Klamath Experiment Station
Sugarbeet Response to Nitrogen Fertilizer Rates
K.A. Rykbost and R.L. Dove
I
ntroduction
Sugarbeet response to nitrogen fertilizer
was evaluated on the mineral soils at KES
in 1992 and 1994. In 1992, following
three years of barley production, nitrogen rates
of 30, 60, 90, 120, and 150 lb N/acre were
evaluated. No significant differences were
found in beet yield, sugar content, total sugar
production, or crop value. Sugar yields ranged
from a low of 6.2 tons/acre at 30 lb N/acre to
a high of 6.7 tons/acre at 120 lb N/acre. In
1994, nitrogen fertilizer rates of 50, 100, 150,
and 200 lb N/acre were evaluated following
five years of grass forage production. Maximum yield, sugar content, total sugar production, and crop value occurred at the 50 lb N/
acre rate. A significant decline in sugar content was observed as N rate increased from 50
to 200 lb N/acre. Responses in yields and crop
value were not statistically significant. In
1995, the study was repeated following a
potato crop.
Procedures
The experimental site was a Hosley sandy
loam soil with pH at 7.0 and 1.0 percent
organic matter content in the surface foot.
Field preparation methods are described on
page 77. A uniform application of 50 lb N/
acre was broadcast and incorporated during
bed forming prior to planting. The experimen-
tal design was a randomized complete block
with five replications. Individual plots were
five 22-inch rows, 36 feet long. Seed of the
WS-62 variety was planted at 0.5-inch depth
with a hand-operated, one-row planter on May
17. Cultural practices for weed and insect
control and irrigation were the same as described for the KES variety trial (page 77).
Nitrogen fertilizer rates of 50, 100, 150, and
200 lb N/acre were achieved by application of
URAN Soln. 32 with a conventional ground
sprayer at rates of 0, 50, 100, or 150 lb N/acre
to appropriate plots on June 24, followed
immediately by 0.5 inches of irrigation. Plants
were hand-thinned to approximately 8-inch
spacing on June 27.
Petiole samples were taken from the center
two rows of all plots on August 2 and
September 7. Nitrate nitrogen content was
determined on the August 2 samples. Complete analyses were performed on all samples
taken on September 7. Beet tops were removed with a flail chopper immediately prior
to harvest on October 16. Beets were handharvested from 30 feet of the center two rows
in each plot, leaving 3-foot borders at each end
of plots. All beets were counted and weighed.
Samples of 10 beets/plot were analyzed for
tare loss and sugar content by Spreckels Sugar
Company laboratory personnel. Data were
processed as described on page 78.
Superintendent/Professor and Associate Professor, respectively, Klamath Experiment Station,
Klamath Falls, OR.
11
Acknowledgment: Partial funding of this study by the California Beet Growers Association and
laboratory analyses of beet sugar content by Spreckels Sugar Company is gratefully recognized.
KLAMATH EXPERIMENT STATION 1995 85
Klamath Experiment Station
Sugarbeet Response to Nitrogen Fertilizer Rates
Results and Discussion
Emergence occurred quite uniformly 7 to
10 days after planting. Beets were in the
cotyledon stage on June 2 when a hail storm,
lasting several minutes, covered the field with
0.25-inch diameter hail stones. All plants were
damaged to some extent. Due to a high
seeding rate, sufficient plants survived and
recovered to produce adequate populations.
The crop was set back at least one week by the
hail damage. Normal growth and development
was experienced through the rest of the season.
Beet tops were smaller and lighter in color
in the lower nitrogen rate treatments by August. Petiole nitrate-N levels were significantly lower than all other treatments at 50 lb
N/acre at both sampling dates (Table 1).
Differences among the three higher N rates
were smaller. Beet tops remained quite vigorous until harvest, particularly in the 150 and
200 lb N/acre treatments.
Nitrogen fertilizer rates did not significantly affect yield, sugar content, or crop value
(Table 1). As in 1994, there was no benefit to
nitrogen fertilizer rates above the 50 lb N/acre
minimum. A trend for reduced sugar content
in response to higher nitrogen rates has been
observed in each year.
Crop nutritional status was monitored
from complete analyses of petiole samples
collected from each plot on September 7
(Table 2). Nitrogen rate did not affect nutrient
content except for potassium, which declined
from 2.1 percent at 50 lb N/acre to 1.5 percent
at 200 lb N/acre. Lower values for phosphorus and magnesium in 1995 are probably due
to later sampling time than in 1992 or 1994.
Other nutrient levels were similar to those
observed in previous years. Sufficiency range
86 KLAMATH EXPERIMENT STATION 1995
estimates have not been established for local
crops. Values reported from an Idaho laboratory are commonly used for comparison with
local data. In each year, results of petiole
analyses suggest serious deficiencies in several
nutrients. However, relatively high yields and
sugar contents were obtained in each year,
indicating that the sufficiency range data are
probably not appropriate for local conditions.
Summary
Delayed planting, crop damage from hail at
the cotyledon stage, and an extended period of
cool weather in late August and early September contributed to lower yields than were
observed in similar trials in 1992 and 1994. In
each year, beet yields were not significantly
affected by nitrogen rate. In both 1994 and
1995, high yield and economic returns were
realized at the lowest nitrogen rate. A trend
for reduced sugar content at high nitrogen
rates was significant in 1994, but not in 1995.
Petiole analysis appears to be a useful
means for monitoring the nitrogen status of
local sugarbeet
crops. The value
of petiole analysis
for determining
the status of
secondary and
micro nutrients is
questionable, at
least when locally
derived sufficiency range data
is unavailable.
Typically, local
data suggest serious deficiencies in calcium,
magnesium, zinc, and copper when compared
with data from other beet production areas.
Klamath Experiment Station
Table 1. Effect of nitrogen fertilizer rate on petiole nitrate-N content, beet yield, sugar content,
total sugar production, and gross crop value of WS-62 sugarbeet at Klamath Falls,
OR, 1995.
Nitrogen
rate
Petiole NO3-N
August 2
September 7
Plant
population
Beet
yield
Sugar
content
Total sugar
production
Gross crop
value
lb N/A
ppm
1000/A
ton/A
%
ton/A
VA
50
100
150
200
Mean
CV (%)
LSD (0.05)
7530
13160
15700
17600
1630
3330
5070
4840
33.3
33.2
33.9
33.7
27.7
26.7
27.2
26.9
17.5
17.2
17.6
16.9
4.85
4.66
4.77
4.53
1230
1160
1210
1140
13500
20
3750
3720
30
1530
33.5
10
NS
27.1
11
NS
17.3
3
NS
4.70
11
NS
1180
11
NS
KLAMATH EXPERIMENT STATION 1995 87
Klamath Experiment Station
Table 2. Sugarbeet petiole nutrient levels observed in mid-July in
1992 and 1994, and in early September in 1995 samples from
nitrogen rate experiments at Klamath Falls, OR.
Sufficiency
Nutrient
P-%
S - `)/0
K-%
Ca - %
Mg _ %
Zrn - ppm
Cu - ppm
Fe - ppm
Mn - ppm
1/
level
1
KES samples
July 1992
0.2
0.2
0.16
0.04
2.5
1.4
0.07
0.17
0.4
0.3
17
5
40
27
8
3
83
17
July 1994
0.28
0.07
0.13
3.9
0.07
0.27
0.24
16
1.8
0.06
0.11
6
2
5
400
98
68
30
As reported by Western Laboratories, Inc., Parma, ID.
88 KLAMATH EXPERIMENT STATION 1995
September, 1995