soil erosion and ground water pollution tradeoffs for nonirrigated farming systems

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATIONVOL. 38, NO. 1 AMERICAN WATER RESOURCES ASSOCIATION FEBRUARY 2002—

SOIL EROSION ANI) GROUND WATER POLLUTIONTRADEOFFS FOR NONIRRIGATED FARMING SYSTEMS'

Josiah Akinsanmi and Gregory M. Perry2

ABSTRACT: Traditional focus on reducing one environmentalexternality may cause another externality to increase. This articleexamines the environmental and economic costs of abating soil lossand (or) nitrate leaching through alternative optimal productionsystems in the nonirrigated farming systems of Northeastern Ore-gon. Models estimating soil loss and nitrate-nitrogen leaching ratesassociated with current production processes, are linked to a Multi-Objective Programming (MOP) model. The results show that sitespecific conditions influence the level of abatement expendituresand optimal production strategies to reduce soil loss and leachingrates. Moreover, while existing production strategies are effectivein reducing soil loss at little cost, no strategies could be identified toreduce nitrate leaching rate on some soils.(KEY TERMS: economics; multiple objective programming; erosion;nitrate nitrogen leaching; nonpoint source pollution.)

INTRODUCTION

The increase in demand for food, coupled with con-version of farmland into urban and industrial uses,has forced agriculture to expand to marginal landsand intensively cultivate existing acreage. Moreintensive farming of fragile lands results in accelerat-ed loss of soil through water erosion. Soil erosion cancause major environmental and economic impacts forfarm operators and society as a whole.

Despite the loss in soil productivity caused byexcessive soil erosion, application of commercial fertil-izers allows farmers to maintain and even increasecrop production (Walker and Young, 1986). However,only a portion of applied fertilizers is used by thegrowing crops. The remainder is retained in the soil,carried off with surface runoff or leached beyond thecrop root zone. In fact, nitrate concentrations inaquifers underlying agricultural land have increased

rapidly over the last two decades (OECD, 1986;Patrick et al., 1987).

The health problems linked to nitrates in waterinclude methemoglobinemia (blue babies), cancer, ner-vous system impairments, and even death in humans(Hallberg, 1986; Patrick et al., 1987; Johnson et al.,1987); abortion and tumors have occurred in farm ani-mals (OECD, 1986). Environmental impacts of hLighnitrate concentrations include rapid eutrophication oflakes and reservoirs, reduced dissolute oxygen, andreduced environmental aesthetic values (Taylor,1990).

Government agencies have generally focused. onmotivating farmers to adopt best management strate-gies to control pollution from agricultural activities.These practices can impose costs on producers, reduc-ing profit margins and placing financial stress onfarm operations. The task facing policy makers is tomaintain a balance between keeping the agriculturalindustry economically viable and at the same timeachieving an acceptable level of environmental quali-ty. Data quantifying the potential costs and reductionin net returns, as well as an understanding of thetradeoffs between net returns and production meth-ods that minimize pollutants, can be extremely usefulwhen assessing implications and impacts of govern-ment regulations and policies.

The primary objective of this study is to evaluatethe on-farm economics and environmental impact ofstrategies aimed at reducing soil erosion and (or)nitrate leaching in the nonirrigated farming systemsof northeastern Oregon. The evaluation will link pro-duction strategies, crop mix, soil erosion, and nit:rateleaching in a multi-objective model to identify least-cost production strategies, cost of abating various

iPaper No. 00105 of the Journal of the American Water Resources Association. Discussions are open until October 1, 2002.2Respectively, Instructor, Trinity Western University, 7600 Glover Road, Langley, BC Canada V2Y 1Y1; and Professor, Department of Ag.

and Resource Economics, 218 Ballard Hall, Oregon State University, Corvallis, Oregon 97330 (E-Mail/Perry: Greg.Perryorst.edu).

JOURNAL OF TI-IE AMERICAN WATER RESOURCES ASSOCIATION 101 JAWRA

Akinsanmi and Perry

levels of pollution, and tradeoffs between soil loss,nitrate leaching, and farm profitability.

STUDY AREA

The empirical focus is on soil erosion and ground-water pollution in the nonirrigated farming area ofUmatilla County, Oregon. Umatilla County is one ofthe major grain producing counties of northeasternOregon, with about 600,000 acres sown annually tononirrigated small grains (USDA, 1988). The Countyspans four Major Land Resource Areas (MLRA): theColumbia Basin, Columbia Plateau, Palouse and NezPerce Prairies (foothills of the Blue Mountains), andthe Northern Rocky Mountains (Blue Mountains)(USDA, 1988). MLRA are defined by the NaturalResource Conservation Service to represent a landarea similar in characteristics such as soil, climate,vegetation, water resources, land use, and type offarming. These four MLRAs extend over much ofnortheastern Oregon and southeastern Washington,making the results here applicable over a much largerarea. Annual precipitation ranges between 8 and 25inches — increasing from west to east.

A joint study by the USDA and the Council onEnvironmental Quality (1981) identified the Palouseand Nez Perce Prairies, and the Columbia Plateau ofeastern Washington, north-central Oregon and west-central Idaho as among areas in the United Stateswith high water erosion rates. In a later study,(USDA, 1983), it was reported that the erosion rate isabove the regeneration rate (or T-value) on over400,000 acres of cropland in the Columbia Plateauarea.

The Oregon Department of Environmental Qualityalso found nitrate levels of up to 80 ppm in someColumbia Basin irrigated cropping areas (Johnson etal., 1991). Leaching of nitrate is more severe whenthere is no crop growing on the field and may contin-ue through the early part of the cropping season,especially on very sandy soils (Williams and Kissel,1988). Hence, a summer fallow crop rotation could bemore prone to nitrate leaching.

This study investigates dryland summer fallow-winter wheat, summer fallow-spring barley and win-ter wheat-green pea cropping systems on four majorsoil types in two MLRA's (the Columbia Plateau, andthe Palouse and Nez Perce Prairies). The soils exam-ined are Walla Walla, Pilot Rock, Ritzville, andAthena. Walla Walla soils are deep and well drainedand produce the largest portion of the wheat grownin Umatilla county. Pilot Rock soils are shallowand less productive because of their limited water-holding capacity. Ritzville soils are deeper and more

productive than Pilot Rock, but receive less rainfall.Athena soils are deep and receive suflicient rainfall tosupport an annual rotation of wheat and peas (Ore-gon State University, 1973; USDA, 1988).

APPROACH AND PROCEDURES

The approach employed in this study involves inte-grating data from three distinct models: The Univer-sal Soil Loss Equation (USLE), the Nitrate Leachingand Economic Analysis Package (NLEAP), and theMicrocomputer Budget Management System (MBMS)package. The results from these three models arethen incorporated into a Multi-Objective Program-ming model (MOP), which is used to identify optimumstrategies. The models use farm site information andfarm input data to generate the results for the analy-sis.

Each farm acreage was subdivided into that withsubstantial slope (7 to 12 percent) and that with lessslope (0 to 7 percent). Production alternatives, encom-passing different tillage practices, crop rotations, fer-tilization practices (rate and timing) and conservationpractices, were developed for each soil and wereapplied equally across all acreage, regardless of slope.A summary of these alternatives for each soil type isprovided in the Appendix. A flow chart illustratingthe links between models is provided in Figure 1.

The Integrated Models

The USLE, the first of the integrated models in theanalysis, was developed by Wischmeier and Smith(1960) and adapted to the Pacific Northwest regionconditions by McCool and George (1983). It estimatesthe long-term average annual soil losses (in tons peracre) and uses a soil depth-yield functional relation-ship (Walker and Young, 1986) to compute associatedyield loss. The values of the yield loss represent theon-site cost of soil loss.

The soil depth-crop yield relationships were calcu-lated based on equations estimated by Walker andYoung (1986) for wheat and Bauer for barley. Eachequation was adjusted based on expected yields foreach soil type. The general form of these equationswas

Y =a+(i_eX(1)t_t)) (1)

where Y is yield in bushels per acre; D is beginningtopsoil depth in year t; A is average annual soil loss

JAWRA 102 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION

Soil Erosion and Ground Water Pollution Tradeoffs for Nonirrigated Farming Systems

(in inches) in year t; and a, 13, and A are equationparameters. The present value of yield loss over a 50-year planning horizon, at 3 percent real rate of inter-est, was computed for each of the ten crop years andresults incorporated into the models. A 50-year timehorizon is assumed as the economic productive life ofa soil. Although, soil productivity can extend beyond50 years, its value after discounting is small enoughthat it can be ignored in an analysis. The ten cropyears represent ten years of historical weather dataand the resulting impact this weather had on erosionand leaching.

Figure 1. Schematic Diagram of Linkages Between Models.

Budgets were generated using components fromthe Microcomputer Budget Management System(MBMS) program package. MBMS was designedby McGrann et al. (1986) at Texas A&M Universityfor use by extension staff, researchers, crop produc-ers, and ranchers in enterprise analysis and planning(McGrann et al., 1986). The budget details the

elements of the gross income, variable cost, fixed cost,and net return.

The third of the integrated models, the Nit:rateLeaching and Economic Analysis Package (NLEAP),was employed to estimate Nitrate-Nitrogen leachedfrom various tillage system and fertilizer levels andproduction alternatives. NLEAP was developed in1991 by a group of USDA-ARS researchers at FortCollins, Colorado State (Shaffer et al., 1991). NLEAPuses farm-specific information to develop a nitrogenbudget and water balance for specified time incre-ments. Given the nitrogen budget and water balance,the program estimates the potential N03-N leachedbeyond the root zone, and provides other informationabout the fertilizer management on the farm. Theleachate estimates provide a better understanding ofthe environmental consequences of fertilizer applica-tion rates and timing, overfertilization and the poten-tial impacts of the leached N03-N on associatedaquifers.

Linking Model

Multiple Objective Programming (MOP), the last ofthe integrated models, has been used extensively tofind solutions to a number of agricultural planningproblems involving optimal compromise amongst twoor more conflicting objectives. At a 1995 Conferenceon multiple objective decision models, researchersused MOP to: (1) identify tradeoffs between economicreturns and soil erosion in Nebraska (Jones et al.,1998); (2) determine optimal fertilization and chemi-cal use strategies that met an array of economic andenvironment objectives in Iowa (Yakowitz, 1998);(3) discover optimal land use in the EU when consid-ering eight economic and environmental objectives(Bessembinder et al., 1998); and (4) identify sustain-able farming systems in Chile that balance risk,returns, and soil erosion (KObrich and Rehman, 1998).Two recent studies examined tradeoffs between eco-nomic returns, nitrate leaching, and soil erosion. Thefirst examined corn and soybean production systemsin Missouri (Ma, 1993). The other examined produc-tion of onions, potatoes, wheat, and corn under irri-gated conditions in Maiheur County, Oregon (Connoret al., 1995).

MOP involves an iterative procedure in which sev-eral objectives are optimized simultaneously, subjectto some constraints. The optimum solutions for thesesimultaneous objectives, however, cannot be defined;therefore the program (MOP) identifies an approxi-mation for a set of nondominated or Pareto-optimalsolutions (Romero et al., 1987). The noninferio:r setestimator (NISE) generating technique of MOPwas employed in this study because of its greater

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 103 JAWRA

efficiency than the alternatives. The algorithm con-verges quickly to identify an efficient set of solutions(Cohon, 1978). Tradeoffs between alternative levels ofthe competing objectives were derived from the set ofoptimal solutions (Atwood et al., 1990).

The MOP approach utilizes results generated fromthe other models for its input data. The data wereorganized and computer analysis conducted using theGeneral Algebraic Modeling System (GAMS) soft-ware. The objective functions, involving a simultane-ous minimization of soil erosion and N03-N leaching,weighted to obtain a set of non-dominated solutions.The objective was minimized subject to net returnrequirements and resource constraints. The problemis formulated as:

vijkl pkqEquation (2) is the objective, which is to minimize

the weighted total environmental impacts from ero-sion (ERA1 and ERBpldq) and leaching (LA andLBpMq) for the two crops grown on that soil (AAkland ABpicjq), across k erosion control practices (stan-dard, divided slopes and strip cropping), 1 crop slopes,j tillage practices for crop A, p tillage practices forcrop B, n fertility strategies for crop A and q fertilitystrategies for crop B. The weight a is a value between

0 and 1 and reflects the relative importance of mini-mizing soil erosion in the overall farm objective.

Equation (3) requires the total net revenue per acre(NRAjicjn and NRBpklq) multiplied by the number ofacres in each crop, be greater than some profit level it.By varying a from 0 to 1, one can identify the set ofnondominated or Pareto-optimal solutions at a givenprofit level. By reducing it by a fixed amount, say$10/acre, an alternative set nondominated solutions


Akinsanmi and Perry

s.t.

MinV=ct jkln pklq

+(1—a) NRAJklfl *AA jbin +NRBpk1q *ABpklq1km pklq

* jkln + NRBpklq* it (3)

jkln pklq

forall AAfkmfl_-AAJk2fl=0 V j,k,n (4)

pklq4-Bpk2q0 V p,k,q (5)

(6)


can be identified that are less harmful to the environ-ment.

Equations (4) and (5) require that a particular setof tillage, soil conservation, and fertilizer timingstrategies be equally practiced on both the steep andless steep soils. These requirements are neededbecause the topography in the study area is too variedto permit a farmer to change these practices within aparticular field based on slope. Equation (6) deter-mines the acreage limit on the farm by acres in a par-ticular slope.

RESULTS

An important initial step in this type of research isto validate the results; that is, compare the predictedvalues with research findings or actual experience.The soil loss rates and potential N03-N leached wereexamined by a group of research scientists at theColumbia Basin Agricultural Research center inPendleton. They concluded that soil loss rates wereconsistent with research conducted on the differentsoil types. No known studies in the Western U.S. haveexamined Nitrate-N leaching under nonirrigated con-ditions. The group determined that leachate valuesobtained seemed reasonable, particularly in makingordinal rankings among soils and production alterna-tives.

Base Case Analysis

The Multi-Objective Programming (MOP) basesolution represented the most profitable productionstrategy assuming farmers ignored the environmentalconsequences of their management decisions. Theoptimal strategy for Walla Walla soils was fallow-winter wheat production under standard practice,using disk plow for primary tillage, followed by chiselchopper and several secondary tillage operations.Fertilization strategy involved a one time preplantapplication of 80 lbs/acre nitrogen fertilizer. This pro-duction strategy generated an average soil loss rate of7.18 tons/acre, an average N03-N leaching rate of 5.02lbs/acre, with a potential maximum return to landand management of $144.88/acre. This strategy is infact typically followed on most Walla Walla soils.

Soil loss on Pilot Rock soils was relatively low (2.52tons/acre) under profit maximization. The poor waterholding capacity characteristics of this soil resulted ina high leaching rate (7.80 lbs/acre). The profit-maximizing strategy was to follow a fallow-winterwheat rotation, using sweep plow for primary tillage

and a single, preplant fertilizer application. The netrevenue was $67.35/acre.

Because Ritzville soils are found in a relatively lowrainfall zone, they generated very low levels of bothsoil erosion (1.93 tons/acre) and N03-N leaching (1.50lbs/acre). The profit maximizing strategy generated$95.20/acre, with the entire farm acreage following afallow-winter wheat rotation, using sweep piow forprimary tillage, no special field layout and a preplantapplication of about 40 lbs/acre nitrogen fertilizer.

Athena soils differ from the other soils because oftheir much higher rainfall. The optimal base solutionstrategy involved use of a disk plow for primarytillage, a cultivator for secondary tillage and standardpractice for both winter wheat and green pea produc-tion with a 60 lbs/acre fertilizer application for wheat.This production strategy generated an average soilloss rate of 6.75 tons/acre and an average leachate of8.60 lbs/acre. Return to land and management was$265.46/acre.

Least Cost Solutions

The maximum profits, associated soil loss, andleaching rates in the base case serve as the beginningpoints in exploring the improvements and tradeoffs inenvironmental externalities (erosion and leachate)that farmers can achieve at the expense of lower prof-its.

The optimal (or noninfenor) production strategiesconsist of combinations of optimal tillage systems,conservation practices, fertilizer application rates andtiming, land reallocation and associated minimumsoil loss and nitrate leaching rates. These strategieswere obtained by allowing the maximum net returnsin the base case to fall by about 7, 20, and 35 percent.These percentages represent necessary abatementexpenditures or costs to producers of adopting least-cost abatement techniques or best management prac-tices (BMP). The dollar values corresponding to thesepercentages varied by soil type, consistent with thereturns to land and management. The locus of theoptimal production strategies (non-inferior frontiersor "iso-abatement curves") corresponding to eachabatement expenditure level are mapped out in Fig-ures 2 to 5. The extreme points on each iso-abatementcurve correspond to the optimal strategy when allresources were directed solely at reducing erosion orleaching. Points in between are results when empha-sis was placed on reducing both pollutants.

Walla Walla Soil. Abatement expenditure levels of$10/acre, $30/acre, and $50/acre, with sole focus onreducing soil erosion, resulted in soil loss reductionsof 52, 78, and 89 percent, at average costs of


10

0I-U)

.30

Cl)

CC

5

Akinsanmi and Perry

Pilot Rock Soils. The abatement expenditure lev-els of $5, $15, and $25 per acre had less of an impacton the Pilot Rock soils, largely because erosion rateswere already modest. The cost of reducing erosion was

'I)C0I-LI)LI)0-J0U)Ca

=C

,.,

0)=0I—

'I,LI)0-J0C/)Co=CC

0 1 2 3 4 5 6 7 8

Annual Nitrate Leached (Lbs/Ac)

Figure 4. Iso-Abatement Frontiers for Ritzville Soil.


$2.70/ton, $5.39/ton, and $7.83/ton, respectively.These costs, for all soils, do not account for the envi-ronmental costs associated with increase (or decrease)in one pollutant as the other is reduced. The optimalstrategies suggest a shift to chisel plow for primarytillage and reduction in the proportion of total farmacreage under standard practice. At $30/acre or 20percent of net return per acre abatement expenditure,the farm shifted toward divided and strip crop prac-tices to achieve larger reductions in soil loss.

15

15

10

5

0

$5/AcAbamentCo

$15/Ac

AbemtCoet

$25/AcAbatement Cost

Base

Scenano

Base 0 1 2 3 4 5 6 7 8


Figure 3. Iso-Abatement Frontiers for Pilot Rock Soil.

15

0

0 1 2 3 4 5 6 7 8


Figure 2. Iso-Abatement Frontiers for Walla Walla Soil.

Similar expenditures solely on reducing leachateresulted in 27, 42, and 56 percent reductions, trans-lating to average costs of $7.25, $14.18, and $17.66per pound of nitrate not leached, respectively. Anincrease in total spring barley acreage and fertiliza-tion options, other than pre-plant for winter wheatcrop, reduced leachate significantly. In general,nitrate leaching was a more difficult (and expensive)externality to control than was soil erosion.

$35/Ac Abatement Ca5t

10

5

0

Base Scenario

$7/Ac Abatement Cent


$11.49, $11.49, and $13.26/ton/acre, respectively,which is up to four times greater than on Walla Wallasoils. Strategies that focused solely on abating nitrateleaching were much more cost effective than on theWalla Walla soils with costs of about $4.90/acre, asmuch as one-third lower than on Walla Walla soil.Spring barley acreage increased as more emphasiswas placed on reducing leaching, using sweep plowtillage system, divided slope and strip crop practices,and a preplant fertilizer application of up to 45lbs/acre.

Ritzville Soil. The optimal tillage systems andpractices were almost identical to those in Pilot Rocksoil, except for the fertilization option. As abatementexpenditure levels increased, spring barley productionbecame the more preferred option when attempting toreduce nitrate leaching. Divided slope and strip crop-ping also became more prominent strategies whenseeking major reductions in soil erosion. Neverthe-less, low rates of soil loss and leaching suggest that

current production systems may have little negativeon erosion or leachate. The costs of reducing soil lossranged from $15.80 to $21.81 per ton per year. Reduc-ing nitrate leaching was even more expensive on a perunit basis, ranging from $28.00 to $40.37 per pound ofnitrate not leached. Based on these results, it appearsthat efforts to reduce soil erosion or nitrate leachingon Ritzville soils is difficult to justify.

15

10

0U)=0I-U)U)0-J0

C,)CD=

BaseSo$20/Ac

nt

$90/AcAb&en Co

5

0

Athena Soil. When the objective was to minimizesoil loss on Athena soils, the optimal strategies wereto place more and more acreage in divided slope andstrip cropping. These moves had major impacts on soilerosion, reducing it from 6.75 tons/acre/year in thebase scenario to 1.1 tons/acre/year under the highestabatement cost program (Figure 5). The costs associ-ated with this soil savings ranged from $7.78 to$15.95 per acre. Nitrate leaching on the Athena soilswas the highest of the four soil types studied. Unfor-tunately, none of the strategies had much impact onreducing this leaching. Costs associated with reducingleaching ranged from $50 to $200 per acre per poundof nitrate not leached. Average rainfall on Athenasoils is 15 to 20 inches per year, significantly morethan the 12 to 15 inches per year on Walla Walla andPilot Rock soils. This higher rainfall, combined withthe wheat-pea rotation system, makes it difficult tokeep nitrates in the root zone.

It is useful to compare these results with those forirrigated agriculture, to obtain a sense as to the rela-tive importance of erosion and nitrate leaching onthese nonirrigated soils, as well as the nature oftradeoffs between the two environmental externali-ties. A good comparator study was conducted by Con-nor, Perry and Adams in Malheur County, Oregon.Their study involved furrow irrigation of high value,shallow rooted crops (onions and potatoes) grown inrotation with wheat and corn. In their base scenario,soil erosion was 10.6 tons/acre/year and nitrate leach-

0 2 4 6 8 10 12 ing was 60.3 lbs/acre/year. Soil erosion levels weresomewhat less than this level, but the real differencewas the much lower nitrate leachate levels on the foursoils examined here. Even on the high rainfall Athenasoils, nitrate leaching was one-seventh the levelreported in the Malheur County study. In addition,there was a much broader range of tradeoffs betweenerosion and leaching in the irrigated study versus thisstudy.

It is important to note that the Malheur Countystudy is in many ways an extreme situation withregards to erosion and nitrate leaching. Furrow irri-gation can be very erosive for some crops if not prop-erly managed. Also, the particular properties ofpotatoes and onions (high value and shallow rootzones) translates to a willingness to overfertilize andoverirrigate both crops. Nevertheless, the comparison


Figure 5. Iso-Abatement Frontiers for Athena Soil.


Akinsanmi and Perry

suggests that nitrate leaching and erosion is less of aproblem on the northeastern Oregon nonirrigatedsoils, but that there are fewer production alternativesavailable to reduce leaching and erosion problems.

CONCLUSIONS

The purpose of this study was to quantify thetradeoffs between soil erosion and nitrate leaching inthe nonirrigated farming systems of northeasternOregon. Specifically, the study focused on the fourmajor soil types that are generally not irrigated in thestudy area — Walla Walla, Ritzville, Pilot Rock, andAthena. These soil types represent a variety of rain-fall and crop production practices. Comparing theseresults permits one to extrapolate how tradeoffsbetween these two environmental externalities arelikely to play out across a range of soil locations andtypes.

Tradeoffs do exist between erosion and nitrateleaching on all four soil types, but the nature of thesetradeoffs varies a great deal. Based on these results,the following is a suggested set of policy prescriptionsto address the erosion-nitrate leading tradeoffs exam-ined here:

1. In areas where rainfall is not sufficient to fill thesoil profile, there is little need to be concerned witheither nitrate leaching or erosion. This is a result thatcould probably have been deduced without conductingthe analysis, but it does illustrate the importance oftargeted policies. Subsidizing practices that reduceerosion or leachate on these soils, for example, isprobably not a particularly efficient use of govern-ment funds.

2. There are some definitely gains that can bemade reducing erosion and nitrate leaching in themoderate rainfall areas. These gains, particularlymodest gains, can be achieved at a relatively low cost.It also became apparent that focusing on one exter-nality can have a major negative impact on the otherexternality on these soils. Policies need to considermultiple externalities to achieve the most desirableoverall social benefit. The impact of leaching and ero-sion is much greater in this moderate rainfall situa-tion if the soils are shallow. Therefore, policymakersshould place these kinds of soils at the top of their pri-ority list when devising programs to reduce eitherexternality.

3. The higher rainfall areas are the most prone toerosion and leaching. However, there were relatively

few options to reduce either externality (particularlyleaching) without incurring some major productioncosts. Erosion and leachate levels on these soils prob-ably approach those on some irrigated soils. Themajor difference is that man can greatly control theexternality problems on the irrigated soils by chang-ing how water is applied. By contrast, man is at themercy of the elements on the nonirrigated soils. It ison the high rainfall nonirrigated soils that more workneeds to be done to identify rotational and tillagestrategies that can minimize the environmental exter-nalities examined here. The key point coming out ofthis study, however, is to recognize that there still aretradeoffs between leaching and erosion on these high-er rainfall soils, so researchers should consider bothin their work.

APPENDIXPRODUCTION ALTERNATIVES BY SOIL TYPE

The following are standard and alternative tillageand fertilization systems found to be feasible on eachof the soils listed. Note that divided slopes and stripcropping are also alternative systems used in combi-nation with each system considered.

A. Walla Walla Soil1. Pillage Options in Fallow Year for Winter

Wheata. Moldboard, 2 cultivations, fertilizer,

1 cultiweedb. Chisel, spray, sweepplow, cultivate,

fertilizer, cultiweedc. Disk, spray, 2 cultivations, fertilizer,

2 cultiweedsd. Disk, burn, 2 disks, fertilizer, 2 culti-

weedse. Disk, chisel chop, fertilizer, 2 culti-

weeds2. Tillage Options in Fallow Year for Spring

Barleya. Moldboard, 2 cultivations, 1 cultiweedb. Chisel, spray, sweepplow, cultivate,

cultiweedc. Disk, spray, 2 cultivations, 2 cultiweedsd. Disk, burn, disk, 2 cultiweedse. Disk, chisel chop, 2 cultiweeds

3. Fertilizer Options for Winter Wheata. 80 pounds preplantb. 80 pounds preplant, 30 pounds in the

springc. 65 pounds preplant, 30 pounds in the

spring



d. 50 pounds preplant, 50 pounds in thespring

e. 30 pounds preplant, 65 pounds in thespring

f. 110 pounds in the spring4. Fertilizer Options for Barley

a. 25 pounds preplantb. 45 pounds preplantc. 65 pounds preplant

B. Ritzville and Pilot Rock Soils1. Tillage Options in Fallow Year for Winter

Wheata. Spray, sweepplow, fertilizer, 2 culti-

weedsb. 2 sweepplows, cultiweed, fertilizer,

cultiweedc. Spray, sweepplow, cultiweed, fertilizer,

cultiweedd. Chisel, spray, sweepplow, cultivate,

cultiweed2. Tillage Options in Fallow Year for Spring

Barleya. Spray, sweepplow, 2 cultiweedsb. 2 sweepplows, 2 cultiweedsc. Chisel, spray, sweepplow, cultivate,

cultiweed3. Fertilizer Options for Winter Wheat

a. 40 pounds preplantb. 40 pounds preplant, 15 pounds in the

springc. 35 pounds preplant, 15 pounds in the

springd. 25 pounds preplant, 25 pounds in the

springe. 15 pounds preplant, 35 pounds in the

springf. 55 pounds in the spring

4. Fertilizer Options for Spring Barleya. 25 pounds preplantb. 45 pounds preplantc. 65 pounds preplant

C. Athena Soil1. Tillage Options in Winter Wheat-Green Pea

Rotationa. Chisel, cultivate, fertilizer, cultiweed,

drill wheat, spray, fertilizer, harvestwheat, disk, cultivate, fertilizer,moldboard, cultivate, spray, fertilizer,cultivate, drill peas, harvest peas

b. Disk, cultivate, fertilizer, cultivate,harrow, drill wheat, spray, fertilizer,harvest wheat, disk, cultivate,fertilizer, cultivate, herbicide, fertilizer,harrow, drill peas, harvest peas

c. Disk, chisel, fertilizer, 2 cultivates, drillwheat, spray, fertilizer, harvest wheat,harrow, disk, fertilizer, moldboard,2 cultivate, fertilizer, drill peas, pack,harvest peas

2. Fertilizer Options in Winter Wheat-GreenPea Rotationa. 60 pounds preplant (wheat), 25 pounds

preplant (green peas)b. 60 pounds preplant (wheat)c. 90 pounds preplant (wheat), 20 pounds

preplant (green peas), 25 pounds post-planting on peas

d. 60 pounds preplant (wheat), 30 poundspost-planting; 20 pounds preplant(green peas), 25 pounds post-plantin.g

Based on these alternatives, 90 summer fallow-winter wheat and 45 summer-fallow barley produc-tion alternatives were considered for the Walla Wallasoils; 72 summer fallow-winter wheat and 27 summerfallow-barley alternatives were considered for theRitzville and Pilot Rock soils; 36 winter wheat-greenpea alternatives were considered for the Athena soils.

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soil erosion and ground water pollution tradeoffs for nonirrigated farming systems

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