Agriculture Reference
In-Depth Information
to note that the recommended rates from these
two regions are remarkably similar when div-
ided by the anticipated days of growth ( 120 ver-
sus 150). The resulting recommended NPK rates
per day of growing season in the UK versus the
Columbia Basin are 2.3 versus 2.6 kg N ha - 1 , 2.1
versus 2.2 kg P 2 O 5 ha - 1 , and 3.0 versus 3.6 kg K 2 O
ha - 1 , respectively. Since both research teams
used a common variety, this observation might
strengthen their recommendations as being uni-
versally acceptable for Russet Burbank.
(0-45 cm) is ideal. Deeper samples may be col-
lected and are especially helpful for tracking and
monitoring nutrient movement through the soil
profile to prevent leaching.
Petioles are commonly used for plant nutri-
ent analysis. Typically, the fourth leaf (newest
fully expanded leaf) from the top of the plant is
removed and the leaves stripped to isolate the
petiole (Stark and Westermann, 2003). Depend-
ing on field size, a representative sample—per-
haps 50 or more petioles—should be collected
randomly throughout each field or field section
and combined for analysis. Due to natural field
variability, larger fields may be divided into sam-
pling grids to allow for sectional management.
Base soil and petiole levels exist for many regions
(Dow, 1980; Rykbost et al ., 1993; Walworth and
Muniz, 1993; Lang et al ., 1999; Stark and West-
ermann, 2003) and may be extrapolated for
regions without recommendations. Table 6.2
displays petiole values common to the Columbia
Basin of Washington. Petioles should be col-
lected from healthy, unstressed plants. McDole
and McMaster (1978) reported that moisture-
stressed plants exhibited higher petiole nitrate
levels than those being grown with optimum
irrigation levels.
Plant and soil nutrient status
In-season nutrient sampling is usually more in-
tense for overhead-irrigated farms than for rain-
fed systems. Real-time data are essential for
overhead-irrigated farms, as fertilizer can and
may need to be applied at any point during the
season via the irrigation water (fertigation).
None the less, all farms can benefit from an
in-season nutrient monitoring program. For effi-
cient and effective nutrient management, plants
and soils should be sampled, analyzed, and
monitored throughout the season. Sampling
soils where most of the potato roots are found
Table 6.2. Typical N, P, K, and S petiole values for three commonly grown cultivars during June and July a
in the Columbia Basin of Washington, USA. Nitrogen petiole values are displayed in a range developed to
maximize economic return for each cultivar. (Based on unpublished data from M.J. Pavek, 2006-2012.)
End of tuber initiation
100% ground cover
Early tuber bulk
Mid tuber bulk
Variety
Nutrient b
15 June
30 June
15 July
30 July
------------------------------ % ------------------------------
Ranger
N
2.6-2.9
2.4-2.7
2.2-2.5
2.1-2.4
Russet
P
0.49
0.36
0.26
0.25
K
10.80
10.30
7.20
6.70
S
0.21
0.20
0.16
0.20
Russet
N
2.4-2.7
2.0-2.3
1.8-2.1
1.5-1.8
Burbank
P
0.44
0.30
0.20
0.14
K
10.90
9.30
7.40
6.50
S
0.22
0.18
0.16
0.20
Umatilla
N
2.8-3.1
2.6-2.9
2.3-2.6
1.9-2.2
Russet
P
0.44
0.41
0.25
0.18
K
10.60
8.90
7.60
6.70
S
0.29
0.24
0.25
0.28
Notes : a Based on ≥150 days of growth from planting to harvest. Typical dates: planting = 15 April; emergence = 15 May;
harvest = 15 September. Typical potato fertilizer rates for depleted soils in the Columbia Basin: N = 400 kg ha - 1 ; P 2 O 5 = 280 kg
ha - 1 ; K 2 O = 540 kg ha - 1 ; and SO 2- = 45 kg ha - 1 . b To convert values to ppm, multiply by 10,000; e.g. 2.6% N = 26,000 ppm N.
 
 
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