves, wilt, or suffer dieback of some branches under severe water shortage, but will survive.
Q. When should trees, shrubs, and other landscape plants be planted in a dry year or if drought is expected?
A. Hold off planting until fall or winter to take advantage of cool weather as well as fall and winter rains. The planting site may be prepared in spring or summer, however.
To access this article in it's entirety, see the August 2015 issue of UC IPM's Green Bulletin or visit the UC Center for Landscape and Urban Horticulture
- Dennis R. Pittenger, Area Environmental Horticulturist, UC Cooperative Extension Los Angeles County/UC Riverside, email@example.com