72nd SWCS International Annual Conference July 30-August 2, 2017 Madison, WI

1. Challenges to adopt BMPs to
reduce nitrate leaching and soil
erosion while improving farm
economics
SWCS Meeting
July 30-Aug 2,
2017, Madison,
WI, USA
M. Khakbazan*, Y. Jiang, J. Nyiraneza, J. Huang, K. Fuller,
V. Rodd

2. Problem
• Conventional potato production contributes little crop
residue to the soil and involves significant tillage
operations and chemical inputs which may result in
leaching or/and runoff of excess nutrients and
degradation of soil resources, including reduced top
soil and diminished soil organic matter.
• Conventional potato production has relied on high
levels of soil disturbance (e.g. fall moldboard
ploughing) in the fall which leaves the soil surface
exposed to erosion until spring, and then multiple
tillage passes in the spring to prepare the seedbed.

3. Potato production in Canada
• Potato farm cash receipts is 1.1B in Canada
• PEI (89,000 ac) Manitoba (64,500 ac), Alberta
(52,300 ac), New Brunswick (46,000 ha)
Changes in average yield (Cwt per acre) of potatoes in AB, MB, PEI, and NB from
1992-2016.
y = 1.4171x + 254.16
R² = 0.1661
y = 1.8238x + 246.9
R² = 0.3594
y = 3.9152x + 208.1
R² = 0.586
y = 4.6018x + 258.65
R² = 0.788
0
50
100
150
200
250
300
350
400
450
CwtperAcre
Year
Prince Edward Island
New Brunswick
Manitoba
Alberta
Linear (Prince Edward Island)
Linear (New Brunswick)
Linear (Manitoba)
Linear (Alberta)

4. Objective
• The overall objective of this study was to
determine if delaying fall ploughing to spring
in forage phase of a potato rotation is a viable
practice for potato growers in PEI. Specific
objective was to evaluate the effect of this
practice on economic returns and risk of
returns trade-offs for potato producers.

5. Methodology
• Three experimental studies were initiated between 2010-
2017.
• To evaluate the potential impacts of postponing the
ploughing of the forage in a barley–forage (mix of red
clover and timothy)–potato rotation from fall to spring on
reducing nitrate leaching and soil erosion and improving
farm economics.
1. Harrington #1: two plowing time (fall and Spring) at 0, 60,
120, 180, 240 kg N ha-1 with three replicates
2. Harrington #2 three plowing temperature based (Early
Fall, Late Fall, Spring) at 0 and 100 kg N ha-1 with three
replicates
3. Souris: three sites on potato growers fields.

6. Methodology
• A combination of budgeting techniques and
economic modelling based on returns and risk
of returns trade-offs was used to determine the
profitability of Fall tillage or delay it until
Spring

7. Fall Ploughing
Pros
● Better distribution of labour (provides more time for other tasks during
the following spring)
● Improved soil tilth, reduced soil lumps, and decreased soil compaction
● Uniform seedbed and seeding operations
● Reduced insects and diseases hazards
● Removal of weeds and volunteer crops
● Replenishment of available plant nutrients and water in the soil
● The land warms earlier and dry earlier during the following spring
Cons
● Wind erosion and water erosion (8 Mg/ha/yr)
● 0.5 to 1 Mg/ha/yr yield loss due to erosion
● Elevated fall N mineralization and nitrate concentrations, and increased
losses of nitrate N
● Leaching of about 16 kg N/ha/yr

8. Spring Ploughing
Pros
● Retention of plant residue soil cover and reduced soil degradation
● Higher soil water content in the early growing season
● Reduced forage-phase nitrate leaching loss by 20 to 61%
Cons
● Substantial growth of weeds and volunteer plants
● Increased insects or diseases harbouring with higher level of crop residue
● Wet and slow-to-warm soil conditions in spring resulting in planting delays
● Increased large clods, lumps, soil compaction and increased plant debris at
harvest
● Poor seedbed preparation and harvest difficulties
● Under-decomposed organic residues
● Additional labour and time constraints during the spring seeding period
with its unpredictable weather

9. Literature Review for Fall vs. Spring Ploughing Potato Yield Impacts
Fall ploughing Spring ploughing Reference
● Similar yield and quality Carter et al. 1998,
2005, 2010
Carter and Sanderson
2001
Holmstrom et al. 2006
Lynch et al. 2008
● Reduced yield by 12% Griffin et al. 2009
● With spring moldboard ploughing of red
clover, higher yields at low N rates and
lower yields at high N rates
Sanderson et al. 1999
● 0.41 Mg/ha/yr yield
loss due to erosion
● Increased yield by 4.5 Mg/ha
● Increased yield by 0.5 Mg/ha
Dehaan et al. 1999
Ochuodho et al. 2013

10. Experimental Results
Effect Mkt Yield (t ha-1
) Net Revenue ($ ha-1
)
Harrington #1 0N F 39.97 3305
0N S 35.97 2393
Diff 4.00 912
60N F 34.71 2035
60N S 27.69 434
Diff 7.02 1600
120N F 36.31 2327
120N S 36.82 2443
Diff -0.51 -115
180N F 27.75 302
180N S 26.32 -23
Diff 1.43 325
240N F 30.27 805
240N S 26.81 17
Diff 3.46 788
Pr > F NS NS
Harrington #2 0N E Fall 27.35 428.5
0N L Fall 30.03 1038.7
0N Spring 29.04 813.0
Diff 2.68 610.0
100N E Fall 36.05 2291.1
100N L Fall 34.60 1960.1
100N Spring 35.44 2153.1
Diff 1.45 331.0
Pr > F NS NS

11. Experimental Results
Effect Rep Mkt Yield (t ha-1) Net Revenue ($ ha-1)
Souris Site-Year
F 1-2015 35.36 2038
F 2-2014 30.13 846
F 3-2014 25.84 -133
Mean 30.44 917
S 1-2015 33.66 1651
S 2-2014 32.05 1284
S 3-2014 28.82 547
Mean 31.51 1160
Pr > F NS NS
Diff -1.07 -243

12. Experimental Results – Combined
Effect Mkt Yield (t ha-1) Fall NR($ ha-1) Effect Mkt Yield (t ha-1) Spring NR($ ha-1) Yield Diff NR Diff($ ha-1)
F 35.36 2038.3S 33.66 1650.7 1.70 387.6
F 30.13 845.8S 32.05 1283.6 -1.92 -437.8
F 25.84 -132.3S 28.82 547.2 -2.98 -679.4
0N F 31.76 1433.50N S 40.74 3480.0 -8.98 -2046.5
0N F 47.32 4981.40N S 28.03 583.7 19.29 4397.7
0N F 40.82 3499.60N S 39.14 3115.4 1.69 384.2
60N F 42.36 3778.760N S 29.79 911.6 12.58 2867.1
60N F 26.37 131.660N S 26.21 95.4 0.16 36.3
60N F 35.42 2194.860N S 27.09 295.8 8.33 1899.0
120N F 37.52 2602.5120N S 41.99 3622.6 -4.47 -1020.1
120N F 36.80 2439.5120N S 39.74 3108.0 -2.93 -668.5
120N F 34.61 1940.2120N S 28.72 597.3 5.89 1342.9
180N F 34.41 1820.8180N S 23.84 -587.8 10.56 2408.6
180N F 33.08 1517.8180N S 18.90 -1713.7 14.17 3231.4
180N F 15.75 -2431.9180N S 36.21 2232.8 -20.46 -4664.7
240N F 26.16 -130.6240N S 32.47 1306.2 -6.30 -1436.9
240N F 31.83 1161.9240N S 28.92 498.4 2.91 663.5
240N F 32.81 1384.2240N S 19.04 -1754.7 13.77 3138.9
0N F 23.94 -349.50N S 24.02 -332.0 -0.08 -17.5
0N F 28.31 647.50N S 30.95 1248.5 -2.64 -601.0
0N F 33.82 1902.80N S 32.15 1522.6 1.67 380.2
100N F 36.03 2286.4100N S 34.05 1836.2 1.97 450.2
100N F 34.85 2017.7100N S 37.08 2526.7 -2.23 -509.0
100N F 35.09 2072.7100N S 35.19 2096.3 -0.10 -23.6
Mean 32.93 1568.9 31.20 1173.8 1.73 395.1

13. Simulation notes
Note A: Tillage cost range from $118 to $174 ha-1 for mouldboard
plus disc followed by two passes of harrows.
Note B: For delayed tillage to spring we added 15% to this range.
Note C: We added extra total yield loss for weed/insects/diseases
(1%) and soil clods and debris (2%) for S tillage at harvest
Note D: We added reduction of yield of zero to 3.36% due to soil
erosion of 8 Mg ha-1 year-1 for F tillage (0.42% yield loss per Mg
soil erosion)
Note E: Zero to 32 kg ha-1 year-1 N loss due to leaching (average
16 kg ha-1 year-1 ) from autumn ploughed plots for F tillage (16 kg
times $1.2 /kg = $19.2)
Note F: Opportunity costs of delayed seeding for S tillage were
simulated at 0%, 2%, 4%, 6% based on crop insurance data in
Manitoba

16. Simulation Results (N = 500 in each site)
0
0.05
0.1
0.15
0.2
0.25
0.3
-2901.01 -1714.34 -527.66 659.01 1845.69 3032.36 4219.04
Fall NI
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
-2117.17 -1256.59 -396.00 464.58 1325.17 2185.75 3046.33
Spring NI

17. Risk Premium:
How much ($ ha-1 year-1) you will
be required, or willing to be given
up, relative to a baseline, to be
indifferent between Fall tillage or
delay it until Spring?

18. Souris
Absolute risk averse coefficient (ARAC)
0.000 0.001 0.002 0.003 0.004 0.005
Riskpremium($ha-1)
-200
0
200
400
600
800
Fall moldboard plowing
Spring moldboard plowing
Spring moldboard plowing, assumed 2% yield reduced
Spring moldboard plowing, assumed 4% yield reduced
Spring moldboard plowing, assumed 6% yield reduced

19. Harrington #1
Absolute risk averse coefficient (ARAC)
0.000 0.001 0.002 0.003 0.004
Riskpremium($ha
-1
)
-1200
-1000
-800
-600
-400
-200
0
200
400
Fall moldboard plowing
Spring moldboard plowing
Spring moldboard plowing, assumed 2% yield reduced
Spring moldboard plowing, assumed 4% yield reduced
Spring moldboard plowing, assumed 6% yield reduced

20. Harrington #2
Absolute risk averse coefficient (ARAC)
0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035
Riskpremium($ha
-1
)
-1000
-800
-600
-400
-200
0
200
Later fall moldboard plowing
Early fall moldboard plowing
Spring moldboard plowing
Spring moldboard plowing, assumed 2% yield reduced
Spring moldboard plowing, assumed 4% yield reduced
Spring moldboard plowing, assumed 6% yield reduced

21. Souris, Harrington #1 & Harrington #2 combined
Absolute risk averse coefficient (ARAC)
0.000 0.001 0.002 0.003 0.004
Riskpremium($ha
-1
)
-1000
-800
-600
-400
-200
0
200
400
600
Fall moldboard plowing
Spring moldboard plowing
Spring moldboard plowing, assumed 2% yield reduced
Spring moldboard plowing, assumed 4% yield reduced
Spring moldboard plowing, assumed 6% yield reduced

22. Question:
How much ($ ha-1 year-1) you will be required, or
willing to be given up, to be indifferent between
Fall tillage or delay it until Spring?
Small PEI potato growers (7) were surveyed and
they all indicated they will be required, on
average, $617 ha-1 year-1 to be indifferent between
Fall tillage or delay it until Spring?