Progressive Crop Consultant - July - August 2017

July - August 2017 Drones in Agriculture Managing California Red Scale in San Joaquin Valley Citrus Plant Growth Regulations have Benefits in Grapes Nitrogen Fertility Issues for San Joaquin Valley Cotton

PUBLICATION

Volume 2 : Issue 4

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PUBLISHER: Jason Scott Email: jason@jcsmarketinginc.com EDITOR: Kathy Coatney Email: article@jcsmarketinginc.com Email: design@jcsmarketinginc.com Phone: 559.352.4456 Fax: 559.472.3113 Web: www.progressivecrop.com

IN THIS ISSUE

CONTRIBUTING WRITERS & INDUSTRY SUPPORT Michael Cahn Irrigation and Water Resources Advisor, UC Cooperative Extension, Monterey County

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Amy Wolfe MPPA, CFRE President & CEO, AgSafe

Jhalendra Rijal, Ph.D. Area Integrated Pest Management AdvisorNorthern San Joaquin Valley, UC Cooperative Extension and Statewide IPM Program

Drones in Agriculture

Worker Safety & Heat Illness Prevention

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Pesticide Use Near Schools and Child Care Facilities Regulation:

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Managing California Red Scale in San Joaquin Valley Citrus

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Plant Growth Regulations have Benefits in Grapes

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Nitrogen Fertility Issues for San Joaquin Valley Cotton

What You Need to Know

Shrini K. Upadhyaya, Professor, Bio and Agr. Eng. Dept., University of California Davis

UC Cooperative Extension Advisory Board Kevin Day

Steven Koike

David Doll

Emily J. Symmes

Dr. Brent Holtz

Kris Tollerup

County Director and UCCE Pomology Farm Advisor, Tulare/Kings County UCCE Farm Advisor, Merced County County Director and UCCE Pomology Farm Advisor, San Joaquin County

UCCE Plant Pathology Farm Advisor, Monterey & Santa Cruz Counties UCCE IPM Advisor, Sacramento Valley UCCE Integrated Pest Management Advisor, Parlier, CA

The articles, research, industry updates, company profiles, and advertisements in this publication are the professional opinions of writers and advertisers. Progressive Crop Consultant does not assume any responsibility for the opinions given in the publication.

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July/August 2017

4 UPCOMING EVENTS: South Valley Nut Conference October 27, 7:00AM - 1:30PM - wcngg.com Tulare County Fairgrounds - Tulare, CA

Come out for a day of free food, CE credits, giveaways, and industry networking.

Mid Valley Nut Conference November 3, 7:00AM - 1:30PM - wcngg.com Modesto Jr. College Ag Pavilion -Modesto, CA

Enjoy experiencing our trade show in the heart of the Central Valley. A scholarship will be given to the Modesto Jr. College ag program.

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An E y e in t h e Sk y:

Drones in Agriculture

Photo courtesy of Terry Brase

By Terry Brase | Precision Ag instructor at West Hills College

O

ne of the most discussed precision ag technologies in the last 4 years has been Unmanned Aerial Systems (UAS), not only because it is a “cool” technology, but also because there is confusion in its use or misuse. Can I fly these without a license and if I’m not getting paid? What do I do with all of this imagery? Do we already have too much data? This article will outline some examples of how West Hills College uses UAS in permanent nut and row crops while educating our students about UAS as tools for the grower.

The Farm of the Future at West Hills College has invested in several types of UAS to educate our students on their use. Precision agriculture courses in Control Systems, Software and Processing, and Geospatial Technologies that apply to UAS are

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under development, but the focus will always be on the capture, processing and interpretation of imagery. The imagery is what makes UAS a tool instead of a toy. Each system listed in this article provides a different level of usefulness in the field or orchard and a different perspective for students to learn from.

Before beginning with specific examples of UAS, some terms need to be defined. A “UAV” is an Unmanned Aerial Vehicle and refers to the aircraft that can be flown autonomously (as opposed to Remote Control aircraft that is also unmanned but designed to be flown remotely using controls). “UAS” refers to the vehicle and the software that controls, assists the flight, and processes the imagery (therefore is it more than a vehicle, it is a system). The term “drone” is a broad term that describes an aerial

July/August 2017

vehicle for autonomous flight usually for military use, though more recently the term is applied to any UAS. One of the first UAV that West Hills College acquired was a DJI Phantom 2. It is a quadcopter (rotor craft) with a RGB (Red, Green, Blue) camera, which amounts to a toy since agriculture applications are somewhat limited. The Phantom 2 has GPS and IMU (Inertial Measurement Units such as gyroscopes and accelerometers) that assist in making its flight more stable. Anybody that has flown a cheap remote controlled craft can attest to how difficult it is to fly even in the quietest areas and much less in outdoors and windy conditions. The GPS and IMU make the Phantom 2 an excellent craft for students to practice flight and taking video or pictures.

There are two problems with the use of this craft for precision agriculture.

First, the RGB camera means Red, Green, and Blue colors are captured.

This type of camera captures the natural reflectance in the same way a person’s naked eye does. The resulting image is

Figure 1/ Photo courtesy of Terry Brase

known as a natural color. The fact that this image is from 200 to 400 feet above ground level allows a person to view an entire field or crop with a “bird’s eye” view. This does allow the user to see some variability and patterns within the field. However natural color is not as good as false color infrared imagery.

(There is a more detailed description of infrared and how an imagery sensor works at the end of this article.)

The other problem with this UAS is that these images cannot be georeferenced. This means that the GPS will calculate a position for the UAV, but it doesn’t get attached to the image.

Without this referencing the images cannot be used within a Geographic Information System for further analysis.

This also means that it cannot be orthocorrected to put the image to scale.

Depending on the height of the flight, a large amount of distortion can occur within the images. The example image

in Figure 1 demonstrates how the ground surface is distorted because of the height of the camera. The main use

by West Hills College is for students to practice calibrating, positioning, and data management with an aerial vehicle. As far as agriculture use, there is little valid use of this device for precision agriculture.

The second example of West Hills College UAS is a DJI Phantom 4 (quad rotor). Similarly to the Phantom 2, it also has GPS and IMU for stable flight and a RGB camera. However this system has a major advantage over the Phantom 2.

The system allows for the geotagging of the imagery. This results in images similar to Figure 2 (page 6) which are rectified and reduces the distortion. These images can also be

Continued on page 6

and the capability to geotag images. It also has the advantage of being a fixed wing, which usually has a faster flight and can cover more acres in one flight.

The real advantage of this specific platform is that it has a multi-spectral camera. A multi-spec camera has the capability to capture reflectance in light ranges outside the visible light, such as infrared. These infrared images can be used to create NDVI (NOTE: many people refer to NDVI as an image.

NDVI is NOT a reflectance band of light or a type of imagery. It is an index that is created from bands of imagery, specifically blue or red and infrared).

hovering high/ Photo courtesy of Terry Brase

Continued from page 5 added as a data layer within a GIS for analysis. In addition, this craft can be flown autonomously. This means that a flight mission is created to guide the craft on a series passes over the field taking pictures. All these pictures are then georeferenced and mosaicked to create a full field view.

The problem though remains that it is still a color image that has limited usefulness for analysis. Some patterns are visible, and the fact that it is georeferenced means that location coordinates can be determined for ground trothing (finding the location on the ground and checking what is actually there).

West Hills has used this imagery for a leaf off evaluation of our pistachio orchard. It has also been used for an evaluation of irrigation in our garlic and for documenting research plots of sugar beets. Figures show examples of each.

The limitation for this system is still limited analysis with a RGB image. The cameras can be replaced, but usually at a major cost that doubles or triples the original cost of the aerial vehicle. Usage is identification of field problems and

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focused scouting. Focused scouting refers to a technique where, instead of randomly passing through a field to find problems, a UAS image is used to focus the scouting to areas that show abnormalities.

The third example of a UAS that West Hills has is a PrecisionHawk Lancaster 5 (fixed wing UAS). This is another step up from the previous example.

Like the Phantom 4, this system will do autonomous flight, has GPS and IMU,

Figure 2

July/August 2017

Another advantage that this UAS offers is scalability in that there is a 2.2 pound payload which can carry not only a multi-spec sensor but can be switched for a multitude of other sensors including: natural color; thermal (for a specific band of infrared that is based on temperature); LiDAR (active sensor that captures very accurate elevation for construction) and others.

In addition the Lancaster 5 has its own software that processes the imagery to create a variety of products. Now this should be taken as a positive and a negative. On the positive side, having a dedicated software means that it is simple and should work well with the imagery coming from the UAV. This

Commercial drone uses specific software will create a variety of vegetative indexes including NDVI, EVI, and multiple others. Each index uses different bands of reflected light and infrared and combines them into a value which interprets different things. The NDVI, for instance, is an indicator of plant stress and vigor as opposed to EVI which is an enhanced version of NDVI which takes into account atmospheric conditions. Therefore, each is used differently, and both are more valuable than a natural color image.

which shows plant stress, which can be used for zone management and analysis for helping to identify cause and effect of variability in the field.

The fourth example of a UAS that West Hills College uses is a DJI S900 (a hexacoptor, 6 rotor UAS) which again is a step up from the previous UAS. The S900 provides flexibility in that with

a proper gimbal (the equipment from which a camera hangs from) a variety of sensors can be used with it. The Lancaster 5 UAS did have several types of sensors, but was limited to Lancaster 5 sensors. The S900 allows the student to set up a UAS from scratch as opposed to using one straight from the box. This means an open source software can be used to process the image rather than

On the negative side, this is proprietary software that only works with this specific device. It is somewhat limiting to have software that only works with one device. It is cloud based that has an advantage that it can be used on any computers that work with the internet. This imagery will be more useful for decision making.

The fixed wing will cover larger fields and more acres and can be used for focused scouting and for individual georeferenced images. But the real value is in the full field mosaicked image,

Continued on page 8

Georeferenced images – focused scouting/ Photo courtesy of Terry Brase July/August 2017

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recombining them into a color image.

Continued from page 7 a proprietary software as the previous platforms. Both increase the flexibility in how the UAS is used and is valuable for the student to know.

Why does this have to be done?

Because digital detectors do not determine wavelength they just

measure how much there is. The filter or separating of color is necessary to determine the color and then it can tell how much red, green, and blue there are for the final color image. The more

At this point, it is important to make a comparison of multi-spectral cameras, or more properly, sensors.

Sensors record the reflectance from objects digitally in the form of color bands of wavelengths. Though it sounds like there are distinct portions of light, actually there is a continuous continuum of light wavelengths which means it’s up to the sensor to capture specific wavelengths that can be used.

Many of the cheaper equipment are consumer grade cameras that come with an installed filter that allows infrared to be captured. Other cheaper cameras use one sensor and then have some way of separating the colors and then tool or toy?/Photo courtesy of Terry Brase

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July/August 2017

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UAS asmall Unmanned Aerial Systems/ Photo courtesy of Terry Brase

expensive and high quality cameras use one sensor for each color bandwidth.

This allows a very specific bandwidth resulting in a more useful image for analysis. Currently West Hills has all single sensor cameras that rely on the software to separate the individual bands for creation of NDVI or other vegetative indexes.

Finally it should be noted that UAS are just one platform for remote sensing data. There is also ground based, satellite, and manned flight. Future articles will focus on these technologies and their value to precision agriculture.

In summary, hopefully this article has provided the background necessary to make a decision on the use of a UAS. If you are interested in purchasing, you may still want to discuss your specific needs with a professional before deciding. Also remember: it is the imagery that you get from the UAS that will make it a tool and not a toy.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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Pesticide Use Near Schools and Child Care Facilities Regulation—What You Need to Know

An example of the map showing the proximity of schools and child care facilities to a specific farm parcel available by the Stanislaus County Office of the Agricultural Commissioner./ photo courtesy Amy Wolfe

By Amy Wolfe, MPPA, CFRE, President and CEO, AgSafe

I

n September 2016, the California Department of Pesticide Regulation (DPR) announced proposed regulatory changes impacting the way agricultural pesticides can be applied on farms near public schools and child care facilities.

The proposal, which had been in discussion by DPR and the regulated community for some time, will have significant impacts on when and how pesticides can be applied.

Since being first released, the proposal has been circulated for stakeholder comments, and, as a result, revisions were made. The latest version of the proposed changes was open again for comment in March and April. Those comments are now under review, and any further changes to the proposed language should be released soon. It is the intent of DPR for these changes to take effect January 1, 2018, and, as such,

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it is essential the agricultural community fully understand the scope of the proposal.

There must be a 25-foot distance restriction when using one of the following:

The proposal will prohibit the application of many pesticides on farms within various distances of public K-12 schools and child care facilities from Monday through Friday between 6 am and 6 pm. Specifically, there must be a minimum quarter mile distance restriction for applications using the following:

Ground-rig sprayer unless using a dust, powder or fumigant and then the quarter mile distance restriction applies.

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Aircraft

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Airblast sprayer

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Sprinkler chemigation equipment

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Dust or powder (with some exceptions)

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Fumigant

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Field soil injection equipment unless using a fumigant and then the quarter mile distance restriction applies. In addition, if applying a dust or powder, there is no minimum distance restriction.

Other application equipment such as drip or flood chemigation equipment.

However, if this type of equipment is used to apply dust, powder, or a fumigant, the quarter mile distance restriction applies.

The proposal does not have any restrictions to use when the application

is made within an enclosed space, such as a greenhouse, when using a bait station, when applying a dust or powder pesticide using field soil injection equipment, when the pesticide is applied as a granule, flake or pellet, or when the application is made using a backpack or hand-pump sprayer. In addition, there is no restriction to use when school classes are not scheduled for the day of application or when the child care facility is closed during the entire day of application. Lastly, fumigants cannot be applied when school classes are scheduled or child care facilities are open within 36 hours following fumigation.

A critical element is knowing if your property is within a quarter mile of a public K-12 school or child care facility. Each county agricultural commissioner (CAC) is addressing this issue individually, and as such, it is critical that you connect with the CAC offices where you farm to determine how they are making this information available. Some counties, such as San Joaquin, are able to provide those details over the phone or in-person using parcel numbers. Other counties, such as Stanislaus, have developed online resources that allow you to enter your pertinent parcel details and a map is generated noting the location of near-by facilities, along with the relevant facility contact details.

The final important aspect of the proposed regulation is the documentation and reporting element.

An annual written notification will need to be submitted to the CAC that lists all the pesticides expected to be used during the upcoming year. This must be provided by April 30th each year.

The grower must keep record of this notification for two years. Specifically, the notice must include, among other things:

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The name of pesticide products and the main active ingredient to be used

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A map showing the location of the field to be treated

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Contact information for the grower/ operator

The web address for the National Pesticide Information Center where additional sources of information or facts on pesticides may be obtained It is important to note that the above elements may be slightly modified again given that DPR is reviewing the most recent round of stakeholder feedback.

However, the number of changes made to the regulation after the first comment period were not sweepingly different and as such, it is unrealistic to expect this final iteration will change meaningfully from what is outlined here.

For more information on this proposed regulation or any worker safety, health, human resources, labor relations, or food safety issues, please visit www. agsafe.org, call us at (209) 526-4400 or email us at safeinfo@agsafe.org. AgSafe is a 501c3 nonprofit providing training, education, outreach and tools in the areas of safety, labor relations, food safety and human resources for the food and farming industries. Since 1991, AgSafe has educated nearly 75,000 employers, supervisors, and workers about these critical issues.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

Proposed regulations from the California Department of Pesticide Regulation will have a significant impact on pesticide applications on farms, near schools, and child care facilities. /photo courtesy Amy Wolfe

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Managing California Red Scale in S a n J o a q u i n Va l l e y C i t r u s

Red scale symptoms on citrus fruit/ photo courtesy of Beth Grafton-Cardwell

by Beth Grafton-Cardwell | IPM Specialist and Research Entomologist, University of California Riverside and Director of Lindcove Research and Extension Center, Exeter, Ca

BY Greg W. Douhan | Area Citrus Advisor, Tulare, Fresno, and Madera Counties, University of California Cooperative Extension, Tulare, Ca

C

alifornia red scale, Aonidiella Aurantii, is a significant pest for California citrus producers, especially for growers in the San Joaquin Valley (SJV). California red scales attack all aerial parts of the tree including twigs, leaves, branches, and fruit. When the pest is abundant on the fruit, it requires a high pressure washer to remove it and may be reduced in grade or culled in the packinghouse, leading to economic losses to the grower. The insect can also defoliate portions of a tree and can even kill branches within the tree when the infestation is significant. Tree damage is

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most likely to occur in late summer and early fall when scale numbers are highest and when moisture stress is high within the tree. Broad spectrum insecticides, organophosphates and carbamates, were used to control California red scale for decades, but resistance to these chemicals developed in the 1990’s. This led to the development of a biologicallybased integrated pest management (IPM) strategy utilizing the insectoryreared parasitoid wasp Aphytis melinus (DeBach) to help control the scale.

These parasitoid’s can be released by growers in February through November

July/August 2017

to help the native Aphytis sp. to reduce scale populations and achieve effective control in a "normal" year (more of this below). In years when biological strategies are not effective enough to reduce populations to an economic level, growers will also use selective insecticides such as oil, Esteem, Centaur, and Movento. When scale populations are extreme or other pests are present, growers also utilize on broad spectrum insecticides such as Lorsban and Sevin XRL Plus. However, these latter products can have a significant impact on natural biological control.

Over the past several years, California red scale has been very difficult to control in the SJV. Why has this been such a difficult issue to deal with compared to previous years?

The most likely reason is that heat and drought have been major contributors to the situation. But there are other issues involved, such as grower treatment practices, which we will emphasize further.

Lifecycle of Red Scale In a normal year, California red scale completes three to four generations per year in the SJV. In this region, the harsh winters eliminate many of the younger

stages of scales, so that the population consists primarily of late stage males and females at the end of winter. The first male flight occurs in March during which mating occurs. Approximately 550 degree-days (DD) later, the 1st generation of crawlers emerge from the female scale bodies (Fig. 1). The exact date of this first crawler emergence depends on temperature and the accumulation of what we call DD. Degree-days for California red scale are defined as the accumulation of the average daily temperatures (maximum temperature-minimum temperature divided by 2) above the scale’s lower developmental threshold of 53oF. At 1,100 DD after the first male flight

another male flight occurs, and at 1,650 DD the second crawler emergence occurs and so on through about four crawler generations (Fig. 1). When temperatures are cool in the spring, it takes about eight weeks to accumulate 550 degree-days (male flight to crawler emergence). When temperatures are hot in the summer, it only takes two to three weeks to accumulate 550 DD, and events happen quickly.

Figure 2 (page 14) shows that during 2010-2011, DD accumulated more slowly than the 30-year average.

In contrast, during the hot dry years

Continued on page 14

figure 1: Major events such as crawler emergence and male scale flights occur every 550 degree days. The population of scale is most synchronized during the first and second crawler generation and so that is the target for insecticide treatments.

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figure 2: Degree days accumulate slower in cool years (2011-2012) and faster in hot years (2015-2016). Hot years allow more generations of California red scale to develop.

Continued from page 13 of 2012-2016 (2015 and 2016 shown), DD accumulated more rapidly than the 30-year average. More heat has a number of consequences. It means that the scale is developing very rapidly, and it makes it harder for the parasitoids to find and parasitize their preferred 3rd instar scale stages. The high heat works against the survival and effectiveness of the parasites, and drought stresses the trees, making them more susceptible to the scales. Finally, the extra DD support an extra partial or full generation of scale at the end of the season on the fruit. To make things worse, we had such a warm winter in 2015-2016, that for the first time in 27 years of

monitoring, California red scale did not diapause during the winter—scales kept reproducing all winter long!

Insecticide Efficacy Issues In addition to weather effects, there are insecticide efficacy issues.

The insecticides work best if the scale population is synchronous—mostly in the crawler to white cap stage. That is why insecticides are recommended during the 1st and 2nd crawler generation (Figure 2). After that, the stages become mixed, and the scale is on the fruit, making insecticide control more difficult. With warm winters allowing young instars to survive, the scale populations have been mixed stages

year round, reducing the effectiveness of insecticide treatments. In addition, insecticides are effective for only about 30 days, which is one scale generation.

If extra generations are tagged on at the end of the season, and scale are moving to fruit early in the season, then a single insecticide application simply can’t do the job. Another factor reducing insecticide efficacy is the practice of growers routinely applying systemic imidacloprid (Admire Pro and generics) to their acreage for various reasons, including leafminers, psyllids, and soft scales. This product does not kill California red scale on wood. Year in and year out use of this product gradually builds scale on the wood that eventually spills out onto leaves and

Continued on page 16

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Continued from page 14 fruit, especially in a hot, dry year. As a consequence of these combined issues of drought, heat, and insecticides, quite a bit of the acreage was treated two to three times for California red scale during 2016.

Control

reduce scales. This makes sense, as male scales at high densities don’t have to crawl very far to find a female.

Whatever methods SJV growers use to control scale, we highly recommend that the scales should be monitored on leaves, twigs and fruit this during the growing season as fruit develop. It is not recommended that growers rely on pheromone trap counts to make treatment decisions because some of the insecticides and the pheromone disruption can create artificially high or low male scale counts. Be sure to drive slowly and use the best possible nozzling and water volume to achieve excellent spray coverage that reaches the scale on the inside wood of the tree.

So what are we going to do about California red scale? The DD for 2017 have accumulated at about the rate of the 30-year average so far because the spring has been cooler than the past five years.

In addition, the winter was colder than the previous five to six years. Colder weather is helpful for slowing the growth of red scale, synchronizing the scale stages and improving both chemical and Comments about this article? We want biological control. So there will likely to hear from you. Feel free to email us be fewer treatments needed this year. A at article@jcsmarketinginc.com newly available scale control option is to utilize pheromone disruption alone or in combination with an insecticide treatment.

Suterra has just begun marketing a slowrelease mesoporous lure for California red scale—180 lures per acre hung in the GREEN VALLEY NATURAL trees just prior to PLANT WASH the 2nd male flight provides season-long suppression of scales.

Dr. Beth GraftonCardwell’s team has experimented with Residues this product and found that it reduces Dust scale on leaves, twigs Debris and fruit by about 50 percent for low from any type of Agricultural commodity, to moderate scale pre or post harvest. OMRI listed. populations. At high Available from Western Nutrients Corp population densities, and only the finest Distributors. the pheromone Manufactured By 245 Industrial Street Info@westernnutrientscorp.com product is not Bakersfield, CA 93307 www.westernnutrientscorp.com Tel. (661) 319-3690 fax (661) 327-1740 effective enough to

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Plant Growth Regulators have

Benefits in G r apes

By Cecilia Parsons

T

he acronym for plant growth regulators (PGR) could also stand for “perfect grape regimen” because that is the reason grape growers choose to apply them.

Kern County University of California Cooperative Extension (UCCE) viticulture advisor Ashram El-kereamy said table grape growers routinely use PGRs to improve quality, size and color of their grapes. Table grape quality does come about naturally, but use of PGRs can enhance the natural thinning and ripening processes if applied correctly.

“We are just adding a little bit to nature,” El-kereamy said. “They are enhancing the natural ripening system.”

Plant hormones are endogenous organic compounds that are active at very low concentrations and are essential for regulating plant growth and development. Plant hormones are

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produced in one tissue of the plant and transferred to another. They have a specific function at a specific stage and concentration and act together in a complex pathway.

Plant Growth Regulators Plant growth regulators are natural or synthetic forms of plant hormones that can be used to control or direct plant growth. They are regulated by the California Department of Pesticide Regulation (DPR) as pesticides and their handling and use must follow the same regulations.

“Growers who want good quality grapes use these products,” El-Kereamy said. The difference between use in older varieties of table grapes and the new varieties is that much less of the product is needed to achieve the best results.

July/August 2017

When Thompson and Flame Seedless were predominant varieties in table grape production, El-kereamy said, PGR user rate was high to enhance berry sizing and quality. More recently, newer varieties of table grapes have been developed that naturally have those desired characteristics. Use of PGRs continues at a much lower concentration, he said, to further improve quality and size.

The primary plant hormones involved in grape ripening includes auxin, which is produced in plant embryos and delays color and ripening and retards abscission; cytokinin which is produced or found in roots and increases fruit set, delays ripening and senescence and stimulates cell division; gibberellins which promote bud growth and cell elongation; abscisic acid which inhibits growth and promotes dormancy and

Continued on page 20

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Continued from page 18 enhances color; and ethylene which promotes fruit ripening and senescence and enhances color.

Auxin, cytokinin and gibberellins are classified as growth promoters. Abscisic acid and Ethlyene are classed as growth inhibitors.

Timing of Applications Timing of PGR applications is critical. said El-kereamy. The wrong timing or concentration of the PGR application may result in loss of both yield and quality.

Knowing grape berry growth cycles helps to determine the best time to apply a PGR. The first cycle is formation with cell formation in pericarp tissue and flowers starts transformation from flower to fruit. Water flows into berries via the xylem and phloem, enlarging the berries. The second cycle is ripening.

During this time sugar accumulates, as well as flavor compounds and color changes. Formation of each compound depends on light and temperature, but ripeness is determined by sugar and color.

There are a number of factors to consider when using PGRs in grapes.

El-kereamy said timing should be determined by the developmental stage not a date because of variations in weather from year to year.

Time of PGR application also depends on the outcome desired. A gibberellic application can be at 50 percent, 70 percent or 100 percent bloom depending on the variety and degree of desired thinning. El-kereamy said the concentration of the gibberellic bloom and sizing spray varies among cultivars. Concentration for bloom can be from 0.5 ppm to 40 ppm for bloom and 10 ppm to 80 ppm for sizing. The 20

Progressive Crop Consultant

main drawback in use is that a high concentration can affect fruitfulness and the number of clusters on the vine.

There are recommendations for using gibberellin acid on specific varieties, El-kereamy said. Where there is no recommendation, he suggests a small trial before using it across the vineyard.

A gibberellin application will reduce the number of berries in the cluster, leaving the others to grow larger. This PGR also creates competition between the canopy and the cluster, making the canopy larger as it takes nutrients from the clusters. Studies show that gibberellin induces nutrient competition between flowers and shoots or among flowers within a cluster. Cytokinin increases berry size by promoting cell division. Response to PGR depends on the variety, developmental stage, concentration of product, and method of application.

Side Effects There can be side effects from specific PGR products. Gibberellin may affect the following season bud fruitfulness if used in higher than recommended concentration. The synthetic cytokinin CPPU does not reduce fruitfulness the

July/August 2017

year following its application. Ripening PGR ethephon may cause soft fruit if applied during hot weather, late or more than once. High concentration of cytokinin can reduce sugar content.

Proper application is essential for the best results. Mixing several materials in the tank when making PGR application is not advised. Plant hormones interact with each other and attentions should be given when mixing or applying more than one PGR. PGR traces also exist in other materials.

A good canopy structure will facilitate PGR applications and increase spray efficiency. El-kereamy said that application method should provide good coverage with small droplet size. The pH of the spray solution should be adjusted depending on the materials used. One example is an ethephon application which could be useless if the water has a high pH. Most applications are delivered via ground rigs with spray directed at clusters.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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Nitrogen Fertility Issues for San Joaquin Valley Cotton

by Robert Hutmacher | Extension Agronomist / Cotton Specialist, Department of Plant Sciences, University of California Davis, and University of California West Side Research and Extension Center

N

itrogen (N) is an essential plant nutrient that must be available at the correct times and in the proper amounts to produce high cotton yields.

Inadequate N can reduce plant growth, number of fruiting sites and reduce yields. Early season cotton N deficiencies are rarely observed in the San Joaquin Valley (SJV), but when they do occur they show up as stunted plants or plants that are pale green in color. N deficiencies can also occur with a very restricted rooting system that limits the plant’s ability to explore a larger volume of soil for N and other nutrients. The reproductive (boll production) growth period (late June through August) is a much more likely timing for nitrogen

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deficiency to occur. During early part of this period, there are significant demands for nitrogen with the large expansion of vegetative growth. Later, as flowers and then bolls develop in significant numbers, most plant nitrogen is being directed to these reproductive structures, and vegetative growth and root growth become less successful in “competing” for available nitrogen. In fact, since some of the major N-containing compounds in plants can be mobilized and translocated early on to new vegetative growth, and later on to supporting boll growth, N deficiencies tend to be most apparent as yellowing of older leaves, progressing to yellowing of younger leaves and reddish coloration of

July/August 2017

leaves, stems and petioles as more severe deficiencies develop.

N fertilization of cotton at the farm level is directed toward optimizing lint yield, while preserving high fiber quality; but achievement of high yields and quality are not the only incentives for improving N management. N management decisions on all crops may affect movement of N in soils and water.

Although there are large differences in growth habit due to type of cotton (Pima versus Upland) and with varieties, cotton is generally indeterminate in growth characteristics. Cotton’s relative N nutrition, among other factors, affects the plant’s balance between vegetative

Table 1. Fertilizer recommendations for Acala cotton for different levels of measured soil residual nitrate-N in the upper 2 feet of soil, based on San Joaquin Valley studies (Univ. CA, Hutmacher et al) Soil Residual Nitrate Levels- Upper 2 feet soil - Spring pre-plant or soon after planting < 55 lbs N as NO3-N 55 to 100 lbs N

Recommendations for N fertilizer applications per year in lbs/acre (values shown are for target yields of 3 to 4 bales/ acre)

Additional Considerations (ie.

What situations would cause you to lower or raise applied fertilizer N amounts?)

125 to 175 lbs (possibility of late water-run if yield potential is high) 100 to 125 lbs (possibility of late water-run if yield potential high)

Apply less N if low yields predicted due to late planting, field history

vigor and adequate reproductive growth.

High cotton yields depend on adequate N fertilization, but excessive N can negatively impact the crop’s balance between reproductive and vegetative growth, often reducing fruit retention and promoting rank growth. N fertilization beyond those rates that produce consistent yield improvements also represent an unnecessary cost. Moreover, application of excessive N fertilizer can have negative impacts on crop production and input costs by increasing cotton’s susceptibility to phloem-feeding insects (Cisneros

Use plant mapping, petiole nitrate to assess yield, N status - apply if > yields and lower than expected petiole NO3 status

and Godfrey, 2001), and increasing the need for growth regulators for vegetative growth control (Hutmacher et al, 2004).

In the late-season, high N availability can cause fruit maturity delays, make defoliation more difficult and costly, and increase chances of regrowth after harvest aid applications. Tight profit margins now and in the future dictate that all unnecessary crop inputs be reduced or eliminated where possible.

If crops grown in rotation have inadequate rooting depth and densities to intercept applied and residual N, soluble forms such as nitrate can move below the vadose zone with water from rainfall and irrigation and contaminate groundwater (Burrow et al., 1998; Franco and Cady, 1997). Groundwater in many

areas can flow laterally into surface water systems, with potential environmental impacts on those ecosystems. Many California cotton fields are grown in a rotation sequence that includes crops such as alfalfa, processing tomatoes, corn or silage crops, small grains, garlic, and a variety of vegetable crops. Some of these crops can contribute N (ie. alfalfa) to the soil profile through N-fixation, or have typical N fertilizer applications that in prior experiences can exceed plant uptake, resulting in unused N (reduced N recovery rates) and potential for losses from the soil-plant system. In this type of situation, cotton production practices alone are clearly not the only source of potential leaching losses and environmental impacts, but must be considered as part of the overall system that requires analysis and improvements.

Acala Cotton Responses to Applied Nitrogen In the late 1990’s and early 2000’s, University of California researchers conducted a large multi-site study of Continued on page 24

July/August 2017

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23

Continued from page 23 Acala cotton cultivars in the San Joaquin Valley to evaluate crop yield responses to applied nitrogen fertilizer amounts that ranged from about 50 lbs/acre to about 200 lbs/acre, with fertilizer applications adjusted downward by adjusting for residual soil nitrate-N in the upper two feet of the soil profile (Hutmacher et al, 2004). The study sites represented a wide range of soil types, crop rotations and were spread across six San Joaquin Valley counties, and yield levels generally ranged from about 1,100 to 1,700 lbs lint/acre, in some cases lower than yields now typical for many current SJV cotton growers. Fertilizers were applied as split applications at early to midsquaring and again at early bloom. The focus at the time was to evaluate newer Acala varieties that tended to be more determinate in fruiting habit (when compared with older varieties) and for target yields averaging three bales of lint/acre or more. The study produced some unanticipated results. N fertilizer

applications as low as 56 kg ha-1 (50 lbs/acre) led to no significant yield reductions in just over half of the 39 large-scale trial sites over a five year period. In fact, of the trials in which a significant yield response to fertilizer N was noted, maximum yields required 168 to 224 kg ha-1 (150 to 200 lbs/acre, respectively) in just over half of the sites in these studies.

When residual soil nitrate changes in the upper two feet of soil during the season and

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Table 2. Recommended values for nitrate-N levels for upper-canopy petioles as a function of growth stage and cotton type (Upland versus Pima cotton) – Univ. of CA, Hutmacher et al.

Petiole Nitrate (NO3-N) – in ppm Upland Cotton Pima Cotton Growth Stage Early square

Borderline to Deficient

Sufficient Upper Level

Borderline to Deficient

Sufficient Upper Level

<14,000

>20,000

<10,000

>12-14,000

<11-12,000

14-18,000

<6,000-7,000

>8,000-10,000

1 flower + 10 days

<8000-10,000

12,000-14,000

<4,000-5,000

>6,500-8,000

Peak bloom

<3,500-5,500

>7,000-9,000

<2,500-3,500

>4,500-6,000

Early open boll

<1,500-2,000

>3,500-4,500

<1,000-1,500

>2,500-3,000

10-15 days after cutout

<750-1,200

>1,500-2,000

<750-1,000

>1,250-1,500

st

1 flower st

24

Progressive Crop Consultant

July/August 2017

applied N were both considered, yield N response data from these studies affirmed the N requirements per bale of about 50 to 60 lbs N per 500 lb bale of lint from earlier California or Arizona studies (Silvertooth and Norton, 1998; Hutmacher et al., 2004; Bassett and Mackenzie, 1970. Table 1 (page 23) shows some recommendations coming out of this study regarding fertilizer N application amounts to consider at three ranges of residual soil nitrate-N levels measured at planting timing (upper two feet of soil).

The key finding in these studies was that in many situations a significant portion of the N needs of the crop could be provided by in-field soil N sources (including residual soil nitrate-N, irrigation water N, carryover in organic residues or manures), thereby reducing the need for N fertilizer applications. Some limited studies done since with Pima varieties suggest N requirements and yield responses may be fairly similar to those found with Acala varieties in these earlier 1990’s-2000’s studies, but the evaluations with Pima have been far few-

er in number and we do not know if the results would be similar under higher yield levels and with more indeterminate cultivars.

Petiole Nitrate Field Evaluations and Crop N Uptake and Removal Estimates.

As part of our field research efforts, we have been doing petiole nitrate eval-

July/August 2017

Continued on page 26

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25

Continued from page 25 uations and some limited above-ground plant nutrient uptake studies in both Upland and Pima types of cotton as part of several irrigation research projects over a number of years at the West Side Research and Extension Center (WSREC) of the University of California. The nitrogen component of these studies was only a subset of the work on the overall projects, so much of this work has not yet been published, but we will be working on those publications.

Current recommendations for borderline deficient and upper level sufficient petiole nitrate-N values developed using petioles from recent, fully-expanded upper canopy leaves are shown in Table 2 (page 24). Note the following: (1) the large differences between values

shown for Pima versus Acala cultivars, in agreement with some previously published information of the University of California; and (2) some of the ranges shown as “borderline” or “sufficient” are fairly large. The range of values shown was largely due to differences seen with drip-irrigated versus furrow-irrigated plants, with the lower values representing plants under drip irrigation.

With new requirements associated with the development of Nitrogen Management Plans, there has been renewed interest in some studies we have done at the University of California West Side Research and Extension Center describing cotton N uptake and N removal with harvest operations. These have been irrigation and cultivar response studies

done over the past 8 years, and shown in Table 3 (page 25) are some averages and standard deviations for: (a) harvest-time total plant N uptake (lbs N in above ground plant parts/acre) and (b) N removal in lint plus seed with harvest (in lbs N/ton of lint plus seed) The values shown in Table 3 (page 25) were determined using small area harvests in field research plots, with plants partitioned in different components, weighed, and then subsampled to

determine N content.

•

generally there were three samples replicates per site for these evaluations.

The average values that we have for N removal with harvest for Pima types of

cotton are actually quite similar to those in some more limited studies we have done using Acala and Upland varieties (Table 3, page 25). These small data sets represent what we feel is just a start in providing estimated uptake and removal numbers representing California cotton production conditions, since the data shown represents: (a) a relatively limited number of evaluations all done in small plots at the same soil type/site; (b) a small number of cultivars; and (c) harvest removal values shown include removal with lint plus seed, but do not account for removal associated with gin trash (which could be significant, especially with more indeterminate, harder to defoliate Pima cultivars). Additional

studies to address some of these concerns will be conducted If funding can be identified.

Summary Key Messages from Nitrogen Studies:

•

•

likely N fertilizer needs–aiming for higher yields is a good profitability strategy, but don’t over apply fertilizers when very high yields are improbable.

•

Soil type, texture, infiltration rate, and physical limitations to the depth and extent of rooting may impact crop growth and your management options.

•

Growing seasons differ in yield potential. Early season weather and soil conditions differ between seasons, and can impact yields and cotton N use. Lower than usual early-season heat unit accumulation may limit yields.

•

Crop rotation patterns and management practices impact both amounts of residual soil N and where it may be located in the soil profile. When cotton follows alfalfa or heavily fertilized corn or tomatoes, residual N may be high; after small grains or sugar beets, lower residual soil N levels usually

Accurate assessment of cotton Continued on page 28 nitrogen (N) fertilizer needs requires an integrated evaluation of the characteristics of your production Scientifically proven to reduce system.

Field history is important.

Yield goals should be reasonably assessed and matched with

female NOW populations and damage with Mass Trapping and Monitoring.

July/August 2017

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27

Continued from page 27

1983. Plant analysis as a guide to cotton fertilization. In: H.M. Reisenauer (ed.), Soil and Plant Tissue Testing in California, pp. 16-17. Berkeley, Univ.

CA, Div. Agric. Sci., Bulletin 1879.

prevail.

•

Pre-plant soil nitrate-N analyses to a depth of at least two feet are useful in estimating readily accessible plant-available N. Adding soil nitrate-N analyses in the third and fourth foot depth can give an even better estimate of available N.

•

Irrigation water may contribute N to your crop budget–It may be necessary to test water for nitrate-N content.

•

•

•

Petiole nitrate monitoring during late squaring through peak bloom can aid in assessing supplemental N needs during the season, particularly under conditions where soil test nitrate-N levels are marginal to moderate and fruit set and yield potentials are high.

Fruit load evaluation , in combination with residual soil nitrate measurements and petiole nitrate-N monitoring, is essential in estimating the need for and likelihood of a favorable response to supplemental N .

Improved N management practices and better assessments of crop N needs should reduce excessive residual soil N levels over time.

Bassett, D.M., and A.J. MacKenzie.

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Progressive Crop Consultant

Burrow, K.R., S.V. Stork, and N.M Dubrovsky. 1998. Nitrate and pesticides in ground water in the eastern San Joaquin Valley, California: Occurrence and trends. USDA Water Resources Investigations Report 98: 4040.

Sacramento, CA. Cisneros, J.J., and L.D. Godfrey. 2001.

Midseason pest status of cotton aphid (Homoptera: Aphididae) in California cotton. Is nitrogen a key factor.

Environ. Entomol. 30: 501-510.

Franco, J. and C.W. Cady. 1997.

Preventing nitrate groundwater contamination in California: A nonregulatory approach. J. Prod. Agric.

10:52-57.

Hutmacher, R.B., R.L. Travis, D.W. Rains, R.N. Vargas, B.A. Roberts, B.L. Weir, S.D. Wright, D.S. Munk, B.H. Marsh, M.P. Keeley, F.B. Fritschi, D.J. Munier, R.L. Nichols, and R. Delgado.

2004. Response of recent Acala cotton varieties to variable nitrogen rates in the San Joaquin Valley of California. Agron.

J. 96:48-62.

Silvertooth, J.C. and E.R. Norton. 1998.

Evaluation of a feedback approach to nitrogen and PIX applications. Cotton.

A College of Agriculture Report. Series P-112. Univ. Arizona, Tucson, AZ, p.

469-475.

Acknowledgments: Much of the funding for past nitrogen research in California was provided by Cotton Incorporated, the CA Cotton Alliance,

July/August 2017

and CA Cotton Growers and Ginners Associations. The following individuals were heavily involved in past research of the University of California on nitrogen management in cotton, and many of the recommendations or concepts mentioned in this article have roots in the work of and discussions with the following people: Robert Travis and William Rains, Professors of Agronomy, Emeritus, Dept. Plant Sciences, Univ. CA Davis; Ron N. Vargas, Univ. CA Coop.

Extension Farm Advisor—Madera and Merced Co’s; Bruce Roberts, Professor Emeritus, Dept. Plant Sci., CA State Univ. Fresno; Steve Wright, Univ. CA Coop. Extension Farm Advisor, Tulare and Kings Co’s; Dan Munk, Univ.CA Coop. Extension Farm Advisor, Fresno County; Bill Weir, Univ. CA Coop.

Extension Farm Advisor, Emeritus, Merced County; Brian Marsh, Univ. CA Coop. Extension Farm Advisor, Kern County; Mark Keeley, Staff Res. Assoc.

Dept. Plant Science, Univ. CA, Davis; Felix B. Fritschi, Research Asst-former, now Assoc. Professor, Univ. of Missouri; Doug J. Munier, Univ. CA Coop.

Extension Farm Advisor, Emeritus– Glenn County; Robert L. Nichols, Sr. Director, Agricultural Research, Cotton Incorporated, Cary, NC.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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