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Continued from Page 39 ing. Using SWP alone, along with the interpretive guidelines presented in this article, gives relatively straightforward insights to the question of when to irrigate and with experience, perhaps how long to irrigate. However, trial and error may not suffice in some situations, and SWP measurements alone may not provide enough information. For example, pressure chamber measurements can show low crop stress in April, May, and early June in orchards, even though irrigation has been postponed or reduced. The trees consume water stored in the root zone from winter rainfall or winter irrigation during this period to satisfy their water requirements. Without some monitoring of soil moisture or tracking of ET, it is possible to experience a sudden and rapid increase in tree water stress in July, August, and September. Meanwhile, a drip or microsprinkler irrigation system will not have the capacity to apply enough water to recharge the soil moisture depletion and sufficiently relieve tree stress. This can be a problem particularly in orchards where soils have slow water infiltration. Irrigation should be initiated before the stored water is depleted excessively. Using SWP in conjunction with soil moisture monitoring or a water budget (or both) can also help overcome some common limitations of soil moisture monitoring and irrigating according to ET. SWP readings that indicate low tree stress, even though soil moisture sensors indicate dry soil, might suggest that trees are getting water from greater depths in the root zone that are not being monitored by soil moisture sensors. This situation could indicate a need for deeper soil moisture monitoring or placing soil moisture sensors in more representative locations. Similarly, SWP readings that indicate desirable levels of tree stress, even when a water budget indicates under-irrigation, suggest the need to reexamine assumptions about ET rates, rooting depth, and available moisture reserves. In a different situation, SWP mea- Continued on Page 42 SWP range (bars) General Stress Level Baseline consideration Water stress symptoms in almond -2 to -6 None (Likely above typical baseline) -6 to -8 Minimal At or near baseline under normal or cool weather conditions -8 to -12 Minimal to Mild -12 to -16 Mild to Moderate -16 to -20 Moderate to High At or near baseline under hot, dry conditions, but may be 2 to 4 bars below baseline under normal or cool conditions May be 2 to 4 bars below baseline under hot, dry conditions, but may be 4 to 6 bars below baseline under normal or cooler weather Within 6 to 8 bars below baseline -20 to -30 High to Severe Within 8 to 20 bars below baseline Below -30 Extreme (Substantially below baseline under all conditions) (Not commonly observed) Typical in March and April. Indicates soil moisture is not limiting. If sustained, higher incidence of root and foliar diseases and tree loss may occur. Favors rapid shoot growth and fruit sizing in orchards when minimal crop stress is sustained from April through mid-June. Suggested mild levels of stress during late June, July, and early August. Shoot growth slowed but fruit sizing unaffected. May help manage energy and irrigation costs. Should be avoided until fruit sizing is completed. Appropriate for late August after fruit sizing is completed. Imposing moderate to high levels of crop stress by reducing irrigation about two weeks before harvest may increase sugar content in fruit and reduce moisture content or “dry-away” (fruit drying costs). More likely to occur in late August and early September during and after harvest. Extended periods of high crop stress before harvest will result in defoliation and exposure of limbs and fruit to sunburn. Extended periods of high stress after harvest may also negatively affect the condition of trees going into dormancy. Extended periods of severe crop stress should be avoided. Trees will defoliate and be exposed to sunburn, increasing the risk of canker diseases. Potentially shorten productive life of orchard. Table 4. SWP levels in prune, consideration of how SWP might compare to baseline values under various weather conditions, and the corresponding water stress symptoms to expect. 40 Progressive Crop Consultant September/October 2017
ADVERTORIAL Ensure season-long control of pre- and post-emergent weeds WEEDS REDUCE TREE HEALTH AND CROP QUALITY. Weeds compete with trees and vines for nutrients, water and light and can impact yield and hinder harvesting practices. Weeds can even compete with target plants for uptake of insecticides and other chemicals, making the crop more susceptible to insects and disease. While cultural and mechanical practices can provide some help in managing weed pressures, most growers utilize herbicides to deal with major threats. Whether or not resistant weeds are currently present, having an integrated approach to weed control can mean the difference to bottom lines. Key weeds present in orchards and vineyards have been found to be resistant to glyphosate. A best practice to slow down weed resistance to herbicides includes using multiple effective modes of action in your pre- and post-emergent herbicide sprays. WEEDS RESISTANT TO GLYPHOSATE Alion ® and Rely ® 280 weed program from Bayer are complementary pre- and post-emergent herbicides for tree nuts, grapes and citrus that effectively eliminate tough grass and broadleaf weeds with long-lasting residual control and excellent crop safety. Together, Alion and Rely offer versatile application approaches to ensure you start and stay weed-free. Horseweed Hairy Fleabane Jungle Rice Russian Thistle CROP SAFETY Keep crop safety in mind when selecting a weed management program. Choose pre- and post-emergent herbicides that provide excellent season-long weed control without impact on roots, fruit or plant vigor. UNIVERSITY OF CALIFORNIA EXTENSION RESEARCH SHOWS: Using Alion ® and Rely ® together results in season-long weed control JUNGLE RICE CONTROL 100% HAIRY FLEABANE CONTROL 99% RYEGRASS CONTROL 90% Application included Alion 3 oz. + Rely + Roundup ® Application included Alion 3.5 oz. + Rely Application included Alion 5 oz. + Rely University Trial for Jungle Rice Control by Brad Hanson, UC Statewide Weed Scientist in Chico, CA, 2014 University Trial for Hairy Fleabane and Ryegrass Control by Brad Hanson, UC IPM, Arbuckle, CA, 2015 Learn more at CropScience.Bayer.us ® © 2017 Bayer CropScience LP, 2 TW Alexander Drive, Research Triangle Park, NC 27709. Bayer, the Bayer Cross, Alion, and Rely are registered trademarks of Bayer. Roundup is a registered trademark of Monsanto Technology LLC. Always read and follow label instructions. Not all products are registered for use in every state. For additional product information, call toll-free 1-866-99-BAYER (1-866-992-2937) or visit our website at www.CropScience.Bayer.us. September/October 2017 www.progressivecrop.com 41
Page 1 and 2: September/October 2017 The Pressure
Page 3 and 4: 4 UPCOMING EVENTS: South Valley Nut
Page 5 and 6: atmosphere (less than -40 bars). Lo
Page 7 and 8: ADVERTORIAL THE GROWING THREAT OF H
Page 9 and 10: The importance of bagging or coveri
Page 11 and 12: Liquid Nutrients High Phos TM 8-25-
Page 13 and 14: the entire foliar canopy can collap
Page 15 and 16: Symptoms Macrophomina Fusarium Phyt
Page 17 and 18: ADVERTORIAL Higher Almond Yields wi
Page 19 and 20: Table: Active ingredients and trade
Page 21 and 22: site-specific, pre-application reco
Page 23 and 24: need to have the following items:
Page 25 and 26: PUT YOUR ALMONDS TO BED WITH THE RI
Page 27 and 28: Figure 3 (pg. 26) perfectly illustr
Page 29 and 30: ADVERTORIAL NEMATODES: ROOT HEALTH
Page 31 and 32: even if the human eye cannot see th
Page 33 and 34: Please Visit us at the CAPCA Confer
Page 35 and 36: CE Credits Offered CCA: 4 Hours PCA
Page 37 and 38: CE Credits Offered CCA: 4 Hours PCA
Page 39: and SWP may also assist with minimi
Page 43 and 44: Why Activate? • Highly concentrat

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