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IA NRS Cost Tool Overview Tyndall & Bowman, 2016 Draft

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This document presents cost and general use information for a number of land-use and edge-of-field Best Management Practices (BMP) associated with the Iowa Nutrient Reduction Strategy. Information included: general use characteristics of each BMP as per the Natural Resource Conservation Service (NRCS), basic cost parameters and outcomes. Practices covered in this document are: Multi-purpose prairie strip ................................................................................................. 4 Cover crops ....................................................................................................................... 7 Riparian forest buffers ...................................................................................................... 10 Vegetative filter strips ....................................................................................................... 10 Saturated buffers ............................................................................................................... 10 Denitrifying bioreactors .................................................................................................... 15 Constructed wetlands ........................................................................................................ 18 Drainage water management:

Controlled drainage ............................................................................................... 22 Shallow drainage ................................................................................................... 22

General Cost Assessment Methodology ........................................................................... 25 Presented info represents 2016 cost updates and expanded analysis as initially presented in: Christianson L, Tyndall JC. Helmers M. (2013) Financial Comparison of Seven Nitrate Reduction Strategies for Midwestern Agricultural Drainage. Water Resources & Economics. http://dx.doi.org/10.1016/j.wre.2013.09.001 All calculations were performed using the Iowa Nutrient Reduction Strategy BMP Cost Decision Tool (currently in Beta form; expected release October 2016). For additional information regarding costs, how costs were constructed for each practice and methods please contact John Tyndall ([email protected]). Important caveat: Please note that the direct and indirect cost of any Best Management Practice can vary considerably from site to site and are largely contingent on: initial conditions, hydrology, soils, crop, practice design, management characteristics and experienced opportunity costs (which can be highly variable). As with all of these types of financial assessments, the costs presented here are simply baseline numbers and are meant to be informative rather than prescriptive. Please cite this as: Tyndall, J., and T. Bowman (2016) Iowa Nutrient Reduction Strategy Best Management Practice Cost Overview Series. Department of Ecology & Natural Resource Management, Iowa State University.


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The following are agricultural Best Management Practices associated with the Iowa Nutrient Reduction Strategy; they are singularly or in combination designed to prevent or otherwise mitigate undesired nutrient and sediment transport from crop fields into Iowa’s surface waters. Information included in this table: general use characteristics of each BMP as designated by the Natural Resource Conservation Service (NRCS), NRCS practice code if available and basic cost parameters.

Best Management Practice (NRCS

practice standard code)

General use of the BMP: For the most part this information comes directly from NRCS practice standard information.

Basic Cost Parameters: Varies considerably from site to site and depends on initial conditions, hydrology, soil, crop, practice design, and management characteristics.

Land Use Practices – Nitrogen and Phosphorus Managemet

Multi-Purpose Prairie Strip (Practice Code 332)

Reduce sheet and rill erosion.

Reduce suspended solids and associated contaminants in runoff.

Restore riparian plant communities.

Reduce erosion by reducing slope length.

Reduce excess sediment, nutrients (N & P).

Site preparation; seed mix (high diversity); planting; mowing and/or periodic burning. Opportunity costs in the form of foregone land rent or crop revenue.

Contour Buffer Strip (Practice Code 332)

Reduce sheet and rill erosion.

Reduce transport of sediment and other water-borne contaminants downslope

Increase water infiltration

Site preparation; seed mix (usually 1or 2 different species); planting; mowing. Opportunity costs in the form of foregone land rent or crop revenue.

Cover Crops (Practice Code 340)

Reduce erosion from wind and water. Increase soil organic matter content. Capture and recycle or redistribute nutrients in the soil profile. Suppress Weeds. Manage soil moisture. Minimize and reduce soil compaction.

Seed costs (usually cereal rye or mix); planting (aerial or broadcast); termination (herbicide or mechanical). Opportunity costs from potential losses from effects on corn and or soybean yield.

Edge of Field Practices– Nitrogen and Phosphorus Managemet

Riparian Buffer (Practice Code 391)


Reduce excess sediment, organic material, nutrients (N & P), and pesticides in surface runoff.

Increase carbon storage.

Site preparation; seed mix (high diversity; multi-species: woody, grasses); planting; mowing and/or periodic burning. Opportunity costs in the form of foregone land rent or crop revenue.

Vegetative Filter Strip (Practice Code 393)


Reduce dissolved contaminant loadings in runoff.

Reduce suspended solids and associated contaminants in irrigation tailwater

Site preparation; seed mix (usually 1-2 different species); planting; mowing. Opportunity costs in the form of foregone land rent or crop revenue.

Wetlands (Practice Code 656)

Reduce nitrogen, phosphorous, pesticides, and sediment loading in intercepted tile drainage or stream systems

Site planning, engineering and preparation; excavation and soil movement; planting; seed costs (wetlands mix), tile redirection. Opportunity costs for foregone land rent or


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Provides wildlife habitat

Provides improved aesthetics

crop revenue.

Bioreactors (Practice Code 747)

Reduction in nitrogen load from tile drainage system

Excavation; tile pipe, wood chip, and control gate purchase, installation and yearly adjustment/maintenance; site surface planting; seed mix (usually 1-2 species); annual grounds keeping, replacement costs at end of practice life.

Re-saturated buffers (no practice standard; new

practice)



Reduce nitrogen loading from redirected tile drainage

Site preparation; seed mix (usually similar to vegetative or riparian buffer strips); planting; mowing. Excavation for tile drainage pipes; control structure purchase and installation; connection tile pipe; control gate yearly maintenance. Opportunity costs in the form of foregone land rent or crop revenue.

Tools in Progress for later release:

Extended Rotations (Practice Code 328)

Reduces application and loss of phosphorus and nitrogen

Reduce sheet, wind, and rill erosion

Improves soil quality

Provides animal feed stocks

Site preparation; seed costs (alfalfa); planting. Opportunity costs due to potential losses in corn/soybean revenue. Potential revenue from alfalfa sales or livestock use. Potential revenue from increased yield effects in subsequent corn and soybean crops.

Terrace (Practice Code 600)

Reduce erosion by reducing slope length. Retain runoff for moisture conservation.

Site preparation (including earth moving and planting bed prep); seed mix (usually 1-2 different species); planting; mowing. Opportunity costs in the form of foregone land rent or crop revenue.

The Four “R’s”: Right source, Right

timing, Right rate, Right place,

The goal of fertilizer BMPs is to match nutrient supply with crop requirements and to minimize nutrient losses from fields.

Savings through optimization of fertilizer use or use of animal waste fertilizer Opportunity cost from potential losses of inadequate fertilizer or missed timing. Potential costs from use of nitrogen inhibitor and potential revenue from increased yield effects from inhibitor use.

“Conservation” tillage (Practice Codes 329 – no-till, Strip till, 345 –

Mulch till)

Erosion control.

Conserves soil moisture.

Improve soil organic matter.

New equipment or equipment modification; may increase dependence on herbicides. Can lower fuel and labor costs.

What follows is a practice-by-practice overview of the general use and basic cost parameters (including establishment, management and relevant opportunity costs). A transaction table itemizing all the general cost-bearing actions and a basic analysis summary is provided for each Practice. All costs presented represent 2016$.


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In and Edge of Field Practice Prairie Strips: Multi-purpose prairie strips are narrow strips of high diversity prairie alternated down the slope with wider cultivated strips that are farmed on the contour. Multi-purpose prairie strips have been shown to reduce sheet and rill erosion, increase water infiltration, and reduce excess sediment and nutrients (table 1 below) from

fields with 2% - 10% slopes. Multi-purpose prairie strips are usually a minimum of 15 feet wide and planted in parallel between 100 to 150 feet apart. In practice, research has determined that no more than 10% of a drainage area (cropped field) needs to be planted to prairie. Vegetation in strips consists of high diversity mixture of native grasses and forbs. NRCS conservation programs may help offset the costs of prairie establishment and long-term land use; e.g., NRCS Practice 332, Contour Buffer Strip. Basic Cost Parameters and Cost Assessment There are five main cost categories that farmers must consider in the use of contour prairie strips: (1) site preparation costs; (2) prairie strip establishment costs

including seed purchase and planting; (3) annual and periodic management costs involving mowing and/or burning for several years following planting and then periodically once the prairie stand is established; (4) relevant annual opportunity costs in the form of foregone land rent or revenues; and 5) any additional costs associated with changes to cropping system management (e.g., new field herbicide application protocols to protect the prairie). On average the annual cost of converting one acre of crop land to prairie would cost in 2016 between $260 to $340 per acre; summarized in table 2. The majority of this cost (80% +) is the opportunity cost of that acre (which is represented here by foregone land rent across a range of soil qualities), the second most expensive individual component is the cost of high diversity prairie seed (~ 10% of the establishment cost). Annual management activities account for up to 15% of the annual cost. In the context of use where no more than 10% of a drainage area (cropped field) would be planted to prairie, the average cost per “treated crop acre” ranges from $26 to $34 per acre per year (e.g., assumes 1 ac of prairie “treats” about 9 ac of row crops). Contrast this with the cost per “treated crop acre” of cover crops being between $40 to $80 per acre per year. Table 2 below presents the general cost bearing activities associated with establishing and management prairie strips. Assessment presented here represents an update of Tyndall et al. (2013).

Table 1. General use characteristics of multi-Purpose Prairie Strips and basic cost parameters.

Best Management Practice (NRCS practice

standard code)



Multi-Purpose Prairie Strip (Qualifies for

FSA CP 15) 1

Reduce sheet and rill erosion. Reduce suspended solids and associated contaminants in runoff. Restore riparian plant communities. Reduce erosion by reducing slope length. Reduce excess sediment, nutrients (N & P).

Site preparation; seed mix (high diversity); planting; mowing and/or periodic burning. Opportunity costs in the form of foregone land rent or crop revenue.

1. Farm Service Agency, CP 15: http://www.fsa.usda.gov/Assets/USDA-FSA-Public/usdafiles/FactSheets/2015/CRPProgramsandInitiatives/Practice_CP15A_Contour_Grass_Strips.pdf

Photo: A MacDonald, ISU


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Table 2. Average annual 2016 costs (per acre per year) of using multi-purpose prairie strips

Annualized Total Costs 1 Higher Quality Land (CSR 83)

Medium Quality Land (CSR 73)

Lower Quality Land (CSR 60)

Per acre of prairie $339 $297 $257

Cost per treated crop acre per year2, 3 ~ $34 ~ $30 ~ $26 Total upfront establishment costs per

acre (including rent) $475 $434 $396 1. Calculated using standard discounted cash-flow procedures using a 4% discount rate and 15-year management horizon. Average 2016 Iowa land rent charge for CSR 83 = $270/ac; CSR 73 = $230/ac; CSR 60 = $191/ac. 2. Assumes 1 ac of prairie “treats” about 9 ac of row crops. 3. In most cases, ≤ 10% of total cost is site prep and establishment, ~ 10% to 15% of cost is management and 80% to 90% of cost is land cost.

References for Prairie Strips Edwards, W. (2009) Natural Resources Custom Rate Survey. Iowa State University. File A3-11

Updated September, 2009

Plastina, A. and A. Johanns (2016) 2016 Iowa farm custom rate survey. Ag Decision Maker. File A3-10; FM 1698 (Revised, March 2016).

Plastina, A., A. Johanns and C. Welter (2016) Cash Rental Rates for Iowa. 2016 Survey. File C2-10. FM 1851 Revised May 2016. Ag Decision Maker.

Tyndall JC, Schulte L, Liebman M, Helmers M. (2013) Field-Level Financial Assessment of Contour Prairie Strips for Environmental Quality Enhancement. Environmental Management. 52(3): 736-747.


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Table 2. Costs associated with planting multi-purpose prairie strips planted after soybeans. Costs presented in 2016 dollars. Data updated from Tyndall et al. 2013. Cost Activities 1/ items Year cost incurred 2 Range of costs

(units)

Mean price (ac)

Notes

Site Preparation Tillage 0 $0 to $30/ acre $15.00 Tillage type will be variable depending

upon initial conditions. Tillage may also be unnecessary, e.g., Prairie seed can be drilled directly into bean stover. Data: Plastina and Johanns (2016): https://www.extension.iastate.edu/agdm/crops/pdf/a3-10.pdf.

Herbicide 0 $40 to $80/gal $15.00 Chemical Mix for Site or Seedbed Prep or Weed Control (Glyphosate $40 to $80/gal. - 1 qt/ac)

Herbicide application 0 $5 to $10/ acre $7.00 Plastina and Johanns (2016)

Prairie Establishment

Prairie Seed 0 Highly variable; depends upon goals of planting. $137.00

There are a number of companies that sell regional genotypic prairie grass and forb seed.

Seed drilling 0 $10 to $25/ acre $15.00 Plastina and Johanns (2016)

Cultipacking 0 $5 to $30/ acre $17.50 Edwards (2009): https://www.extension.iastate.edu/agdm/crops/html/a3-11.html

Prairie Management

Mow, rake/row, bale & move

3 x in yr 1; annually 2-15 after $28 to $61/ acre $44.00 Plastina and Johanns (2016)

Burning 3

Mow 3x in yr 1; Mow, rake/row &

bale yr 2; burn every 3 yrs after

Mow & bale ~ $23/ acre. Burning $60 to $200/acre ---

SNR Foundation 2007 & Edwards 2009; inflated to 2016 $ rounded to nearest dollar.

General operating costs Annual 1-3% of upfront costs — --

Opportunity Costs 4

Land rent Annual Variable $120 - $400

Plastina, Johanns and Welter, (2016): https://store.extension.iastate.edu/Product/fm1851-pdf

1 Establishment and management of prairie strips will vary somewhat from site to site depending on initial conditions, soil, previous cropping system, and practice design. 2 Assumes early spring expenditure.3 Burning the prairie is an alternative to mowing and baling; assumption is land manager would either mow/bale or burn. 4 Note that research has shown no negative yield impacts on crops adjacent to prairie.


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Land Use Practices Cover Crops (Cereal Rye example): Cover crops are plants that are used to protect soils during the period between the harvest and establishment of crops such as corn and soybeans (table 1). They have the capacity to scavenge/ retain nitrates, reduce erosion in the field and reduce the movement of

phosphorus. Based on the science summary produced by the Iowa Nutrient Reduction Strategy (Lawrence 2013), cereal rye cover crops result in an average 31% reduction in nitrate (N) field loss and about 29% reduction in phosphate (P) loss (though it should be noted that the standard deviations are quite high indicating highly variable results). There are many other cover crop types suitable for different regions in Iowa; cover crop choice is a matter of field level land use goals and regional crop suitability. The Midwest Cover Crops Council has developed and made available online, a comprehensive field guide and species selection decision tool; this can be found at: http://www.mccc.msu.edu/index.htm.

Table 1. General practice characteristics of cereal rye cover crops as used in Iowa and basic cost parameters. This practice can be cost shared with the NRCS via the EQIP cover crop program.

Best Management

Practice Goals of Practice Basic Cost Parameters

Cover Crops (NRCS Practice

Code 340)

Reduce erosion from wind and water. Increase soil organic matter content. Capture and recycle or redistribute nutrients (particularly N) in the soil profile. Suppress Weeds. Manage soil moisture. Minimize and reduce soil compaction.

Seed costs (usually cereal rye or mix). Planting (aerial or broadcast). Termination (herbicide or mechanical). Opportunity costs from potential losses from effects on corn or bean yield. General extra management costs (e.g., walking fields, adjusting equipment, etc.)

Cost Overview for Cereal Rye Cover Crops: Depending on the method of seeding (drilling, aerial, broadcast) and cover crop termination (chemical or mechanical) the total average annual cost ranges from a low of about $57 per acre to a high of about $68 per acre (see table 2 below). The single costliest aspect of using cover crops based on this analysis is the cost of seed (based on 2016 prices from online Cornbelt region seed dealers); less expensive, local seed sources may well be available variably by region within the state. Aerial seeding is in general more expensive than broadcast seeding and herbicide termination is generally more expensive than mechanical methods. Table 3 below outlines various cost bearing activities generally associated with establishing and managing cereal rye cover crops in Iowa (note: management activities may vary from farm to farm). For more information, please see Roley et al. (2016).

Cereal Rye. Photo: Iowa Learning Farm


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Table 2: Average costs 1 for Cereal Rye Winter Cover Crops in Iowa 2016.

Aerial option total cost per acre (herbicide

termination)

Broadcast option total cost per acre (herbicide

termination)

EQIP2 Aerial option total cost per acre

(herbicide termination)

EQIP2 Broadcast option total cost per

acre (herbicide termination)

~ $65 ~ $63 ~ $25 ~ $23

Min $42; Max $84 Min $37; Max $80 Min $2; Max $44 Min $0; Max $40

1. Assumes no negative or positive yield effects.

2. 2016 Iowa EQIP Basic Payment Rates Chemical or mechanical kill species—$40.13/Ac; http://www.nrcs.usda.gov/wps/PA_NRCSConsumption/download?cid=nrcseprd420279&ext=pdf

References for Cover Crops Iowa Learning Farms and Practical Farmers of Iowa. (2014) Winter Cereal Rye Cover Crop Effect on Cash Crop

Yield. Available at: http://practicalfarmers.org/farmer-knowledge/research-reports/2014/winter-cereal-rye-cover-crop-effect-cash-crop-yield/

Lawrence J. 2013. Iowa Strategy to Reduce Nutrient Loss: Nitrogen and Phosphorus Practices. Iowa State University Extension and Outreach. SP 0435. February 2013.

The Midwest Cover Crops Council Field Guide and species selection decision tool; Available at: http://www.mccc.msu.edu/index.htm.

Plastina, A. and A. Johanns (2016) 2016 Iowa farm custom rate survey. Ag Decision Maker. File A3-10; FM 1698 (Revised, March 2016). Avialable at: https://www.extension.iastate.edu/agdm/crops/pdf/a3-10.pdf

Roley, S., Tank, J., Tyndall, J.C., Witter, J. (2016) How cost-effective are cover crops, wetlands, and two-stage ditches for nitrogen removal in the Mississippi River Basin? Water Resources & Economics.


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Table 3. Custom rate costs associated with winter cereal rye cover crop (Secale cereal)1 planted in Iowa; primary cover goal is nitrogen scavenging. Costs presented in 2016 dollars. Data updated from Roley et al., 2016.

1 There are a number of different cover crops that are suitable in Iowa under certain conduction and locations. Cover crop choice is a matter of field level land use goals and regional crop suitability. The Midwest Cover Croup Council has a tool that can help farmers make cover crop selection choices: http://www.mccc.msu.edu/selectorintro.html 2 Establishment and management of cover crops will vary depending on initial conditions, soil, previous cropping system, and practice design (including choice of crop, planting and termination).

Cost Activities 2 Year cost

incurred

Range of costs (units)

Mean price (ac)

Notes Data Sources

Seed cost -Planting option 1 aerial

0 $0.20 - $0.40/lbs $36 120 lbs per acre seeding rate. There are a number of regional seed companies that

feature seeds for cover crops of all kinds.

Seed cost – Planting option 2 broadcast

0 $0.20 - $0.40/lbs $30 100 lbs per acre seeding rate. There are a number of regional seed companies that

feature seeds for cover crops of all kinds.

Planting cost option 1 - aerial 0 $7.50 to

$16.00/ acre $11.00 Typical aerial Seeding Rate: 83-150 lb./Ac PLS. Seeding rate: http://mccc.msu.edu/states/Iowa.html; Cost information: Plastina and Johanns (2016):

Planting cost option 2 - broadcast

0 $8.00 to $15.00/acre $12.25 Typical broadcast Seeding Rate: 69-125 lb./A PLS.

Seeding rate: http://mccc.msu.edu/states/Iowa.html; Cost information: Plastina and Johanns (2016): Seed drilling is also an option and costs on average ~ $17.00 per acre.

Cover termination - herbicide

0 Variable $18.43

Glyphosate: $18.70/ gal.; AMS: $0.35/lb.; Nonionic surfactant: $26/gal; Application: $7.23/acre = 64 oz. glyphosate + 2.5 lb. AMS + 4.8 oz. NIS = Total: $18.43/acre.

Cost data modified from: Holmes 2014 http://www.agribizshowcase.com/wp-content/uploads/2012/02/Cover-Crops-in-Iowa-Holmes.pdf; Glyphosate cost estimate: http://www.nass.usda.gov/Statistics_by_State/Iowa/Publications/Prices/reports/IA_PRICESPAID_04_14.pdf

Cover termination - disking

0 $8.00 to $25.50/ acre $16.75

Cover crop termination by disking could involve 2 + passes, yet one pass is likely to occur regardless of the presence of cover crops so only one pass is counted here.

Cost data: Plastina and Johanns (2016)

Increased crop management 0 Variable Variable

Increased Management cost is a general category; includes extra time spent: walking fields to assess cover crop progress, adjusting equipment, etc. Assumed to be 3% of establishment & Mgt cost.

General management information from The Iowa Learning Farm: http://www.extension.iastate.edu/ilf/content/cover-crop-resources

Impacts on crop yield 0 Variable -- Based on Iowa field trials, the impact of cereal rye

on corn and bean yields is assumed to be negligible. Yield trial data: Iowa Learning Farms & PFI 2014


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Edge of Field Practices Riparian Forest Buffers and Vegetative Filter Strips: Riparian buffers and filter strips are strategically located vegetated areas adjacent to water resources that protect water from nonpoint source pollution, provide bank stabilization and aquatic and wildlife habitat (figure 1). These buffers utilize a mix of trees, shrubs and or grasses. Regionally, research has demonstrated that riparian buffers and filter strips are very effective in reducing excess sediment, organic material, nutrients (N & P), and pesticides in surface runoff by: reducing the rate of run off, decreasing suspended solids, reducing edge of field sheet and rill erosion, and increasing infiltration, microbial activity, evapotranspiration, and overall water storage capacity (see LCSA, 2000). Based on the science summary produced by the Iowa Nutrient Reduction Strategy (Lawrence 2013), cereal rye cover crops result in an average 91% reduction in nitrate (N) and about 58% reduction in phosphate (P) (though it should be noted that the standard deviations are quite high indicating highly variable results). The lifespan of buffer practices are indefinite; as with all Best Management Practices based on perennial vegetation, there is an idealized expectation that these practices are effectively permanent (though it is technically possible to return the land base to agricultural production). Saturated buffers: A “saturated buffer” is a riparian buffer in which the water table is artificially raised by diverting a substantial portion (up to 60%) of subsurface drainage parallel to an existing riparian buffer. This is accomplished by installing a water control structure in the main drainage outlet at the buffer interface. In Iowa, this practice is being investigated as a way to reduce nitrate and phosphate loading to surface waters (see Isenhart and Jaynes 2015). Table 1 below summarizes the general use characteristics of these practices and overviews their basic cost aspects.

Figure 1. Riparian forest buffer (left) and vegetative filter strip (right). Table 1. General use characteristics of Riparian Forest Buffers (Practice Code 391), Vegetative Filter Strip (Practice Code 393), Saturated buffers (practice standard in development for Iowa) and basic cost parameters.

Best Management

Practice (NRCS practice

standard code)



Riparian Forest Buffer (Practice

Code 391)1


Reduce excess sediment, organic material, nutrients (N & P), and pesticides in surface runoff.

Increase carbon storage.

Site preparation; seed mix (high diversity; multi-species: woody, grasses); planting; mowing and/or periodic burning. Opportunity costs in the form of foregone land rent or crop revenue.

Forested(Buffer,(Photo:(ISU( Grassed(buffer/(riparian(filter(strip,(Photo:(OH(NRCS(


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Vegetative Filter Strip (Practice

Code 393)2

Reduce suspended solids & associated contaminants in runoff.


Reduce suspended solids and associated contaminants in irrigation tailwater

Site preparation; seed mix (usually 1-2 different species); planting; mowing. Opportunity costs in the form of foregone land rent or crop revenue.

Saturated buffers (Practice Code

604; Draft)3



Reduce nitrogen loading from redirected tile drainage

Site preparation; seed mix (e.g., similar to vegetative or riparian buffer strips); planting; mowing. Excavation for tile drainage pipes; control structure purchase & installation; connection tile pipe; control gate yearly maintenance. Opportunity costs (e.g., foregone land rent or crop revenue).

1. Riparian Forest Buffer (Practice Code 391): http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs143_026098.pdf.

2. Vegetative Filter Strip (Practice Code 393): https://efotg.sc.egov.usda.gov/references/public/IA/Filter_Strip_393_STD_2010_02.pdf.

3. Saturated buffers (Practice Code 604; Draft): http://www.saturatedbufferstrips.com/images/ncrs.pdf

Cost Overview for Riparian Forest Buffers, Vegetative Filter Strip and Saturated buffers: With regard to riparian forest buffers and vegetative filter strips the primary upfront costs are associated with site preparation, planting stock and establishment. The primary management costs are associated with annual maintenance activities (e.g., mowing, replanting/seeding if needed). The significant long-term cost of these practices is the annual opportunity cost of foregone rent or revenue associated with any crop-land that is effectively retired. The annualized costs for a 66-foot-wide riparian forest buffer comes to about $460 per acre per year, for a vegetative filter strip annualized costs come to ~ $300 per acre per year (the main difference in cost between these buffer types is the woody planting stock and increased management needs required for the riparian forest buffer). For saturated buffers the primary costs are associated with control structures and tile extensions. Saturated buffers are in addition to the buffers themselves, so in practicality, the buffer costs apply as well.

There are conservation programs that will offset some of the cost to landowners. Both Riparian Forest Buffer (Practice Code 391; CP 22) and Vegetative Filter Strip (Practice Code 393; CP 21) qualify for continuous CRP (10-15 year initial contract lengths), 90% cost share on establishment, a $10 per acre/year practice incentive, and a 20% rental payment bump on top of weighted average rental payment (based on soils); for Riparian forest buffers there is also a one-time bonus of at least $100/ acre for planting trees. Note that program payments may vary somewhat from county to county and year to year;

Average annual 2016 costs (per acre per year) of using either a 66-foot wide riparian forest buffer or a riparian vegetative filter strip (e.g., planted to a CP21 compliant mix)

Practice Average annualized cost per acre 1

Riparian Forest Buffer $330 Vegetative Filter Strip $233

Saturated Buffer 2 $360 2 1. Calculated using standard discounted cash-flow procedures using a 4% discount rate and 20-year management horizon. Assumes land rent cost of $100/acre; 2. Assumes a 20 acre drainage area.


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References for Buffer Systems

Isenhart, T. and D. Jaynes (2015) Cleaning Iowa's Waters with Saturated Buffers in Iowa Watersheds. Iowa State University Extension and Outreach. WQ 0005, October 2015. Available at: https://store.extension.iastate.edu/Product/14441

Jaynes, D.B. and T. Isenhart (2011) Re-saturating Riparian Buffers in Tile Drained Landscapes. A Presentation of the 2011 IA-MN-SD Drainage Research Forum. November 22, 2011. Okoboji, IA �

LCSA - Leopold Center for Sustainable Agriculture (2000) Frequently asked questions about riparian buffer management systems. Available at: http://www.buffer.forestry.iastate.edu/Assets/FAQ.pdf

Plastina and Johanns (2016) 2016 Iowa farm custom rate survey. Iowa State University Extension and Outreach, Ag Decision Maker File A3-10; FM 1698 (Revised, March 2016).

Plastina, Johanns and Welter (2016) Cash Rental Rates for Iowa. 2016 Survey. Iowa State University Extension and Outreach, Ag Decision Maker File C2-10. FM 1851 Revised May 2016.

Schultz, R.C., Colletti, J.C., Isenhart, T., Marquez, C.O., Simpkins, W.W., and C.J. Ball (2000) Riparian buffer practices. Chapter in North American Agroforestry: An integrated Science and practice. American Society of Agronomy, Madison WI.

Tyndall, J.C. and R.C. Grala (2009) Financial Feasibility of Using Shelterbelts for Swine Odor Mitigation. Agroforestry Systems 76:237–250.


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Table 3. Custom rate costs associated with multi-species, vegetative and saturated buffers installed in Iowa; primary goal is nitrogen reduction from agricultural runoff. Costs presented in 2016 dollars. Data updated from Christianson et al. 2013. Cost Activities 1/ items Year cost

incurred Range of costs

(units) Mean

price (ac) Notes Data Source

Buffer Site design 0 $0 - $300/ design $0 Typically, buffer designs will be gratis from NRCS, but

more complex buffers may need outside assistance Cost data: Plastina, A., and A., Johanns 2016

Site preparation 0 $133.80 - $219.30/ acre $174.40

Includes disking, harrowing, site clearing, herbicide (various) and fertilizer application (lime, K, P). In some cases it might be recommended that in the fall prior to buffer establishment, the site is disked and planted to a winter cover (e.g., winter rye or timothy). This would add ~$40 per acre to site prep costs.

Cost data: Plastina, A., and A., Johanns 2016; Site preparation data: Schultz et al. 2000

Multi-species Buffer (Trees, shrubs, grass)

Planting stock (bare root seedlings) 0

$38.50 to $53.50 per 100

seedlings Variable

Species choice is a matter of soil conditions, landowner goals, and expected/emerging pest and pathogen concerns. Total costs of planting stock depends upon buffer design (e.g., total number of tree/shrub rows, spacing between trees/shrubs).

Iowa DNR State Nursery 2016: http://www.iowadnr.gov/Portals/idnr/uploads/forestry/nursery/seedlingcatalog.pdf

Trees and shrubs planting cost (machine planting)

0 $80 to $400 per acre. ~$240.00 Edwards 2009 (inflated to 2016$)

Replanting (trees) 0-5

$38.50 to $53.50 per 100

seedlings; $1 per tree hand planting

Variable Natural mortality of at least 10% is common in the first several years of buffer establishment. Replanting may be required to fill significant gaps in the buffer.

Tyndall and Grala 2009

Drilling grass seed 0 $46 to $121.50/ acre $70.35

Includes seeds and seed drilling. A basic seed selection is a CP21 compliant mix (wet to mesic soil mixes are available). There are a number of companies that sell regional genotypic prairie grass and forb seed.

Cost data: Plastina, A., and A., Johanns 2016

Pre-emergent Herbicide 1 $40 to $80/gal $30 A mix of oxyfloufen and oryzalin should control both grasses and broadleaves.; 0.5 gallons per acre. Management information: Schultz et al. 2003

Herbicide narrow-band application 0 $11 to $45/ acre $25 Cost data: Plastina, A., and A., Johanns 2016;

Edwards 2009 (inflated to 2016$)

Buffer mowing cost 0-5 $20 - $60/ acre $36.70 Vegetative buffers should be mown twice yearly Cost data: Plastina, A., and A., Johanns 2016

Vegetative buffer only (grasses)

Drilling grass seed 0 $46 to $121.50/ acre $70.35

Includes seeds and seed drilling. A basic seed selection is a CP21 compliant mix (wet to mesic soil mixes are available). There are a number of companies that sell regional genotypic prairie grass and forb seed.

Cost data: Plastina, A., and A., Johanns 2016; Christiansen et al. 2013.


14

Buffer mowing (management option 1) 0-lifespan $20 - $60/ acre $36.70 Mow 2 x in yr 1 during stand establishment phase; annually

after. Material does not necessarily need to be baled. Cost data: Plastina, A., and A., Johanns 2016; Christiansen et al. 2013.

Mow, rake/row, bale & move (management option 2)

Variable $28 to $61/ acre $44.00 Mow 2 x in yr 1 during stand establishment phase; annually after Cost data: Plastina and Johanns (2016)

Burning Variable

Mow & bale ~ $23/ acre.

Burning $60 to $200/acre

---

Burning the grass is an alternative to mowing and baling; assumption is land manager would either mow/bale or burn. Mow 2 x in yr 1 -2 during stand establishment phase; burn every 3 yrs after

SNR Foundation 2007 & Edwards 2009; inflated to 2016 $ rounded to nearest dollar.

General operating costs Annual 1-3% of upfront costs — This would involve general monitoring of the buffer and

record keeping.

Opportunity Cost of Land

Land rent Annual Variable $120 - $400

Varies considerably throughout Iowa and changes year by year. Average rental rates in Iowa have dropped 15% since 2013. In 2016, the statewide average for cropland was $230/acre, for improved pasture land it was $80/acre.

Plastina, Johanns and Welter, (2016):

Impacts on adjacent upland crop yield Annual Variable -- The impact of vegetative buffers on corn and bean yields is

assumed to be negligible.

Saturated buffer component

Saturated buffer structures 0

$2290 to $5890/ drainage area

(20 ac.) $4120.00

Includes 2 control structures, contracting costs to install structures (backhoe @ 8 hrs), and 1000’ of connecting tile to route drainage from 20 acres

Christiansen et al. 2013; Design data: Jaynes and Isenhart 2011.

Saturated buffer maintenance – adjust control gates

Annual $20.00 to

$40.00/ drainage area (20 ac.)

$28.40 Control structures must be adjusted seasonally to account for crop growth and field operations

Cost data: Christiansen et al. 2013; Design data: Jaynes and Isenhart 2011.

Saturated buffer maintenance – replace control gates

Every 8 years

$141.70 to 153.20/ drainage

area (20 ac.) $147.50 Control structure gates must be replaced every 8 years to

maintain correct operation Cost data: Christiansen et al. 2013; Design data: Jaynes and Isenhart 2011.

IA NRS Cost Tool Overview Tyndall & Bowman, 2016

15

Edge of Field Practice Denitrifying Bioreactors A denitrifying bioreactor is an edge-of field-nitrogen management practice that involves a trench in the ground packed with carbonaceous material such as woodchips that facilitate colonization of soil bacteria that convert nitrate in drainage water to nitrogen gas; see figure 1 for a generalized schematic. Bioreactors are most suitable for 6”-10” tile lines and most current bioreactor designs in use in Iowa have been successful at treating nitrate in drainage areas from 30 to 80 acres in size and have life spans of at least 15 years (before material fill need replacing/or control structures need significant maintenance). Because this is an edge-of-field practice, in-field yields will not be affected. Likewise, bioreactors will have no impact on soil quality. Regional research regarding the effectiveness of bioreactors has demonstrated nitrate reduction in drainage water between 30 to 70% (Christianson and Helmers, 2011).

Figure 1. Simplified diagram demonstrating the basic bio-physical principles of a denitrifying woodchip bioreactor and its structure. Design, scale, and function of denitrifying bioreactors are site-specific and contingent upon site conditions and management goals. Image: Christianson, 2014 Woodchip Bioreactor Cost Overview and Example:

The primary cost of a woodchip bioreactor is associated with planning and design, excavation, control structures and obtaining, transporting, and handling fill material; these represent upfront costs that occur in years 0 and 1; see table 1. There are no land-use opportunity costs associated with the utilization of bioreactors. The functional lifespan of this practice is estimated to be between 15 to 20 years (though it could be longer) after this time period, control structures and the fill may need to be replaced.

Table 1. General practice characteristics of bioreactors as used in Iowa and basic cost parameters. This practice can be cost shared with the NRCS via the EQIP program.

Best Management

Practice (NRCS practice standard

code)



Bioreactors (Practice Code

747) 1

Reduction in nitrogen load from tile drainage system

Design and planning; excavation; tile pipe, wood chip, and control gate purchase, installation and yearly adjustment/maintenance; site surface planting; seed mix (usually 1-2 species); annual grounds keeping, replacement costs at end of practice lifespan.

1. NRCS Practice Standard for Bioreactors, Practice Code 747: https://efotg.sc.egov.usda.gov/references/Agency/IA/Archived_Denitrifying_Bioreactor_747_STD_2014_04_151015.pdf


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Because the total costs of a bioreactor are use specific and contingent upon the overall scale/ drainage area being treated, below is an example cost assessment for a bioreactor suitable for a 50-acre drainage treatment. Basic bioreactor parameters for cost example: 40-acre drainage treatment. Design capacity is to treat a flow equivalent to a drainage coefficient of 1/8ʺper day or 20% of the calculated peak flow from the drainage system. Four-hour hydrologic retention time. The annualized costs over a 20-year period come to slightly over $800 per year. Total upfront costs for design and full installation come to $10,250. Table 2 below summarizes the outcome of this example. The Iowa NRCS Environmental Quality Incentives Program (EQIP) will pay $24.85 per cubic yard of pit excavation. The bioreactor in this example has an excavated pit volume of 333 cubic yards (e.g. 6 feet deep, 15 feet wide and 100 feet long) and would pay $8,275 or 80% of the total installation costs. Table 3 overviews all the custom rate costs associated with this practice.

Table 2. First year and annualized costs of a denitrifying bioreactor designed for a 50-acre drainage area. Annualized using a 4% discount rate. Costs are in 2016$.

First year costs (Design and installation) $10,150 1, 2

Annualized costs over 20 year lifespan $675 3

Annual management costs ~ $50

1. No productive land is removed from production so opportunity costs are negligible. The vast majority of total costs are in installation and in chip replacement after 20 years;

2. Iowa 2016 EQIP program will pay $24.85 per cubic yard of bioreactor pit excavation assuming the practice is maintained for at least 10 years. (The Iowa 2016 EQIP payment schedule:http://www.nrcs.usda.gov/wps/PA_NRCSConsumption/download?cid=nrcseprd420279&ext=pdf (Bioreactors, page 108);

3. Costs were calculated and annualized using standard discounted cashflow procedures for structural water quality Best Management Practices. For more detail see Tyndall and Roesch, 2014.

References Denitrifying Bioreactor

Christianson, Laura. (2014) Bioreactors: Benefits and potential challenges. Iowa Learning Farm Webinar Series. November 2014. Available at: https://iowalearningfarms.wordpress.com/2014/11/17/top-ten-webinars-4-bioreactors-benefits-and-potential-challenges/

Christianson, L. and M. Helmers. (2011) Woodchip Bioreactors for Nitrate in Agricultural Drainage. Iowa State University Extension & Outreach. PMR 1008. October 2011. Available at: https://store.extension.iastate.edu/Product/13691

Christianson, L., Tyndall, J.C., Helmers, M. (2013) Financial Comparison of Seven Nitrate Reduction Strategies for Midwestern Agricultural Drainage. Water Resources & Economics. http://dx.doi.org/10.1016/j.wre.2013.09.001

Tyndall JC, and G. Roesch (2014) A Standardized Approach to the Financial Analysis of Structural Water Quality BMPs. Journal of Extension. Vol. 52, Num. 3, 3FEA10.


17

Table 3. Custom rate costs associated with bioreactors installed in Iowa; primary goal is nitrogen reduction in tile drainage. Costs presented in 2016 dollars. All data updated from Christianson et al. 2013.

Cost Activities 1/ items

Year(s) cost

incurred

Average cost (per bioreactor)

Average cost (per year; 20

years) Notes/ Assumptions

Bioreactor design 0 $1000 $61 Bioreactor design is generally available without cost from a government service agency (such as the NRCS); however, more complex designs may require an engineering firm (~ 10 hours at $100/hr).

Control Structures 0 $2630 $161 Cost and installation of control structures (2 for every 50 drainage acres at $530 - $2100 per structure).

Connection pipe/tile 0 $1650 $101 1000’ of connection pipe (at $0.30 - $3.00 per foot).

Trenching (backhoeing) 0, 20 $1140 $70 Bioreactor trenching (backhoeing); at average cost of $95/hour for 12 hours. In year 20

the woodchips may need replacing. A backhoe may be used to remove old woodchips

Woodchips (with transportation) 0, 20 $3600 $220

Two semi loads of woodchips at $1600 per load, $200 transport ea. There may be locally available woodchips at significantly reduced cost. Ideally, woodchips are should be uniform in size and free of debris. Bulk sales of woodchips from retail outlets can cost ~ $30/ cubic yard, or about $10,000. In year 20 it is possible that the woodchips will need to be replaced.

Grass cover seed 0

$60

$4 $0.02/ft^2 bioreactor area; total area < 3,000 square feet.

Planting grass cover 0 $10 $1 Includes broadcast seeding from a tractor or ATV.

Mow bioreactor grass cover 0-20 $10 $10

$0.01 to $0.09/ drainage acre. This management action will likely be incremental to mowing activities in the edge of field. The bioreactor’s grass cover should be mown at least once per year.

Bioreactor maintenance – adjust control gates

0-20 $40 $40 $20.00 per hour labor. Control gates must be adjusted seasonally to account for crop growth and field operations.

Bioreactor maintenance – replace control gates

8, 16 $75 $7 Every 8 years, the gates within the control structures must be replaces to maintain correct operation. 5 Gates per structure ($15.00 per ea. for 15 cm structure) 2 structures per 50 acres drainage area.

Impacts on crop yield 0 $0.00 $0.00 The impact of bioreactors on corn and bean yields is assumed to be negligible.

A NRS Cost Tool Overview Tyndall & Bowman, 2016 Draft

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Edge or In-field Practice Constructed Wetlands: Constructed and/or restored wetlands are engineered nitrate, phosphorus and sediment treatment systems that function under a variety of conditions and when used in strategic watershed positions have the potential to significantly improve water quality in Iowa’s agricultural watersheds (Figure 1; Table 1). US Midwest region research has measured wetland nutrient removal rates in drainage water of up to 68% for nitrate-nitrogen and 43% for phosphorus, although these outcomes vary considerably from site to site (Woltemade 2000). Wetlands slow the movement of water and allow sediment in runoff to settle. Further, constructed wetlands intercept tile drainage water and microbially denitrifies nitrate-nitrogen, releasing it to the atmosphere as nitrogen gas. Perennial wetland vegetation, or as part of the planned buffer surrounding wetlands, have the capacity to remove excess phosphorus from wetlands and thus provide an opportunity for addressing phosphorus in drainage water. These systems also provide important habitat to all sorts of terrestrial, migratory and aquatic species (figure 1). A constructed wetland is scaled according to its treatment drainage area; typically, a 0.5% - 2% range in wetland/watershed area ratio is the standard. Maximum wetland depth is typically no deeper than 10 feet and edge depth will vary throughout the year. For a broad overview of wetland function and their use as a conservation practice, see Iowa Learning Farms (2014).

Figure 1: Constructed wetland system in Black Hawk County Soil and Water Conservation District, Iowa; http://blackhawkswcd.org/conservation-projects/. Table 1. General use characteristics of Constructed Wetlands (Practice Code 656) and basic cost parameters.





Constructed Wetlands (Practice

Code 656)1, 2

Reduce nitrogen, phosphorous, pesticides, and sediment loading in intercepted tile drainage or stream systems

Provides wildlife habitat

Provides improved aesthetics

Site planning, design, engineering and preparation; excavation and soil movement; planting; seed costs (wetlands mix), tile redirection. Opportunity costs for foregone land rent or crop revenue.

1. Iowa NRCS Constructed Wetlands Practice Code 656: http://efotg.sc.egov.usda.gov/references/public/IA/Constructed_Wetland_656_SOW_2015-09.pdf

2. There are a number of wetland related conservation programs that may apply in certain situations. Ultimately, it is advisable that one contact their county or regional NRCS office and make inquiries regarding wetland cost share and other program opportunities: http://www.nrcs.usda.gov/wps/portal/nrcs/site/ia/home/


19

Wetland Cost Overview and Example: The installation and long-term costs of a constructed wetland will vary considerably depending upon design and scale. The costliest components of constructed wetlands are typically associated with site planning and design, excavation activities, control structures required and the opportunity cost of any land removed from agricultural production (over the long term, opportunity costs in the form of foregone land rent or net revenues typically represent between 50% and 70% of the total costs of this practice). Depending on the context for wetland use, overall scale of the project or program tie-in (e.g., USDA CREP wetland program)1, engineering planning and design costs can be significant upfront costs. The average 2016 costs (first year costs and per acre per year) of an example one acre constructed wetland located on land with a high Corn Suitability Rating (CSR 80) treating about 100 acres of drainage, would cost just over $10,000 for design and installation, or just under $800 per acre per year when annualized (analyzed over a 40-year time period; wetlands have indefinite lifespans and are expected to be permanent landscape elements); see table 2 for a summary of this assessment. There are a number of EQIP and CRP programs associated with different types of wetlands in different construction/ reconstruction and landscape contexts. For example, in the context of the Conservation Reserve Program (CRP), which is administered by the USDA FSA, regional programming pays a minimum of 50% of direct wetlands restoration cost, a one-time sign up incentive, along with an annual rental payment to account for opportunity costs (i.e., foregone rent or profit loss from not growing crops). Contact your local NRCS/ FSA office for more specific information. Table 3 below displays a comprehensive average cost breakdown for constructed wetlands in Iowa (2016$). All data adapted from Christianson et al. 2013.

Table 2. Cost example of a 1 acre constructed wetland treating about 100 acres of drainage area. Costs in 2016$.

First year per acre costs (Design and construction) $10,0221

Annualized per acre costs over 40 year lifespan $785 2

1. Costs can be quite variable depending upon initial site conditions, total wetland area/ drainage area, and initial design costs. This example has 1 wetland acre treating about 100 acres of drainage. The cost is for the wetland itself as well as a grassed buffer. The total area of the grassed buffer is typically 3.5% of the drainage area.

2. Calculated using standard discounted cash-flow procedures using a 4% discount rate and 20-year management horizon. Assumes 2016 state average land rent cost of $230/acre.

1 Iowa CREP Program Overview: http://www.fsa.usda.gov/Assets/USDA-FSA-Public/usdafiles/Conservation/PDF/crepiafactsheet.pdf


20

Table 3. Comprehensive average cost breakdown for constructed wetlands in Iowa (2016$). Table adapted from Christianson et al. 2013 .

Upfront Cost Activities / items

Year cost incurred

Mean price (wetland

acre)

Mean price per drainage (treated) acre

Notes

Wetland design cost (Engineer) 1 $1,000 $10.00

Assumption: 10 hours at $100/hr for a 1-acre wetland site (treating 100 acres of drainage). Information: Christianson, L. 2014. Personal communication. The total amount of this cost will depend on the context for wetland use and or program tie-in (e.g., USDA CREP wetland program). Cost may be significantly reduced by working with the NRCS.

Constructing basin 1 $1,500 $15.00 Building ponds ~15 hours at ~$50/hr for 1-acre wetland (encompasses range of activities for excavation, berm building, structure placement, etc.), not including buffer seeding time. Data source: Christianson et al. 2013.

Wetland plants (seeds and plugs) and planting 1 $640 $6.40

For shallow wetland systems, 100-150 plants per acre will help ensure sufficient establishment in open water areas. A wetland seed mix that covers wetland banks (~1/3 of the basin area) is also advisable. Wetland plant species plug regionally sell in bulk for about $1.00 to $2.00 per plug; wetland seed mixes range $75 to $100 per pound of seed (~ 5 pounds, drilled). In certain areas where wetland conditions are being restored, it is possible that there is a vaible wetland plant seed bed that would revegetate the wetland without additional seed/plants; such outcomes are uncertain and variable.

Wetland buffer seed 1 $131 $1.31

Total Wetland buffer area =3.5% of the total drainage area. Buffer area assumption: Helmers, M. 2014 Personal communication. Cost information: Plastina, A. and A. Johanns (2016). Average Regional seed costs: $131.00/ac for CRP "economy" wetland Program Mix 15lb/ac; for 3.5% wetland buffer area. There are a number of companies that sell regional genotypic wetland grass and forb seed.

Seeding buffer (broadcast with tractor) 1 $40 $0.40 Data Source: Edwards, 2009 (Inflated to 2016$).

Weir Plate 1 $600 $6.00 Assumption: $30 per sq. ft for 200 sq. ft sheet pile plate, for 1 ac site; Information: Christiansen, L. 2014. Personal communication.

Control Structure 1 $2,100 $21.00 One control structure ranging from 5 ft deep, 18 inch pipe ($1,300 per ac.) to 10ft deep, 24 inch pipe ($2,900 per ac) for 10 ac wetland site. Information: Personal communication with Agri-Drain Corp. Adair, Iowa (www.agridrain.com)

Long-term management costs

Time to manage (mowing buffer) 3-n l $3.06 $0.03 Data source: Plastina, A. and A. Johanns (2016).

Replace control structure gates

Every 8 yrs $15 $0.15 Data source: Christianson et al. 2013.

Land rent for wetland acre 0-n l $230 $2.30 State wide average land rent for 2016 was $230 per acre. Note: this would be an annual cost. For


21

reference, the present value of $230/ac/year over a 50-year period (the expected lifespan of the wetland) @ 4% would be $35,113.

Land rent for buffer per ac of wetland (3.5 % of 1 ac) 1-n l $8 $0.08 State wide average land rent for 2016 was $230 per acre, Plastina et al. (2016).

Control structure and weir replacement ~ 40 $935 $9.35 Financial data is presented undiscounted.

Conservation Reserve Program payments 1, 1-n l Variable Variable

Program parameters and payment schedules will vary. For example, with the USDA Farm Service Agency Wetland Restoration Initiative Conservation Reserve Program (CRP; utilizing Practice Standards CP23, CP23A for wetland Restoration, Inside/ outside the 100-year floodplain) a farmer might receive: 1) up to 50% cost share for wetland establishment; 2) there is also a one-time practice incentive payment equal to 40 percent of the eligible costs of installing the practice; 3) annual rental payments for�a 10- to 15-year period. The rental rate is based on the weighted average dry-land cash rent; 4) one time, upfront CRP signing incentive payments range from $100 to $150 per ac. Contact your local NRCS/ FSA office for more information.

General References for Constructed Wetlands

Iowa Learning Farm (2015) Wetlands Implementation. Iowa Learning Farms, Iowa State University. Available at: http://www.extension.iastate.edu/ilf/sites/www.extension.iastate.edu/files/ilf/Wetlands_think-piece_revised_4-9.pdf.


Plastina, A. and A. Johanns (2016) 2016 Iowa farm custom rate survey. Ag Decision Maker. File A3-10; FM 1698 (Revised, March 2016).

Plastina, A., A. Johanns and C. Welter (2016) Cash Rental Rates for Iowa. 2016 Survey. File C2-10. FM 1851 Revised May 2016. Ag Decision Maker.

Woltemade, C. J. (2000) Ability of restored wetlands to reduce nitrogen and phosphorus concentrations in agricultural drainage water. Journal of Soil and Water Conservation, 55(3), 303-309.


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In-field Management Practices Drainage Water Management: Controlled Drainage or shallow drainage The process of managing water discharges from surface and/or subsurface agricultural drainage systems with artificial drainage structures; the purpose of these systems is to actively manage the water table. Drainage water management is applicable to agricultural lands with surface or subsurface agricultural drainage systems that are adapted to allow management of drainage discharges.

As described in Frankenberger (2014) controlled drainage involves placing simple water control structures at various locations in a tiled system to raise the water elevation at certain points in a growing season (see figure 1 below, table 1). This effectively raises the water table and decreases the drained depth of the field. Reductions in nitrate losses from fields may occur primarily due to reductions in the volume of water drained and by enhancing the anaerobic conditions for denitrification in the soil; published research has noted reductions in annual nitrate load in drain flow has ranged from about 15% to 75% (Frankenberger 2014; though it has been argued that nitrate reductions are associated more with shallow ground water and less so with tile outflow). In certain situations, it has been noted that controlled drainage has the potential to improve crop yields by making more water available to plants at critical points in the growing season. Controlled drainage systems (including shallow drainage; see below) require relatively flat fields with 0.5%-1% grades. Such systems can be installed on new tile or retro-fitted to existing tile systems.

Shallow drainage systems reduce drainage flow volume by raising tiles to a depth of 2.5 to 3 feet (typical subsurface drainage depth in the Midwest is ~ 4 to 4.5 feet). Adjusting tile depth, reduces the drainable soil volume by 25 percent. As such, the water table is higher throughout the year resulting in a larger anaerobic zone that promotes the conditions for denitrification. Shallow drainage systems may lead to similar outcomes (in terms of nitrate reduction in shallow ground water and crop yields) yet they do not provide the same flexibility as controlled drainage does and tend to be more expensive due to the need for expanded tile coverage.

Figure 1. Generalized diagram showing general processes involved with both controlled drainage and shallow drainage practices. Controlled drainage diagram (left had side): J. Frankenberger, Purdue University, 2014; Shallow drainage diagram (right hand side): Bushman and Sands, 2012.

Outlet&is&raised&a,er&harvest&to&reduce&nitrate&delivery&

Outlet&is&lowered&a&few&weeks&before&

plan8ng&&&harvest&to&allow&for&field&drainage&

Outlet&is&raised&a,er&plan8ng&to&store&water&

for&crops&

Diagram:&J.&Frankenberger,&Purdue&University&

Controlled)drainage) Shallow)drainage)

Diagram:)UMN)Extension))

Conven:onal)drainage)

Shallow)drainage)


23

Table 1. General practice characteristics for drainage water management as used in Iowa and basic cost parameters. This practice can be cost shared with the NRCS via the EQIP drainage water management program.





Drainage water Management (Practice code

554) 1

Reduce nutrient, pathogen, and/or pesticide loading from drainage systems into downstream receiving waters

Improve productivity, health, and vigor of plants Reduce oxidation of organic matter in soils

Reduce wind erosion or particulate matter (dust) emissions

Provide seasonal wildlife habitat

Site planning, design, and contractor fees; control and supporting structures; stop log/ gate replacement.

1. NRCS Practice Standard for Bioreactors, Practice Code 554: http://efotg.sc.egov.usda.gov/references/public/IA/Drainage_Water_Management_554_STD_2010_07.pdf

Cost Assessment The majority of the costs associated with drainage management are associated with site planning, design fees as well as the installation of various control structures. The major cost of controlled drainage is the capital expense of the structures and their installation. The practicable life span of the practice is assumed to be 40 years; at this time the structures themselves would likely need to be replaced. Regarding more long-term costs, the cost of maintenance for this practice includes landowner time to manipulate the control structures; this would vary based on the number of structures, distance between them, and the chosen management intensity.

Table. Average 2016 costs (first year costs and annual costs) for a 20 acre controlled drainage system. There is EQIP funding available in Iowa for controlled drainage1.

First year costs (Design and installation) $1,656 total or $83 per treated acre

Annualized costs over 20 year lifespan ~ $150 2 Annual maintenance costs $20 1. For a drainage area > 10 acres, 2016 Iowa EQIP will pay at least $3.19 per managed drainage acre.

2. Costs were calculated and annualized using standard discounted cashflow procedures for structural water quality Best Management Practices. For more methodological detail see Tyndall and Roesch, 2014.

Average 2016 costs for shallow drainage for a 20 acre system (2.5 foot depth) would cost about $10,000 (or about 38%) more than a tile system working as a 4.5 foot depth due to the increase in total tile coverage.


24

Table 2. Custom rate costs associated with controlled drainage; a practice for reducing nitrate loads in drainage water in Iowa. Costs presented in 2016 dollars. All data updated from Christianson et al. 2013.

Cost Activities 1/ items

Year(s) cost

incurred

Range of costs (units)

Mean price

(drainage ac)

Notes

Structure cost 0 $25.00 - $100.00

or $50.00 to $200.00 per drainage acre

$75 or $150

New drainage system: 1 structure per 20 acres at $500–$2000 per ea. Includes delivery to site. Existing drainage system: 1 structure per 10 acres at $500–$2000 per ea.�As per the NRCS, a typical system would involve a 75 acre field with existing drainage tile lines and 5 installed water control structures.

Design costs1 0 $93 - $874/ drainage acre $346 For new drainage systems but also included as design cost of existing�

New tile 0 $0.50 to $3.00 per foot of tile. Plus ~

$50 per inlet

Highly Variable

Depending the type of tiling system and installation, tiling in Iowa can range from ~ $500 to $800 per acre.

Structure installation 0 $0.02 - $0.09 / ft^2 bioreactor area $2.00 Structure installation: Back hoeing ranges from $35.00 per 125.00 per hour for 8h to

treat 150 acres.

Time to raise/ lower gates 0 $0.10 to $0.44/

drainage acre $0.24 Four hours two to four times a year; labor�at $8–$20 per hour, 150 acre treatment area

Stop log/gate replacement 0-20 $0.01 to $0.09/

drainage acre $0.05 Summation of single sum TPV every eight years for 5 gates per structure at original cost of $14.17–$15.32 per ea. for 15 cm structures,�1 structure per 4 (Existing) or 8.1 (New) ha

For Shallow Drainage 0 $0.50 to $3.00 per

foot of tile. Highly

Variable New tile installations, or when splitting lateral spacing. Depending the type of tiling system and installation, tiling in Iowa can range from ~ $500 to $800 per acre

Impacts on crop yield 0 Variable -- The impact of controlled drainage or shallow drainage on corn and bean yields is assumed to be negligible.

1. Iowa EQIP Practice Code 130 will cover the cost of a written Drainage Water Management Plan (DWMP). This plan would be developed for relatively flat crop fields with patterned drainage systems, and where a map of the tile system is available. The DWMP will document soil, topographic, and drainage system maps of the site, and identify the number and location of water control structures that are needed to implement drainage water management according to Field Office Technical Guide standards (associated with Practice Code 554).


25

References for Drainage Water Management: Controlled Drainage or shallow drainage

Bushman, L. and G. Sands (2012) Agricultural Drainage Publication Series: Issues and Answers. Available online at: http://www.extension.umn.edu/agriculture/water/agricultural-drainage-publication-series/index.html


Frankenberger, J. (2014) Drainage Water Management in the Corn Belt. Resilient Agriculture. Aug. 2014: 14-15. Available on-line at: https://store.extension.iastate.edu/Product/Drainage-Water-Management-in-the-Corn-Belt

Frankenberger, J., Kladivko, E., Sands, G., Jaynes, D. B., Fausey, N., Helmers, M. J., Cook., R., Strock., J., Nelson, K., & Brown, L. C. (2004). Drainage water management for the Midwest: Questions and Answers. Ourdue University Extension. WQ-44. 8p. Available on-line at: https://works.bepress.com/matthew_helmers/101/download/

Tyndall JC, and G. Roesch (2014) A Standardized Approach to the Financial Analysis of Structural Water Quality BMPs. Journal of Extension. Vol. 52, Num. 3, 3FEA10.

General Cost Analysis Methodology: This cost tool updates and expands upon Christianson et al. (2013) and utilizes standardized discounted cash flow techniques relevant to water quality oriented agricultural Best Management Practices. For a more detailed overview of these methods please see:

Christianson L, Tyndall JC. Helmers M. (2013) Financial Comparison of Seven Nitrate Reduction Strategies for Midwestern Agricultural Drainage. Water Resources & Economics. http://dx.doi.org/10.1016/j.wre.2013.09.001

Tyndall JC, Roesch G. (2014) A Standardized Approach to the Financial Analysis of Structural Water Quality BMPs. Journal of Extension. Vol. 52, Num. 3, 3FEA10.

ia nrs cost tool overview tyndall & bowman, 2016 draft · ia nrs cost tool overview tyndall...

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