Malheur Experiment Station
|
Information for Sustainable Agriculture
|
TREATMENT OF ONION BULBS WITH "SURROUND" TO REDUCE TEMPERATURE AND BULB SUNSCALD
Clinton C. Shock, Erik B. G. Feibert, and Lamont D. Saunders
Malheur Experiment Station
Oregon State University
Ontario, OR, 2003
Introduction
Onion prices generally decrease starting in September when harvest
intensifies. Harvesting earlier from overwintered, transplanted,
or normally planted full season onions could increase profits, but
mechanized early harvest runs the risk of increased losses to
sunscald. Sunscald occurs when the side of the bulb exposed to
afternoon sun becomes excessively hot. Sunscald results in a
flattened and shrunken area on the bulb surface. The
59-year-average maximum air temperature at the Malheur Experiment
Station is 91, 90, and 80°F for July, August, and September,
respectively. Maximum air temperatures in July and August often
exceed 100°F, which can result in very high unprotected bulb
temperatures and result in sunscald. "Surround" (Engelhard
Corp., Iselin, NJ) is a product made from kaolinite clay and works by
forming a white coating on surfaces, thus reflecting solar
radiation. "Surround" is a wettable powder that is labeled for
reduction of sunscald in fruits and vegetables. Application of
"Surround" after onions are lifted could reduce sunscald and make early
mechanized harvests more feasible.
Methods
The trial was conducted in two fields.
Procedures for Growing Onions in Field 1
The onions were grown with subsurface drip irrigation 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 on March 17, 2003. The procedures can be found in
the article "Effect of Short Duration Water Stress on Onion
Single Centeredness and Translucent Scale" found in this report (Shock
et al. 2004a).
Procedures for Growing Onions in Field 2
The onions were grown with furrow irrigation on a Greenleaf silt loam
previously planted to wheat. Onion seed ('Vaquero' Sunseeds,
Parma, ID) was planted on March 17, 2003. The procedures can be
found in the article "2003 Onion Variety Trials" found in this
report (Shock et al. 2004b).
Procedures for Surround Treatments
Four rows of onions in each field were lifted on August 11. The
lifted onions were divided into plots 25 ft long. The
experimental designs were randomized complete blocks with four
replicates in each field. There were seven treatments:
treatment 1 was untreated, treatment 2 received one "Surround"
application after lifting, treatment 3 received a "Surround"
application after lifting and windrowing, and treatment 4 was treated
after windrowing (Table 1). Treatments 5-7 were the same as
treatments 2-4, except that a different formulation of "Surround" was
used. The "Surround" formulation (type 2) used for treatments 5-7
was made to be more light reflecting than type 1. The "Surround"
was applied after lifting on August 11 with a ground sprayer and a boom
with 9 nozzles spaced 10 inches apart. The "Surround" was applied
at 50 lb/acre in 112 gallons of water per acre with 8004 nozzles at 40
psi.
Prior to the "Surround" application temperature probes were installed
in bulbs at 0.5-cm depth. The temperature probes in the monitored
bulbs were positioned so that they faced to the south-southeast and
placed in a position receiving direct sun. Three replicates in
the drip-irrigated field and two replicates in the furrow-irrigated
field each had one bulb monitored for temperature. The
temperature probes were read hourly by a datalogger (Hobo datalogger,
Onset Computer Corp., Bourne, MA).
On August 14 the temperature probes and probed onions were removed and
the onions were topped and windrowed by hand. After windrowing
the temperature probes were reinserted in different onions as
before. The onion windrow was sprayed with "Surround" using a
ground sprayer with 3 nozzles spaced 10 inches apart. Application
rates and specifications were the same as the initial "Surround"
application. Since only the windrow was sprayed (one-third of the
field), only 17 lb of "Surround" were actually used per acre of onions.
The onions were bagged on August 21 and placed into storage. On
December 11 the onions were graded. Bulbs were separated
according to quality: bulbs without blemishes (No. 1s), bulbs with
sunscald damage, double 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 by
weighing and counting all supercolossal bulbs during grading.
To reduce the influence on the statistical analysis of the variability
in onion yield and size between plots, the data for each field were
normalized in relation to the average total yield for that field.
Normalized data were subjected to analysis of variance.
Results and Discussion
The highest air temperature reached after lifting of the onions and
before topping and windrowing was 93°F (Table 2). The highest
bulb temperature reached after lifting of the onions and before topping
and windrowing was 123°F. Following the application of
"Surround" after lifting, average maximum bulb temperatures were
reduced 4-5°F compared to the untreated bulbs. There was no
difference in maximum bulb temperature between "Surround" types, except
on August 11, when only "Surround" type 2 reduced maximum bulb
temperature.
The highest air temperature reached after topping and windrowing was
99°F (Table 3). The highest bulb temperature reached after
topping and windrowing was 121°F. For the onions treated with
"Surround" after topping and windrowing, average maximum bulb
temperatures were reduced by 2-4°F compared to the untreated
check. There was a trend for "Surround" type 2 to reduce bulb
temperatures more than "Surround" type 1, but the difference was only
significant on August 15, when "Surround" type 1 did not reduce bulb
temperatures compared to the check.
The furrow-irrigated field (field 2) had higher marketable yield, and
yield of onions with sunscald and rot than the drip-irrigated field
(field 1, Table 4). In the furrow-irrigated field, one or two
applications of "Surround" type 1 and application of "Surround" type 2
before and after windrowing or only after windrowing, resulted in
significantly higher marketable onion yield (Table 4). Averaged
over the two fields, one or two applications of "Surround" type 1 and
application of "Surround" type 2 before and after windrowing or only
after windrowing resulted in significantly higher marketable onion
yield. In the furrow-irrigated field, one or two applications of
either type of "Surround" resulted in lower bulb rot. Averaged
over the two fields, one or two applications of "Surround" type 1 and
application of "Surround" type 2 before and after windrowing or only
before windrowing resulted in lower yield of onions with
sunscald. Averaged over the two fields, two applications of
"Surround" type 1 or type 2, and application of "Surround" type 2 after
windrowing resulted in lower bulb rot.
References
Shock, C.C., E.B.G. Feibert, and L.D. Saunders. 2004a. Effects of
short-duration water stress on onion single centeredness and
translucent scale. Malheur Experiment Station Annual Report, Oregon
State University Agricultural Experiment Station Special Report
1055:53-56.
Shock, C.C., E.B.G. Feibert, and L.D. Saunders. 2004b. 2003 onion
variety trials. Malheur Experiment Station Annual Report, Oregon State
University Agricultural Experiment Station Special Report 1055:36-44.
Table 1. Treatments applied to onions to evaluate two types of
"Surround". "Surround" type 2 is a new formulation designed to be
more reflective of sunlight. Malheur Experiment Station, Oregon
State University, Ontario, OR, 2003.
Treatment
|
Surround type
|
Post lifting Surround application |
Post topping
and windrowing Surround application |
1
|
none
|
No
|
No |
2
|
1
|
Yes
|
No |
3
|
1
|
Yes
|
Yes |
4
|
1
|
No
|
Yes |
5
|
2
|
Yes
|
No |
6
|
2
|
Yes
|
Yes |
7
|
2
|
No
|
Yes |
Table 2. Maximum daily air temperature and maximum bulb
temperature (°F) at 0.5-cm depth for onions treated with two types
of "Surround" after lifting. "Surround" type 2 is a new
formulation designed to be more reflective of sunlight. Malheur
Experiment Station, Oregon State University, Ontario, OR, 2003.
Date
|
Maximum air temperature |
Solar radiation
|
Surround type
|
Surround type |
Surround type |
LSD (0.05) |
|
|
|
none
|
1
|
2 |
|
11 Aug
|
93
|
7259
|
120.6
|
118.1
|
114.9
|
(3.3)* |
12 Aug
|
92
|
7226
|
119.9
|
115.2
|
113.5
|
2.3 |
13 Aug
|
93
|
7245
|
123.0
|
118.5
|
118.2
|
2.6 |
Average
|
|
|
121.2
|
117.0
|
116.7
|
(2.8)* |
*significant at the 0.10 level.
Table 3. Maximum daily air temperature, solar radiation, and
maximum bulb temperature (°F) at 0.5-cm depth for onions treated
with two types of "Surround" after topping and windrowing.
"Surround" type 2 is a new formulation designed to be more reflective
of sunlight. Malheur Experiment Station, Oregon State University,
Ontario, OR, 2003.
Date
|
Maximum air temperature
|
Solar radiation
|
Surround type
|
Surround type |
Surround type |
LSD (0.05) |
|
|
|
none
|
1
|
2 |
|
14 Aug
|
96
|
6446
|
119.1
|
116.9
|
116.8
|
1.5 |
15 Aug
|
99
|
5345
|
115.0
|
113.8
|
112.8
|
1.7 |
16 Aug
|
90
|
7262
|
112.6
|
113.5
|
109.8
|
NS |
17 Aug
|
91
|
7114
|
117.2
|
118.2
|
112.7 |
NS |
18 Aug
|
94
|
6898
|
118.6
|
na
|
116.2
|
NS |
19 Aug
|
98
|
6593
|
121.1
|
na
|
118.7
|
NS |
20 Aug
|
93
|
6969
|
118.5
|
na
|
112.8
|
3.2 |
Average
|
|
|
117.3
|
114.6
|
113.8
|
1.3 |
Table 4. Onion yield and grade response to application of two types of
"Surround" in a drip-irrigated field (field 1) and in a
furrow-irrigated field (field 2). "Surround" type 2 is a new
formulation designed to be more reflective of sunlight. Malheur
Experiment Station, Oregon State University, Ontario, OR, 2003.
|
|
|
Marketable
yield
|
Marketable
yield |
Non-marketable yield |
Non-marketable yield |
Non-marketable yield |
Non-marketable yield |
Type
|
1st-applic.
|
2nd-applic.
|
|
|
Small
|
Doubles
|
Scald
|
Rot |
|
|
|
cwt/acre
|
% |
cwt/acre |
cwt/acre |
cwt/acre |
cwt/acre |
Field 1
|
|
|
|
|
|
|
|
|
none
|
No
|
No
|
580.6
|
94.8
|
4.1
|
0.9
|
12.6
|
13.9 |
Type 1
|
Yes
|
No
|
581.5
|
95.0
|
6.3
|
0.4
|
8.2
|
15.8 |
Type 1
|
Yes
|
Yes
|
587.9
|
96.0
|
4.7
|
0.9
|
6.4
|
12.3 |
Type 1
|
No
|
Yes
|
557.3
|
91.0
|
6.2
|
0.4
|
7.8
|
40.5 |
Type 2
|
Yes
|
No
|
564.2
|
92.2
|
5.7
|
0.6
|
14.9
|
26.8 |
Type 2
|
Yes
|
Yes
|
590.0
|
96.4
|
5.8
|
0.5
|
5.8
|
10.1 |
Type 2
|
No
|
Yes
|
580.0
|
94.7
|
6.3
|
1.0
|
5.4
|
19.5 |
average
|
|
|
577.4
|
94.3
|
5.6
|
0.7
|
8.7
|
19.8 |
Field 2
|
|
|
|
|
|
|
|
|
| none |
No
|
No
|
540.4
|
74.4
|
2.8
|
2.9
|
89.7
|
90.8 |
| Type 1 |
Yes
|
No
|
610.4
|
84.0
|
3.6
|
2.6
|
51.4
|
58.6 |
| Type 1 |
Yes
|
Yes
|
628.5
|
86.5
|
2.6
|
1.3
|
58.4
|
32.8 |
Type 1
|
No
|
Yes
|
621.5
|
85.5
|
2.3
|
6.0
|
66.1
|
33.2 |
Type 2
|
Yes
|
No
|
584.0
|
80.4
|
4.0
|
0.6
|
88.4
|
49.6 |
| Type 2 |
Yes
|
Yes
|
614.8
|
84.6
|
3.2
|
3.3
|
72.6
|
32.6 |
Type 2
|
No
|
Yes
|
614.5
|
84.6
|
2.9
|
1.4
|
67.6
|
40.2 |
average
|
|
|
602.0
|
82.9
|
3.0
|
2.6
|
70.6
|
48.3 |
Field 1, Field 2 average
|
|
|
|
|
|
|
|
|
none
|
No
|
No
|
560.5
|
84.6
|
3.5
|
1.9
|
51.1
|
52.3 |
Type 1
|
Yes
|
No
|
596.0
|
89.5
|
4.9
|
1.5
|
29.8
|
37.2 |
| Type 1 |
Yes
|
Yes
|
608.2
|
91.3
|
3.7
|
1.1
|
32.4
|
22.6 |
Type 1
|
No
|
Yes
|
589.4
|
88.3
|
4.2
|
3.2
|
37.0
|
36.9 |
Type 2
|
Yes
|
No
|
574.1
|
86.3
|
4.8
|
0.6
|
51.6
|
38.2 |
Type 2
|
Yes
|
Yes
|
602.4
|
90.5
|
4.5
|
1.9
|
39.2
|
21.4 |
Type 2
|
No
|
Yes
|
597.3
|
89.7
|
4.6
|
1.2
|
36.5
|
29.8 |
LSD(0.05)Trt
|
|
|
23.5
|
3.5
|
NS
|
NS
|
(14.2)*
|
(21.3)* |
LSD(0.05)Field
|
|
|
12.8
|
1.9
|
1.5
|
1.7
|
(7.7)*
|
(10.8)* |
LSD(0.05)TrtXFld
|
|
|
33.9
|
5.1
|
NS
|
NS
|
NS
|
(28.5)* |
*significant at the 0.10 level.
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
Wednesday July 7, 2004 .
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