I love rainy days. . .I love the pitter-patter sound of it, the smell of wet dirt, and fresh air. Rain nourishes our gardens, turns into snow in the Sierra Mountains (which in turn eventually melts and flows into our rivers), and provides balm for our spirits. Earth is appropriately called the “Blue Planet” since about 71% of it is water. However, 96.5% of that water is ocean salt water which is unavailable for human purposes. Only about 0.26% of the Earth's total water is freshwater and much of it is stored in glaciers and thus inaccessible. Of the remaining freshwater, about half remains in rivers and lakes for nature's use, with the other half being available for human usage. About 80% of the human portion is used for agricultural needs to provide our food, leaving only 20% freshwater for our gardens and homes! So, we must use this valuable freshwater wisely. 

Rainy days are becoming scarce in California with droughts happening more often. Paleoclimate records going back more than one thousand years show many significantly dry periods. Droughts occurred frequently during the 20^th century. Due to climate change, droughts are expected to become more common with longer durations in the 21^st century. The last major drought was just a few years ago in 2012-2016. 

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.  

If you have lawn, consider reducing the amount you have, since lawns are the major source of where garden water goes. Water only as needed to maintain your lawn. If you have water runoff (aka “urban drool”) onto concrete areas or the street gutter, water is being wasted. If this occurs, reduce the length of time and/or frequency you water your lawn. Also, set mower blades to three inches, which encourages deeper roots. Leave some lawn clippings behind when cutting, which is known as grass-cycling A half an inch layer of thatch functions as mulch, moderating the temperature of the soil, helping it retain moisture. 

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. 

Knowing your soil type is valuable information. There are three basic types of soil:  sandy, loamy, and clay. Each has different water-holding capacity and thus your watering scheduling needs to be adjusted accordingly. To learn how to determine your soil type, go to: https://ucanr.edu/sites/CEStanislausCo/files/348681.pdf

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 29^th 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                                  

 

 

 

 

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

 

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:

1. There are substantial pressure differences amongst different models and designs during backflush and filtration

2. The main pressure loss is at the backflush valves

3. If designed right large backflush flow rates can be accomplished at low backflush pressures (this is critical for proper detritus removal).

4. There are substantial differences among underdrains of various models which affects pressure requirements

5. No large intimal high pressure was necessary to break up the media bed, a common practice.

6. Different underdrain designs create different patterns of cleaning the media.

7. 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

[From the August 2015 issue of the UC IPM Green Bulletin]

Q.  How much water do landscapes use in California?
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. 

Q.  How much can irrigation be reduced without hurting trees, shrubs, and other landscape plants? 
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, dennis.pittenger@ucr.edu