nitrogen uptake dynamics of spinachcesantabarbara.ucanr.edu/files/145921.pdf · comparison of...
TRANSCRIPT
Nitrogen Uptake Dynamics of Spinach
Richard Smith, Aaron Heinrich and Tricia Love
UC Cooperative Extension, Monterey County
Background
Spinach is an “at risk” crop in the new
regulations by the Central Coast
Regional Water Quality Control Board
(CCRWQCB)
Due to the nitrogen uptake dynamics,
rooting depth and non-agronomic
quality demands from the market place
(e.g. deep green color), it is going to be
difficult to comply with the 1.0 nitrogen
balance goal stipulated by the Regional
Water Quality Control Board
2011 Trials
Four fertilizer trials and surveys of the
nitrogen uptake dynamics of 11 spinach
fields were conducted
2011 Trials
Fertilizer trials:
Two first crop sites with low residual
soil nitrate (one light and one heavier
soil type)
Two second crop sites with high
residual soil nitrate (one medium and
one heavier soil type)
First Crop vs Second Crop
• First crop – Low residual soil nitrate following winter fallow
• Second crop – Higher residual soil nitrate from residual fertilizer, soil mineralization, crop residue mineralization of the prior crop
Winter
Fallow
Fall
Tillage
Second
Crop
Tillage
First Crop Spinach Fertilizer Trial
Preplant application carries the crop for the first
two weeks; only 15-20 lbs of N is taken up by the
crop in the first two weeks, prior to the topdress
application
First Crop Spinach on Sandy Loam Soil Yield (T/A)
• At planting treatments (ammonium sulfate):
0, 20, 40 & 80 lbs N/A
• Top dress applications:
18 DAP 63 lbs N/A
25 DAP 39 lbs N/A
29 DAP 32 lbs N/A
Total 134 lbs N/A 0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
18 27 32
Days after planting
*
Soil Nitrate-N Over the Growth Cycle
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
0 6 13 18 27 35
Days After Planting
0
20
40
80 lbs N/A
Yield of First Crop Spinach Mean of Two Trials
Fre
sh
To
ns/A
Second Crop Spinach
• Following lettuce and cole crops
• High residual soil nitrogen
• Better growing conditions
Second Crop Spinach on Loam Soil Yield (T/A)
• At planting treatments:
None were applied due to high residual soil nitrate
• Top dress applications applied at 17 DAP:
• 0, 25, 50, 75, 105 lbs N/A
0
2
4
6
8
10
12
14
16
20 24 28
Days after planting
Soil Nitrate Over the Growth Cycle Second Crop Spinach
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
12 20 24 28 DAP
Lbs N/A
105
75
50
25
0
Yield of Second Crop Spinach Mean of Two Trials
Comparison of Spinach vs Lettuce Biomass and N Uptake
Lettuce
Dry Biomass (lbs/A)
3000 to 5000
N Uptake (lbs/A)
120 to 140 or more
Percent N at harvest
Generally 3.0 to 3.5
Overall N Uptake/day
3.5 to 4.5 lbs/A/day
Clipped Spinach
Dry Biomass (lbs/A)
1200 to 2400
N Uptake (lbs/A)
80 to 100
Percent N at harvest
4.5 to 6.4
Overall N Uptake/day
4.2 to over 7.0 lbs/A/day
• At harvest pits dug
to 2 feet (4 sites)
• Roots exposed with pressurized sprayer
• Roots counted in each grid
• Nitrate measured in each grid
Rooting Depth Evaluations
0
5
10
15
20
25
30
35
40
45
0-4 4-8 8-12 12-16 16-20 20-24
% o
f to
tal
roo
ts
Depth (in)
88% of all roots found in top 12” of soil at harvest
Root distribution
0
4
8
12
16
20
24
0-4
4-8
8-1
2
12
-16
16
-20
20-2
4
NO
3-N
(m
g/k
g s
oil)
Depth (in)
Nitrate distribution
Spinach Nitrogen Uptake - All Sites
Sitesfields
• 11 lbs N/A in first 2 wks
• 5.1 lbs N/A/d from 13 d to harvest
• 7.3 lbs N/A/d in the week prior to harvest
DAGW
0 10 20 30 40 50
lbs
N/A
0
25
50
75
100
125
150
y = 5.1x -66.8
R2 = 0.74
Nitrogen Content of Unharvested Spinach Residue
Clipped:
44% of N remains in the field
Bunch:
35% of N remains in the field
Residue ~5% Nitrogen
Nitrogen Uptake by Spinach Products lbs N/A
0
20
40
60
80
100
120
140
Baby Teenage Bunch
Spinach Potassium Uptake
• 7.2 lbs K/A in first 2 wks
• 9.3 lbs K/A/day from 13 d to harvest
• ~160 lbs K/A at harvest
0 20 40 60 80
100 120 140 160 180
0-17 19-27 28+
lbs
K/A
DAGW
Spinach Phosphorus Uptake
• 0.7 lbs P/A in first 2 wks
• 0.7 lbs P/A/d from 13 d to harvest
• 12 lbs P/A at harvest
0
2
4
6
8
10
12
14
0-17 19-27 28+
lbs
P/A
DAG
Enhanced Nitrogen Fertilizer
Technology
Nitrification inhibitors
Foliar fertilizers
Controlled Release Fertilizers
NH4+ NO3-
Nitrification - conversion of
ammonium to nitrate
In warm soils (>50 °F), it occurs in
2-3 weeks
Impact of Dicyandiamide (DCD)
on Nitrate Leaching Tim Hartz, 2011
2011 Lettuce Yield (T/A)
Nitrification Inhibitor Trial
Lbs N/A
Foliar Fertilizer N Trial Romaine 2011
Treatment Total N/A
applied
Lbs/A
Fresh
yield
tons/A
Lettuce
N content
% N
Lettuce
N content
lbs N/A
Untreated 0.0 30.9 1.9 81
Impact – foliar 29.2 33.7 2.2 95
Green Feed - foliar 29.2 32.0 2.2 94
Standard fertilizer 138.4 38.4 2.7 125
2012 Evaluation of Controlled Release Fertilizer on Spinach Yield
Duration 45
0
0.5
1
1.5
2
2.5
1 2 3 4 5 6 7 8
Untreated
Standard
182 lbs N/A
120 CR
at planting
0 topdress
120 CR
at planting
80 topdress
80 CR
at planting
80 topdress
Spinach Nitrogen Nutrition Evaluations
• These evaluations showed that it is very difficult to reduce nitrogen applications to first crop spinach when residual soil nitrate levels are low in the spring
• Residual soil nitrate may be more effectively utilized in second crop spinach
• Nitrogen uptake by spinach in the week prior to harvest is very high
Spinach Nitrogen Nutrition Evaluations
• Spinach is a heavy user of potassium
• Fertilizer technologies such as nitrification inhibitors and controlled release fertilizers may have a role to play in managing N
Herbicide Update on Coastal Vegetables
Lettuce
Kerb is firmly in limbo for leaf lettuce
Dual Magnum and Prowl H2O are in the registration pipeline for use on transplanted lettuces
Other Crops
It finally looks like some progress will be made on the registration of prometryn on cilantro
Chateau registered for use in the furrow bottom of peppers
Acknowledgements
California Leafy Greens Research
Board
Koch Industries
Agrium Corp.