89
Foliar Fertilization of Russet Burbank Potatoes
K.A. Rykbost and J. Maxwell'
INTRODUCTION
Soil and plant tissue analyses suggest that at least a portion of
the mineral soils used for potato production in the Klamath Basin are
marginally deficient in boron and zinc. These nutrients can be provided
from commercially available sources. Local growers are currently using
several foliarly applied products but responses are not documented.
This experiment was initiated in 1988 to determine the nutrient
status of Russet Burbank potatoes grown on soil low in zinc and boron,
and to evaluate effects on yield, quality and nutritional status following foliar fertilization with a range of materials. Preliminary
results obtained in 1988 indicated economic benefits were realized from
applications of blended products including both major and minor nutrients, even though plant tissue analysis failed to detect changes in
plant nutrient status. With one change in products evaluated, the study
was continued in 1989.
PROCEDURES
Russet Burbank potatoes were planted at 12-inch seed spacing in 32inch rows on May 25. Fertilizer included 600 lbs/A of 16-16-16 banded
at planting and 80 lbs N/A applied as solution 32 on June 6. Standard
cultural practices were followed (page 44).
Foliar fertilizer products were applied to four-row plots, 40 feet
long, with a hand-held plot sprayer. All products were applied in 30
gpa of solution in calm conditions during morning hours. The experiment
was a randomized complete block design with four replications.
Vines were desiccated with diquat applied at 1.0 pint/A on September
21 and potatoes were harvested on October 10. Harvest areas included
the two center rows, trimmed to 37-foot length to eliminate border
effects. Total tuber weights were determined in the field. Approximately 120-pound samples were stored and graded in early November. Crop
values were calculated using prices described in the previous section of
this report (page 83).
1/ Superintendent/Associate Professor, Biological Sciences Research
Technician, respectively, Klamath Experiment Station
Acknowledgments: Partial funding by the Oregon Potato Commission and
Leffingwell Company contributed to this research project.
90
RESULTS AND DISCUSSION
Soil samples collected prior to planting indicated very high soil P,
K and Mg, medium Ca and Na, and low Zn, S and B levels. Soil pH was 6.1
and organic matter content was 0.3 percent.
Petiole samples were collected on August 23 from vigorous and healthy appearing plants. Samples from replications I and II and from III
and IV were batched to provide two samples per treatment for analysis.
Petiole analysis data was not analyzed statistically, but variability
between replications was less than that observed in the Russet Burbank
N, P, K and S experiment.
With the exception of zinc, plant tissue analysis did not detect
changes in plant nutrient status attributable to fertilizer treatments
(Table 1). However, it is interesting to note the discrepancies in
nitrogen and potassium status between this experiment and the Russet
Burbank N, P, K and S rate experiment (Page 83). Both experiments were
planted the same day with the same seed source. With the exception of
fertilizer application methods, cultural practices were the same. Plant
vigor appeared to be very similar throughout the season. Phosphorous
and potassium fertilizer rates in this experiment were similar to those
in several treatments in the N, P, K and S study. However, petiole K
levels were considerably lower in this experiment. The largest discrepancy between experiments was in N levels. On August 23 N levels were
very low in all treatments in the N, P, K and S rate study and high in
all treatments in this experiment. Canopy condition appeared the same
in both trials. Although samples were analyzed in different laboratories differences should not have been as great as those observed. There
was good agreement in P and S levels for the two trials.
Foliar fertilizer treatments did not alter petiole levels of any
nutrients tested except zinc. All Leffingwell products (treatments 4-8)
appeared to correct, at least to some extent, a zinc deficiency. Tracite
did not increase zinc levels in petioles.
Yields were quite different between this study and the N, P, K and S
experiment. In this trial the basic fertilizer rate was approximately
180-100-100. Total yield of US No. l's for the control treatment was
284 cwt/A (Table 2) compared to 372 cwt/A for the 180-120-120 treatment
in the N, P, K and S rate experiment. This difference is difficult to
account for. Canopy appearance was similar throughout the season.
Foliar fertilization did not result in large yield responses. Crop
economic values were lower than the control for treatments Nutra-Phos 24
+ Nutra-Phos Super K and Nutra-Phos 24 + Sorba-Spray CaB. All other
treatments increased crop value by at least $150/A. For products evaluated in both years, all except Nutra-Phos 24 + Sorba-Spray CaB resulted
in economic gains well above the product costs of approximately $20/A.
91
SUMMARY AND CONCLUSIONS
In two years of trials several foliar fertilization products have
produced small but economical yield responses. Although crop prices
have been unusually high during these two years, the responses obtained
would be economical at more typical prices.
In both years plant zinc levels were elevated slightly following
treatments that included zinc. Tissue boron levels have not been
changed by any of the boron treatments but solubor produced a slight
yield increase in 1989. The experiment will be continued for at least
one more year to further quantify responses.
In two years of trials there have not been good correlations between
fertilization rates, petiole nutrient status and crop performance. Many
local growers utilize plant tissue analysis services to make decisions
on applications of nutrients, particularly N, through irrigation systems
on Russet Burbank crops. Data from the two Russet Burbank fertility
experiments does not support the validity of this practice under local
conditions. Preliminary observations suggest that in the short growing
season of the Klamath Basin, the use of petiole analysis as a basis for
fertilization may not be justifiable. In fact, maintaining petiole N at
levels considered sufficient in other regions may be detrimental. A
more extensive study of the relationships between fertilization
practices, tissue nutrient status and crop performance is needed.
92
Table 1. Petiole nutrient levels in Russet Burbank treated
with several foliar fertilizers, Klamath Experiment
Station, 1989.
Treatment'
1
2
3
4
5
6
7
8
N
P
K
Ca
2.43
2.75
2.74
2.30
.30
7.0
7.8
7.3
7.5
2.0
2.2
.19
8
35
.38
.28
.30
1.9
1.7
1.8
2.0
1.9
1.7
.17
.16
.17
10
15
34
31
33
1.9
2.0
1.9
1.9
1.9
2.2
1.8
.18
.15
.18
12
20
14
16
33
33
33
33
2.73
2.50
2.63
2.45
.31
.23
.34
.31
8.0
6.4
7.7
6.8
Mg
2.1
S
.16
Zn
B
---ppm---
9
1/ Trt. 1 - Control - water applied at 30 gpa July 14 and
July 26.
2
Solubor
(20% B) - applied at 1.25 lbs/A in 30
Trt.
gpa water on July 14 and July 26.
Trt. 3 - Tracite (1% Mn, 4X zn, 1% Fe, 3.5% S) applied at 1 qt/A in 30 gpa water July 14 and
July 26.
Trt. 4 - Nutra-Phos 24(24% P 2 0 5 , 20% Ca, 6% S, 12 % Zn)
- applied at 5.0 lbs/A in 30 gpa water July
Trt. 5 Trt. 6 Trt. 7 Trt. 7 -
14, and Nutra-Phos Super K (16% P 2 0, 16% K 2 0,
31% Zn) - applied at 5.0 lbs/A in 30 gpa water
July 26.
Nutra-Phos 24 at 5.0 lbs/A and Sorba-Spray Ca
(6% N, 8% Ca) at 2 qts/A applied in 30 gpa
solution July 14 and July 26.
Nutra-Phos 24 at 5.0 lbs/A and Sorba-Spray CaB
(3% N, 5% Ca, 0.5% B) at 2 qts/A applied in 30
gpa solution July 14 and July 26.
Nutra-Phos 24 at 5.0 lbs/A and Sorba-Spray ZBK
(1% N, 6% K2 0, 1% Zn, 1% B) at 2 qts/A in 30
gpa solution July 14 and July 26.
Nutra-Phos 24 at 5.0 lbs/A and Sorba-Spray ZPK
(16% P 2 0 5 , 9% K 2 0, 1% Zn) at 2 qts/A in 30 gpa
solution July 14 and July 26.
Table 2. Effects of foliar fertilization on yield, grade and crop values of Russet Burbank in 1988 and 1989, Klamath
Experiment Station.
4-6 oz
Treatment
Yield US No. l's
'88 Total
Total
6-10 oz
>10 oz
cwt/A B's
Yield
2's & Culls
Total
Crop value
1989
1988
$/A
Specific
Gravity
Control
150
88
46
284
292
88
52
424
2796
2793
1.080
Solubor
147
124
47
318
296
74
37
429
3165
2912
1.080
Tracite'
173
91
60
324
246
76
52
452
3173
2287
1.081
Nutra-Phos 24+
Nutra-Phos Super K
168
90
37
295
318
95
38
428
2755
2963
1.082
Nutra-Phos 24 +
Sorba-Spray Ca
158
117
41
317
355
75
46
438
3070
3245
1.081
Nutra-Phos 24 +
Sorba-Spray CaB
151
81
35
267
309
76
46
389
2527
2953
1.080
Nutra-Phos 24 +
Sorba-Spray ZBK
160
115
46
321
325
97
38
456
3136
3000
1.081
Nutra-Phos 24 +
Sorba-Spray ZPK
142
108
46
296
322
77
47
420
2948
2955
1.079
Average
CV (X)
LSD (.05)
156
12
27
102
27
40
45
33
22
303
12
52
308
11
49
82
18
21
45
67
NS
429
8
51
2946
2889
1.080
0.300
NS
1/ In 1988 this treatment was ZnSO4