cropping systems affecting over- winter soil nitrate dynamics and leaching chengci chen, michael...
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Cropping Systems Affecting Over-winter Soil Nitrate Dynamics and
Leaching
Chengci Chen, Michael Bestwick, and Yesuf Mohammed
Central Ag Research CenterMontana State University
Nitrate in Montana Hydrologic Systems 2014 Conference, April 23-24, Helena, MT
Introduction
• Soil and weather conditions in central Montana
Soi
l pro
file
Precipitation and Crop Growth Curves
Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Prec
ipita
tion
(mm
)
0
20
40
60
80
100
Long-term Average
Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Biom
ass (
kg h
a-1
)
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
Biomass Accumulation
Objectives
• The goal of my research is to improve nitrogen use efficiency, crop yield, and reduce N loss.
Approach
Application timing: Fall vs. SpringCrop rotations: Fallow-winter wheat vs. Annual croppingApplication amount and method:
Fall application of N and Br
0 50 100 150 200 2500
2
4
6
8
10
12
14
16
18
20
217 Br-
Background10/10/124/1/20136/20/2013
Dept
h (in
)
0 20 40 60 80 100 120 140 160 180 2000
2
4
6
8
10
12
14
16
18
20
Background10/10/20124/1/20136/20/2013
217 NO3-
Dept
h (in
)
Frozen soil in early spring
Surface runoff
Crop Rotations
Soil NO3 under different crop rotations
Rotation 2005-2006 2007-2008 2009-2010 Fall Spring Diff Fall Spring Diff Fall Spring Diff
F-WW 54.7 78.0 23.3* 35.2 48.9 13.7* 47.7 35.7 -12 SP-WW 30.6 68.0 37.4* 9.4 26.7 17.3* 21.6 29.5 7.9 SW-WW 38.2 38.5 0.3 5.4 10.1 4.7 30.7 24.4 -6.3 WP-WW 32.1 71.0 38.9* 16.8 32.1 15.3* 35.1 47.9 12.8
Yield of Winter Wheat Following Different Crop Rotations
Crop Rotation
FW-WW SP-WW SW-WW WP-WW
Yie
ld (
kg h
a-1
)
0
500
1000
1500
2000
2500
3000
a
c
b
a
Winter wheat response to different rotations
Spring wheat yield response to N input in 2013
0 40 80
N Rate (lb/a)
1,247
1,429
1,611
1,793
1,975
2,157
Gra
in Y
ield
(lb/
a)
0 40 80
N Rate (lb/a)
8.0
9.8
11.6
13.4
15.2
17.0
Pro
tein
co
nte
nts
(%
)
Conclusions• Fall-applied N is prone to leaching in central Montana
with shallow soil profiles.• Fall-applied N may have subjected to surface runoff
during snow thawing in the early spring.• Crop rotations affected water and N uptake by crops
and N mineralization in soils, thereby affecting mineral N contents in the soil profiles.
• Managing N from leaching to groundwater or runoff to surface water should not sacrifice crop yield and farm profits.
Thank You !