This document reports on a project studying carbon and nitrogen cycling on diversified horticulture farms. The project has three main objectives: 1) Compare nitrogen dynamics and losses across farming systems representing different intensities, 2) Identify how sensitive a soil model is to parameters describing plant growth and soil processes, and 3) Better understand whole-system carbon balances using energy analysis approaches. Preliminary results are shown for greenhouse gas fluxes measured in different systems, as well as soil carbon dioxide fluxes over one year and their relationship to soil moisture.

1. Toward Sustainable Nitrogen and
Carbon Cycling on Diversified
Horticulture Farms Serving Community
Food Systems
Krista L. Jacobsen, Debendra Shresta, Department of Horticulture, University of
Kentucky
Ole Wendroth*, Department of Plant and Soil Sciences, University of Kentucky
John Schramski, College of Engineering, University of Georgia
*presenting author
2013-67019-21403

2. Introduction
 Project Background & Context
 Project overview
 Highlights from one of the field experiments
 Overview of modeling objectives and goals

3. Background and Context
 Small- and medium-scale, diversified farms are important
sources of agricultural products for the local and regional food
movement
 Local food purchases are increasingly valued by the public for
perceptions of healthier products due to “freshness,”
conservation of local farm lands, and/or supporting local farmers
(Onozaka et al, 2010)
 Horticultural crops are a large part of this market
 Fruits, vegetables and nuts were 70% of local food sales in 2007
(Low & Vogel, 2011).
 Diversification into horticultural crops serving local markets is a
global trend for small-holder farmers (Weinberger and Lumpkin,
2007), as horticultural crops are typically higher in value per unit
area than cereals (USDA-NASS, 2009)

4. Background and Context
 However, much of what we know about C and N cycling in agroecosystems
comes from agronomic systems, less research in horticulture systems (e.g.
West & Post, 2002; Ma & Shaffer, 2001)
 Further, production practices are highly variable, with little standard rotation
varying degree of intensity
Example: A lower input
system, with no
supplemental irrigation,
“living mulch” between
rows, and seasonal
production
Example: Green bean
production in a high tunnel
system, with drip
supplemental irrigation,
intense-tillage, in a year-
round production system

5. Project Objectives
 Broadly, to improve our understanding of how intensification on diversified
horticulture-based farms influences (1) nitrogen availability, efficiency, and
retention and (2) soil carbon dynamics in labile carbon pools.

6. Project Objectives:
 Specifically…
 (i) In addition to C and N dynamics, we are also seeking to better understand the net
effects of intensification on whole system C balances using Energy Returned on Energy
Invested (akin to life cycle analysis) approaches.
 More on this next year…

7. Project Objectives
 Specifically…
(ii) to compare the nitrogen dynamics and key loss pathways in five farming
systems, including four organic systems, representing a gradient of
intensification (characterized by quantity of inputs, and the frequency of tillage
and fallow periods)

8. Project Objectives:
 Specifically…
 (iii) to identify the sensitivity of a model to measured parameters to describe the key
plant growth and soil processes.
Soil input:
Soil hydraulic properties
Status of soil moisture and
different C- and N-
fractions
Plant input:
Growth status, root
development

9. -30
-20
-10
0
10
20
30
0
1
2
3
4
5
AirTemp(°C)
Precipitation(inch)
Precipitati
on (Inch)
0
200
400
600
800
TOTALFLUX(MGCO2M-2HR-1
CO2 FLUX
Extensive Organic system Conventional system Stationary Organic High Tunnel system
-100
-50
0
50
100
150
200
250
300
350
400
N2OFLUXUGM-2HR-1
N2O FLUX
Extensive Organic system Conventional system Stationary Organic High Tunnel system
First results on GHG fluxes in different horticultural systems

10. New RZWQM GHG Submodel (Fang et al., 2015)
N2O emission (N2O_nit) from DAYCENT, fixed proportion of
nitrification (Rnit) modified by a soil water factor (FSW_Nit) (Gillette et
al., 2017) with WFPS as the water-filled pore space
nitNitSWNitnit RFFr  _ON_2 _ON 2
04.1
04.14.0
_



WFPS
WFPS
F NitSW
denDenONden RFrON  __2 2
New: diffusion factor for taking into account N2O diffusion across
different soil depths.

11. 09/01/2009 02/28/2010 08/27/2010 02/23/2011 08/22/2011
0
50
100
150
PRECIPITATION(mm)
-15
-5
5
15
25
35
Tavg
PRECIP.
AIR-TEMP.
09/01/2009 02/28/2010 08/27/2010 02/23/2011 08/22/2011
0.00
0.04
0.08
0.12
0.16
0.20
N2O-FLUX(kgN/ha/day)
N2O-MEASURED
N2O SIMULATED
CROP (WHEAT)
n = 30
09/01/2009 02/28/2010 08/27/2010 02/23/2011 08/22/2011
Date
0.0
0.1
0.2
0.3
0.4
0.5
SWC(cm3
cm-3
)
SWC 0-10 cm

12. 6/1/2010 8/1/2010 10/1/2010 12/1/2010 1/31/2011 4/2/2011 6/2/2011
0
40
80
DAILYPRECIP.
(mm)
-10
10
30
AIRTEMP.(C)
PREC.
AIR-TEMP.
6/1/2010 8/1/2010 10/1/2010 12/1/2010 1/31/2011 4/2/2011 6/2/2011
5
7
9
SWS0-30cm
(cm)
-10
10
30
SOILTEMP.(C)
SWS SOIL TEMP.
6/1/2010 8/1/2010 10/1/2010 12/1/2010 1/31/2011 4/2/2011 6/2/2011
0
10
20
qCO2
(mgm-2
min-1
)
0.0
0.5
1.0
1.5
CVqCO2
qCO2 CVqCO2
6/1/2010 8/1/2010 10/1/2010 12/1/2010 1/31/2011 4/2/2011 6/2/2011
0
5
10
15
NUGGETC0
(mgm-2
min-1
)2
0
50
100
150
200
250
RANGEa(m)
NUGGET C0qCO2
RANGE aqCO2
6/1/2010 8/1/2010 10/1/2010 12/1/2010 1/31/2011 4/2/2011 6/2/2011
DATE
0.0
0.5
1.0
C0/(C+C0)
0
10
20
STDqCO2
NUGGET/SILL qCO2
STD qCO2

13. RESULTS
• Temporal stability of CO2 flux
• rank relationship to surface soil water storage
• What are the main drivers of CO2 flux

14. 6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
JUNE 08, 2010
6/1/2010 8/1/2010 10/1/2010 12/1/2010 1/31/2011 4/2/2011 6/2/2011
5
7
9
SWS0-30cm
(cm)
-10
10
30
SOILTEMP.(C)
SWS SOIL TEMP.
CO2 flux Pattern Development and Dependence on Soil Moisture during
one year.

15. 6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
JUNE 08, 2010
6/1/2010 8/1/2010 10/1/2010 12/1/2010 1/31/2011 4/2/2011 6/2/2011
5
7
9
SWS0-30cm
(cm)
-10
10
30
SOILTEMP.(C)
SWS SOIL TEMP.
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
JUNE 21, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
JULY 06, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
JULY 19, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
AUG. 02, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
AUG. 16, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
SEP. 02, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
SEP. 16, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
SEP. 30, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
OCT. 15, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
OCT. 28, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
NOV. 11, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
NOV. 25, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
DEC. 31, 2010
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
JAN. 31, 2011
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
FEB. 15, 2011
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
MAR. 01, 2011
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
MAR. 17, 2011
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
MAR. 28, 2011
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
APR. 13, 2011
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
APR. 28, 2011
6/1/2010 8/31/2010 11/30/2010 3/1/2011 5/31/2011
DATE OF MEASUREMENT
-1.0
-0.5
0.0
0.5
1.0
SPEARMANRANKCORRELATIONrs
qCO2
qCO2 - WS0-30
JUNE 08, 2011

16. Conclusions
 GHG fluxes and relevant soil state variables (moisture,
nitrogen) measured over two seasons.
 GHG flux behavior locally driven (SWC and T influence gas
flux only on a relative not on an absolute basis).
 First steps in modeling N2O fluxes with RZWQM
 Next steps:
• model sensitivity to measured soil parameters
• dynamics at different time-scales

17. Thank you
to USDA-AFRI for supporting our research.