Post on 21-Jan-2017
Claire Baffaut
Nutrient Management and Edge of Field monitoring: from the Great Lakes to the Gulf
Memphis, TN 2015
Multi-scale Monitoring for Improved Nutrient Management
Challenges of tracking progress
in streams
Additional processes
Lack of targeting
Lack of control:
Conflicting factors
Lack of spatial and temporal
information
No replication
Data interpretation
is difficult.
Changes are small and difficult to
detect.
• Stream bank erosion
• Subsurface and ground water contributions.
• Nutrient storage in and resuspension from the streambed sediment.
• Filtering and nutrient uptake by riparian buffers.
Multiple processes
Bank sediment
87%
Overland sediment
13%
Instream sediment in Otter and Crooked Creek
Bank nitrogen
23%
Overland nitrogen
77%
Instream nitrogen in Otter and Crooked Creek
Willett et al., JSWC 2012.
Replication
Relatively easy at the plot scale:- Same soils- Same slope- Same initial conditions- Same weather- Same size and shape- Same orientation
Repeated treatments on several plots allow statistical analysis to
detect significant differences
Other monitoring and analysis strategies
• Before and after analysis: difficult because change in land agricultural practices is gradual.
• Trend analysis.
• Multiple regression analysis.
• Multiple scale monitoring.
• Before and after analysis.
• Trend analysis:
– Issues with conflicting factors.
– Effect of a strong random component
• Multiple regression analysis.
• Multiple scale monitoring.
Other monitoring and analysis strategies
Trend Analysis of Flow in GCEW
Year peak flow : 8 mm more per decadeNumber of flooded days: 2 more days per decade
Soil erosion and water storage capacity
• 13 cm (5.1 in) in 150 years
• 3.5 cm (1.4 in) in 40 years
• 14% of water storage capacity.
Top soil loss (cm)
-45 -20 0 20 45
(Lerch et al. 2005, JSWC)
Conservation Practices
0
2
4
6
8
10
12
14
16
18
0
50
100
150
200
250
% w
ate
rsh
ed
pro
tect
ed
Are
a p
rote
cte
d (
he
ctar
es)
Grassed waterway
Terraces
Seeding
Sod busting
Grazing system
Lagoon
Filter Strip
Diversion
CP33,CRP
Buffer
Cumulative % landprotected
• Before and after analysis.
• Trend analysis.
• Multiple regression analysis: requires good spatial and temporal knowledge of what is happening in the watershed.
• Multiple scale monitoring.
Other monitoring and analysis strategies
Multiple regression analysis
• Requires good spatial and temporal information of:– Weather
– Land use
– Crop distribution
– Land management, including• Cropland management and best management practices
• Sanitary sewage treatment
• Management of urban areas
• Management of pastures
Multiple regression
• No trend of nitrate loads over 92-06 in GCEW (O’Donnell, 2010).
• Decreasing trend over 1992-2010 (Lerch et al., 2015), possibly linked to decrease in wheat production.
• No BMP linked variable found significant.
• Not the right BMPs?• Not the right location?
Crop land
Pasture & grass
Impervious areas
Critical areas
Conservation practices
Time needed to detect change
• Mean Square Error of model was used to estimate the monitoring period needed to detect a future change
Predicted number of years needed to detect load reduction
Nitrate load reduction
Season 5% 10% 20% 25%
Year 92 24 7 4
Spring 185 49 13 9
O’Donnell, 2010
• Before and after analysis.
• Trend analysis.
• Multiple regression analysis: requires good spatial and temporal knowledge of what is happening in the watershed.
• Multiple scale monitoring.
Other monitoring and analysis strategies
Multiple scale monitoring
Stream Weir W1
Field
1993-2002Mulch tilled
corn-soybean
2004-2014Precision
Agricultural System (PAS)
Field 1
Pre-PAS 1993-2002 PAS 2004-2013South 40 acres North 52 acres
Odd year Corn (sorghum in 95)
N: pre-plant UAN,
incorporated
P: 1993, 1995, 2001
incorporated
Cultivation
Corn / Cover Crop
N: at planting + top
dress early summer
No-till
Wheat / Cover Crop
N: top dress in April
No-till
Even
year
Soybean
Cultivation
Soybean / Cover Crop
P: 2004, 2006, 2008
broadcast
No-till
Soybean / wheat
N: at wheat planting
P: 2004, 2006, 2008
broadcast
No-till
Summary• No-till and cover crops did: Reduce sediment
Did not change Nitrate-N transport
Did increase Dissolved P transport
• Agronomic practices, land use change, urbanization,
stream processes and climate all contribute to
modifying the runoff/sediment/nutrient yield regime of a watershed and make it difficult to:
detect a trend,
discern whether detected trends are due to any one factor.
Implications
To improve detection of water quality trends resulting from management changes, these changes should be:
• Implemented within a short time.
• Spatially targeted.• Of large magnitude.
• Addressing the processes that cause the problem
documented by the monitoring. Scale matters!
Data Management
• Equipment fails data gaps fill in the gaps
• Sediment loss measurements
• Inaccurate data
– Flow > Precipitation
– Issues with small events
• Meta data