PRESSURE BOMB COMPARISON ACROSS ALL FIELDS

 The above figure for 2020 shows that the non-saline Eastside and Westside fields are closer than they were for 2019.  As of June, the semi-saline Mid Salt site is about -2 bars more SWP stress than the non-saline fields and the saline HiSalt site is about -4 bars more stress.  I can't say why, but as of July 23, the SWP for the MidSalt and HiSalt sites showed a virtually non-stressed value of -12 bars, the same as the Eastside Low Salt field.  The additional osmotic stress from the salt should cause an SWP that is at least -2 bars more stress than the non-saline field.

NON-SALINE EASTSIDE FIELD

AERIAL IMAGERY:  
The green to red image on the left indicates the volume and vigor of the canopy foliage as a Normalized Differential Vegetative Index (NDVI).  The right image shows the relative water stress across the orchard as calculated using the infrared canopy temperature.  The Demo monitoring is mostly for the western 80 acres in this image and the relative non-stressed SWP of about -12 bars makes sense with the mostly blue and green shown in this CERES water stress canopy temperature image.  However, we have a -17 bar SWP in the NE field and mostly yellow and red in the CERES image, which indicates stress.  This was not obvious from looking at the trees and this field was irrigated with almost exactly the same amount of water as the other fields.

TREE STRESS:  Using the tree as the continuous integrated moisture sensor is somewhat possible using a dendrometer that measures the real-time daily shrink/swell and growth of the tree.  The Phytech company is helping us do that by generating this average growth information in the below figure over three trees instrumented with dendrometers:

This is exactly the pattern that you want to see, up to mid-July – steadily increasing growth running 15-30 microns/day over the spring and early summer.  From Mid-June to July 17 these trees averaged 6000 microns (6 mm) additional radial growth.  That's a 12 mm, or almost ½ inch increase in trunk diameter.  The blue bars indicate the timing and duration of irrigation of this high frequency double-line drip system.  But from the end of July all growth ceases – probably due to the carbohydrate demand from the filling nuts.  You would still like to see a little growth but the good news is that the daily shrink/swell (shown by the daily high and low in the chart) is in the non-stressed range of 30-40 microns.

So what about the -17 bar SWP stress we measured on the NE block?  We are fortunate to have 3 dendrometers on this block also which show a similar steady growth increase through July, as we did with the west 80 acres, but the slope is a little less and erratic compared to the west 80 acres. This would confirm a bit more water stress in this block and as of August 1 the growth stalls out like the 80 acres, but as of August 5 some positive growth restarts – indicating either less stress or maybe a lighter crop load, which is consistent with visual observation in the field.

SOIL MOISTURE:

The ROOTZONE SUM chart below from the Jain Logic monitoring system using a Sentek Drill & Drop capacitance probe that measures soil moisture to a depth of 46 inches shows that the total root zone soil moisture has increased about 10% since the start of May.  The numbers on the left access are the sum of the percent soil moisture measured by each sensor placed every 4 inches.  If these numbers were absolutely accurate, it would mean that this Nord Series fine sandy loam soil would hold 42% water (5.0”/ft) at field capacity, which is impossibly high.  The correct number is about 28%, 3.4 inches/foot as measured by a neutron probe.  But the good news is that the trends in increased and decreased water content are very real and dependable.  So the infiltration chart (below right) is an accurate indicator of how deep water penetrates (dark blue columns) every irrigation.  This shows that the water only went to 46” one time over the last month, so there is virtually no deep percolation lost below the root zone.

NON-SALINE WESTSIDE FIELD

AERIAL IMAGERY:  Okay, this picture makes me feel a little more stressed than the Eastside CERES image – less blue and more yellow and red – especially around the edges and middle of the field at the ends of the hoses.  The SWP (numbers in white) are -1 to -2 bars more negative (stressed) then the eastside SWP but both blocks received almost the same irrigation (8.8 and 9.1”).  However, there is more windrun and higher ETo (potential evapotranspiration) across the westside Pleasant Valley area near Coalinga. This is also a 300-acre block with ½ mile rows N to S with only 2 hose runs of ¼ mile each that appear to show weak pressure and water delivery in the middle and at the N and S sides of this block.

TREE STRESS:  Unfortunately, cell phone/web reception at this field is not good and only a little of the Phytech dendrometers data came through.  However, the 4 days data show as good of growth as the best Eastside block but a higher amount of daily shrink/swell of the trunk.  This indicates that the tree has more stress on it moving the water up from the soil and out the leaf to meet ET during the day.  This could be due to the higher ETo of the Pleasant Valley area.

SOIL MOISTURE:  We have two sites in this field with instrumentation.  The NO COVER site below is 80 rows east of the west edge of the field with the soil classed as a Cerrini sandy loam.  The soil at this site is sandier than the Eastside field. The irrigation system is a single-line drip with four 1 gallon/hr drippers per tree.  Irrigation is typically a 24 hr set every other day starting in June.  The Root Zone Sum chart shows a fairly steady water content.  The Infiltration chart on the right shows a couple irrigations in July-August penetrated to 46” – less than the 5 irrigations to 46” in June.

The COVER crop site (below) is 30 rows from the eastern edge of the field and is a Calflax clay loam with a definitely higher water holding capacity than the Cerrini SL in the NO_COVER area.  This location and the NO_COVER location are in the same irrigation set, receiving water at the same time and duration – typically 24 hours.  But with a heavier soil, this site is showing water infiltrating nearly every irrigation as opposed to the sandy loam area just 50 rows to the east.  There is possibly a crack adjacent to a dripper that connects with the Sentek probe and pipes water down the side.  That said, this field now has the most negative SWP of all sites, averaging -13.5 bars, and with potentially the largest crop on the trees in the last 4 years and the hot wind that blows through Pleasant Valley, the grower is concerned about sufficient water for the nuts.  Therefore, starting July 24 (as you can see in the infiltration chart on the right) he has fired up another filter station running with canal water to irrigate the entire field (designed as a two set system) at one time – running for 6 days straight, off one day and then back on. Of all the sites to have a failure in the Phytech dendrometers, this is possibly the worst one.  Calculated flowrate for this 17x19 foot spacing with 4, 1 gph netafim button emitters/tree = 0.48 inches/day.

SEMI-SALINE, SALINE LEMOORE FIELD

AERIAL IMAGERY:  As expected, the significant variability in canopy growth caused by excess salt and poor soil structure in this field produces the lowest and most variable Normalized Differential Vegetative Index (NDVI, left) and usually more WATER STRESS than in any other field.  Should more leaching have been done during the winter to further reduce root zone salt loads?  Perhaps the grower could have done more, but he applied 10 inches during the winter, which takes forever to penetrate in this saline-sodic Lethent silty clay loam, and his June 2020 SWP was less negative than June 2019 and now the July 2019 shows even less stress than June.  This is square quarter-section field with a double-line high frequency automated drip system with two ¼ mile hose runs, running in 3 to 8 hour sets.  There is a distinct stress pattern along the hose ends in the center and N and S borders of this field very similar to what we saw in the non-saline westside field with similar lengths of hose run.  These are all pressure compensated drip emitters and any time I have checked the pressure at the hose end it is >12 psi which should be sufficient for max flow.  So I'm guessing more emitters just get clogged and don't clean out during flushing.  Maybe it would help to increase filter station/booster pressure and flush hoses more often.  The grower used to run longer sets but that exacerbated the waterlogging problem.

TREE STRESS, SEMI-SALINE:  Even though there is definite canopy size, ET and yield reduction in the best semi-saline area of this block compared to our non-saline fields, there was still excellent growth recorded by the Phytech dendrometers from May to July.  In fact, the three trees with dendrometers in the NE area (D05) of this block put on an average 10,000 microns (10 mm) additional radial growth.  That's a 20 mm, or ¾  inch increase in trunk diameter – the highest growth rate of all our monitoring sites even with extra stress from the salt!  Must be the seaweed extract this grower uses, hmmm.  That growth has slowed way down for July-August, but it has not stalled out – indicating minimal stress problems.

TREE STRESS, SALINE:  This severely affected saline area in the south central part of the block surprised us last year with about half the growth of the D05 Area.  Nevertheless, this year it has had essentially ZERO growth all season and even shows slight shrinkage for this July-August.  The shrink/swell change over 24 hours is also the largest of any site – measuring about 60-70 microns.

SOIL MOISTURE, SEMI-SALINE:  The second highest total Root Zone Summed water content is this area – reflecting a soil texture finer than any of the non-saline problem fields and very slow drainage through the profile. The deepest penetration during an irrigation is only 18”.  The impact of this anoxia, waterlogging, has just as much negative impact on pistachio growth as does the higher salinity.  Still, the trees need the water and this grower has increased hours per irrigation, while still allowing enough off time for at least some reoxygenation of the rootzone.

SOIL MOISTURE, SALINE:  The highest total Root Zone Summed water content is in this area (D03) of the field.  Frequently prone to ponding many trees have died here.  The deepest recorded irrigation penetration for any 3 to 8 hour event is 6”.  Installing an automated WiseCon irrigation system to run very short sets as often as daily has been the best strategy the grower found to reduce anaerobic conditions in the root zone and improve tree growth.