EVALUATION OF INTRACEPT® FOR ONION PRODUCTION


Clinton C. Shock, Erik B. G. Feibert, and Lamont D. Saunders

Malheur Experiment Station

Oregon State University

Ontario, OR


Introduction

The objective of this trial was to evaluate the effect of Intracept® on onion yield and grade.  Intracept is manufactured by Northwest Agricultural Products (Pasco, WA) and is marketed as a foliar-applied micronutrient fertilizer and plant growth enhancer. 

 
Methods

The trials were conducted on both a drip-irrigated and furrow-irrigated field at the Malheur Experiment Station.  The experimental designs were randomized complete blocks with seven replicates.  The two treatments were an untreated check and Intracept applied at 16 oz/acre on June 2.  Intracept was applied as a foliar spray in 13 gal of water per acre using 8004 nozzles spaced 20 inches apart at a pressure of 40 PSI.  Each plot was four double onion rows 25 ft long.

Furrow-irrigated field
The field was irrigated when the soil water tension at 8-inch depth reached 25 cb (1 cb = 1 kPa).  The field was sidedressed with 100 lb of N/acre as urea on May 25 and on June 21.  The last irrigation was on August 23.  An onion root tissue analysis on July 14 from onions in the untreated check plots showed the need for potassium (Table 1).  On July 21, potassium was water run at 20 lb/acre during a normal irrigation.

Drip-irrigated field
Drip tape (T-tape, T-systems International, San Diego, CA) was laid at 4-inch depth between the two double onion rows at the same time as planting.  The distance between the tape and the double row was 11 inches.  The drip tape had emitters spaced 12 inches apart and a flow rate of 0.22 gal/min/100 ft.  The field was irrigated when the soil water tension at 8-inch depth reached 20 cb (1 cb = 1 kPa).  The last irrigation was on August 31.  The field had 50 lb of N/acre as urea applied through the drip tape on June 8 and June 22.  An onion root tissue analysis on July 14 from onions in the untreated check plots showed the need for potassium (Table 1).  On July 21, potassium at 20 lb/acre was injected through the drip tape.

Both fields
The onions in both fields were grown on Owyhee silt loam previously planted to wheat.  In the fall of 2005, the wheat stubble was shredded and the fields were irrigated and disked.  Soil analyses on September 13, 2005 (Table 2) for both fields indicated the need for 100 lb phosphate/acre, 100 lb sulfur/acre, 2 lb copper/acre, and 1 lb/acre of boron, which were broadcast in the fall of 2005 after disking.  The fields were then moldboard-plowed, groundhogged, roller-harrowed, and bedded. 

Onion (cv. ‘Vaquero’, Nunhems, Parma, ID) 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 23 in the furrow-irrigated field and on March 28 in the drip-irrigated field.  The two rows in the double row were spaced 3 inches apart.  Onion was planted at 150,000 seeds/acre.  For preventive control of onion maggot, 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.

The onions were managed to avoid yield reductions from weeds, pests, and diseases.  Weeds were controlled with an application of Prowl® at 1 lb ai/acre on April 28.  On May 9, Goal® at 0.1 lb ai/acre, Buctril® at 0.3 lb ai/acre, and Select® at 0.25 lb ai/acre were applied.  On May 17, Goal at 0.2 lb ai/acre and Buctril at 0.3 lb ai/acre were applied.  On May 30, Goal at 0.2 lb ai/acre, Buctril at 0.3 lb ai/acre, and Select at 0.25 lb ai/acre were applied.  After lay-by the field was hand weeded as necessary.  Thrips were controlled with aerial applications of the following insecticides: June 12, Warrior®; June 18, Warrior plus Lannate®; July 1, Carzol®; July 17, Warrior plus Mustang®; July 24, Carzol; July 29, Warrior plus MSR®; August 10, Warrior plus Lannate.  Carzol was applied at 0.69 lb ai/acre, Warrior at 0.03 lb ai/acre, Lannate at 0.45 lb ai/acre, Mustang at 0.05 lb ai/acre, and MSR at 0.5 lb ai/acre.

Soil water tension was monitored by six granular matrix sensors (GMS, Watermark Soil Moisture Sensors Model 200SS, Irrometer Co. Inc., Riverside, CA) installed in mid-June below the onion row at 8-inch depth.  The sensors were automatically read hourly with an Irrometer monitor (Irrometer Co.). 

After lifting on September 8, onions from the central 20 ft of the middle two rows in each plot were topped, bagged, and hauled to a barn on September 15. 

On September 29 the onions were graded.  During grading, bulbs were separated according to quality: bulbs without blemishes (No. 1s), split bulbs (No. 2s), neck rot (bulbs infected with the fungus Botrytisallii 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 (<2.25 inches), medium (2.25-3 inches), jumbo (3-4 inches), colossal (4-4.25 inches), and supercolossal (>4.25 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. 

Treatment differences were compared using ANOVA and least significant differences at the 5 percent probability level, LSD (0.05). 

Results

There was no significant difference in onion yield and grade between the Intracept-treated onions and the untreated onions in either of the two fields or when the data from the two fields were combined (Table 3).  The furrow-irrigated field has a long-term history of high yields in previous years and had significantly higher total, marketable, and jumbo onion yields than the drip-irrigated field in 2006.  This result was expected based on field history.

Intracept contains copper, iron, manganese, zinc, sulfur, and unknown polysaccharides and organic acids (Table 4).  The amounts of these nutrients that were actually applied in one application of 16 oz of product per acre are listed in Table 4.  Based on the onion root tissue analyses (Table 1) for the 2006 drip- and furrow-irrigated fields at the Malheur Experiment Station, the nutrients in the Intracept were not in short supply.

 

Table 1. Analysis of onion root tissue samples. Malheur Experiment Station, Oregon State University, Ontario, OR, 2006.

Field

NO3

P

K

S

Ca

Mg

Zn

Cu

Mn

Fe

B


ppm

---------------------- % ----------------------

----------- ppm -----------

June 21












Furrow

6,193a

0.88

3.3

0.81

0.73

0.44

168

220

17

4,864

26

Drip

3,787a

0.97

4.02

1.63

0.66

0.43

101

274

15

3,321

25

Sufficiency rangeb

11,800

0.32-0.7

2.7-6

0.24-0.85

0.4-1.2

0.3-0.6

25-50

35-100

6-20

60-250

19-60

July 14












Furrow

7,083c

1.39

2.531

0.87

0.61

0.32

41

139

13

1,930

73

Drip

4,430c

1

2.341

1.36

0.69

0.36

72

209

13

1,958

67

Sufficiency range

8,125

0.32-0.7

2.7-6

0.24-0.85

0.4-1.2

0.3-0.6

25-50

35-100

6-20

60-250

19-60

aThese results were followed by corrective fertilizer.

bWestern Labs, Parma, ID.

cLate season N was not applied.



Table 2. Analysis of soil sample taken on September 13, 2005. Malheur Experiment Station, Oregon State University, Ontario, OR, 2006.

Field

pH

O.M.

NO3

P

K

Sulfate

Ca

Mg

Na

Zn

Cu

Mn

Fe

B



%

----------------------------------------------- ppm --------------------------------------------

Furrow

7.4

1.52

5

24

353

13

1,982

549

114

2.1

0.6

12

11

0.5

Drip

7.5

1.87

12

36

546

24

2,530

539

151

3.3

0.5

18

8

0.5

Table 3. Yield and grade for onions treated with Intracept® compared to an untreated check. Malheur Experiment Station, Oregon State University, Ontario, OR, 2006.


Total yield

Marketable yield by grade


Non-marketable yield

Treatment


Total

>4¼ in

4-4¼ in

3-4 in

2¼-3 in


Total rot

No. 2s

Small


---------------------- cwt/acre ----------------------


% of total yield

-- cwt/acre --

Drip-irrigated field










Check

658.6

632.4

0.0

50.5

542.6

39.3


0.8

2.8

17.8

Intracept

654.9

634.3

2.8

38.4

556.7

36.5


0.5

0.9

16.8

Average

656.8

633.4

1.4

44.4

549.6

37.9


0.7

1.9

17.3

Furrow-irrigated field










Check

756.6

739.5

0.0

33.4

666.3

39.9


0.1

1.6

14.6

Intracept

745.2

725.7

0.0

35.8

650.0

39.9


0.3

4.1

13.0

Average

750.9

732.6

0.0

34.6

658.1

39.9


0.2

2.9

13.9

Average











Check

707.6

686.0

0.0

41.9

604.5

39.6


0.5

2.2

16.2

Intracept

700.0

680.0

1.4

37.1

603.3

38.2


0.4

2.5

14.9

Average

703.8

683.0

0.7

39.5

603.9

38.9


0.5

2.4

15.6

LSD (0.05)











Treatment

NS

NS

NS

NS

NS

NS


NS

NS

NS

Field

33.8

37.3

NS

NS

51.3

NS


NS

NS

NS

Trt X field

NS

NS

NS

NS

NS

NS


NS

NS

NS

Table 4. Intracept® nutrient content and the actual amounts of nutrients applied via Intracept. Malheur Experiment Station, Oregon State University, Ontario, OR, 2006.


Cu

Fe

Mn

Zn

S

Polysaccharides

Organic acids


----------------------------------------- % by weight ----------------------------------------

Product analysisa

0.10

0.10

0.33

0.40

1.00

0.82

1.00


------------------------------------ lbs/acre --------------------------------------

Amounts appliedb

0.00121

0.00121

0.004

0.005

0.0121

0.0099

0.0121

aGuaranteed analysis in product label. Product density is 9.75 lbs/gal.

bAmounts of each nutrient actually applied based on an application of 16 oz/acre of product.