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A PILOT STUDY ON THE IMPACT OF AIR INJECTED
INTO WATER DELIVERED THROUGH SUBSURFACE
DRIP IRRIGATION TAPE ON THE GROWTH AND
YIELD OF BELL PEPPERS
California Agricultural Technology Institute
California State University, Fresno
Colleges of
Agriculture at
CALIFORNIA
STATE
UNIVERSITY,
FRESNO
CALIFORNIA
POLYTECHNIC
STATE
UNIVERSITY,
SAN LUIS O BISPO
CALIFORNIA
STATE
POLYTECHNIC
UNIVERSITY,
POMONA
CALIFORNIA
STATE
UNIVERSITY,
CHICO
by:
Dave Goorahoo
Genett Carstensen
Angelo Mazzei
Published by the
California Agricultural Technology Institute
February 2001 CATI Pub. #010201
Compiled by:
Dave Goorahoo
Genett Carstensen
and
Angelo Mazzei of Mazzei Injector Corp.
California Agricultural Technology Institute
California State University, Fresno
Fresno, California
A PILOT STUDY ON THE IMPACT OF AIR INJECTED INTO
WATER DELIVERED THROUGH SUBSURFACE DRIP IRRIGATION
TAPE ON THE GROWTH AND YIELD OF BELL PEPPERS
Design & Layout by:
Mike Rivera
Publications Assistant
California State University, Fresno
Acknowledgements ..................................................................................... v
Executive Summary..................................................................................... 1
Introduction .............................................................................................. 1
Procedure ................................................................................................. 3
Results .................................................................................................... 5
Discussion & Suggestions for Future Studies ....................................................... 7
Conclusion ................................................................................................ 9
Bibliography .............................................................................................. 9
List of Tables & Figures
Table 1: Scheduled weekly run times (calculated) ...................................................... 10
Table 2: Summary of actual run times and water applied (measured) ............................... 10
Table 3: Summary of injected air content measurements ............................................. 11
Table 4: Data from first picking dated July 31 .......................................................... 11
Table 5: Data from second picking dated August 28 ................................................... 12
Table 6: Data from third picking dated October 19 .................................................... 12
Figure 1: Supply manifold setup .......................................................................... 13
Figure 2: Plastic mulched plots showing dieback ....................................................... 13
Figure 3: Non-mulched plots showing a good stand and vigorous growth........................... 13
Figure 4: Peppers from the first harvest of location B18 ............................................. 14
Figure 5: Peppers from the third harvest of location A81 ............................................. 14
Figure 6: Total quantity of bell peppers picked during the study ..................................... 15
Figure 7: Total weight of peppers picked during the study ........................................... 15
Figure 8: Total quantity of peppers picked as a function of distance from supply mainfold .... 15
Figure 9: Total weight of peppers picked as a function of distance from supply manifold ...... 16
Figure 10: Total peppers harvested by location of aerated and non-aerated plots ................ 16
Figure 11: Total dry weights of roots, stems and leaves of mature pepper plants ................ 17
Figure 12: Representative root mass configuration of all plots (aerated and non-aerated) ..... 18
List of Appendicies
Appendix I: Irrigation layout, configuration, and harvest results ................................... 19
Appendix II: The Mazzei Injector ......................................................................... 21
Appendix III: Crop Log ..................................................................................... 23
Table of Contents
ACKNOWLEDGEMENTS
The following commercial organizations contributed to
the support of this research study:
Mazzei Injector Corp.
Angelo Mazzei, owner
Bakersfield, California
Contribution included a share of the project
expenses and the air injection equipment.
TORO Ag
El Cajon, California
Contribution included the drip tape
with related fittings.
Center for Irrigation Technology (CIT) project staff:
David F. Zoldoske, Ph.D., Director
Greg Jorgensen, Field Research Manager
Ed Norum, Ag Engineer
Dave Goorahoo, Ph.D., Soil Scientist
Genett Carstensen, Research Technician
Rafael Allende, Assistant Technician
Hector Llamas, Assistant Technician
Funding was also provided by the
California Agricultural Technology Institute (CATI).
This project would not have been possible without the
participation of all those listed above. Their contribution
is duly acknowledged.
V
A Pilot Study on the Impact of... Page 1
EXECUTIVE
SUMMARY
INTRODUCTION
Modifying root zone environments by injecting air has continued to
intrigue investigators. However, the cost of a single purpose, air-only
injection system, separate from the irrigation system, detracts from the
commercial attractiveness of the idea. With the acceptance of subsurface
drip irrigation (SDI) by commercial growers, the air injection system is at
least potentially applicable to the SDI system. Unfortunately, when air
alone is supplied to the SDI system it emits as a vertical “stream,” moving
above the emitter outlet directly to the soil surface. As a consequence, the
air affected soil volume is probably limited to a chimney column directly
above the emitter outlet. Balancing the air/water relationships as well as
changing soil temperature could affect growing conditions, yield, and time
of harvest, particularly in locations with limited growing seasons. The
This is a pilot study that attempts to apply scientific logic to a
concept for improving crop yield by injecting air into water delivered
through subsurface drip tape irrigation (SDI) systems. Small plots were
installed using TORO-Ag Aqua Traxx® drip tape as the irrigation method and
planted with bell peppers. A Mazzei® differential pressure injector was used
to supply air to the irrigation water at the rate of 12 percent air by volume.
The irrigation system was managed using California Irrigation Management
Information System (CIMIS) data to calculate weekly run times. After the
initial rounds to get the transplants rooted, the total water applied was 58
percent of the Reference Evapotranspiration (Eto). The plots were har-
vested three times with individual bell peppers counted and weighed. In all
three harvests, the aerated plots exceeded the non-aerated plots in both
bell pepper count and total weight. Combining the three harvest data sets
showed a 33 percent increase in bell pepper count and 39 percent increase
in total weight. An analysis of yield vs. location, as measured from the drip
tape inlet, suggested that the effect of the aerated water positively af-
fected production in the first 168 feet of bed length sampled in the study
(190 feet total length). The dry weight measurement of the root and shoot
mass indicated a statistically significant increase in weight for the plants
receiving aerated water as compared to the plants receiving water only. In
addition, there was a significant difference, at the p<0.001 level, between
the root weight to total plant weight ratios for the aerated plants (0.031)
and the non-aerated plants (0.021). The current findings justify follow-up
fieldwork on larger plots approaching commercial scale. However, any such
work should include monitoring additional parameters such as pepper
diameters and maturity; soil moisture content; soil oxygen content; soil and
plant nutrient status; crop canopy; and pressure and velocity measurements
along the irrigation system. These additional measurements would allow for
a more comprehensive investigation into any air-water slurry and soil-plant
relationships.
A Pilot Study on the Impact of...Page 2
concept of aerating the irrigation water increases the potential for the
air to travel with water movement within the root zone more generally
and affect crop growth.
Through work in other areas, the Mazzei Corporation has devel-
oped high efficiency venturi injectors capable of aerating water with
fine air bubbles. In previous work with growers on a commercial test plot
basis, the Mazzei Corporation has demonstrated bell pepper yield in-
creases of 12.8 percent and 8.1 percent for premium and processed bell
peppers, respectively. The value of the increased yield is, however,
partially offset by increased energy costs (see Appendix 1, Page 19).
This project is an initial effort to more scientifically characterize
the impact of aerated water on plant growth and yield. The main objec-
tives of the current pilot project were to (1) determine the impact of
air injected into water delivered through SDI on yield of bell peppers;
and (2) identify additional yield, soil and plant parameters that should
be monitored in any subsequent investigations. Favorable commercial
results could justify more scientific investigation of the root zone
environment. In the remainder of the introduction of this report, a
partial summary of the current understanding of root zone air, and a
brief description of the air injector technology are presented. This is
followed by a description of the experimental procedures, results, and
major conclusions with identification of research gaps for future work.
Root zone air: The spaces within a soil, known as soil pores, can
be filled with liquid and/or gases. Physical, chemical, and biological soil
characteristics that influence crop growth and yield depend on the
relative proportions of these two phases within the root zone. For
example, a soil that is well aerated will favor increased root respiration
and aerobic microbial activity (Mengel and Kirkby, 1982). Conversely, in
soils where the pores are filled with liquid, or waterlogged soils typical
of poor drainage, anaerobic conditions prevail. A brief review of the soil
science literature on the importance of oxygen (O2) in the root zone will
help in explaining the impact of root zone air.
Oxygen (O2) is essential for root respiration. Immediately after
the roots have been surrounded by water they can no longer respire
normally. The liquid impedes diffusion of metabolites such as carbon
dioxide and ethylene. This causes the plant to be stunted because
ethylene is a growth inhibitor (Arkin and Taylor, 1981). When air is
injected into the water within the root zone, diffusion of ethylene and
carbon dioxide away from the roots may be increased. This increased
diffusion rate should result in improved growing conditions.
Increased oxygen diffusion rates to the root have shown to
increase nitrogen (N2) fixation in legumes (Paul and Clark, 1989). Atmo-
spheric O2 concentrations greater than 20% have been found to increase
N2 fixation, but levels higher than 50% result in inhibition (Paul and
Clark, 1989). The supply of available carbon and the supply of O2 both
A Pilot Study on the Impact of... Page 3
PROCEDURE
have major effects on symbiotic fixation. The amount of adenosine
triphosphate (ATP) generated using a given quantity of O2 appears
greater when carbohydrate is oxidized than when hydrogen (H2) is
oxidized (Arkin and Taylor, 1981). Plants use ATP as the major carrier of
phosphate and growth energy. Furthermore, increased N2 fixation can be
attributed directly to an increase of atmospheric O2 in the root zone. The
first regions to suffer oxygen deficiency are the regions of highest
metabolic activity, such as the zones of cell division and elongation at
the end of the roots (Paul and Clark, 1989). Hence, adding air to the root
zone could result in less stress overall on the plants.
Oxygen is also essential for most soil microorganisms. It has been
estimated that in a fertile soil, microorganisms consume more O2 than
crop plants (Wolf, 1999). Hence, sufficient oxygen is important for soil
processes such as Nitrification and Ammonification, which involves the
Nitrosomonas and Nitrobacter species, respectively (Stevenson, 1982).
Shortages of O2 can lead to denitrification, whereby important amounts
of nitrogen are lost for crop production as nitrate is reduced to volatile
nitrogen compounds (Wolf, 1999). In addition, oxygen is also needed for
large groups of soil fauna. These include a number of insects, nema-
todes, mites, spiders and earthworms, which improve the soil physical,
biological and chemical properties.
The lack of air in the root zone from areas with low permeability
caused by high clay content in the soils has been well documented.
Although anaerobic soil conditions can be found worldwide, the most
common anaerobic soil conditions can be found in flooded areas (Mengel
and Kirkby, 1982). These anaerobic conditions are produced when the O2
that is carried in the water is depleted. The rate of O2 depletion can also
be influenced by the soil texture (Arkin and Taylor, 1981).
Injector Technology: As water under pressure enters the injec-
tor inlet (see Appendix 2, Page 21), it is constricted in the injection
chamber (throat) and its velocity increases. The increase in velocity
through the injection chamber, according to the Bernoulli equation, can
result in a decrease in pressure below atmospheric in the chamber. This
drop in pressure enables air to be drawn through the suction port and be
entrained into the water stream. As the water stream moves toward the
injector outlet, its velocity is reduced and the dynamic energy is recon-
verted into pressure energy. The aerated water from the injector is
supplied to the irrigation system. The fluid mixture delivered to the root
zone of the plant is best characterized as an air/water slurry.
In the initial experimental layout, the field plots consisted of
approximately 1/4 ac. of bell peppers with plastic film mulch compared
to approximately 1/4 ac. without plastic film mulch. The soil is classified
as a fine sandy loam. Within the half-acre experimental area there were
A Pilot Study on the Impact of...Page 4
8 pairs of rows approximately 380 ft. long. Each pair of rows was in a
bed configuration with beds and drip lines spaced 60-in. center to
center. Alternate beds were irrigated with aerated and non-aerated
water, respectvely. The bell pepper plant rows were offset 12 in. from
both sides of the drip line. The drip line was TORO-Ag® Aqua Traxx drip
tape (8 ml) rated 0.34 gpm per 100 ft. at 8 psi. Emitter spacing was 12-
in. center to center. Soil cover over the drip line was 5-6 inches. The
manifolds for each treatment were fitted with dual flowmeters, pres-
sure gauges and pressure regulators. The aeration manifold was fitted
with a Mazzei model 584 differential pressure injector (see Figure 1,
page 14). The Mazzei® injector gas inlet port was fitted with a throt-
tling valve and setup to attach to a rotometer capable of measuring
airflow rates up to 20 cubic feet per hour (CFH).
Pre-germinated bell pepper plants were planted on May 4, 2000
at a down-the-row spacing of 12 in. Plants were then monitored for
growth vigor and overall growing conditions in order to carry out
weeding and fertilizer applications (see Appendix 3, Page 23). Monitor-
ing parameters included number of dead or wilted plants, green color
and canopy cover for assessing vegetative growth, and proportion of
weeds in plots. Both mulched and unmulched plots were subject to the
same irrigation schedule.
An effort was made to maintain adequate levels of soil moisture
for the specific needs of pre-germinated plants especially given the
late planting date of May 2000 and the onset of relatively hot field
conditions. Early observations revealed that a high percentage of plants
were dying in the plastic film mulch plots. On closer inspection, the
stalks seemed to be atrophied at the point where they emerge from the
plastic mulch (see Figure 2, Page 13). Probable causes for this atrophy
include root fungi, viral infection, mechanical action of the plant stalk
rubbing against the plastic film, and sunlight reflection. Excess soil
water because of the mulch preventing evaporation may also be a
reason for death of plants. In any case, it was obvious that the mulched
plots required a different irrigation regimen than the un-mulched plots.
With a common manifold, this was impossible. Given the poor stand in
the mulched plots and the inherent manifold restriction, the mulched
plots were abandoned. The non-mulched plots exhibited a good stand
and vigorous growth (see Figure 3, Page 13), and were therefore used
for the rest of this study.
Early irrigations were made as needed to maintain a moist root
zone. As the pre-germinated plants took root it was possible to sched-
ule irrigation at 7-day intervals. Calculated run times were modified as
needed to ensure the wetting front moved the 12 inches from the drip
line to the plant in order to provide contact with the plant’s root
system. Table 1 (Page 10) gives a summary of the irrigation schedules.
The Reference Evapotranspiration (Eto) was obtained from a California
A Pilot Study on the Impact of... Page 5
RESULTS
Irrigation Management Information System (CIMIS) station on the Califor-
nia State University, Fresno campus. The canopy factor was developed
by field observations. The crop factor (Kc) was taken from the literature.
A system efficiency of 80% was assumed. The actual water applied, as
determined from flowmeter readings, is shown in Table 2 (Page 10).
While no root zone or plant stress measurements were made, the plants
did not appear to be significantly stressed at any time.
Previous field experience, suggested that air to water volume
ratio should be 0.11 to 1.0 (11% gas to liquid). Table 3 (Page 11) gives a
summary of field measurements taken during irrigation rounds. Control
over the injected air was good with a mean value of 12% and a range of
11.0 to 13.5%.
The plots had a total of 8 rows, consisting of 4 receiving aerated
water and 4 receiving non-aerated water. Rows 1, 2, 5 and 6 received
aerated water and the others received non-aerated water. Rows 1 and 8
were considered as guard rows and were not involved in the test harvest-
ing. Row 2 (aerated) and row 3 (non-aerated) were paired together and
designated as “A” pair. Likewise, rows 4 & 5 were designated “B” pair
and rows 6 & 7 were designated “C” pair. Using a table of random num-
bers, four 10-ft. sections of test rows were identified in each A, B, & C
pair and harvested for data collection and analyses. These 12 sample
plots were accepted only if there were similar numbers of plants in the
aerated and non-aerated treatments. Harvest data was coded to identify
location. For example, B18A was from Pair B, 18 ft. from the drip line
inlet and “A” for aerated. Data identified as C149W would be from Pair
C, 149 ft. from the inlet, and “W” for non-aerated (water only). Peppers
were harvested three times during the growing season at 88, 116 and 168
days after planting. At the end of the final harvest, one aerated and one
non-aerated plant from each of the twelve sample plots were examined
for root and shoot (stem and leaves) mass. The representative plants
were dug up, washed clean, separated into above and below ground
portions, oven dried, and weighed.
Tables 4, 5, and 6 (pages 11-12) give the descriptive statistics of
the harvest data for the 1st, 2nd, and 3rd pickings, respectively. Only
saleable peppers within the 10-ft. section of rows were used in the data
analyses. Saleable peppers were defined as those with no sunburn, no
insect holes, and at least 50 grams. For each 10-ft. section, the following
parameters were determined: Mean weight of individual bell peppers in
grams; Median weight of individual bell peppers in grams; Sum, in grams,
of all saleable bell peppers collected; Count, the number of bell peppers
harvested; Largest, the weight of largest pepper in grams; and, Smallest,
the weight of the smallest bell pepper in grams. Photographs were taken
A Pilot Study on the Impact of...Page 6
of the bell peppers harvested at each location for all three harvests.
Figures 4 and 5 (Page 14) show representative samples.
It was possible to harvest saleable peppers from all locations at
88, 116 and 168 days after planting (Tables 4, 5, and 6), with the
exception of the second picking at location C38 for the plots receiving
water only (Table 5). Average weights (± standard deviation) for the
aerated and non-aerated peppers were 103.7 (± 12.02) and 99.4 (±
11.49) grams respectively. Based on a t-test statistic performed at the
95% probability level, there was no significant difference between
mean weights of bell peppers from the aerated and non-aerated treat-
ments. Weights of saleable peppers ranged from 50.57 grams (at
B18,Table 5) to 285.51 grams (at A81, Table 6) for plants receiving water
only, and from 50.55 grams to 440.81 grams (at A81,Table 6) for plants
receiving both air and water. The lowest number of saleable peppers
was obtained during the second picking, conducted 116 days after
planting (Table 5). The highest number of bell peppers from a given
sample plot was 67, and this was obtained during the third picking of
the aerated peppers at location A81 (Table 6).
When the three pickings were combined, the aerated plants
had a production increase in both the number (Figure 6, Page 15) and
total weight (Figure 7, Page 15). Because of the similarity in the mean
weight of individual bell peppers from the aerated and non-aerated
treatments, this production increase was due primarily to differences in
the number of peppers from the different treatments. There were 212
more peppers, equivalent to a 33% increase, harvested from the aer-
ated plots compared to plots that received only water (Figure 6). The
aerated plants had a production increase of approximately 25.4 kg, a
39% increase, over the non-aerated plants (Figure 7). A paired t-test
indicated that there was a significant difference, at the p<0.01 level,
between the number of saleable peppers harvested from the aerated
and non-aerated treatments at the various sampling locations. The
mean total numbers (± standard deviation) of bell peppers harvested
during the study from the aerated and non-aerated sample plots were
71.5 (± 19.0) and 54.25 (± 14.38), respectively.
Indexing the sections of rows harvested from supply manifold
along the drip tape provides an opportunity to evaluate possible posi-
tion effects. Figures 8 and 9 (pages 15-16) show the distribution of the
total quantity and total weight of bell peppers picked, respectively, as
a function of distance from the supply manifold. Generally, there was
increased production from the beginning of the row to a maximum
value at the 81-foot location. Yield then decreased down the row to a
minimum value at the 168 feet location. As indicated above, the
difference in production was due mainly to number of peppers in each
plot. An attempt was made to curve fit the total pepper count versus
location data, in order to ascertain a model to describe a relationship
A Pilot Study on the Impact of... Page 7
between these two parameters (Figure 10, Page 16). For the aerated
irrigation treatment (Figure 10a), the relationship was best described by
2
005.078.08.57 xxy −+= Eq.1
where y is the total pepper count and x is the distance (feet) from
source. The non linear regression given by Eq.1 had an r2 = 0.54 and was
significant at the p<0.01 level. For the water only treatment, there was
no significant correlation between the total pepper count and distance
(Figure 10b).
The final part of this study involved examination of the dry
weights of roots, stems and leaves of mature pepper plants. When the
total root and shoot dry weights of the plant material from the twelve
test plots were combined, it was found that (1) the aerated plants had a
root weight increase of 17.53 grams, equivalent to a 54% increase, over
the water only plants (Figure 11a, Page 17); and (2) the aerated plants
had a stem and leaf weight increase of 68.98 grams, equivalent to a 5%
increase, over the water only plants (Figure 11b). More importantly,
there was a significant difference (p<0.001) between the root dry
weight: total plant dry weight ratio (R:P) for the aerated and non aer-
ated treatments. The ratio, R:P, was calculated for each of the 12
locations using [root dry weight] divided by [root dry weight + stem and
leaves dry weight]. For the aerated plants, R:P ranged from 0.025 to
0.04 with a mean of 0.031 and standard deviation of 0.005. For the non-
aerated plants, R:P ranged from 0.014 to 0.032 with a mean of 0.021 and
standard deviation of 0.006. Assuming that water and nutrient availability
were adequate for both the aerated and non-aerated plants, the increase
in proportion of root mass in the aerated plants could be attributed to
the air injection. Greater root mass is most likely associated with greater
surface area of root material within the soil, thereby permitting the
roots increased accessibility to water and nutrient supply. Ultimately, the
plants can utilize the increased water and nutrients to produce more
peppers. Figure 12 (Page 18) shows typical root mass configurations for
samples from the aerated and non-aerated plots.
All the above data analyses were conducted on saleable peppers.
Throughout this pilot study, harvesting of peppers was dictated mainly by
the availability of personnel. This limitation resulted in a relatively
small, but possibly significant, number of peppers being culled because
they were classified as non-saleable. In subsequent studies, it is recom-
mended that adequate labor and budgetary provisions are available to
allow more frequent sampling. In addition, all peppers harvested should
be used in order to investigate the impact of the various treatments on
other yield parameters besides pepper weights, pepper numbers and
DISCUSSION &
SUGGESTIONS
FOR FUTURE
STUDIES
A Pilot Study on the Impact of...Page 8
plant dry weight. For example, any correlation between aerated and
non-aerated treat-ments on pepper size and susceptibility of peppers to
insect attack could be investigated. Furthermore, subsequent studies
should look at the impacts of the air-water slurry injection on the yield
and growth of other vegetable crops.
In addition to yield parameters, future studies should also
investigate any inter-relationships between the air/water treatments
and soil, water and plant properties. For example, during the pilot
study there appeared to be a more extensive crop canopy for the plants
receiving the aerated irrigation. This probably influenced the number
of bell peppers that were sun burnt. Hence, there is a need to quantify
the degree of crop canopy associated with the various treatments.
Although some plant dry weight analyses were conducted in the present
study, it will be useful to adopt other monitoring technologies, such as
using a digital imaging camera to quantify the degree of crop cover
throughout the course of the investigation. Because of the interactive
effects of air, water and nutrient availability on crop yields, any future
studies should involve monitoring of soil moisture, as well as soil and
plant tissue nutrient analysis. Soil temperature and O2 content should
also be monitored. In addition to root dry weight, root analysis should
include both chemical and physical methods to assess any nutrient and
structural differences, respectively, as a result of the air injection.
The quadratic relationship between the total pepper count and
distance from air injection source (given by Eq.1) instead of a linear
relationship may be indicative of the fact that air and water are not the
only factors influencing the bell pepper yields. Subsequent studies
should therefore incorporate additional parameters such as pressure
and velocity measurements along the drip tape. In addition, nutrient
status of the soil in the harvested plots should also be monitored,
especially since the fertilizers were added in the irrigation water. By
incorporating these additional parameters, it may be possible to better
describe any relationship between pepper yield and distance from the
supply manifold.
Further experiments should include additional instrumentation
and some modification to the experimental design used in the current
study. In order to monitor soil water content frequently, either Time
Domain Reflectometry (TDR) probes or moisture blocks should be
installed within the plant rows. Instrumentation for monitoring pressure
and water velocity at intervals along the irrigation lines would be
helpful in being able to investigate the influence of these parameters
as a function from the inlet of the air and water mixture.
With respect to improvement in experimental design, follow-up
studies should have increased row lengths and at least one more
sampling plot located at the end of the crop row. In commercial terms,
the drip tape lengths in this study are relatively short (approximately
A Pilot Study on the Impact of... Page 9
BIBLIOGRAPHY
CONCLUSION
190 ft.) compared to production fields with up to 640 ft. or more. It is
possible that longer runs would result in a better assessment of any
relationship between the impact of air injection on yield and distance
from source. Finally, crop rows should be oriented in an East-West
direction, unlike the North-South direction used in the current study, to
mitigate the adverse effects of prolonged exposure to sunlight on the
bell peppers.
The study shows that delivering aerated water to the plant root
zone through subsurface drip lines resulted in a 33% increase in num-
ber, and a 39% increase in the weight of bell peppers produced. There
were also significant increases in the dry weights of root and shoots
from plants receiving aerated water as compared to plants receiving
water only. These statistically significant results on a small plot (0.10
ac.) support reported results obtained on tests conducted on a com-
mercial farm, and are sufficiently encouraging to justify follow-up
fieldwork on larger plots. Further fieldwork should be performed on
various plant types and should include air/water ratio, and soil root
zone moisture, temperature, and nutrient status measurements. Of
special interest in the potential application of this air injection tech-
nology is the characterization of how the beneficial effect may vary
with the length of drip lines. Subsequent studies should attempt to
monitor pressure and velocity changes along the drip system and
correlate these with plant yield and soil parameters.
Arkin G. F.: Modifying the Root Environment to Reduce Crop Stress.
American Society of Agricultural Engineers, 141–150 (1981)
Mengel K. and Kirkby E. A.: Principles of Plant Nutrition, 3rd Edition,
International Potash Institute Bern, Switzerland, 44-50 (1982)
Paul E. A. and Clark F.E.: Soil Microbiology and Biochemistry, Harcourt
Bruce Jovanovich, publishers, 182–188 (1989)
Stevenson F. J.: Nitrogen in Agricultural Soils. Agronomy Series
No. 22: ASA, CSSA, SSSA, Madison, WI. (1992)
Wolf B.: The Fertile Triangle, The Interrelationship of Air, Water,
and Nutrients in Maximizing Soil Productivity. Haworth
Press, Inc. New York, Ch 1 (1999)
A Pilot Study on the Impact of...Page 10
Table 1: Scheduled weekly run times (calculated).
Date Interval Eto
(#) (days) (in.) (%) (Kc) (in) (in/hr) (hours)
1 5/30/2000 7 1.88 80 0.5 0.94 0.061 19.26
2 6/6/2000 7 1.98 80 0.5 0.99 0.063 19.64
3 6/13/2000 7 0.95 80 0.5 0.47 0.064 9.18
4 6/20/2000 7 1.99 80 0.5 0.995 0.059 6.33
5 6/27/2000 7 2.05 80 0.5 1.025 0.059 10.68
6 7/3/2000 7 2.16 80 0.5 1.08 0.065 20.176
7 7/10/2000 7 1.86 80 0.5 0.93 0.053 23.25
8 7/17/2000 7 1.97 80 0.5 0.99 0.061 20.63
9 7/24/2000 7 1.97 80 0.5 0.99 0.059 20.63
10 7/31/2000 7 1.99 80 0.5 0.995 0.059 21.08
11 8/7/2000 7 1.87 80 0.5 0.935 0.063 18.55
12 8/14/2000 7 1.81 80 0.5 0.905 0.057 19.85
13 8/21/2000 7 1.81 80 0.5 0.905 0.066 19.85
14 8/28/2000 7 1.65 80 0.5 0.825 0.065 15.86
15 9/5/2000 7 1.17 80 0.5 0.585 0.065 11.25
16 9/12/2000 7 1.46 80 0.5 0.73 0.067 13.62
17 9/18/2000 7 1.31 80 0.5 0.655 0.068 12.04
18 9/26/2000 7 1.14 80 0.5 0.57 0.063 11.3
Totals 31.02 14.819 293.18
ETo = Reference Evapotranspiration
Effs = System Efficiency
Kc = Crop Coefficient
ETc = Crop Evapotranspiration
ETo x Kc = RA
Run time =( RA / Effs ) / Appl. Rate
Appl.
Rate
Sch. Run
Time
Sch.
Round
Effs
Crop
Factor
Req.
Appl.
(RA)
Table 2: Summary of actual run times and water applied (measured).
Actual
Round
Begin
Round
End
Round
Vol.
Applied
Actual
Applied
Date
(#) (hours) (gal.) (gal.) (gal.) (in.)
1 5/30/2000 21 21 13106.1 13106.1 1.3
2 6/6/2000 20 13106.1 23987.1 10881 1.1
3 6/13/2000 10 23987.1 30757.6 6770.5 0.7
4 6/20/2000 10 30757.6 37668 6910.4 0.7
5 6/27/2000 10.7 37667.9 43606.7 5938.7 0.6
6 7/3/2000 21 43606.7 54310.9 10704.2 1.1
7 7/10/2000 10 54310.9 66226.3 11915.4 1.2
8 7/17/2000 20.7 66226.3 76885.2 10659 1.1
9 7/24/2000 20.7 76885.2 89815.4 12930.2 1.3
10 7/31/2000 21.1 89815.4 103381 13565.5 1.3
11 8/7/2000 18 103381 117765 14384.3 1.4
12 8/14/2000 13.2 117765 127618 9852.9 1
13 8/21/2000 17.1 127618 135666 8047.7 0.8
14 8/28/2000 15.6 135666 143995 8328.9 0.8
15 9/5/2000 10.6 143995 149223 5228.6 0.5
16 9/12/2000 13.6 149223 160720 11496.5 1.1
17 9/18/2000 12 160720 173828 13108.3 1.3
18 9/26/2000 11.3 173828 181883 8055.5 0.8
Totals 276.6 181883 18
Actual
Run
Time
A Pilot Study on the Impact of... Page 11
Table 4: Data from first picking dated July 31 (88 days after planting).
Location
B18A A20A A36A C38A B54A A81A B97A C100A B118A C149
A
Mean 116.5872 122.4032 117.5026 113.9157 114.4658 112.6753 111.4374 120.9987 107.2705 97.76
9
Median 113.655 121.71 115.48 111.53 110.5 108.33 109.65 119.35 99.995 9
3
Sum 3730.79 3427.29 5052.61 6379.28 2747.18 3830.96 2117.31 5565.94 2359.95 1
2
Count 322843562434194622
Lar
g
est 170.51 177.39 168.21 199.01 166.49 194.39 152.18 185.08 182.05 1
3
Smallest 84.5 86.98 81.73 80.97 80.61 80.19 83.4 80.5 83.69 8
3
Location
B18W A20W A36W C38W B54W A81W B97W C100W B118W C149
W
Mean 106.5004 115.5877 131.9113 106.2713 105.1663 112.0169 107.7894 102.3711 115.385 104.0
2
Median 101.585 109.58 132.8 106.25 101.8 109.21 98.32 97.38 108.245
9
Sum 2769.01 4507.92 2110.58 2550.51 1682.66 3248.49 1832.42 1842.68 2076.93 176
8
Count 263916241629171818
Lar
g
est 157.95 204.78 195.16 146.66 170.77 155.93 181.03 137.09 158.99 16
7
Smallest 82.26 80.33 85.67 81.25 80.02 82.69 82.11 70.05 80.45 8
1
Aerated Rows
Non-Aerated Rows
Table 3: Summary of injected air content measurements.
Irrig. Date #1 Flow
Rate
#2 Flow
Rate
Average
Flow
Rate
System
Pressure
(1)
(#) (gpm) (gpm) (gpm) (psi) (cfh) (%)
1 5/30/2000 5.05 5.15 5.1 10 6.0 12.8
2 6/6/2000 5.4 5.2 5.3 10 6.0 12.0
3 6/13/2000 5.4 5.2 5.3 10 6.0 12.0
4 6/20/2000 5.1 4.9 5.0 10 6.0 13.0
5 6/27/2000 6 5.1 5.5 10 5.5 11.0
6 7/3/2000 5.9 5.1 5.5 10 6.0 12.0
7 7/10/2000 5.5 4.9 5.2 10 5.5 11.6
8 7/17/2000 5.5 4.9 5.2 10 5.5 11.7
9 7/24/2000 5.1 4.9 5.0 10 5.5 12.0
10 7/31/2000 5.1 4.9 5.0 10 5.5 12.0
11 8/7/2000 5.8 4.9 5.3 10 5.5 11.0
12 8/14/2000 4.9 4.7 4.8 10 6.0 13.5
13 8/21/2000 6.1 5 5.6 10 6.0 11.8
14 8/28/2000 6.1 5 5.6 10 6.0 11.8
15 9/5/2000 6.1 5 5.6 10 6.0 11.8
16 9/12/2000 6.4 5.1 5.7 10 6.0 11.5
17 9/18/2000 6.4 5.1 5.7 10 6.0 11.6
18 9/26/2000 5.7 5 5.3 10 6.0 12.3
Average 12
(1) Supply pressure to drip manifold
Water Meter Reading Pressure Read
Air
Injected
Flow
Rate
Injected
Air
Content
A Pilot Study on the Impact of...Page 12
Table 5: Data from second picking dated August 28 (116 days dater planting)
Location
B18A A20A A36A C38A B54A A81A B97A C100A B118A C
Mean 101.84 97.903 95.55111 108.873 100.9406 90.194 127.2638 97.11643 117.0216 9
8
Median 86.81 94.37 100.51 104.63 95.72 83.4 118.685 94.055 105.49
Su
m
305.52 1958.06 859.96 1088.73 1715.99 450.97 1018.11 1359.63 2925.54
Count 3 20 9 10 17 5 8 14 25
Lar
g
est 138 122.92 109.44 158.55 145.04 109.68 175.43 131.53 177.76
Smalles
t
80.71 80.48 82.66 82.79 82.32 80.05 85.92 80.92 82.48
Location
B18W A20W A36W C38W B54W A81W B97W C100W B118W C
1
Mean 90.43333 84.545 99.94667 0 99.42111 99.738 117.1107 94.865 101.4358
Median 90.74 84.545 96.6 0 97.76 96.42 118.24 98.585 91.21
Su
m
542.6 169.09 599.68 0 894.79 1496.07 1639.55 758.92 1927.28
Count 626091514819
Lar
g
est 102.73 86.66 123.29 0 120.98 132.2 153.95 102.1 146.98
Smalles
t
80.08 82.43 80.51 0 80.35 84.16 81.33 81.83 82.45
Aerated Rows
Non-Aerated Rows
Table 6: Data from third picking dated October 19 (168 days after planting)
Location
B18A A20A A36A C38A B54A A81A B97A C100A B118A C
1
Mea
n
105.2804 80.15143 79.842 104.8786 86.33324 95.59672 109.1994 109.4971 102.6804 9
1
Media
n
96.735 74.51 74.18 104.07 78.87 89.21 86.1 99.61 90.005
Su
m
2947.85 2244.24 1996.05 2307.33 2935.33 6404.98 3385.18 3394.41 2875.05
2
Coun
t
28 28 25 22 34 67 31 31 28
Lar
g
est 211.53 140.49 142.23 166.43 152.17 440.81 291.56 202 203.65
Smalles
t
50.64 51.45 52.75 53.37 54.63 50.55 54.43 53.57 51.55
Location
B18W A20W A36W C38W B54W A81W B97W C100W B118W C
1
Mea
n
84.8119 85.85314 85.60053 79.47118 96.50313 110.8425 103.6356 95.73757 94.505 9
0
Media
n
80.87 82.53 80.65 71.68 101.745 95.51 99.915 91.76 92.455
Su
m
1781.05 3004.86 1626.41 1351.01 1544.05 3546.96 3523.61 3542.29 2835.15
2
Coun
t
21 35 19 17 16 32 34 37 30
Lar
g
est 133.28 155.11 124.96 127.94 169.93 285.51 209.85 172.21 163.2
Smalles
t
50.57 52.87 50.91 55.87 52.85 55 52.23 51.26 52.66
Aerated Rows
Non-Aerated Rows
A Pilot Study on the Impact of... Page 13
Figure 1
Supply manifold setup.
Note: The differential pressure
injector in the lower center of
the photograph between the
pressure gauges.
Plastic mulched plots showing
the dieback.
Figure 2
Figure 3
Non-mulched plots showing
a generally good stand and
vigorous growth. This is an
example of a plot sampled
for yield.
A Pilot Study on the Impact of...Page 14
Peppers from the third
harvest from location A81
for (a) aerated (A81A) and
(b) non-aerated (A81W)
treatments.
Figure 5
Figure 4: Peppers from the
first harvest from location
B18 for (a) aerated (B18A)
and (b) non-aerated (B18W)
treatments.
Figure 4 (A)
(B)
(A)
(B)
A Pilot Study on the Impact of... Page 15
Figure 7
Figure 8
Figure 6
Total quantity of bell peppers
picked during study (all plots).
Total weight (grams) of bell
peppers picked during the
study (all plots).
Total quantity of peppers
picked as a function of
distance from supply
manifold.
A Pilot Study on the Impact of...Page 16
Figure 9
Figure 10
Total weight (grams) of
peppers picked as a function
of distance from supply
maniford.
Total peppers harvested by
location for (a) aerated and
(b) non-aerated irrigation plots. (A)
(B)
A Pilot Study on the Impact of... Page 17
Figure 11
(a) Total dry weight (grams)
of roots of mature bell
pepper plants.
(b) Total dry weight (grams)
of stems and leaves of
mature bell pepper plants
(A)
(B)
A Pilot Study on the Impact of...Page 18
Figure 12
Representative root mass
configurations at locations 81A
and B18A (aerated plots) and
A81W and B18W (non-
aerated plots).
(A)
(B)
A Pilot Study on the Impact of... Page 19
Appendix I
Mazzei AirJection® Irrigation
Patent # 6,173,526
Johnston Farms - Bell Pepper Test
Summer 2000
Planting - March 2000
Field Acreage - 66.96
(38.11 Control Acres & 28.85 AirJection® Acres)
Bell Pepper Variety - Baron
Soil Type - Loam to Sandy Loam
Both the Non-Aerated Control and AirJection® Aerated plots used the following irrigation layout:
Sub-surface drip tape (3.40 gpm / 1000 ft) buried 5 inches deep
98 rows x 40" spacing x 640' per block = 213 gpm total water flow per block
The AirJection® Aerated test plot used the following configuration to supply the air/water mixture:
6 - Model 3090 Mazzei AirJection® irrigation units
90+ % of the water flows through the injector
Pressure at the injector = 60 psig
Pressure at the tape = 12 psig
A Pilot Study on the Impact of...Page 20
Appendix I
(cont.)
End of Season Harvest Results - September 2000
Non-Aerated Control Acreage = 38.11 AirJection® Aerate
d
Green Premium Red Premium Red Processed Total Total Red Processed
22.38 17.72 43.26 83.36 Bins /Acre 91.96 46.74
403 319 778 150
0
Cartons/A cre 165
5
841
11194 8861 21611 41666 Lbs ./Acre 4597
2
23361
Premium Cartons/Acre Control = 722 AirJection® = 814
Processed Cartons/Acre Control = 778 AirJection® = 841
** 1 bin = approximately 18 cartons = 500 lbs. **
Conclusions
Premium production INCREASE per AirJection® aerated acre = 92 Cartons = 2556 lbs., an increase of 12.8%.
Processed production INCREASE per AirJection® aerated acre = 63 Cartons = 1750 lbs., an increase of 8.1%.
Total production INCREASE per Ai rJect ion® aerated acre = 155 Cartons = 4306 lbs., an increase of 10.3% .
Premium INCREASE in yield = 92 cartons per acre at an average price of $5.00 per carton = $460.00 per acre
($5.00 per carton is after deducting harvest, packing, and carton costs)
Processed INCREASE in yield = 63 cartons per acre at an average price of $1.25 per carton = $78.75 per acre
Total INCREASE in income = $538.75 per acre
Additional energy costs for water pressure increase to operate the AirJection® units = $46.94 per acre
(1.04 kW per acre x 450 hours x $0.10 per kWh)
A Pilot Study on the Impact of... Page 21
Mazzei Injector Corporation
Mazzei injectors (patented) are extremely efficient,
compact differential pressure injection devices currently
operating successfully in thousands of installations
worldwide. Mazzei Injectors offer a reliable, accurate,
and economical method to inject virtually any liquid or
gas substance into a pressurized fluid stream.
Function
How Mazzei Injector works
When a pressurized operating (motive) fluid enters
the injector inlet, it is constricted toward the injection
chamber and changes into a high velocity jet stream.
The increase in velocity through the injection chamber
results in a decrease in pressure, thereby enabling
an additive material to be drawn through the suction
port and entrained into the motive stream. As the
jet stream is diffused toward the injector outlet, its
velocity is reduced and it is reconverted into pressure
energy (but at a pressure level lower than injector
inlet pressure).
Mazzei Injectors are extremely efficient. They operate
over a wide range of pressures and require only a
minimal pressure differential between the inlet and
outlet sides to initiate a vacuum at the suction port.
Advantages
· Molded from high quality thermoplastics with
superior strength, high temperature capability,
resistant to most chemicals.
· No moving parts, low-maintenance trouble-tree
operation
· Unique design allows maximum cavitation in
the injection chamber, thereby providing
instantaneous mixing
· Ideally suited for continuous mixing functions,
require no secondary blending devices
· Initial cost and installation cost are low
· Powered by the motive fluid, no external energy
required for most installations
· Available in a broad range of sizes, flows and
injection capacities
Appendix II
Mazzei Injector
A Pilot Study on the Impact of...Page 22
Applications
The highly versatile Mazzei Injectors are suitable for a
wide variety of applications.
Agriculture
Ag Irrigation Systems — to inject fertilizers and other
chemicals or water treatment additives.
Ag Spray Systems — for mixing and/or the transfer of
concentrated pesticide materials
Food Processing — for water chlorination, injection of
detergents, bacterial agents, other water treatment or
purification additives
Home and Garden
Irrigation Systems — for application of liquid fertilizer
through landscape sprinkler or drip irrigation systems,
hose-end sprinklers and/or spray nozzles.
Industrial/Commercial
Water Treatment — to inject air, liquids, gases
(ozone), and other water purification chemicals for
cooling tower or other water or fluid recirculatory
systems, waste water systems, potable water systems.
Washing & Cleaning — to inject detergents, solvents
and other cleaning agents into carpet cleaning
equipment, car wash systems, dishwashing
equipment and other industrial cleaning processes.
Pools and Spas — to inject ozone or chlorine gas for
water purification of swimming pools and spas.
Specialty Applications — to aerate or mix liquids,
to exhaust vapors or gases, to saturate liquids with
gases, to elevate water or other fluids to use as
vacuum control device.
Appendix II
(cont.)
A Pilot Study on the Impact of... Page 23
Crop Log
5/30/00
New transplants doing poorly, many dying
6/6/00
Yellow – green and struggling
6/13/00
Fertilized with 10 gal. CAN17
6/20/00
Good color in plants.
6/27/00
Needs weeding
7/3/00
Big weeds
7/10/00
Weeded on Friday
Fertilized with 10 gal. CAN17
7/17/00
Fertilized with 5 gal. UN32
7/24/00
Ready for harvest
Appendix III
7/31/00
First Harvest
8/21/00
Peppers ready for harvest
8/28/00
Second Harvest
9/5/00
Plants look good
9/26/00
Plants look full
10/2/00
Rain
310/19/00
Third Harvest
11/10/00
Plants Picked for Dry Weight
