This document summarizes a discussion on implementing nutrient best management practices for small landholders and limited resource farmers in three areas: Chilika Lake in India, the Kagera River Catchment in Lake Victoria Basin, and Manila Bay in the Philippines. It focuses on adopting a participatory approach and adapting practices to fit the four As - applicability, adaptability, affordability, and acceptability. Key practices discussed include nutrient management following the 4Rs (right source, right rate, right time, right place), conservation tillage, cover crops, grazing management, and manure management. The goal is to improve water quality while maintaining economic viability for small-scale farmers.

1. Nutrient Best Management Practices
for Water Quality Protection
(Focused on Small Landholders & Limited Resource Farmers)
Training and Discussion Session
IWC-7
October 31, 2013
Tom Simpson and Ron Korcak
Water Stewardship
Annapolis, Maryland, USA
E-mail:
toms@waterstewardshipinc.org
ronk@waterstewardshipinc.org
1

2. Funded as part of the
Global Program for Nutrient Management
(GPNM) under the leadership of UNEP
This project is a sub-project funded by, and part of, the
overall UNEP GPNM coordination programme, led by
the Global Environmental Technology Foundation
2

3. Excess Nitrogen and Phosphorus:
1) N and P: Stimulate algal growth, consumes O2 that
degrades riverine and coastal habitats
2) Drinking water contamination (Nitrate-groundwater
and phosphorus-lakes/reservoirs)
Degraded underwater grasses:
Impaired clarity in shallows
Fish kills : Low oxygen
3

4. This discussion will focus on BMP systems
specific to three GPNM “hot spot” areas
• Chilika Lake (Lagoon), India
• Kagera River Catchment (Lake Victoria Basin)
• Manila Bay, The Philippines (not just Ag)
• Focus: Small Landholders/Limited Resource Farmers (SL-LRF)
Kagera
River
Catchment
Farms adjacent to Chilika Lake
4

5. Managing Agricultural Nutrients for Water Quality:
• Strong multi-disciplinary science and engineering team
• Includes economist and social and policy scientists
• Local input and knowledge tailored to local systems
The Participatory Approach in Manila Bay
Experience from SL-LRFs focused projects, suggests that an
engaged, participatory approach is necessary for success with these
farmers and communities. The SANREM CRSP Project in the
Manila Bay area of the Philippines concluded that:
“The Participatory Approach uses the premise that one
does not come to the community with a solution to the
problem when farmers do not know they have a problem
in the first place, and that farmers are part of the solution.”
5

6. Most current practices and BMPs were
developed for large, intensive agricultural systems
but this work is focused on BMP implementation by
Small Landholders/Limited Resource Farmers
• Small Landholder: usually farms < 5 ha
• Limited Resource Farmer: Economic
limitation on purchased inputs (e.g.
fertilizer), equipment and/or technology
• Frequently suboptimal productivity/
yields and/or net revenues due to
limited resources and size
• Trying to move “SL-LRF” up the yield
and income curve with reduced or
minimal impacts on water quality
Kagera River Basin
6

7. Farm and Field Scale Nutrient
(and Sediment) BMPs
We will discuss the 4Rs, being widely promoted for fertilizer
use, as relevant to SL-LRFs but will first propose:
The 4As for BMP implementation for
SL and LRF
•
•
•
•
Applicability
Adaptability
Affordability
Acceptability
The 4As interact with and affect each other.
7

8. The 4As - Applicability
• Is BMP applicable to crops or animals produced,
soils, climate?
• Do scale, resources, technology and/or management
capacity limit applicability?
– If so can BMP be adapted to overcome limitations?
– Is there a role for multi-SL farmer collaborative enterprises
to overcome scale or technology constraints while gaining
economic benefits?
8

9. The 4As- Adaptability
• Certain practices require land retirement and are not
suited to a SL farm (e.g. buffers)
– Multi-SF collaborative enterprise could help, if acceptable
• Must be adapted to fit within management and
technology constraints
• If adapted for SL-LRFs, is effectiveness of BMP
different? Can we estimate the difference?
• Can adaptation enhance affordability and/or
acceptability (or harm it)?
9

10. The 4As- Affordability
• For SL-LRF, cannot afford to implement BMPs with
substantial cost to them, so:
1. Promote BMPs that have positive impact on income?
2. Is it cost neutral or very low cost?
3. Can it be adapted so it is income positive or low/no cost?
• Could government, NGO or supply chain provide costshare or incentives to make it more affordable?
• If reducing impairment to water, can a “Payment for
Ecosystem Services” system be established with
annual payments for providing a public service?
10

11. The 4As: Acceptability
• Are there cultural/social/peer barriers to acceptability?
• Can it be adapted to minimize land/production loss?
• How can it be adapted to be more acceptable?
• Can “affordability’ incentives make it acceptable?
• Can it include desirable collateral benefits?
11

12. ~6 meter plum tree lined mini-buffer along ~7 km
of degraded stream In the Western Ukraine
Collateral benefits: 1) Future “flash” grazing of
Cows on rope leads. 2) Plums for fruit and vodka.
12

13. Eight Primary BMPs
•
•
•
•
•
•
•
•
Nutrient Management
Ecological/Organic Production Systems
Erosion Control/Conservation Tillage
Grazing Management
Cover Crops
Manure Management
Riparian Buffers
Wetland Restoration/Treatment Systems
- Not all BMPs will be applicable, efficient or needed on all farms/regions
- Other BMPs may be equal/more important in specific cases
- Apply BMPs systematically for greatest effect and to “back-up” each other
13

14. Applying a Systems Approach to
Agricultural Nutrient Pollution Control
Industrial Pollution Control Systems Approach
Pollution
Prevention
Process
Management
Facility
Management
On-site
Treatment
Off-site
Remediation
Agricultural Nutrient Pollution Control Systems Approach
Nutrient
Balancing
Nutrient
Use Efficiency
Field
Management
In-field
Treatment
Edge of Field
Management
Examples of Agricultural Nutrient Pollution Control System Practices
Conservation
Feed
Riparian
Nutrient
Tillage
Cover Crops
Management
Buffers
Management
Limit Cattle
Soil P
Nutrient rate
Access to
Wetland
Precision Ag
Remediation
reduction
Waterways
Treatment
14
T Simpson, 2008

15. A “Nested Landscape Systems Approach" to BMPs for
nutrient and sediment pollution control
In the Lake Chilika Basin in India:
•
Begin with field level systems
•
Build the system throughout all aspects of the farm
•
Link individual farm systems together to assure multi-farm and
enterprise systems approach to water quality protection
•
Link farms and multi-farm enterprise systems into a catchment
wide system approach to achieve a water quality based goal
•
Consider and link broader ecological, governance, and policy
systems in which the agro-environmental systems are nested.
Whole farm/enterprise/catchment systems approach allows
many small actions to add up to major nutrient reductions
15

16. Field scale: Nutrient management
The 4Rs: Concept developed and promoted by the
International Plant Nutrition Institute
• Match nutrient supply with crop requirements and to
minimize nutrient losses from fields
• The 4Rs of fertilizer BMP emphasize:
– the Right rate
– the Right source
– the Right time
– the Right place
Designed for intensive, high input, high yield agriculture but can be adapted to SL-LRFs

17. The 4Rs and Small Landholders –
Limited Resource Farmers
• Right source may be limited to manures, legumes, sanitary
wastes and inorganic materials they can access and afford
• Right rate must be based on all yield constraints and will likely
be below max yields due to nutrient input and other constraints
• Right placement may allow SL-LRF to increase efficiency by
manual placement for efficient plant use
– manual placement could achieve this better than mechanized (w/training)
• Right timing may allow SL-LRF to increase efficiency by
applying small amounts at key times based on plant needs
17

18. Soil Fertility and Yield Response
Principle of limiting factor (critical concept for SL-LRF):
Production can be no greater than allowed by the
most limiting plant growth/yield factor.
– Apply balanced fertilizer levels based on limiting yield factor
– Do not apply N or P for yields above those possible by other
limiting factors (nutrients, soil, climate or management)
– Soil testing recommendations based on realistic yield history
or expectations (can this service be provided to SL-LRFs?)
Barrel A: Nitrogen limited
Barrel B: Potassium limited
18

19. Maximum profit per hectare vs. maximum ROI
Maximum Profit
• The last $1 of input just
gives you $1.01 back
- maximum profit but
low use efficiency as
approach max yield
- high loss potential
100
90
$ Crop Response
80
70
60
50
40
30
20
10
0
5
10 15 20 25
30 35 40 45 50 55
$ Cost for Nutrients
Max Return on Investment
Provides the most yield
return per kg of nutrient
added (purchased or farm
generated
– high use efficiency
– low loss)
19
(Adapted from Beegle, PSU)

20. What is the right
rate for SL-LRF?
Recommended for
Maximum Economic Yield
High ROI
Ecological optimum?
Insurance
application?
Grain Yield (Mg/ha)
SL-LRF
in practice?
Small
return
6
150
Large
return
4
2
Large
N loss
100
Low-Moderate
N loss
50
100
50
150
200
Fertilizer-N applied (kg/ha)
Fertilizer N not recovered (kg/ha)
200
8
250
20
Graph only, adapted from
US NRC, 1993

21. The Right Rate: Phosphorus
• Use of manure as primary nutrient source usually results in
soil P levels above crop needs over time
• If soil P is high from past manure use, “mine” it down to soil test
recommended levels w/o further P application or yield impact
• Rotate manure use to build up soil P levels
• Best choice is manage P at agronomic (crop need) levels based
on soil test recommendations and realistic yield expectations
• For many SL/LRFs, reaching agronomic P levels is challenging
21

22. Right Time: Nitrogen
(Graph is for Northern Hemisphere temperate climate)
Try to match N availability for crop to peak crop N needs
Corn N uptake vs. growth stage
SL-LRF applies a little at planting
and 1 or 2 small applications at V-10
through tassle (at V-10
for manures)
22
Source: Soil and Water Conservation Unit, USDA

23. The Right Place – Field Scale P
Phosphorus Placement
• Broadcasting
- Builds up soil P levels uniformly over field
- Contact with most of soil so high fixation
• Banding
- Maximize soil contact by incorporating
- Place near roots
– P does not move to roots,
roots must grow to the P
- Reduces amount needed for target yield
• Combination often the best
- Broadcast to build up the soil P
- Band for better immediate efficiency
- For SL-LRF, manure incorporated pre-plant
in row area may be “hybrid” combination
23
(Beegle, PSU)

24. Adapting the 4Rs: “Micro-dosing”
• In Lake Victoria watershed and Chilika Lake, India
– application of small amounts of fertilizer with seed at planting resulted in
yield increases
– could be organic or inorganic source or combination (integrated sources)
• Not applying full amount at planting with small applications one
to two more times at critical growth stages, incorporated near
plant, can increase yield with same amount of N or P
– Small land base may make this feasible
– Manual/low technology application may allow mid-season applications at
critical crop need periods (e.g. pre-tassle to early “milk” stages for maize)
– Availability of labor for SL-LRF may help enable this
24

25. Nutrient Management – Take Home Message
• Fundamental BAP – “Balancing the soil and the crop”
• Goal is most efficient use of nutrients – follow the 4R’s
but adapt them for SL-LRFs
• Develop soil testing protocol & incentive program
• Ecological Optimum Yield as target yield for SL-LRF (?)
• Some decision support tools exist to support NM decision
making SL-LRFs but unclear if water quality is considered.
• “Breaking News”: On 25 Oct, IPNI announced release of computer
based “Nutrient Expert” software to help small landholders in parts of
rural China make nutrient application decisions to maximize yield and
profit recognizing resource constraints and not requiring soil test. Water
quality considerations in the tool were not discussed in press release.
25

26. Farm Scale: Ecological/Organic Production
Systems: Manure and Legume Management
Organic approaches: Manure as a fertilizer
• Fertilizer NPK + Micronutrients
• Added Organic Matter
–
–
–
–
–
Water Holding Capacity
Infiltration Rate
Cation Exchange
Capacity
Aggregate Stability
Bulk Density
– Improved soil quality!
26

27. Using manure as primary nutrient source
requires long-term planning
• Organic sources can improve soil quality but must carefully
time and manage applications to allow organic nutrient release
while minimizing loss in runoff
• Long term manure application
based on crop N needs will
increase risks of P losses
(Manure P:N ratio crop P:N needs)
27

28. Organic Approaches: Legumes for N inputs
• Properly inoculated legumes
meet their N requirement by
fixing atmospheric N.
• Significant N remains in
residue from legume when
crops are rotated.
• Legumes can supply all N
needed for following crop.
28
(Beegle, PSU)

29. 3
Mean N2O Emissions
residue retained
resdiue retained,
decreased N fertilizer
wheat or corn residue
removed
-1
kg N ha yr
-1
Cropping systems impact on N and P losses:
2
(Rotations Matter!)
1
Different cropping systems can trap residual soil nutrients
and risks of nutrient loss and save nutrients for next crop
0
wheat
-1
kg N ha yr
-1
Grain following potatoes lowers N levels
45
40
35
30
25
20
15
10
5
0
corn/soy bean
Mean NO3 Leached
residue retained
resdiue retained,
decreased N fertilizer
wheat or corn residue
removed
wheat
(Adapted from: Delgado, J.A., R.R. Riggenbach, R.T. Sparks, M.A.
Dillon, L.M. Kawanabe, and R.J. Ristau.
corn
corn
corn/soy bean
(Adapted from:Delgado, J.A., S. J. Del Grosso, and S. M.
Ogle. 2010
29

30. Ecological/Organic Production Systems
Take Home Message
• Balancing N and P for expected yield makes appropriate
use of manures and legumes critical in organic system
• Eco-efficient agriculture adapts technologies from
intensive agriculture and combines them with practices to
reduce environmental impacts (including water quality)
•
Ecological-based adaptation (EBA) is new approach that
can include water quality BMPs in an economically viable
system that may provide greater revenue to SL-LRF
30

31. Farm and Field Scale:
Erosion Control Conservation Tillage
• Keep the soil covered, covered, covered!
– Perennials
– Cover crops
– Crop residue
•
•
•
•
Rotations with perennials help reduce erosion
Farm on contour where scale allows
Graze the most erosive lands but maintain good cover
Plowing exposes soil, oxidizes organic matter and
reduces soil quality; avoid or minimize
31

32. Whether crop residue or growing crop/grass/perennial,
effect is the same
32

33. Conservation Agricultural Production Systems
(CAPS) in the Manila Bay Catchment
SL-LRF that are successful CAPS will:
•
•
•
•
Maintain a year-round soil cover
Minimize soil disturbance by tillage
Utilize crop rotation systems
“Promote conservation agriculture as a technologically-feasible,
economically-viable, environmentally-sustainable, and genderresponsive production system that will contribute to food security
of small farm communities in the Philippines.”
CAPS can also include many of the other “Eight Priority Practices” and promote
a “Systems Approach” as proposed in earlier slides.
33

34. Conservation Tillage & Erosion Control
Take Home Message
• Keep the soil covered as much as possible
• Leave crop residues on soil surface
• Use cover crops to keep soil covered when residue
is harvested or inadequate
• Include perennials in rotation and on erosive sites
• Discontinue plowing and minimize soil disturbance
• Create Incentive program for carbon sequestration for
long-term commitment to perennials and/or residue
management that increases soil organic carbon (?)
34

35. Field Management Practices: Cover crops:
Cover crops capture residual N from prior crop to minimize
leaching AND can be plowed into soil as N source for next
crop or harvested for livestock feed
40
100
Sampled Dec. 1
80
30
Sufficiency Level 25 ppm
60
20
40
NO3-N (ppm)
Total Accumulated N (lb/ac)
Melnick Farm 2006
10
20
0
0
Sept. 8
Sept. 15
Sept. 22
Sept. 29
Oct. 6
Cover Crop Planting Date
(planting dates for cool temperate climate)
35
(Herbert, UMASS)

36. Legume cover crops
• “Grow” N for next crop but not as effective at
trapping residual N
• Provides cover for erosion control
• Non-legume and legume mixes show promise
for fall trapping followed by spring N fixation
– Working on mix where non-legume matures or is
winter killed and releases N for next crop to
supplement legume N
36

37. Cover Crops – Take Home Message
•
Reduces sediment loss & saves excess nutrients
•
Supports erosion control & nutrient management BMPs
•
Legumes provide cover but mixes may trap residual
nutrients and supplement legume fixed N for next crop
•
Develop an incentive program and/or cost share for
seed costs and establishment
37

38. Farm Scale: Manure management:
Challenging, but critical, for SL-LRF
• Small parcels close to
neighbors & water
resources – especially
drinking water wells
• May lack equipment & land for
handling & recycling manure
• Manure may contain wood
products from bedding
–could result in high C:N ratio
unfavorable for subsequent crop
– If high carbon, compost or let “age”
38

39. Solid manure storage
• Keep away from drinking
water wells, ponds, flood
plains
x
• Covered facilities or
stockpiles, where possible
• Stack/stockpile in well-drained
area for later application
• Stockpile on flat area away
from streams or swales
39

40. Composting for manure and sanitary
sewage and solid waste management
• Stabilizes N into slow release organic forms (~10% plant
available N). Need to credit release over many years
• Don’t over apply P
• Compost can improve soil quality
Water, CO2, Heat, Ammonia
Organic matter
C, N, H2O, other
nutrients
C:N ≈ 40:1
Organic matter
O2
<C, N, <H2O,
other nutrients
Microorganisms
C:N ≈ 15-20:1
Compost Pile
40

41. Covered compost bins:
Raw uncovered compost
can leak high nutrient
loads into soil or water
Turning the compost mix enhances
aeration and creates stable
compost faster (Manual turning,
“roller bins” and “multi-stage” bins
could all be used by SL-LRF)
(Adapted from Westendorf, Rutgers Univ.)
41

42. Manure Management – Take Home Message
• Optimize animal nutrition for both nitrogen and phosphorous
- Incentive programs to optimize N & P in ration would provide
high rate of return on investment
• Proper collection/storage to maximize nutrient content is critical
• Manure storage structures can be made scalable to community level
• Learn from current incentive programs on manure/compost facilities
• Provides nutrients for crop production (replace purchased fertilizers?)
-Develop a manure nutrient testing program (?)
* Can be an important part of an organic production system
* Composting can be a viable option as part of manure and other biobased waste management
42

43. Field Scale: Pasture and Grazing Management
• Restrict animal access to streams to control
– Streambank erosion
– Pathogen contamination
– Direct inputs of nutrients
• Fencing
• Alternative water
sources
• Controlled grazing-good cover
• Land loss and costs are
challenges for SL-LRF
• Incentives & cost-shared
•
are practices needed
43

44. Reduce direct access of animals to streams
through the use of fencing, vegetated buffers,
alternative water sources and off-stream shade
Stop direct access to streams
Alternative water sources
can reduce livestock
(Sciarappa and Obropta, 44
stream use by 50-90%
Rutgers Univ.).

45. Grazing Management –Take Home Message
• Socio-Economic issues abound
• Fencing cost
• Loss of land for pasture with stream fencing
• “Free range”, “commons” culture
• Land degradation control and stream fencing/protection
should be priorities for SL-LRF
• Develop incentive and/or cost share program for fencing
and alternate water sources
• Deposited manure can be managed to help fertilize pasture
45

46. Landscape Scale: Buffers
Stream buffers trap pollutants and
protect stream banks
4 year old RFB
46
Dosskey, U.S. Forest Service

47. Landscape-scale Multi-function Stream Buffer
How applicable is this to SL-LRFs?
Can mini-buffers be adapted for SL multi-farm
collaborative and how effective will they be?
Grass
Forest
Trap sediment and
nutrients
Vegetation
Control
erosion
Function
(Dosskey, U.S. Forest Service)
47

48. Reality for SL-LRFs is that they must “farm to the edge” and
cannot afford to idle land. Either produce something of value
in the buffer or develop multi-SL-LRF enterprises that allow
strategic land retirement to increase buffer implementation.
Photo from Kagera River Basin
48

49. Collateral benefit: Agro-forestry: Coupling water
quality with biomass production in riparian buffers
• Traditional Coppicing – sustainable
understory tree “sprouts” regularly
harvested – renewed interest in UK
• Recent work with riparian tree
plantations
• rapid rotation and high biomass production
for fuel, fencing, etc.
Coppicing at Ast Wood
Herefordshire, UK
Remember the
plum vodka
mini-buffer?
49

50. Farm/Community Management: Treatment Wetlands
• Requires “designed” flow/retention pattern and aerobic
conditions before entering wetland (or last wetland cell)
• Shallow < 0.8 m
•> 4-10 day retention times
Free water surface constructed wetland
Risk Management Research U.S. EPA 625/R-00/008
UNEP-IETC. Eco-Sanitation
Technologies Offer Natural
Waste Treatment
50

51. 1.0-2.0% of small catchment converted to wetland and 7-10
days detention is optimal but challenging
Note: Curve numbers: 20=0.2%, 40=0.4%, etc.
51

52. Riparian Forest or Grass Buffers – Take Home Message
•
The first 10m of width is critical for nitrogen removal
•
Buffers have a low to moderate phosphorous removal efficiency
• Requires conversion of arable land
• Incentive programs to offset land conversion or;
• Collaborative enterprise that “pools” land resources to allow
buffer implementation (with incentives or other economic return)
• Wetlands – “Offsite treatment” to remove nutrients and sediments
• Reduces nutrient/sediment losses but requires land retirement
•
Could be used for stormwater & sewage treatment (pathogens?);
• System of small wetlands that each treat small flow may work best
52

53. Observations and recommendations
• Develop low cost applicable versions of the 8 priority BMPs and
use in a systems approach for SL-LRFs
– Standard BMPs may be hard to implement on small landholdings
– May need research, demonstration and outreach to adapt “mini” versions
of BMPs for SL-LRF
– Based on our experience, outcome based projects will provide more
consistent, implementable and transferable results
• Emphasize outcome based reporting and web based information as products
• External expert collaborator/advisor to help plan and implement for outcomes
• If possible, adapt BMPs so SL-LRFs will adopt without subsidy
or incentives (positive/neutral revenue or collateral benefits)
• Cost share, incentives and payments for ecosystem services
could accelerate adoption by SL-LRF
53

54. Applying BMP knowledge base to SL-LRFs
• Science is the same but much current information developed for
large scale, intensive systems and must be adapted for SL-LRFs
• The 4Rs still apply but must be adapted to SL-LRFs and should
be documented by field research/demonstrations
– Non-nutrient factors often limit yield; limit apply nutrients to achieve
realistic yield expectations
– SL-LRS often farm degraded lands; increasing nutrient application without
improving soil quality may not increase yields, but may increase losses
• Small size of SL-LRFs limits implementation of BMPs like buffers,
wetlands, contour tillage, etc.
– Need economic incentives and/or to explore multi-SF-LRF collaborative
enterprises to create larger management units.
– Requires social and political engagement and willingness to develop such
enterprises but may offer both economic and environmental benefits
54

55. TOP 4 SCALABLE PRACTICE FUNDING PRIORITIES
• Crop nutrient management:
• Nutrient management (adapted 4Rs)
• Manure application management
• Erosion control:
•
•
•
•
Minimize soil disturbance
Conservation tillage
Perennials in rotation
Grazing management
• Cover crops:
• Non-legumes (cereal grains, canola, etc.) to trap nutrients after
primary crop
• Legumes to “grow” Nitrogen for next crop
• Legumes – non-legume mix to do both
• Pasture management and stream fencing (including miniriparian buffers)
55

56. TOP FOUR INCENTIVE FUNDING PRIORITIES for SL-LRFs
(preliminary list)
• Collaborative enterprises: To share the burden of land
conversions for buffers & wetlands
• Novel cropping systems: On-farm demonstrations. Cost share
seed and establishment cost
• Mobile technologies: Crop and animal production support &
information with associated water quality protection practices
(apps, websites, tweets)
• Feed management: On-farm demonstrations; Incentive
payments based on kg N and P kept out of feed or manure
Funding to adapt BMPs to facilitate SL-LRF adoption and to
support/assure outcome based projects, with clear reporting
expectations, may be as important as the incentives above.
56

57. AND REMEMBER THE
4As!!!
•
•
•
•
Applicability
Adaptability
Affordability
Acceptability
57

58. Acknowledgements
This module was developed by Drs. Tom Simpson and Ron Korcak, Water
Stewardship Inc, but it includes information compiled previously
by Dr. Art Gold, Professor, University of Rhode Island
Dr. Gold acknowledged the individuals below for contributing to his compilation
(and we thank Dr. Gold and the scientists whose information was included above).
Dr. T. Bauder, Colo. St. Univ
Dr. D. Beegle, Penn. St. Univ.
Dr. B. Costa Pierce, Univ. of RI
Dr. H. Darby, Univ. of Vermont
Dr. J. Delgado, USDA-ARS
Dr. M. Dosskey, U.S. Forest Service
K. Hagos, Univ. of RI
G. Loomis, Univ. of RI
L. Moody, 4R Nutrient Stewardship
Dr. S. Oakley, Chico St. Univ.
Dr. D. Osmond, N. Carolina St. Univ.
Dr. B. Posadas, Miss. St. Univ.
Dr. M. Risse, U. of Georgia
Dr. W. Robertson, U. of Waterloo
Dr. L. Schipper, U. of Waikato, NZ
Dr. R. Schultz, Iowa St. Univ.
Dr. R. Waskom, Colo. St. Univ.
Dr. M. Westendorf, Rutgers Univ.
Contact Dr. Tom Simpson at toms@waterstewardshipinc.org
or by phone at +1-301-873-2268 58

59. 59