- Email: [email protected]
Economic-environmental tradeoffs among alternative crop rotations
Agriculture Ecosystems & Environment ELSEVIER
Agriculture,Ecosystems and Environment60 (1996) 17-28
Economic-environmental tradeoffs among alternative crop rotations Terry C. Kelly a, Yao-chi Lu b,, ,1, John Teasdale c a Department of Agricultural and Horticultural Systems Management, Massey University, Private Bag 11222, Palmerston North, New Zealand b Systems Research Lab, Agricultural Research Service, U.S. Department of Agriculture, Bldg. 007, Rm. 8, BARC-West. Beltsville. MD 20705, USA c Weed Science Lab, Agricultural Research Service, US Department of Agriculture, Beltsville, MD 20705. USA
Accepted 3 May 1996
Abstract Simulated long-term impacts of different cropping systems are evaluated and analyzed in terms of the tradeoffs among net returns and different components of environmental quality. The cropping systems are modeled after the BARC Sustainable Agriculture Demonstration Farm. EPIC was used to obtain crop yields, soil erosion, and the environmental fate of nitrogen, phosphorous, and herbicides in response to weather and management practices over a simulated 30 year period. This procedure provides a way to estimate the environmental impact of cropping rotations, and to analyze the tradeoffs between competing objectives, whether they are farm income, erosion control, or the reduction of multiple hazards. The results indicate that the no-till rotation provides the greatest net returns, followed by the conventional rotation. The net returns on the two cover crop rotations are lowest. In terms of environmental impacts, no-till rotation dominates all other rotations with lowest nitrogen loss, and the covercrop rotations perform best in terms of erosion and phosphorous loss. However because herbicides are necessary to control weeds in no-till, the pesticide hazard index is very high, suggesting a tradeoff between pesticide hazard and other environmental considerations. To provide decision makers with better information, an environmental hazard index was constructed to analyze the tradeoffs between potential chemical contamination and net returns. Depending on preference structure, any one of three rotations could be preferred: no-till; manure at medium application rates; and cover crop without fertilizer. Keywords: Cropping systems; Simulation;Environmentalhazard; Economics;Nitrogen; Pesticides; Erosion
1. Introduction Cultivation of the soil is an important component of sustainable agricultural strategies. Plowing soils
* Corresponding author. Tel: 301-504-5821; fax: 301-504-5823 email: [email protected]. This research was conducted while Terry Kelly was with the Agricultural Research Service of the USDA.
prior to planting kills weeds and releases nutrients from existing vegetation. Cultivation incorporates animal manure or cover crops, providing nutrients for plant growth and reducing the need for commercial fertilizer use. Interrow cultivation after planting can control weeds and reduce herbicide applications. However, cultivation also can result in loss of soil organic matter, deterioration of soil structure, increased soil erosion, and thus, reduced productivity
0167-8809/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. PII S01 67-8809(96)0 1064-X
18
T.C. Kelly et al./ Agriculture, Ecosystems and Environment 60 (1996) 17-28
of soils. A significant proportion of farmland in the Mid-Atlantic states as well as other regions of the United States is subject to soil erosion, and reducedtillage systems have been developed to preserve the viability of erodible land. However, reduced-tillage systems require more chemical fertilizer and herbicide inputs than conventional tillage, resulting in greater potential for water pollution. Water quality concerns are especially paramount in the Chesapeake Bay drainage. The coastal plains and the Piedmont regions of the MidAtlantic and southeastern United States are extremely vulnerable to pesticide and nitrate leaching (Kellogg et al., 1994). Since the goal of obtaining maximum profits may conflict with the goal of minimizing environmental damages, the agricultural research community is challenged to develop profitable cropping systems that incorporate reduced tillage as well as reduced dependence on fertilizer and herbicide inputs. As part of the Sustainable Agriculture Project at the USDA's Beltsville Agricultural Research Center (BARC), a 15 acre site on the South Farm with 2% to 15% slope has been set aside for demonstrating several alternative corn-based cropping rotations to evaluate the viability of sustainable agricultural strategies that are compatible with reduced-tillage systems required on erodible land. The experiments will be continued for at least five cycles of the 2-year rotation to permit long-term evaluation. However, in the absence of field data prior to the completion of the experiments, one way to develop timely and accurate information is to use biophysical simulation models that can examine multiple variables under different scenarios. The objectives of this paper are to: (1) evaluate the long-term impacts of different cropping systems on net returns (or gross margin), soil erosion, and environmental quality; and (2) analyze the tradeoffs among net returns, soil erosion, and other components of environmental quality. Data for the analyses are generated by biophysical simulation models.
2. Materials and methods
To assess the economic and environmental impacts of alternative cropping systems, the Erosion-
Productivity Impact Calculator (EPIC) (Sharpley and Williams, 1990; Williams et al., 1990) was used to generate crop yields, soil erosion, and the environmental fate of nitrogen, phosphorous, and herbicides in response to weather and management practices over a simulated 30 year period. EPIC, a comprehensive cropping systems model, was designed to analyze alternative cropping systems and help decision makers predict their environmental and economic sustainability (Jones et al., 1991) by estimating crop yields, chemical loss to the environment, and soil degradation in response to soil, weather, and management variables. EPIC has been extensively tested and validated under a wide variety of conditions for most of the common agronomic crops, and in most cases, simulated yields were not significantly different from measured yields (Jones et al., 1991). Pesticide components in EPIC are modifications of those used in GLEAMS, a non-point source pollution model that is widely used for water quality planning purposes (Leonard et al., 1987). Wauchope et al. (1990) found excellent agreement between observed pesticide losses and GLEAMS predicted losses. In recent years, EPIC has been widely used to examine the environmental impacts of alternative farming practices and the tradeoffs between reduced contamination and farm income. Kim and Mapp (1993) employed the EPIC-PST model to complete the coefficient matrix of a linear programming model in order to evaluate alternative scenarios for achieving a certain level of water pollution control. Hughes et al. (1995) combined EPIC with a whole-farm model and budget analysis to evaluate the short-run profitability and the long-run sustainability of agricultural practices in the barley cropping area of Jordan. EPIC was used in a study of rice-wheat rotations in the Indian Punjab in order to estimate soil erosion and current and future crop yields for each rotation under different tillage and fertilization alternatives (Faeth, 1993). Faeth et al. (1991) developed a framework that combined the EPIC simulation model with an agricultural sector model and an accounting model in order to quantify economic, fiscal, and environmental costs and benefits of agricultural policy options. Finally, Teague et al. (1995) used EPIC output to create environmental indices for pesticides and nitrates to measure environmental risk and the sensitivity of net returns to reductions in
T.C. Kelly et al. /Agriculture, Ecosystems and Environment 60 (1996) 17-28
potential water contamination from pesticides and nitrates. The sustainable agriculture demonstrations at BARC are on a complex soil with varying, and sometimes steep slope. Sassafras soil is one of the soil series represented at this site, and is the one used for the analysis in this paper. Four separate 2-year cropping rotations constitute the demonstrations at BARC: (1) a no-till corn-double cropped wheatsoybean rotation; (2) a crownvetch living mulch corn-winter wheat-soybean rotation; (3) a cover crop corn-full season soybean rotation; and (4) a manurebased corn-wheat-forage rotation. The crownvetch in the second rotation has been slow to establish, and because of limitations in EPIC preventing the simulation of two crops growing simultaneously, the crownvetch rotation is not included in this analysis. The cover crop rotation is analyzed with and without added nitrogen and phosphorous, and the manure rotation is analyzed at three different levels of manure applications. A conventional tillage corn-double cropped wheat-soybean rotation is included in the analysis as a control. A total of seven rotations were simulated using EPIC with management input based on the sustainable agriculture demonstration at BARC. Sassafras soils with 8% slope and weather generated from data at Owings Ferry Landing in southern Maryland are used for the simulations. In each rotation, corn is planted on 11 May and harvested on 7 October. Winter wheat following corn is planted on 19 October and, except in the two cover crop rotations, is harvested on 6 July the following year, with the straw baled on 7 July. Double-cropped soybeans are planted on 8 July and harvested on 14 November, while full-season soybeans in the cover crop rotations are planted on 13 May and harvested 1 October. Specific details of the rotations are described as follows. 2.1. Conventional
This is a conventional 2-year corn-winter wheatsoybean rotation with conventional tillage (chisel plow and disk) prior to planting all three crops. Weed control in corn is maintained with a preemergence herbicide treatment of 1.49 kg ha-~ atrazine and 1.87 kg ha-1 metolachlor (applied together as
19
4.67 1 ha-~ of Bicep). Composite fertilizer (19-19-19) is applied on 6 May prior to tillage and corn planting at a rate of 224 kg ha - l , fertilizer (10-20-10) is applied with planter at 168 kg ha - j , and corn is sidedressed with 224 kg ha-~ UAN (28% N) on 20 June. On 19 October, prior to tillage and planting winter wheat, 336 kg ha -~ of 5-10-10 fertilizer is applied, and a further 240 kg ha-E UAN is applied in the spring on 15 March together with an application of 35 g ha- 1 of Harmony Extra herbicide (26 g ha -1 thifensulfuron). On 8 July, a preemergence treatment for soybeans is applied as 1.75 1 haGramoxone Extra (0.56 kg ha-~ of paraquat), 2.3 1 h a - i Dual (2.24 kg ha-~ metolachlor), and 2.24 kg ha - l Lorox (1.12 kg ha -~ linuron). 2.2. No-till
This rotation is similar to the conventional except that there is no-tillage prior to planting, and the preemergence herbicide application on corn is increased to 1.79 kg ha-~ atrazine and 2.24 kg hametolachlor (5.6 1 ha-1 Bicep) and includes additionally 1.75 1 ha- 1 Gramoxone Extra (0.56 kg haof paraquat). 2.3. Cover crop
This is a zero tillage rotation in which cover crops are used to control erosion and provide some of the required nutrients. Corn is planted into a hairy vetch cover and is followed by winter wheat, which is planted strictly as a cover crop and therefore is not harvested for grain. There is not sufficient time to harvest both wheat and soybeans for grain and plant a hairy vetch cover crop. Fertilizer (10-20-10) is applied with planter at 168 kg ha -1. The wheat is mowed on 12 May, and full-season soybeans are planted into the mown wheat on 13 May. Hairy vetch is no-till planted on 2 October following the soybean harvest. Fertilizer (0-15-30) is applied prior to corn planting at a rate of 224 kg ha -~, and the corn is sidedressed with UAN at a rate of 224 kg ha -1 on 20 June. On 23 May, 0.58 1 ha-~ of a postemergence herbicide (Banvel) is applied at a rate of 0.28 kg ha- t dicamba to kill the hairy vetch, and grass weeds are controlled with a postemergence application of Accent at a rate of 47 g ha-~ (35 g
20
T.C. Kelly et al./ Agriculture, Ecosystems and Environment 60 (1996) 17-28
ha- t nicosulfuron) on 20 June. Phosphorous is added to the wheat crop on 6 May prior to mowing at the rate of 67.2 kg P2Os per ha. Weeds are controlled in the soybeans with a postemergence application of Poast (0.22 kg ha-l Sethoxydim) and Blazer (0.28 kg ha-~ Acifluorfen) on 20 June. 2.4. Cover crop-zero
This rotation is identical to the cover crop rotation except that there is no added fertilizer N or P. 2.5. Manure-high
Organic practices are represented in the manure rotations. No synthetic fertilizers or chemical pesticides are used. The manure rotations are 2-year rotations with corn followed by winter wheat followed by a forage legume, in this case red clover. Red clover is overseeded in the wheat on 6 April (in EPIC, it is planted immediately after wheat harvest, since EPIC does not allow more than one crop grown simultaneously), is cut and baled on 5 October, and then is plowed under prior to corn planting the following 11 May. Tillage, chisel plow and disk, is performed prior to corn planting and prior to wheat planting. Manure is applied twice in the 2 years, once at a rate of 23.76 MT ha-J on 5 May prior to tillage and corn planting, and another at a rate of 11.2 MT ha- l on 19 October prior to tillage and wheat planting. The manure is old cow manure with the following nutrient content as a percent of dry weight: 0% mineral N; 0.7% organic N; 0.2% mineral P; and 0.1% organic P. Weeds are controlled in corn through cultivation, with two rotary hoe operations (17 and 24 May) and two cultivations (7 and 21 June). 2.6. Manure-medium
This is the same as the manure-high rotation with the manure applications cut in half, that is, 11.88 MT ha- ~ in the first application and 5.6 MT ha- 1 in the second application. 2.7. Manure-low
This is the same as the manure-high rotation with the manure applications reduced to one-fourth, that
is, 5.94 MT ha- ~ in the first application and 2.8 MT ha-~ in the second application. In this study an income/environmental hazard frontier is used to present tradeoffs related to nitrogen, phosphorous, and herbicide applications. An advantage of this approach is that the opportunity costs (in terms of lower net income) of reducing pollution can be compared between any two strategies (Hoag and Hornsby, 1992). The tradeoff frontier contains all the points that are not clearly dominated by one or more of the other points, and the slope of the frontier between two points measures the degree of the tradeoff between those points. The frontier can be customized to a particular farm or watershed situation, thereby contributing additional information toward decision making. An environmental hazard index (EHI) is derived for each rotation based on potential contamination from nitrates, phosphorous, and pesticides. An index is defined for each of these contaminants by assigning the highest loading level (or in the case of pesticides, the highest pesticide hazard) across rotations a value of 100 and indexing the remaining levels according to their ratio to the highest level. The EHI is a weighted average of the three individual indices, with weights determined by their relative environmental hazards in a specific situation. Whereas nitrate and pesticides present health hazards when present in ground and surface waters, the main environmental hazard of phosphorous is the disruption of the balance of aquatic systems through promotion of algae growth. However, in this study, no attempt is made to evaluate the relative hazards of these three components of the EHI; thus, they are assigned equal weights for illustrative purposes here. The pesticide component of the EHI is determined by the pesticide hazard level from pesticide application, which is defined for each rotation based on the relative toxicities of the pesticides and amounts lost to the environment (Hoag and Hornsby, 1992; Hoag, 1990). Relative toxicity in this study is described by the LCs0 of a pesticide, which is the lethal concentration (in mg 1-L ) for aquatic species in which 50% of a particular species, in this case rainbow trout, are killed after exposure for a period of 96 h. The lower the LCs0, the greater is the level of toxicity of that pesticide. A better measure of toxicity would be the lifetime health advisory level (HAL) or maximum
T.C. Kelly et al./ Agriculture, Ecosystems and Environment 60 (1996) 17-28
contaminant level (MCL) as defined by the EPA for human beings. However, HALs or MCLs have not been defined for many of the herbicides in this study. The pesticide hazard level for a particular rotation is the sum of the hazards from all pesticides applied in that rotation. The hazard attributed to each pesticide is the total amount lost to the environment (g ha -~) divided by its relative toxicity. The pesticide hazard level is based on average annual chemical loading below the root zone and at field boundary for each chemical, and therefore represents potential hazard at that point in time. It is assumed that the risks are additive for a multiple chemical application. 2.8. Data sources
Crop yields and loading levels of nitrate, phosphorous, and herbicides were derived as annual averages from 30 year simulations with EPIC using random weather from Owings Ferry Landing. Crop prices used were typical 1994 prices for this region (Dale Johnson, personal communication). The price used for hay was 75% of the price for other hay because of the reported high weed content of the hay. One metric ton of hay or straw was assumed to equal 44.1 bales (50 lb. per bale) for budget calculations. The quantities of seeds, fertilizers, and chemicals used were actual values for the demonstration farm, with their respective current prices. Custom hire charges were the typical charges for the state of Maryland (Johnson, 1993), and are presented in Table 1. These charges were assumed to cover labor, machinery operating and depreciation costs, and associated insurance and taxes. Custom hire charges were used instead of breaking down individual operations and costing the components. Arguments can be made both that these charges underestimate and overestimate actual costs to farmers. Farmers' out of pocket costs cannot be determined from these charges. Annual production costs for each rotation are detailed in Table 2. Seed, fertilizer, and chemical costs were provided by Dale Johnson (personal communication) and are indicative of costs faced by farmers in 1994. Operating interest is for 6 months at an annual rate of 12%. Total variable production costs for each rotation are calculated as the simple average of the two rotation components (corn and
21
wheat/soybean/hay), assuming that half the area is planted in each of them.
3. Results and discussion Yields, total returns, variable costs, and gross margins are presented in Table 3. The relatively higher corn yields in the no-till as compared with the cover crop treatments is contrary to research conducted on other Maryland soils where unfertilized no-till corn following a hairy vetch cover crop performed equally well compared with fertilized no-till corn after fallow (Hanson et al., 1993). Also, the crop growth model in EPIC assumes that weeds and disease are completely controlled and, therefore, nonlimiting. In this study, comparing the relative yields across treatments assumes that weed control practices, i.e. herbicides and cultivation, are equally effective. In reality, this may not be true. These suggest that simulated yields from EPIC should be interpreted with caution, and that more testing of cover crops and weed competition in cropping systems simulation models such as EPIC is needed. The returns by crop presented in Table 3 are for a half hectare, which assumes that both years of the rotation are represented in a hectare. Total returns is simply the sum of returns of the individual crops. Gross margin is the total returns less total variable costs. The no-till rotation provides the greatest net returns ($331), followed by conventional ($306) and manure-high ($306), and then the other two manure rotations ($291, and $256, respectively, for medium and low manure applications). The net returns on the two cover crop rotations are relatively low, $117 for cover crop and $169 for cover crop with no fertilizer, because only two rather than three crops contribute to the returns. The yield increase from full-season soybeans does not compensate for the lost revenue from the wheat. The environmental impacts of each rotation are measured by the total loadings of a contaminant or total soil lost to erosion (Table 4). Loadings are calculated as the sum of the amounts lost through leaching, runoff, subsurface flow (SSflow), and attached to sediment. In Table 4, pesticide loss for each pesticide is the sum of the loadings of that pesticide through leaching, runoff, subsurface flow,
22
T.C. Kelly et a l . / Agriculture, Ecosystems and Environment 60 (1996) 1 7 - 2 8
"7
[
~.$.
Z
<
,
Z <
ml
CqC.I~kQ~
,.=
t¢5
~24
Z <
M
"~
0
g
q
-
_
- r c ~
o -
Z
•
"~,
N
a~
-
-
-r-:tc
[-
-x.
.e o
~. .. ~~ z. o
6
~
=o _.:~.~
~ ' ~~
T.C. Kelly et a l . / Agriculture, Ecosystems and Environment 60 (1996) 17-28
•
~
°
23
°
o
o<
Z
<
O0
o~ -n oo
oo
-
©
I!
~
-
~-
~
oo
. . . . . .
~
"~-
~ o ~
o
z 2
~o6~
C
a ~o o
o tn
¢>
rq
24
T.C. Kelly et a l . / Agricuhure, Ecosystems and Environment 60 (1996) 1 7 - 2 8
and sediment loss. The pesticide hazard level is calculated from the pesticide loss and relative toxicities as described above. Soil lost to erosion was lowest for the cover crop rotations, followed by the no-till and manure rotations. The greatest erosion was found in the conventional rotation. The cover crop rotations also had the lowest phosphorous loss, again followed by the no-till and manure rotations, with conventional showing the highest. However, with respect to nitrogen loss, the cover crop rotation was the highest, followed by the high manure and conventional rotations. Decreasing the manure application by half reduced nitrogen loss by almost 60%, and eliminating the fertilizer in the cover crop rotation resulted in a greater than 60% reduction in lost nitrogen. The no-till rotation had the lowest nitrogen loss. Pesticide hazard was greatest in the conventional and no-till rotations by a wide margin. Reducing the environmental impact must be measured against any resulting loss in income to the producer. Table 3 indicates that little income is lost
when moving from high to medium application levels in the manure rotations, and to no fertilizer in the cover crop rotations; yet these moves result in substantial decreases in nitrogen loss (Table 4). The tradeoffs between income and environmental impact from the rotations with respect to erosion and chemical contamination are shown in Fig. 1. Since higher net returns are preferred to lower, and less contamination is preferred to greater, a rotation is preferable to all other rotations that are below and to the right of it in the graphs in Fig. 1. For example, in the income-erosion tradeoff (Fig. 1a), the no-till rotation would be preferred over all other rotations except for the two cover crop rotations. Depending on an indiv i d u a l ' s preferences, a rational decision maker could choose either of the cover crop rotations or the no-till rotation with respect to income and erosion. In the tradeoff between income and nitrogen loss (Fig. 1b), the no-till rotation dominates all other rotations. A clear tradeoff exists when choosing between the low phosphorus loss with the cover crop systems or
Table 3 Average simulated yields (MT ha- i ) and returns and gross margins ($ ha- i ) for sustainable agriculture rotations CONVNTNL NO-TILL CVRCROP-h CVRCROP-z MANURE-h MANURE-m MANURE-I Yields" ( M T ha - ~)
Corn Winter wheat Wheat straw Soybean Hay
7.593 4.318 3.553 2.068
7.603 4.419 3.636 2.039
6.954
6.854
2.950
2.944
7.134 4.452 3.663
6.838 4.295 3.534
6.584 3.879 3.193
4.170
4.160
4.136
Returns
Corn ($88.60/MT) Win. wheat ($113.93/MT) Wheat straw ($66/MT) Soybean ($202.13/MT) Hay ($77/MT) Total returns
336.35 246.00 117.26 208.%
336.81 251.74 120.00 206.10
308.06 0.00 0.00 298.10
303.63 0.00 0.00 297.53
316.01 253.63 I20.88
302.92 244.68 116.62
291.68 220.98 105.36
$908.56
$914.65
$606.16
$601.16
160.54 $851.06
160.17 $824.39
159.24 $777.25
Seeds Fertilizers Chemicals Custom hire Operating int. Total variable costs
82.41 46.94 76.64 362.63 34.12 $602.78
87.16 46.94 100.99 315.74 33.05 $583.93
106.99 32.60 68.92 232.18 24.29 $488.85
106.99
70.13
70.13
68.92 232.18 24.49 $432.62
444.39 30.87 $545.40
433.19 30.20 $533.53
421.93 29.52 $521.59
Total gross margin
$305.78
$330.72
$117.31
$168.54
$305.67
$290.86
$255.66
Variable costs a
a Variable cost figures are simple averages in summary form of variable costs detailed in Table 2.
70.13
25
T.C. Kelly et al./Agriculture, Ecosystems and Environment 60 (1996) 17-28
h i g h e r g r o s s m a r g i n s w i t h the no-till s y s t e m (Fig.
w h e t h e r they are p r o d u c i n g the c r o p s or a d v i s i n g
lc). It is o n l y in the t r a d e o f f b e t w e e n i n c o m e a n d p e s t i c i d e h a z a r d that a m a n u r e r o t a t i o n m i g h t b e
p r o d u c e r s or p o l i c y m a k e r s , w i t h b e t t e r i n f o r m a t i o n
p r e f e r r e d (Fig. ld).
s e n t e d here, the t h r e e c o n t r i b u t o r s to the index, n i t r o g e n loss, p h o s p h o r o u s loss, a n d p e s t i c i d e hazard, are a c c o r d e d e q u a l w e i g h t s in the c o m p i l a t i o n o f the index. F o r e x a m p l e (see T a b l e 4), the E H I for
A n e n v i r o n m e n t a l h a z a r d i n d e x ( E H I ) is u s e d to a g g r e g a t e p o t e n t i a l c o n t a m i n a t i o n f r o m agricultural c h e m i c a l s ( T a b l e 4) to p r o v i d e d e c i s i o n m a k e r s ,
to assess e n v i r o n m e n t a l i m p a c t s . In the case pre-
Table 4 Environmental impacts of the sustainable agricultural rotations CONVNTNL
NO-TILL
CVRCROP-h
CVRCROP-z
MANURE-b
MANURE-m
MANURE-I
Erosion (MT ha - 1) Water 10.971 Wind 0.000 Total 10.971
1.996 0.001 1.997
1.497 0.000 1.497
1.501 0.000 1.501
3.634 0.002 3.636
5.029 0.002 5.031
6.851 0.000 6.851
Nitrogen loss (kg ha- 1) a Sediment 9.562 Runoff 0.162 Leach 4.053 SSflow 3.011 Total 16.789
2.998 0.181 3.884 3.044 10,106
3.114 0.219 35.560 6.829 45.722
3.071 0.198 10.441 4.452 18.161
4.906 0.143 21.922 5.119 32,090
5.818 0.105 4.813 2.610 13.346
7.184 0.085 3.6% 1.907 12.842
Phosphorous loss (kg ha- I) Sediment 1.660 Runoff 0.365 Leach 1.564 Total 3.589
0.701 0.405 1.597 2.703
0.456 0.398 1.132 1.987
0.410 0.304 0.816 1.530
0.982 0.636 1.559 3.176
0.977 0.362 1.546 2.886
1,174 0.20 l 1.507 2.882
0.372
0.402
0.740 0.965 0.304 0.039
0.745 0.998 0.293 0.040
0
0
0
70.2 88.5 0.0 52.9
29.2 80.4 0.0 36.5
28.1 80.3 0.0 36.1
Pesticide loss (g ha- i) Relative toxicity (LC50 (mg 1- ~)) Atrazine 4.5 12.552 Metolachlor 2 43.572 Paraquat 32 28.702 Thifensulfuron 0.501 100 Linuron 3.15 17.384 Nicosulfuron 1000 Acifluorfen 31 Dicamba 135 Sethoxyclim 38 Pesticide hazard 30.996 level Environmental hazard index Nloss 36.7 PIoss 100.0 Pesticide hazard 100.0 EHI 78.9
13.828 42.768 28.556 0.512 14.478
29.951
22.1 75.3 96.6 64.7
100.0 55.4 0.1 51.8
39.7 42.6 0.1 27.5
a Sediment refers to contaminant losses attached to soil particles lost through water erosion; Runoff refers to contaminant losses in solution in runoff, Leach refers to contaminant losses in solution through leaching; and SSflow refers to contaminant losses through lateral movement in solution below ground level.
T.C. Kelly et aL /Agriculture, Ecosystems and Enuironment 60 (1996) 17-28
26 500 k
(a)
4(30
(b)
• e¢oJ'au,. .~,,~
300 =
• ~IURE.41 . . . . ° MANURE~
.
.
.
.
.
• MANURE4
L~
m
E
(n 200 + m 1
o
.
.
I
.
.
.
.
.
.
.
.
.
.
.
.
.
.
• t~o-/lld. qu,d ~ N T ~
c 300 . . . . . . . . . . . . . . . . "~
.
. . . .
o ~U~UR~,~
O'MANURE4
1::200 . . . . . . . . . . . . . . .
,,cv~,op.
~'~
1
• CONVF.NTNL
I
•CVRCROP 100 - -
.
.
.
.
.
.
.
.
.
.
~oo
J F
0
5Cz0
2
8
10
12
10
20
30
40
50
N-loss (kglha)
(d) .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
NO-TILL 0 . . . . MANU~ MANURE.-mg
!
E
6
Erosion (MT/ha)
(c) .
~30~ [;;
4
ecwc~
.
.
.
.
.
.
.
.
.
.
.
.....
.
l
~ l t
;
~ ............
• MANUREd
~
CVRCRO~O
i
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
o ~O=TILL eGONVENTNL . . .
.
!~'~"°'~ I
. . . . . . .
.
CVRCROP •
100
~
I 0
0
5
10
15
~ n
/
1
~
I--
2
~
•
+
3
P-loss (kg/ha)
I-
,
20
25
30
35
Pesticide Hazard Index
-
4
5
Fig. 1. Tradeoffs between income and environmental impact from alternative cropping rotations. (a) Income-erosion tradeoff; (b) income-nitrogen loss tradeoff; (c) income-phosphorous tradeoff; (d) income-pesticide hazard tradeoff.
cover crop-high is 51.8, which is the weighted (equal) average of N-loss, P-loss, and pesticide hazard. Since the N-loss for this rotation is the highest of all the rotations, it is assigned 100. P-loss is 55.4% of the highest P-loss (conventional), and the pesticide hazard is 0.1% of the highest pesticide hazard (also conventional). The tradeoff between environmental hazard, as defined by the EHI, and income is shown with the tradeoff frontier in Fig. 2. Depending on the individual's (or society's) preferences, any one of three rotations could be preferred: no-till; manure-medium; and cover crop-zero. Only the conventional and cover crop with high fertilizer rotations are clearly dominated by one or more of the others, and manure-high and manure-low are dominated by a combination of the other three. Given the kinked nature of the frontier, the manure-medium rotation would be the choice under the widest range of preference struc-
tures. Only individuals with very flat indifference maps, those with a strong preference for income, would choose no-till, while individuals with very steep indifference maps containing strong preferences for reducing environmental hazard might prefer cover crop-zero fertilizer rotation. 5OO
~4oo m300
....
E
~.~ 200
-
eOte~ENTNL O
. . . .
//
CVRCROP~b
I
I
CVRCROPO
_= 0 I 0
= --P---~
t
10
20
,
I
I
30
40
-
i 50
+ 60
70
80
90
100
EnvironmentalHazard Index Fig. 2. Tradeoff between income and environmental hazard from ahemative cropping rotations.
T.C. Kelly et al./ Agrieulture, Ecosystems and Environment 60 (1996) 17-28
'2tliii ~
] 0 M~URE~
6
"~o
1
e MANURE~
I~1
] * MANURE-h
,
0
.
.
.
.
.
o cv~¢Rop~
10
20
.
I
ONO-rlI.L
4
OCVRCROP
30 40 50 60 70 Environmental H a z a r d Index
I
80
90
100
Fig. 3. Tradeoff between erosion and environmental hazard from alternative cropping rotations.
A tradeoff between environmental hazard from chemical contamination and erosion is not clearly evident. Fig. 3 shows that cover crop-zero fertilizer rotation is the lowest in both erosion and environmental hazard while the conventional rotation is highest in both, suggesting a direct relationship between erosion and chemical contamination. Between individual rotations, however, there are tradeoffs between erosion and environmental hazard, as, for example, between manure-medium, manure-high, and no-till. Since on both axes in Fig. 3, lower is preferred to higher, a point dominates all those points above and to the right. Cover crop-zero fertilizer dominates all other rotations with respect to erosion and chemical contamination.
4. Summary and conclusions This paper evaluates the simulated long-term impacts of different cropping systems on net returns and environmental quality; and analyzes the tradeoffs among net returns and different components of environmental quality. The cropping systems are modeled after the BARC Sustainable Agriculture Demonstration Farm. Since field data will become available only after a number of years, EPIC was used to obtain crop yields, soil erosion, and the environmental fate of nitrogen, phosphorous, and herbicides in response to weather and management practices over a simulated 30 year period to provide data for the analyses. This procedure provides a way to estimate the environmental impact of cropping rotations, and to analyze the tradeoffs between corn-
27
peting objectives, whether they are income and environmental protection, or the reduction of multiple hazards. The results indicate that the no-till rotation provides the greatest net returns, followed by the conventional rotation. The net returns on the two cover crop rotations is the lowest because only two rather than three crops contribute to the returns. The yield increase from full-season soybeans does not make up for the lost revenue from the wheat. In terms of environmental impacts, the no-till rotation dominates all other rotations in regard to the loss of nitrogen, and outperforms all but the two cover crop rotations regarding erosion and phosphorous loss. However, because herbicides are necessary to control weeds in no-till, the pesticide hazard index is very high, suggesting that there may be a tradeoff between pesticide hazard and other environmental considerations. The results also indicate that there are potential ways to gain significantly on one objective without sacrificing significantly on another objective. For example, this analysis revealed that fertilizer could be removed from the cover crop rotation without significant loss in income but with substantial reduction in environmental contamination. The potential for nitrogen loss can be high in supposedly sustainable rotations such as those with manure applications or leguminous cover crops. The choice between measures to reduce environmental hazard from chemical contamination and erosion is not always obvious. Cover crop-zero fertilizer dominates all other rotations with the lowest level of both erosion and chemical contamination while the conventional rotation is dominated by all other rotations with the highest levels of erosion and environmental hazard. However, there are tradeoffs between erosion and environmental hazard for manure and no-till rotations. To provide decision makers with better information, an environmental hazard index (EHI) was constructed to analyze the tradeoffs between potential chemical contamination and net returns. Depending on the individual's (or society's) preferences, any one of three rotations could be preferred: no-till; manure at medium application rates; and cover crop without fertilizer. If the producer's (or society's) preference is known, it is possible to identify the
28
T.C. Kelly et al./ Agriculture, Ecosystems and Environment 60 (1996) 17-28
optimal rotation in terms of net returns and environmental hazard. Given the kinked nature of the tradeoff frontier, the manure-medium rotation would be the choice under the widest range of preference structures. Only individuals with very flat indifference maps, those with a strong preference for income, would choose no-till, while individuals with very steep indifference maps containing strong preferences for reducing environmental hazard might prefer cover crop-zero fertilizer rotation.
References Faeth, P. (Editor), 1993. Agricultural Policy and Sustainability: Case Studies from India, Chile, the Philippines and the United States. World Resources Institute, Washington, DC. Faeth, P., Repetto, R., Kroll, K., Dai, Q. and Helmets, G., 1991. Paying the Farm Bill: U.S. Agricultural Policy and the Transition to Sustainable Agriculture. World Resources Institute, Washington, DC. Hanson, J.C., Lichtenberg, E., Decker, A.M. and Clark, A.J., 1993. Profitability of no-tillage corn following a hairy vetch cover crop. J. Prod. Agr., 6: 432-437. Hoag, D., 1990. Least-Cost Mitigation of Groundwater Contamination from Soybean Herbicides. Presented at the Annual Meeting of the American Association for the Advancement of Science, New Orleans, LA. Hoag, D.L. and Hornsby, A.G., 1992. Coupling groundwater contamination with economic returns when applying farm pesticides. J. Environ. Qual., 21: 579-586.
Hughes, D., Butcher, W., Jaradat, A. and Penaranda, W., 1995. Economic analysis of the long-term consequences of farming practices in the barley cropping area of Jordan. Agr. Systems, 47 (1): 39-58. Johnson, D.M., 1993. Custom work charges in Maryland. Information Series No. 209303, Department of Agricultural and Resource Economics, University of Maryland at College Park, MD. Jones, C.A., Dyke, P.T., Williams, J.R., Kinery, J.R., Benson, V.W. and Griggs, R.H., 1991. EPIC: an operational model for evaluation of agricultural sustainability. Agr. Systems, 35: 341-350. Kellogg, R.L., Maizel, M.S. and Goss, D.W., 1994. The potential for leaching of agrichemicals used in crop production: a national perspective. J. Water and Soil Cons., 49 (3): 294-298. Kim, S. and Mapp, H.P., 1993. A farmlevel economic analysis of agricultural pollution control, presented at the AAEA Annual Meetings, Orlando, FL, Aug. 1-4. Leonard, R.A., Knisel, W.G. and Still, D.A., 1987. GLEAMS: Groundwater loading effects of agricultural management systems. Trans. ASAE, 30: 1403-1418. Sharpley, A.N. and Williams, J.R. (Editors), 1990. EPIC-Erosion/Productivity Impact Calculator: 2. Model Documentation. USDA-ARS Technical Bulletin Number 1768. Teague, M.L., Bemardo, D.J. and Mapp H.P., 1995. Farm-level economic analysis incorporating stochastic environmental risk assessment. Am. J. Agr. Econ., 77 (1): 8-19. Wauchope, R.D., Williams, R.G. and Marti, L.R., 1990. Runoff of sulfometuron-methyl and cyanazine from small plots: effects of formulation and grass cover. J. Environ. Quality, 19 (1): 119-125. Williams, J.R., Dyke, P.T., Fuchs, W.W., Benson, V.W., Rice, O.W. and Taylor, E.D., 1990. EPIC-Erosion/Productivity Impact Calculator: 2. User Manual. USDA-ARS Technical Bulletin Number 1768.
Agriculture,Ecosystems and Environment60 (1996) 17-28
Economic-environmental tradeoffs among alternative crop rotations Terry C. Kelly a, Yao-chi Lu b,, ,1, John Teasdale c a Department of Agricultural and Horticultural Systems Management, Massey University, Private Bag 11222, Palmerston North, New Zealand b Systems Research Lab, Agricultural Research Service, U.S. Department of Agriculture, Bldg. 007, Rm. 8, BARC-West. Beltsville. MD 20705, USA c Weed Science Lab, Agricultural Research Service, US Department of Agriculture, Beltsville, MD 20705. USA
Accepted 3 May 1996
Abstract Simulated long-term impacts of different cropping systems are evaluated and analyzed in terms of the tradeoffs among net returns and different components of environmental quality. The cropping systems are modeled after the BARC Sustainable Agriculture Demonstration Farm. EPIC was used to obtain crop yields, soil erosion, and the environmental fate of nitrogen, phosphorous, and herbicides in response to weather and management practices over a simulated 30 year period. This procedure provides a way to estimate the environmental impact of cropping rotations, and to analyze the tradeoffs between competing objectives, whether they are farm income, erosion control, or the reduction of multiple hazards. The results indicate that the no-till rotation provides the greatest net returns, followed by the conventional rotation. The net returns on the two cover crop rotations are lowest. In terms of environmental impacts, no-till rotation dominates all other rotations with lowest nitrogen loss, and the covercrop rotations perform best in terms of erosion and phosphorous loss. However because herbicides are necessary to control weeds in no-till, the pesticide hazard index is very high, suggesting a tradeoff between pesticide hazard and other environmental considerations. To provide decision makers with better information, an environmental hazard index was constructed to analyze the tradeoffs between potential chemical contamination and net returns. Depending on preference structure, any one of three rotations could be preferred: no-till; manure at medium application rates; and cover crop without fertilizer. Keywords: Cropping systems; Simulation;Environmentalhazard; Economics;Nitrogen; Pesticides; Erosion
1. Introduction Cultivation of the soil is an important component of sustainable agricultural strategies. Plowing soils
* Corresponding author. Tel: 301-504-5821; fax: 301-504-5823 email: [email protected]. This research was conducted while Terry Kelly was with the Agricultural Research Service of the USDA.
prior to planting kills weeds and releases nutrients from existing vegetation. Cultivation incorporates animal manure or cover crops, providing nutrients for plant growth and reducing the need for commercial fertilizer use. Interrow cultivation after planting can control weeds and reduce herbicide applications. However, cultivation also can result in loss of soil organic matter, deterioration of soil structure, increased soil erosion, and thus, reduced productivity
0167-8809/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. PII S01 67-8809(96)0 1064-X
18
T.C. Kelly et al./ Agriculture, Ecosystems and Environment 60 (1996) 17-28
of soils. A significant proportion of farmland in the Mid-Atlantic states as well as other regions of the United States is subject to soil erosion, and reducedtillage systems have been developed to preserve the viability of erodible land. However, reduced-tillage systems require more chemical fertilizer and herbicide inputs than conventional tillage, resulting in greater potential for water pollution. Water quality concerns are especially paramount in the Chesapeake Bay drainage. The coastal plains and the Piedmont regions of the MidAtlantic and southeastern United States are extremely vulnerable to pesticide and nitrate leaching (Kellogg et al., 1994). Since the goal of obtaining maximum profits may conflict with the goal of minimizing environmental damages, the agricultural research community is challenged to develop profitable cropping systems that incorporate reduced tillage as well as reduced dependence on fertilizer and herbicide inputs. As part of the Sustainable Agriculture Project at the USDA's Beltsville Agricultural Research Center (BARC), a 15 acre site on the South Farm with 2% to 15% slope has been set aside for demonstrating several alternative corn-based cropping rotations to evaluate the viability of sustainable agricultural strategies that are compatible with reduced-tillage systems required on erodible land. The experiments will be continued for at least five cycles of the 2-year rotation to permit long-term evaluation. However, in the absence of field data prior to the completion of the experiments, one way to develop timely and accurate information is to use biophysical simulation models that can examine multiple variables under different scenarios. The objectives of this paper are to: (1) evaluate the long-term impacts of different cropping systems on net returns (or gross margin), soil erosion, and environmental quality; and (2) analyze the tradeoffs among net returns, soil erosion, and other components of environmental quality. Data for the analyses are generated by biophysical simulation models.
2. Materials and methods
To assess the economic and environmental impacts of alternative cropping systems, the Erosion-
Productivity Impact Calculator (EPIC) (Sharpley and Williams, 1990; Williams et al., 1990) was used to generate crop yields, soil erosion, and the environmental fate of nitrogen, phosphorous, and herbicides in response to weather and management practices over a simulated 30 year period. EPIC, a comprehensive cropping systems model, was designed to analyze alternative cropping systems and help decision makers predict their environmental and economic sustainability (Jones et al., 1991) by estimating crop yields, chemical loss to the environment, and soil degradation in response to soil, weather, and management variables. EPIC has been extensively tested and validated under a wide variety of conditions for most of the common agronomic crops, and in most cases, simulated yields were not significantly different from measured yields (Jones et al., 1991). Pesticide components in EPIC are modifications of those used in GLEAMS, a non-point source pollution model that is widely used for water quality planning purposes (Leonard et al., 1987). Wauchope et al. (1990) found excellent agreement between observed pesticide losses and GLEAMS predicted losses. In recent years, EPIC has been widely used to examine the environmental impacts of alternative farming practices and the tradeoffs between reduced contamination and farm income. Kim and Mapp (1993) employed the EPIC-PST model to complete the coefficient matrix of a linear programming model in order to evaluate alternative scenarios for achieving a certain level of water pollution control. Hughes et al. (1995) combined EPIC with a whole-farm model and budget analysis to evaluate the short-run profitability and the long-run sustainability of agricultural practices in the barley cropping area of Jordan. EPIC was used in a study of rice-wheat rotations in the Indian Punjab in order to estimate soil erosion and current and future crop yields for each rotation under different tillage and fertilization alternatives (Faeth, 1993). Faeth et al. (1991) developed a framework that combined the EPIC simulation model with an agricultural sector model and an accounting model in order to quantify economic, fiscal, and environmental costs and benefits of agricultural policy options. Finally, Teague et al. (1995) used EPIC output to create environmental indices for pesticides and nitrates to measure environmental risk and the sensitivity of net returns to reductions in
T.C. Kelly et al. /Agriculture, Ecosystems and Environment 60 (1996) 17-28
potential water contamination from pesticides and nitrates. The sustainable agriculture demonstrations at BARC are on a complex soil with varying, and sometimes steep slope. Sassafras soil is one of the soil series represented at this site, and is the one used for the analysis in this paper. Four separate 2-year cropping rotations constitute the demonstrations at BARC: (1) a no-till corn-double cropped wheatsoybean rotation; (2) a crownvetch living mulch corn-winter wheat-soybean rotation; (3) a cover crop corn-full season soybean rotation; and (4) a manurebased corn-wheat-forage rotation. The crownvetch in the second rotation has been slow to establish, and because of limitations in EPIC preventing the simulation of two crops growing simultaneously, the crownvetch rotation is not included in this analysis. The cover crop rotation is analyzed with and without added nitrogen and phosphorous, and the manure rotation is analyzed at three different levels of manure applications. A conventional tillage corn-double cropped wheat-soybean rotation is included in the analysis as a control. A total of seven rotations were simulated using EPIC with management input based on the sustainable agriculture demonstration at BARC. Sassafras soils with 8% slope and weather generated from data at Owings Ferry Landing in southern Maryland are used for the simulations. In each rotation, corn is planted on 11 May and harvested on 7 October. Winter wheat following corn is planted on 19 October and, except in the two cover crop rotations, is harvested on 6 July the following year, with the straw baled on 7 July. Double-cropped soybeans are planted on 8 July and harvested on 14 November, while full-season soybeans in the cover crop rotations are planted on 13 May and harvested 1 October. Specific details of the rotations are described as follows. 2.1. Conventional
This is a conventional 2-year corn-winter wheatsoybean rotation with conventional tillage (chisel plow and disk) prior to planting all three crops. Weed control in corn is maintained with a preemergence herbicide treatment of 1.49 kg ha-~ atrazine and 1.87 kg ha-1 metolachlor (applied together as
19
4.67 1 ha-~ of Bicep). Composite fertilizer (19-19-19) is applied on 6 May prior to tillage and corn planting at a rate of 224 kg ha - l , fertilizer (10-20-10) is applied with planter at 168 kg ha - j , and corn is sidedressed with 224 kg ha-~ UAN (28% N) on 20 June. On 19 October, prior to tillage and planting winter wheat, 336 kg ha -~ of 5-10-10 fertilizer is applied, and a further 240 kg ha-E UAN is applied in the spring on 15 March together with an application of 35 g ha- 1 of Harmony Extra herbicide (26 g ha -1 thifensulfuron). On 8 July, a preemergence treatment for soybeans is applied as 1.75 1 haGramoxone Extra (0.56 kg ha-~ of paraquat), 2.3 1 h a - i Dual (2.24 kg ha-~ metolachlor), and 2.24 kg ha - l Lorox (1.12 kg ha -~ linuron). 2.2. No-till
This rotation is similar to the conventional except that there is no-tillage prior to planting, and the preemergence herbicide application on corn is increased to 1.79 kg ha-~ atrazine and 2.24 kg hametolachlor (5.6 1 ha-1 Bicep) and includes additionally 1.75 1 ha- 1 Gramoxone Extra (0.56 kg haof paraquat). 2.3. Cover crop
This is a zero tillage rotation in which cover crops are used to control erosion and provide some of the required nutrients. Corn is planted into a hairy vetch cover and is followed by winter wheat, which is planted strictly as a cover crop and therefore is not harvested for grain. There is not sufficient time to harvest both wheat and soybeans for grain and plant a hairy vetch cover crop. Fertilizer (10-20-10) is applied with planter at 168 kg ha -1. The wheat is mowed on 12 May, and full-season soybeans are planted into the mown wheat on 13 May. Hairy vetch is no-till planted on 2 October following the soybean harvest. Fertilizer (0-15-30) is applied prior to corn planting at a rate of 224 kg ha -~, and the corn is sidedressed with UAN at a rate of 224 kg ha -1 on 20 June. On 23 May, 0.58 1 ha-~ of a postemergence herbicide (Banvel) is applied at a rate of 0.28 kg ha- t dicamba to kill the hairy vetch, and grass weeds are controlled with a postemergence application of Accent at a rate of 47 g ha-~ (35 g
20
T.C. Kelly et al./ Agriculture, Ecosystems and Environment 60 (1996) 17-28
ha- t nicosulfuron) on 20 June. Phosphorous is added to the wheat crop on 6 May prior to mowing at the rate of 67.2 kg P2Os per ha. Weeds are controlled in the soybeans with a postemergence application of Poast (0.22 kg ha-l Sethoxydim) and Blazer (0.28 kg ha-~ Acifluorfen) on 20 June. 2.4. Cover crop-zero
This rotation is identical to the cover crop rotation except that there is no added fertilizer N or P. 2.5. Manure-high
Organic practices are represented in the manure rotations. No synthetic fertilizers or chemical pesticides are used. The manure rotations are 2-year rotations with corn followed by winter wheat followed by a forage legume, in this case red clover. Red clover is overseeded in the wheat on 6 April (in EPIC, it is planted immediately after wheat harvest, since EPIC does not allow more than one crop grown simultaneously), is cut and baled on 5 October, and then is plowed under prior to corn planting the following 11 May. Tillage, chisel plow and disk, is performed prior to corn planting and prior to wheat planting. Manure is applied twice in the 2 years, once at a rate of 23.76 MT ha-J on 5 May prior to tillage and corn planting, and another at a rate of 11.2 MT ha- l on 19 October prior to tillage and wheat planting. The manure is old cow manure with the following nutrient content as a percent of dry weight: 0% mineral N; 0.7% organic N; 0.2% mineral P; and 0.1% organic P. Weeds are controlled in corn through cultivation, with two rotary hoe operations (17 and 24 May) and two cultivations (7 and 21 June). 2.6. Manure-medium
This is the same as the manure-high rotation with the manure applications cut in half, that is, 11.88 MT ha- ~ in the first application and 5.6 MT ha- 1 in the second application. 2.7. Manure-low
This is the same as the manure-high rotation with the manure applications reduced to one-fourth, that
is, 5.94 MT ha- ~ in the first application and 2.8 MT ha-~ in the second application. In this study an income/environmental hazard frontier is used to present tradeoffs related to nitrogen, phosphorous, and herbicide applications. An advantage of this approach is that the opportunity costs (in terms of lower net income) of reducing pollution can be compared between any two strategies (Hoag and Hornsby, 1992). The tradeoff frontier contains all the points that are not clearly dominated by one or more of the other points, and the slope of the frontier between two points measures the degree of the tradeoff between those points. The frontier can be customized to a particular farm or watershed situation, thereby contributing additional information toward decision making. An environmental hazard index (EHI) is derived for each rotation based on potential contamination from nitrates, phosphorous, and pesticides. An index is defined for each of these contaminants by assigning the highest loading level (or in the case of pesticides, the highest pesticide hazard) across rotations a value of 100 and indexing the remaining levels according to their ratio to the highest level. The EHI is a weighted average of the three individual indices, with weights determined by their relative environmental hazards in a specific situation. Whereas nitrate and pesticides present health hazards when present in ground and surface waters, the main environmental hazard of phosphorous is the disruption of the balance of aquatic systems through promotion of algae growth. However, in this study, no attempt is made to evaluate the relative hazards of these three components of the EHI; thus, they are assigned equal weights for illustrative purposes here. The pesticide component of the EHI is determined by the pesticide hazard level from pesticide application, which is defined for each rotation based on the relative toxicities of the pesticides and amounts lost to the environment (Hoag and Hornsby, 1992; Hoag, 1990). Relative toxicity in this study is described by the LCs0 of a pesticide, which is the lethal concentration (in mg 1-L ) for aquatic species in which 50% of a particular species, in this case rainbow trout, are killed after exposure for a period of 96 h. The lower the LCs0, the greater is the level of toxicity of that pesticide. A better measure of toxicity would be the lifetime health advisory level (HAL) or maximum
T.C. Kelly et al./ Agriculture, Ecosystems and Environment 60 (1996) 17-28
contaminant level (MCL) as defined by the EPA for human beings. However, HALs or MCLs have not been defined for many of the herbicides in this study. The pesticide hazard level for a particular rotation is the sum of the hazards from all pesticides applied in that rotation. The hazard attributed to each pesticide is the total amount lost to the environment (g ha -~) divided by its relative toxicity. The pesticide hazard level is based on average annual chemical loading below the root zone and at field boundary for each chemical, and therefore represents potential hazard at that point in time. It is assumed that the risks are additive for a multiple chemical application. 2.8. Data sources
Crop yields and loading levels of nitrate, phosphorous, and herbicides were derived as annual averages from 30 year simulations with EPIC using random weather from Owings Ferry Landing. Crop prices used were typical 1994 prices for this region (Dale Johnson, personal communication). The price used for hay was 75% of the price for other hay because of the reported high weed content of the hay. One metric ton of hay or straw was assumed to equal 44.1 bales (50 lb. per bale) for budget calculations. The quantities of seeds, fertilizers, and chemicals used were actual values for the demonstration farm, with their respective current prices. Custom hire charges were the typical charges for the state of Maryland (Johnson, 1993), and are presented in Table 1. These charges were assumed to cover labor, machinery operating and depreciation costs, and associated insurance and taxes. Custom hire charges were used instead of breaking down individual operations and costing the components. Arguments can be made both that these charges underestimate and overestimate actual costs to farmers. Farmers' out of pocket costs cannot be determined from these charges. Annual production costs for each rotation are detailed in Table 2. Seed, fertilizer, and chemical costs were provided by Dale Johnson (personal communication) and are indicative of costs faced by farmers in 1994. Operating interest is for 6 months at an annual rate of 12%. Total variable production costs for each rotation are calculated as the simple average of the two rotation components (corn and
21
wheat/soybean/hay), assuming that half the area is planted in each of them.
3. Results and discussion Yields, total returns, variable costs, and gross margins are presented in Table 3. The relatively higher corn yields in the no-till as compared with the cover crop treatments is contrary to research conducted on other Maryland soils where unfertilized no-till corn following a hairy vetch cover crop performed equally well compared with fertilized no-till corn after fallow (Hanson et al., 1993). Also, the crop growth model in EPIC assumes that weeds and disease are completely controlled and, therefore, nonlimiting. In this study, comparing the relative yields across treatments assumes that weed control practices, i.e. herbicides and cultivation, are equally effective. In reality, this may not be true. These suggest that simulated yields from EPIC should be interpreted with caution, and that more testing of cover crops and weed competition in cropping systems simulation models such as EPIC is needed. The returns by crop presented in Table 3 are for a half hectare, which assumes that both years of the rotation are represented in a hectare. Total returns is simply the sum of returns of the individual crops. Gross margin is the total returns less total variable costs. The no-till rotation provides the greatest net returns ($331), followed by conventional ($306) and manure-high ($306), and then the other two manure rotations ($291, and $256, respectively, for medium and low manure applications). The net returns on the two cover crop rotations are relatively low, $117 for cover crop and $169 for cover crop with no fertilizer, because only two rather than three crops contribute to the returns. The yield increase from full-season soybeans does not compensate for the lost revenue from the wheat. The environmental impacts of each rotation are measured by the total loadings of a contaminant or total soil lost to erosion (Table 4). Loadings are calculated as the sum of the amounts lost through leaching, runoff, subsurface flow (SSflow), and attached to sediment. In Table 4, pesticide loss for each pesticide is the sum of the loadings of that pesticide through leaching, runoff, subsurface flow,
22
T.C. Kelly et a l . / Agriculture, Ecosystems and Environment 60 (1996) 1 7 - 2 8
"7
[
~.$.
Z
<
,
Z <
ml
CqC.I~kQ~
,.=
t¢5
~24
Z <
M
"~
0
g
q
-
_
- r c ~
o -
Z
•
"~,
N
a~
-
-
-r-:tc
[-
-x.
.e o
~. .. ~~ z. o
6
~
=o _.:~.~
~ ' ~~
T.C. Kelly et a l . / Agriculture, Ecosystems and Environment 60 (1996) 17-28
•
~
°
23
°
o
o<
Z
<
O0
o~ -n oo
oo
-
©
I!
~
-
~-
~
oo
. . . . . .
~
"~-
~ o ~
o
z 2
~o6~
C
a ~o o
o tn
¢>
rq
24
T.C. Kelly et a l . / Agricuhure, Ecosystems and Environment 60 (1996) 1 7 - 2 8
and sediment loss. The pesticide hazard level is calculated from the pesticide loss and relative toxicities as described above. Soil lost to erosion was lowest for the cover crop rotations, followed by the no-till and manure rotations. The greatest erosion was found in the conventional rotation. The cover crop rotations also had the lowest phosphorous loss, again followed by the no-till and manure rotations, with conventional showing the highest. However, with respect to nitrogen loss, the cover crop rotation was the highest, followed by the high manure and conventional rotations. Decreasing the manure application by half reduced nitrogen loss by almost 60%, and eliminating the fertilizer in the cover crop rotation resulted in a greater than 60% reduction in lost nitrogen. The no-till rotation had the lowest nitrogen loss. Pesticide hazard was greatest in the conventional and no-till rotations by a wide margin. Reducing the environmental impact must be measured against any resulting loss in income to the producer. Table 3 indicates that little income is lost
when moving from high to medium application levels in the manure rotations, and to no fertilizer in the cover crop rotations; yet these moves result in substantial decreases in nitrogen loss (Table 4). The tradeoffs between income and environmental impact from the rotations with respect to erosion and chemical contamination are shown in Fig. 1. Since higher net returns are preferred to lower, and less contamination is preferred to greater, a rotation is preferable to all other rotations that are below and to the right of it in the graphs in Fig. 1. For example, in the income-erosion tradeoff (Fig. 1a), the no-till rotation would be preferred over all other rotations except for the two cover crop rotations. Depending on an indiv i d u a l ' s preferences, a rational decision maker could choose either of the cover crop rotations or the no-till rotation with respect to income and erosion. In the tradeoff between income and nitrogen loss (Fig. 1b), the no-till rotation dominates all other rotations. A clear tradeoff exists when choosing between the low phosphorus loss with the cover crop systems or
Table 3 Average simulated yields (MT ha- i ) and returns and gross margins ($ ha- i ) for sustainable agriculture rotations CONVNTNL NO-TILL CVRCROP-h CVRCROP-z MANURE-h MANURE-m MANURE-I Yields" ( M T ha - ~)
Corn Winter wheat Wheat straw Soybean Hay
7.593 4.318 3.553 2.068
7.603 4.419 3.636 2.039
6.954
6.854
2.950
2.944
7.134 4.452 3.663
6.838 4.295 3.534
6.584 3.879 3.193
4.170
4.160
4.136
Returns
Corn ($88.60/MT) Win. wheat ($113.93/MT) Wheat straw ($66/MT) Soybean ($202.13/MT) Hay ($77/MT) Total returns
336.35 246.00 117.26 208.%
336.81 251.74 120.00 206.10
308.06 0.00 0.00 298.10
303.63 0.00 0.00 297.53
316.01 253.63 I20.88
302.92 244.68 116.62
291.68 220.98 105.36
$908.56
$914.65
$606.16
$601.16
160.54 $851.06
160.17 $824.39
159.24 $777.25
Seeds Fertilizers Chemicals Custom hire Operating int. Total variable costs
82.41 46.94 76.64 362.63 34.12 $602.78
87.16 46.94 100.99 315.74 33.05 $583.93
106.99 32.60 68.92 232.18 24.29 $488.85
106.99
70.13
70.13
68.92 232.18 24.49 $432.62
444.39 30.87 $545.40
433.19 30.20 $533.53
421.93 29.52 $521.59
Total gross margin
$305.78
$330.72
$117.31
$168.54
$305.67
$290.86
$255.66
Variable costs a
a Variable cost figures are simple averages in summary form of variable costs detailed in Table 2.
70.13
25
T.C. Kelly et al./Agriculture, Ecosystems and Environment 60 (1996) 17-28
h i g h e r g r o s s m a r g i n s w i t h the no-till s y s t e m (Fig.
w h e t h e r they are p r o d u c i n g the c r o p s or a d v i s i n g
lc). It is o n l y in the t r a d e o f f b e t w e e n i n c o m e a n d p e s t i c i d e h a z a r d that a m a n u r e r o t a t i o n m i g h t b e
p r o d u c e r s or p o l i c y m a k e r s , w i t h b e t t e r i n f o r m a t i o n
p r e f e r r e d (Fig. ld).
s e n t e d here, the t h r e e c o n t r i b u t o r s to the index, n i t r o g e n loss, p h o s p h o r o u s loss, a n d p e s t i c i d e hazard, are a c c o r d e d e q u a l w e i g h t s in the c o m p i l a t i o n o f the index. F o r e x a m p l e (see T a b l e 4), the E H I for
A n e n v i r o n m e n t a l h a z a r d i n d e x ( E H I ) is u s e d to a g g r e g a t e p o t e n t i a l c o n t a m i n a t i o n f r o m agricultural c h e m i c a l s ( T a b l e 4) to p r o v i d e d e c i s i o n m a k e r s ,
to assess e n v i r o n m e n t a l i m p a c t s . In the case pre-
Table 4 Environmental impacts of the sustainable agricultural rotations CONVNTNL
NO-TILL
CVRCROP-h
CVRCROP-z
MANURE-b
MANURE-m
MANURE-I
Erosion (MT ha - 1) Water 10.971 Wind 0.000 Total 10.971
1.996 0.001 1.997
1.497 0.000 1.497
1.501 0.000 1.501
3.634 0.002 3.636
5.029 0.002 5.031
6.851 0.000 6.851
Nitrogen loss (kg ha- 1) a Sediment 9.562 Runoff 0.162 Leach 4.053 SSflow 3.011 Total 16.789
2.998 0.181 3.884 3.044 10,106
3.114 0.219 35.560 6.829 45.722
3.071 0.198 10.441 4.452 18.161
4.906 0.143 21.922 5.119 32,090
5.818 0.105 4.813 2.610 13.346
7.184 0.085 3.6% 1.907 12.842
Phosphorous loss (kg ha- I) Sediment 1.660 Runoff 0.365 Leach 1.564 Total 3.589
0.701 0.405 1.597 2.703
0.456 0.398 1.132 1.987
0.410 0.304 0.816 1.530
0.982 0.636 1.559 3.176
0.977 0.362 1.546 2.886
1,174 0.20 l 1.507 2.882
0.372
0.402
0.740 0.965 0.304 0.039
0.745 0.998 0.293 0.040
0
0
0
70.2 88.5 0.0 52.9
29.2 80.4 0.0 36.5
28.1 80.3 0.0 36.1
Pesticide loss (g ha- i) Relative toxicity (LC50 (mg 1- ~)) Atrazine 4.5 12.552 Metolachlor 2 43.572 Paraquat 32 28.702 Thifensulfuron 0.501 100 Linuron 3.15 17.384 Nicosulfuron 1000 Acifluorfen 31 Dicamba 135 Sethoxyclim 38 Pesticide hazard 30.996 level Environmental hazard index Nloss 36.7 PIoss 100.0 Pesticide hazard 100.0 EHI 78.9
13.828 42.768 28.556 0.512 14.478
29.951
22.1 75.3 96.6 64.7
100.0 55.4 0.1 51.8
39.7 42.6 0.1 27.5
a Sediment refers to contaminant losses attached to soil particles lost through water erosion; Runoff refers to contaminant losses in solution in runoff, Leach refers to contaminant losses in solution through leaching; and SSflow refers to contaminant losses through lateral movement in solution below ground level.
T.C. Kelly et aL /Agriculture, Ecosystems and Enuironment 60 (1996) 17-28
26 500 k
(a)
4(30
(b)
• e¢oJ'au,. .~,,~
300 =
• ~IURE.41 . . . . ° MANURE~
.
.
.
.
.
• MANURE4
L~
m
E
(n 200 + m 1
o
.
.
I
.
.
.
.
.
.
.
.
.
.
.
.
.
.
• t~o-/lld. qu,d ~ N T ~
c 300 . . . . . . . . . . . . . . . . "~
.
. . . .
o ~U~UR~,~
O'MANURE4
1::200 . . . . . . . . . . . . . . .
,,cv~,op.
~'~
1
• CONVF.NTNL
I
•CVRCROP 100 - -
.
.
.
.
.
.
.
.
.
.
~oo
J F
0
5Cz0
2
8
10
12
10
20
30
40
50
N-loss (kglha)
(d) .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
NO-TILL 0 . . . . MANU~ MANURE.-mg
!
E
6
Erosion (MT/ha)
(c) .
~30~ [;;
4
ecwc~
.
.
.
.
.
.
.
.
.
.
.
.....
.
l
~ l t
;
~ ............
• MANUREd
~
CVRCRO~O
i
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
o ~O=TILL eGONVENTNL . . .
.
!~'~"°'~ I
. . . . . . .
.
CVRCROP •
100
~
I 0
0
5
10
15
~ n
/
1
~
I--
2
~
•
+
3
P-loss (kg/ha)
I-
,
20
25
30
35
Pesticide Hazard Index
-
4
5
Fig. 1. Tradeoffs between income and environmental impact from alternative cropping rotations. (a) Income-erosion tradeoff; (b) income-nitrogen loss tradeoff; (c) income-phosphorous tradeoff; (d) income-pesticide hazard tradeoff.
cover crop-high is 51.8, which is the weighted (equal) average of N-loss, P-loss, and pesticide hazard. Since the N-loss for this rotation is the highest of all the rotations, it is assigned 100. P-loss is 55.4% of the highest P-loss (conventional), and the pesticide hazard is 0.1% of the highest pesticide hazard (also conventional). The tradeoff between environmental hazard, as defined by the EHI, and income is shown with the tradeoff frontier in Fig. 2. Depending on the individual's (or society's) preferences, any one of three rotations could be preferred: no-till; manure-medium; and cover crop-zero. Only the conventional and cover crop with high fertilizer rotations are clearly dominated by one or more of the others, and manure-high and manure-low are dominated by a combination of the other three. Given the kinked nature of the frontier, the manure-medium rotation would be the choice under the widest range of preference struc-
tures. Only individuals with very flat indifference maps, those with a strong preference for income, would choose no-till, while individuals with very steep indifference maps containing strong preferences for reducing environmental hazard might prefer cover crop-zero fertilizer rotation. 5OO
~4oo m300
....
E
~.~ 200
-
eOte~ENTNL O
. . . .
//
CVRCROP~b
I
I
CVRCROPO
_= 0 I 0
= --P---~
t
10
20
,
I
I
30
40
-
i 50
+ 60
70
80
90
100
EnvironmentalHazard Index Fig. 2. Tradeoff between income and environmental hazard from ahemative cropping rotations.
T.C. Kelly et al./ Agrieulture, Ecosystems and Environment 60 (1996) 17-28
'2tliii ~
] 0 M~URE~
6
"~o
1
e MANURE~
I~1
] * MANURE-h
,
0
.
.
.
.
.
o cv~¢Rop~
10
20
.
I
ONO-rlI.L
4
OCVRCROP
30 40 50 60 70 Environmental H a z a r d Index
I
80
90
100
Fig. 3. Tradeoff between erosion and environmental hazard from alternative cropping rotations.
A tradeoff between environmental hazard from chemical contamination and erosion is not clearly evident. Fig. 3 shows that cover crop-zero fertilizer rotation is the lowest in both erosion and environmental hazard while the conventional rotation is highest in both, suggesting a direct relationship between erosion and chemical contamination. Between individual rotations, however, there are tradeoffs between erosion and environmental hazard, as, for example, between manure-medium, manure-high, and no-till. Since on both axes in Fig. 3, lower is preferred to higher, a point dominates all those points above and to the right. Cover crop-zero fertilizer dominates all other rotations with respect to erosion and chemical contamination.
4. Summary and conclusions This paper evaluates the simulated long-term impacts of different cropping systems on net returns and environmental quality; and analyzes the tradeoffs among net returns and different components of environmental quality. The cropping systems are modeled after the BARC Sustainable Agriculture Demonstration Farm. Since field data will become available only after a number of years, EPIC was used to obtain crop yields, soil erosion, and the environmental fate of nitrogen, phosphorous, and herbicides in response to weather and management practices over a simulated 30 year period to provide data for the analyses. This procedure provides a way to estimate the environmental impact of cropping rotations, and to analyze the tradeoffs between corn-
27
peting objectives, whether they are income and environmental protection, or the reduction of multiple hazards. The results indicate that the no-till rotation provides the greatest net returns, followed by the conventional rotation. The net returns on the two cover crop rotations is the lowest because only two rather than three crops contribute to the returns. The yield increase from full-season soybeans does not make up for the lost revenue from the wheat. In terms of environmental impacts, the no-till rotation dominates all other rotations in regard to the loss of nitrogen, and outperforms all but the two cover crop rotations regarding erosion and phosphorous loss. However, because herbicides are necessary to control weeds in no-till, the pesticide hazard index is very high, suggesting that there may be a tradeoff between pesticide hazard and other environmental considerations. The results also indicate that there are potential ways to gain significantly on one objective without sacrificing significantly on another objective. For example, this analysis revealed that fertilizer could be removed from the cover crop rotation without significant loss in income but with substantial reduction in environmental contamination. The potential for nitrogen loss can be high in supposedly sustainable rotations such as those with manure applications or leguminous cover crops. The choice between measures to reduce environmental hazard from chemical contamination and erosion is not always obvious. Cover crop-zero fertilizer dominates all other rotations with the lowest level of both erosion and chemical contamination while the conventional rotation is dominated by all other rotations with the highest levels of erosion and environmental hazard. However, there are tradeoffs between erosion and environmental hazard for manure and no-till rotations. To provide decision makers with better information, an environmental hazard index (EHI) was constructed to analyze the tradeoffs between potential chemical contamination and net returns. Depending on the individual's (or society's) preferences, any one of three rotations could be preferred: no-till; manure at medium application rates; and cover crop without fertilizer. If the producer's (or society's) preference is known, it is possible to identify the
28
T.C. Kelly et al./ Agriculture, Ecosystems and Environment 60 (1996) 17-28
optimal rotation in terms of net returns and environmental hazard. Given the kinked nature of the tradeoff frontier, the manure-medium rotation would be the choice under the widest range of preference structures. Only individuals with very flat indifference maps, those with a strong preference for income, would choose no-till, while individuals with very steep indifference maps containing strong preferences for reducing environmental hazard might prefer cover crop-zero fertilizer rotation.
References Faeth, P. (Editor), 1993. Agricultural Policy and Sustainability: Case Studies from India, Chile, the Philippines and the United States. World Resources Institute, Washington, DC. Faeth, P., Repetto, R., Kroll, K., Dai, Q. and Helmets, G., 1991. Paying the Farm Bill: U.S. Agricultural Policy and the Transition to Sustainable Agriculture. World Resources Institute, Washington, DC. Hanson, J.C., Lichtenberg, E., Decker, A.M. and Clark, A.J., 1993. Profitability of no-tillage corn following a hairy vetch cover crop. J. Prod. Agr., 6: 432-437. Hoag, D., 1990. Least-Cost Mitigation of Groundwater Contamination from Soybean Herbicides. Presented at the Annual Meeting of the American Association for the Advancement of Science, New Orleans, LA. Hoag, D.L. and Hornsby, A.G., 1992. Coupling groundwater contamination with economic returns when applying farm pesticides. J. Environ. Qual., 21: 579-586.
Hughes, D., Butcher, W., Jaradat, A. and Penaranda, W., 1995. Economic analysis of the long-term consequences of farming practices in the barley cropping area of Jordan. Agr. Systems, 47 (1): 39-58. Johnson, D.M., 1993. Custom work charges in Maryland. Information Series No. 209303, Department of Agricultural and Resource Economics, University of Maryland at College Park, MD. Jones, C.A., Dyke, P.T., Williams, J.R., Kinery, J.R., Benson, V.W. and Griggs, R.H., 1991. EPIC: an operational model for evaluation of agricultural sustainability. Agr. Systems, 35: 341-350. Kellogg, R.L., Maizel, M.S. and Goss, D.W., 1994. The potential for leaching of agrichemicals used in crop production: a national perspective. J. Water and Soil Cons., 49 (3): 294-298. Kim, S. and Mapp, H.P., 1993. A farmlevel economic analysis of agricultural pollution control, presented at the AAEA Annual Meetings, Orlando, FL, Aug. 1-4. Leonard, R.A., Knisel, W.G. and Still, D.A., 1987. GLEAMS: Groundwater loading effects of agricultural management systems. Trans. ASAE, 30: 1403-1418. Sharpley, A.N. and Williams, J.R. (Editors), 1990. EPIC-Erosion/Productivity Impact Calculator: 2. Model Documentation. USDA-ARS Technical Bulletin Number 1768. Teague, M.L., Bemardo, D.J. and Mapp H.P., 1995. Farm-level economic analysis incorporating stochastic environmental risk assessment. Am. J. Agr. Econ., 77 (1): 8-19. Wauchope, R.D., Williams, R.G. and Marti, L.R., 1990. Runoff of sulfometuron-methyl and cyanazine from small plots: effects of formulation and grass cover. J. Environ. Quality, 19 (1): 119-125. Williams, J.R., Dyke, P.T., Fuchs, W.W., Benson, V.W., Rice, O.W. and Taylor, E.D., 1990. EPIC-Erosion/Productivity Impact Calculator: 2. User Manual. USDA-ARS Technical Bulletin Number 1768.