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 !