Malheur Experiment Station
|
Information for Sustainable Agriculture
|
IRRIGATION FREQUENCY, DRIP TAPE FLOW RATE, AND ONION PERFORMANCE
Clinton C. Shock, Erik Feibert, and Lamont Saunders
Malheur Experiment Station
Oregon State University
Ontario, OR, 2003
Introduction
Onion production with subsurface drip irrigation has proven at
the Malheur Experiment Station to be highly productive on sites that
are difficult to irrigate. In 1997 and 1998 onions were submitted to
five soil water potential treatments using an automated, high frequency
irrigation system (Shock et al. 2000a). The soil water potential was
maintained relatively constant by applying 0.06 inch of water up to
eight times a day, depending on soil water potential readings. The soil
water potential at 8-inch depth that resulted in maximum onion yield,
grade, and quality after storage was determined to be -20 kPa. An
irrigation frequency of up to eight times a day in small increments is
not feasible on a commercial scale. Would reducing the irrigation
frequency result in lower water use efficiencies and lower onion yield
and quality?
The drip tape that has been used at the Malheur Experiment
Station has a flow rate of 0.22 gal/min/100 ft of tape. A reduced flow
rate could theoretically result in an improved soil wetting pattern and
less water lost to deep percolation. An improved soil wetting pattern
could result in the onions on the outside row of a double row receiving
more uniform soil moisture. New "ultra low flow" drip irrigation tapes
with reduced emitter flow rates are being introduced by drip tape
manufacturers. This trial tested four irrigation frequencies and two
drip tape flow rates for their effect on onion yield and quality.
Materials and Methods
The onions were grown at the Malheur Experiment Station,
Ontario, Oregon on an Owyhee silt loam previously planted to wheat.
Onion (cv. 'Vaquero', Sunseeds, Morgan Hill, CA) was planted in two
double rows, spaced 22 inches apart (center of double row to center of
double row) on 44-inch beds on March 17, 2003. The rows in the "double
row" were spaced 3 inches apart. Onion was planted at 150,000
seeds/acre. Drip tape (T-tape, T-systems International,
San Diego, CA) was laid at 4-inch depth between the two double onion
rows on March 28. The distance between the tape and the double row was
11 inches. The drip tape had emitters spaced 12 inches apart and either
of two flow rates: low flow (0.22 gal/min/100 ft) and ultra low flow (0.11 gal/min/100 ft).
Immediately after planting the onion rows received 3.7 oz of
Lorsban 15G per 1,000 ft of row (0.82 lb ai/acre), and the soil surface
was rolled. Onion emergence started on April 7. The trial was irrigated on April 14 with a
minisprinkler system (R10 Turbo Rotator, Nelson Irrigation Corp., Walla
Walla, WA) for even stand establishment. Risers were spaced 25 ft apart
along the flexible polyethylene hose laterals, which were spaced 30 ft
apart.
Onion tissue was sampled for nutrient
content on June 19. The roots from 25 onion plants taken from plot
border rows representative of the field were washed with deionized
water and analyzed for nutrient content by Western Labs, Parma, Idaho.
The onions in all treatments were fertilized according to the nutrient
analyses (Table 1). Fertilizer was applied through the drip tape:
ammonium sulfate at 25 lb N/acre on May 30, urea ammonium nitrate
solution at 25 lb N/acre on June 5, 16, and 25, and zinc chelate at
0.25 lb Zn/acre and copper chelate at 0.2 lb Cu/acre on June 25.
Roundup at 24 oz/acre was
sprayed on March 28. The field had Prowl (1lb ai/acre) broadcast on
April 21 for postemergence weed control. Approximately 0.4 inch of
water was applied through the minisprinkler system on April 21 to
incorporate the Prowl. The field had Buctril at 0.12 lb ai/acre
and Poast at 0.4 lb ai/acre applied on April 28. Thrips were controlled
with one aerial application of Warrior on June 5 and two aerial
applications of Warrior (0.03 lb ai/acre) plus Lannate (0.4 lb ai/acre)
on July 16 and August 4.
The experimental design was a randomized complete
block with four replicates. The onions were submitted to eight
treatments consisting of a combination of two drip tape flow rates and
four daily irrigation frequency/duration treatments (Table 2). The
onions in each plot (four double rows by 50 ft) were submitted to one
irrigation frequency and one tape flow rate. The irrigation frequencies
were the daily time interval by which the datalogger (CR10, Campbell
Scientific, Logan, UT) checked the sensors and made irrigation
decisions. Each plot was irrigated independently when the average soil
water potential at 8-inch depth in the plot reached -20 kPa. The
irrigation durations for each treatment were adjusted so that when
irrigated the maximum number of times, all treatments had the capacity
to deliver a maximum of 0.48 inch of water per day.
Soil water potential was measured in each plot
with four granular matrix sensors (GMS, Watermark Soil Moisture Sensors
Model 200SS, Irrometer Co., Riverside, CA) installed at 8-inch depth in
the center of the double row. Sensors were calibrated to swp (Shock et
al. 1998a). The GMS were connected to the datalogger via five
multiplexers (AM 410 multiplexer, Campbell Scientific, Logan, UT). The
datalogger read the sensors and recorded the soil water potential every
3 hours. The irrigations were controlled by the datalogger using a
controller (SDM CD16AC controller, Campbell Scientific, Logan, UT)
connected to solenoid valves in each plot. The pressure in the drip
lines was maintained at 10 psi by pressure regulators in each plot. The
amount of water applied to each plot was recorded daily at 8:00 a.m.
from a water meter installed between the solenoid valve and the drip
tape. The automated drip irrigation system was started on May 22.
Irrigations were terminated on September 2.
Onion evapotranspiration (Etc)was calculated with a modified Penman equation
(Wright 1982) using data collected at the Malheur Experiment Station by an AgriMet weather
station. Onion Etc was estimated and recorded from crop emergence on April 7 until the final irrigation.
On September 11 the onions were lifted to field
cure. On September 17, onions in the central 40 ft of the middle two
double rows in each subplot were topped and bagged. The bags were
placed into storage on September 29. The storage shed was managed to maintain an air temperature
of approximately 34°F. Onions were graded on December 11.
During grading bulbs, were separated according to quality: bulbs
without blemishes (No. 1s), split bulbs (No. 2s), neck rot (bulbs
infected with the fungus Botrytis allii in the neck or side), plate rot
(bulbs infected with the fungus Fusarium oxysporum), and black mold (bulbs infected with
the fungus Aspergillus niger). The No. 1 bulbs were graded according to diameter: small
(<2¼ inches), medium (2¼-3 inches), jumbo (3-4 inches), colossal
(4-4¼ inches), and supercolossal (>4¼ inches).
Bulb counts per 50 lb of supercolossal onions were determined for each
plot of every variety by weighing and counting all supercolossal bulbs
during grading.
Results
In the analysis of variance, the year effect was significant for
total marketable and jumbo onion yields, both being higher in 2002. The
yield of the larger bulb size classes was limited in these trials by
the high plant population (Shock et al. 2004). While the yields are
above the county average, they are in the range achieved by growers
using drip irrigation.
There was no interaction between emitter type or irrigation
frequency and year, so the results are analyzed and discussed as the
average over the 2 years. Averaged over irrigation frequencies, the
drip tape with 0.13 gal/hour emitters had significantly higher total
yield, marketable yield, and colossal onion yield than the tape with
0.07 gal/hour emitters (Table 2). Averaged over emitter type, the once
per day irrigation frequency (0.48 inch of water applied per
irrigation) had among the highest total and marketable onion yields.
Averaged over emitter type, the once per day irrigation frequency
resulted in the highest colossal onion yield.
There was no significant difference in average soil water
potential between treatments (Table 2). The standard deviation of the
soil water potential increased with decreasing irrigation frequency,
reflecting the higher amplitude of soil water potential oscillation
around the criteria of -20 kPa (Table 2, Figs. 1 and 2). There was no
significant difference in total water applied between treatments, with,
on average, 32 and 28 inches applied in 2002 and 2003, respectively.
Onion Etc from emergence to the last irrigation totaled 30.2 and 32 inches in 2002 and
2003, respectively. The total amount of water applied includes 2 and 0.52 inches of water
applied with the minisprinkler system after emergence, and 0.84 and
1.28 inches of precipitation, in 2002 and 2003, respectively.
Water applications to all treatments closely followed Etc during the season
(Figs. 3 and 4).
Discussion
An explanation for the increased bulb size with the
lowest irrigation frequency could be that, since the lowest irrigation
frequencies had the highest amplitude of soil water potential
oscillation, the onions might have responded to the soil becoming
wetter during irrigations than with the lower irrigation frequencies.
Our past research has shown that onions will respond to irrigation
criteria higher than -20 kPa with increased bulb size (Shock et al.
1998b, Shock et al. 2000b). An irrigation criteria higher than -20 kPa
is not recommended on silt loam soils, because of the unpredictability
of onion storage quality, which in some years can be low with
irrigation criteria higher than -20 kPa.
The results of this study suggest that the drip tape with 0.066
gal/hour emitters should not be recommended for onion production in the
Treasure Valley, since onion yield and size were lower and there were
no apparent irrigation benefits.
References
Shock, C.C., J.M. Barnum, and M. Seddigh. 1998a. Calibration
of Watermark Soil Moisture Sensors for irrigation management. Pages
139-146 in Proceedings of the International Irrigation Show, Irrigation Association, San
Diego, CA.
Shock, C.C., E.B.G. Feibert, and L.D. Saunders.
1998b. Onion yield and quality affected by soil water potential as
irrigation threshold. HortScience 33:1188-1191.
Shock, C.C., E.B.G. Feibert, and L.D. Saunders. 2000a. Irrigation criteria for drip-irrigated
onions. HortScience 35:63-66.
Shock, C.C., E.B.G. Feibert, and L.D. Saunders. 2004. Plant
population and nitrogen fertilization for subsurface drip-irrigated
onion. HortScience: In Press.
Shock, C.C., J.K. Ishida, E.P. Eldredge, and L.D. Saunders.
2000b. Yield of yellow onion cultivars in eastern Oregon and
southwestern Idaho. HortTechnology 10:613-620.
Wright, J.L. 1982. New evapotranspiration crop coefficients. J. Irrig. Drain. Div.,
ASCE 108:57-74.
Table 1. Onion root nutrient concentrations on June 19, 2003.
Malheur Experiment Station, Oregon State University, Ontario, OR.
| Nutrient |
Sufficiency range* |
Analysis |
| NO3 (ppm) |
6,200 |
4,251 |
| P (%) |
0.32 - 0.70 |
0.59 |
| K (%) |
2.7 - 7.0 |
4.95 |
| S (%) |
0.24 - 1.4 |
0.61 |
| Ca (%) |
0.4 - 1.6 |
1.69 |
| Mg (%) |
0.3 - 0.6 |
0.41 |
| Zn (ppm) |
32 - 100 |
27 |
| Mn (ppm) |
35 - 100 |
91 |
| Cu (ppm) |
8 - 30 |
8 |
| Fe (ppm) |
60 - 250 |
448 |
| B (ppm) |
19 - 80 |
27 |
*supplied by Western Labs, Parma, ID.
Table 2. Effect of irrigation
frequency and drip tape emitter flow rate on onion yield and size,
Malheur Experiment Station, Oregon State University, Ontario, OR.
Emitter flow rate |
Irrigation frequency |
Irrigation duration |
Water applied |
Avg soil water potential |
Total yield |
Marketable yield |
| Per irrigation |
Total |
Total |
Super colossal |
Colossal |
Jumbo |
Medium |
| gal/h |
h |
h |
(inch) |
(inch) |
(kPa) |
(cwt/acre) |
(cwt/acre) |
(cwt/acre) |
(cwt/acre) |
(cwt/acre) |
(cwt/acre) |
2002 |
|
|
|
|
|
|
|
|
|
|
|
| 0.13 |
3 |
1 |
0.06 |
32.7 |
-20.3 ! 3.1 |
1,042 |
1028 |
6 |
239 |
764 |
20 |
| 0.13 |
6 |
2 |
0.12 |
32.2 |
-19.9 ! 3.4 |
985 |
970 |
11 |
192 |
738 |
30 |
| 0.13 |
12 |
4 |
0.24 |
32.6 |
-20.3 ! 3.5 |
1,041 |
1,028 |
9 |
192 |
800 |
28 |
| 0.13 |
24 |
8 |
0.48 |
31.5 |
-18.8 ! 4.1 |
1,052 |
1,028 |
16 |
287 |
708 |
16 |
| Avg |
|
|
|
32.3 |
-19.8 |
1,030 |
1,014 |
10 |
227 |
753 |
24 |
|
|
|
|
|
|
|
|
|
|
|
|
| 0.066 |
3 |
2 |
0.06 |
32.6 |
-19.8 ! 2.9 |
969 |
952 |
13 |
185 |
736 |
18 |
| 0.066 |
6 |
4 |
0.12 |
31.2 |
-21.2 ! 3.9 |
994 |
972 |
3 |
190 |
751 |
28 |
| 0.066 |
12 |
8 |
0.24 |
32.9 |
-19.8 ! 4.2 |
977 |
958 |
10 |
178 |
746 |
24 |
| 0.066 |
24 |
16 |
0.48 |
31.5 |
-19.9 ! 5.4 |
1,041 |
1,025 |
11 |
213 |
778 |
23 |
| Avg |
|
|
|
32.0 |
-20.2 |
995 |
977 |
9 |
192 |
753 |
23 |
|
|
|
|
|
|
|
|
|
|
|
|
| Avg over tape types |
3 |
|
0.06 |
32.7 |
-20.0 |
1,005 |
990 |
9 |
212 |
750 |
19 |
| 6 |
|
0.12 |
31.8 |
-20.4 |
989 |
971 |
8 |
191 |
744 |
29 |
| 12 |
|
0.24 |
32.7 |
-20.1 |
1,009 |
993 |
10 |
185 |
773 |
26 |
|
24 |
|
0.48 |
31.5 |
-19.4 |
1,047 |
1,027 |
14 |
256 |
738 |
19 |
2003 |
|
|
|
|
|
|
|
|
|
|
|
| 0.13 |
3 |
1 |
0.06 |
28.5 |
-18.0 ! 2.7 |
861 |
846 |
17 |
164 |
649 |
17 |
| 0.13 |
6 |
2 |
0.12 |
28.0 |
-19.4 ! 3.0 |
880 |
846 |
9 |
211 |
610 |
16 |
| 0.13 |
12 |
4 |
0.24 |
27.7 |
-18.9 ! 3.3 |
902 |
894 |
6 |
194 |
677 |
18 |
| 0.13 |
24 |
8 |
0.48 |
29.2 |
-17.4 ! 4.5 |
947 |
925 |
26 |
269 |
615 |
15 |
| Avg |
|
|
|
28.4 |
-18.4 |
897 |
878 |
14 |
209 |
637 |
17 |
|
|
|
|
|
|
|
|
|
|
|
|
| 0.066 |
3 |
2 |
0.06 |
26.9 |
-18.9 ! 2.8 |
849 |
834 |
2 |
138 |
673 |
20 |
| 0.066 |
6 |
4 |
0.12 |
28.8 |
-18.9 ! 2.4 |
805 |
786 |
16 |
150 |
599 |
22 |
| 0.066 |
12 |
8 |
0.24 |
24.9 |
-19.6 ! 3.3 |
940 |
901 |
5 |
186 |
692 |
18 |
| 0.066 |
24 |
16 |
0.48 |
31.1 |
-18.7 ! 4.1 |
882 |
859 |
13 |
197 |
630 |
19 |
| Avg |
|
|
|
27.9 |
-19.0 |
869 |
845 |
9 |
168 |
649 |
20 |
|
|
|
|
|
|
|
|
|
|
|
|
| Avg over tape types |
3 |
|
0.06 |
28.0 |
-18.5 |
855 |
840 |
10 |
151 |
661 |
18 |
| 6 |
|
0.12 |
28.3 |
-19.2 |
842 |
816 |
12 |
180 |
605 |
19 |
| 12 |
|
0.24 |
26.8 |
-19.2 |
921 |
897 |
6 |
190 |
684 |
18 |
|
24 |
|
0.48 |
29.9 |
-18.1 |
914 |
892 |
19 |
233 |
622 |
17 |
| 2002-2003 avg |
|
|
|
|
|
|
|
|
|
|
|
| 0.13 |
3 |
1 |
0.06 |
29.9 |
-18.8 |
952 |
937 |
11 |
201 |
706 |
18 |
| 0.13 |
6 |
2 |
0.12 |
29.8 |
-19.6 |
932 |
908 |
10 |
201 |
674 |
23 |
| 0.13 |
12 |
4 |
0.24 |
29.8 |
-19.5 |
972 |
961 |
7 |
193 |
738 |
23 |
| 0.13 |
24 |
8 |
0.48 |
30.0 |
-17.9 |
1,000 |
976 |
21 |
278 |
662 |
16 |
| Avg |
|
|
|
29.9 |
-18.9 |
964 |
946 |
12 |
218 |
695 |
20 |
|
|
|
|
|
|
|
|
|
|
|
|
| 0.066 |
3 |
2 |
0.06 |
29.8 |
-19.2 |
909 |
893 |
8 |
162 |
705 |
19 |
| 0.066 |
6 |
4 |
0.12 |
30.0 |
-19.6 |
886 |
866 |
10 |
167 |
664 |
24 |
| 0.066 |
12 |
8 |
0.24 |
28.9 |
-19.7 |
958 |
930 |
8 |
182 |
719 |
21 |
| 0.066 |
24 |
16 |
0.48 |
31.3 |
-19.1 |
950 |
930 |
12 |
204 |
693 |
21 |
| Avg |
|
|
|
30.0 |
-19.4 |
926 |
905 |
9 |
179 |
695 |
21 |
|
|
|
|
|
|
|
|
|
|
|
|
| Avg over tape types |
3 |
|
0.06 |
29.8 |
-19.0 |
930 |
915 |
9 |
181 |
705 |
19 |
| 6 |
|
0.12 |
29.9 |
-19.6 |
911 |
889 |
10 |
185 |
669 |
24 |
| 12 |
|
0.24 |
29.5 |
-19.6 |
965 |
945 |
8 |
187 |
729 |
22 |
|
24 |
|
0.48 |
30.5 |
-18.5 |
976 |
955 |
17 |
244 |
676 |
18 |
| LSD (0.05) Emitter |
|
|
NS |
NS |
36 |
34 |
NS |
4 |
NS |
NS |
| LSD (0.05) Water applied |
NS |
NS |
50 |
48 |
9 |
50 |
44 |
1 |
| LSD (0.05) Emitter X Water applied |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
| LSD (0.05) Emitter X Water appl. X Year |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
Figure 1. Soil water potential over time for drip-irrigated onion
using a tape flow rate of 0.22 gal/min/100 ft and four irrigation
frequencies (time interval used by datalogger for checking sensors and
making irrigation decisions). Soil water potential is the average of 16
sensors. Malheur Experiment Station, Oregon State University, Ontario,
OR, 2003.
Figure 2. Soil water potential over time for drip-irrigated onion using a tape
flow rate of 0.11 gal/min/100 ft and four irrigation frequencies (time
interval used by datalogger for checking sensors and making irrigation
decisions). Soil water potential is the average of 16 sensors. Malheur
Experiment Station, Oregon State University, Ontario, OR, 2003.
Figure 3. Cumulative water applied and Etc
over time for drip-irrigated onion using a tape flow rate of 0.22
gal/min/100 ft and four irrigation frequencies. Water applied is the
average of four plots. Malheur Experiment Station, Oregon State
University, Ontario, OR, 2003.
Figure 4. Cumulative water applied and Etc over time
for drip-irrigated onion using a tape flow rate of 0.11 gal/min/100 ft
and four irrigation frequencies. Water applied is the average of four
plots. Malheur Experiment Station, Oregon State University, Ontario,
OR, 2003.
MES
Publications, MES
Notice of events, Vegetation,Malheur County, Leslie Gulch,Succor Creek,Owyhee River,Local wildlife,Strawberry
Mountain, Eagle
Caps
For
additional information about the Malheur Agricultural Experiment
Station, please send an e-mail request to:
Dr. Clinton C. Shock
Clinton.Shock@oregonstate.edu
Malheur Agricultural Experiment
Station
595 Onion Avenue
Ontario, OR 97914
(541) 889-2174
FAX (541) 889-7831
Last updated
Tuesday June 28, 2011.
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