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Environmental, Energetic, and Economic Comparisons of Organic and Conventional Farming Systems



Various organic technologies have been utilized for about 6000 years to make agriculture sustainable while conserving soil, water, energy, and biological resources. Among the benefits of organic technologies are higher soil organic matter and nitrogen, lower fossil energy inputs, yields similar to those of conventional systems, and conservation of soil moisture and water resources (especially advantageous under drought conditions). Conventional agriculture can be made more sustainable and ecologically sound by adopting some traditional organic farming technologies.
July 2005 / Vol. 55 No. 7 • BioScience 573
Heavy agricultural reliance on synthetic chemical
fertilizers and pesticides is having serious impacts on
public health and the environment (Pimentel et al. 2005).For
example, more than 90% of US corn farmers rely on herbi-
cides for weed control (Pimentel et al. 1993),and one of the
most widely used of those herbicides, atrazine, is also one of
the most commonly found pesticides in streams and ground-
water (USGS 2001). The estimated environmental and health
care costs of pesticide use at recommended levels in the
United States run about $12 billion every year (Pimentel
Other aspects of conventional agriculture also have adverse
effects on environmental and human health, as well as a high
price tag. Nutrients from fertilizer and animal manure have
been associated with the deterioration of some large fisheries
in North America (Frankenberger and Turco 2003), and
runoff of soil and nitrogen fertilizer from agricultural pro-
duction in the Corn Belt has contributed to the “dead zone”
in the Gulf of Mexico. The National Research Council
(BANR/NRC 2003) reports that the cost of excessive fertilizer
use—that is, fertilizer inputs that exceed the amount crops can
use—is $2.5 billion per year.Modern agricultural practices can
also contribute to the erosion of soil. The estimated annual
costs of public and environmental health losses related to soil
erosion exceed $45 billion (Pimentel 1995).
Integrated pest and nutrient management systems and
certified organic agriculture can reduce reliance on agro-
chemical inputs as well as make agriculture environmentally
and economically sound. Pimentel and Pimentel (1996) and
the National Research Council (BANR/NRC 2003) have
demonstrated that sound management practices can reduce
pesticide inputs while maintaining high crop yields and im-
proving farm economics. Some government programs in
Sweden, Canada,and Indonesia have demonstrated that pes-
ticide use can be reduced by 50% to 65% without sacrificing
high crop yields and quality (BANR/NRC 2003).
The aim of organic agriculture is to augment ecological
processes that foster plant nutrition yet conserve soil and
water resources. Organic systems eliminate agrochemicals
and reduce other external inputs to improve the environment
and farm economics. The National Organic Program (a pro-
gram of the USDA Agricultural Marketing Service; 7 CFR pt.
205 [2002]) codifies organic production methods that are
based on certified practices verified by independent third-party
reviewers. These systems give consumers assurance of how
their food is produced and enable consumers to choose foods
on the basis of the methods by which they were produced. The
David Pimentel (e-mail: works in the Department of En-
tomology, College of Agriculture and Life Sciences, at Cornell University,
Ithaca, NY 14853. Paul Hepperly and Rita Seidel are with the Rodale
Institute, 611 Siegfriedale Road, Kutztown, PA 19530. James Hanson works
in the Department of Agricultural and Resource Economics at the University
of Maryland, College Park, MD 20742. David Douds is with the USDA
Agricultural Research Service, Eastern Regional Research Center, 600 E.
Mermaid Lane, Wyndmoor, PA 19038. © 2005 American Institute of
Biological Sciences.
Environmental, Energetic,
and Economic Comparisons
of Organic and Conventional
Farming Systems
Various organic technologies have been utilized for about 6000 years to make agriculture sustainable while conserving soil, water, energy, and
biological resources. Among the benefits of organic technologies are higher soil organic matter and nitrogen, lower fossil energy inputs, yields similar
to those of conventional systems, and conservation of soil moisture and water resources (especially advantageous under drought conditions). Conventional
agriculture can be made more sustainable and ecologically sound by adopting traditional organic farming technologies.
Keywords: organic, agriculture, conventional
National Organic Standards Program prohibits the use of
synthetic chemicals, genetically modified organisms, and
sewage sludge in organically certified production.
Organic agriculture is a fast-growing agricultural section
in the United States. Dimitri and Greene (2002) report a
doubling of area in organic production from 1992 to 1997,
currently on more than 500,000 hectares (ha). Organic food
sales total more than $7 billion per year and are growing at
double-digit rates (Greene 2000, 2004, ERS 2003).With con-
tinuing consumer concerns about the environment and the
chemicals used in food production, and with the growing
availability of certified organic production, the outlook for
continuing growth of organic production is bright (Dimitri
and Greene 2002).
Since 1981, the Rodale Institute Farming Systems Trial
(FST) has compared organic and conventional grain-based
farming systems. The results presented here represent a 22-
year study of these farming systems, based on environmen-
tal impacts, economic feasibility, energetic efficiency, soil
quality, and other performance criteria. The information
from this trial can be a tool for developing agricultural poli-
cies more in tune with the environment while increasing en-
ergy efficiency and economic returns.
The Rodale Institute Farming Systems Trial
From 1981 through 2002, field investigations were conducted
at the Rodale Institute FST in Kutztown, Pennsylvania, on 6.1
ha. The soil at the study site is a moderately well-drained
Comly silt loam. The growing climate is subhumid temper-
ate (average temperature is 12.4 degrees Celsius and average
rainfall is 1105 millimeters [mm] per year).
The experimental design included three cropping systems
(main plots). These systems, detailed below, included
(a) conventional, (b) animal manure and legume-based or-
ganic (hereafter organic animal-based), and (c) legume-
based organic systems. The main plots were 18 ×92 meters
(m), and these were split into three 6 ×92 m subplots,which
allowed for same-crop comparisons in any one year. The
main plots were separated with a 1.5-m grass strip to mini-
mize cross movement of soil, fertilizers, and pesticides. The
subplots were large enough that farm-scale equipment could
be used for operations and harvesting. Each of the three
cropping systems was replicated eight times.
Conventional cropping. The conventional cropping system,
based on synthetic fertilizer and herbicide use, represented a
typical cash-grain, row-crop farming unit and used a simple
5-year crop rotation (corn, corn, soybeans, corn, soybeans) that
reflects commercial conventional operations in the region and
throughout the Midwest (more than 40 million ha are in
this production system in North America; USDA 2003). Fer-
tilizer and pesticide applications for corn and soybeans fol-
lowed Pennsylvania State University Cooperative Extension
recommendations. Crop residues were left on the surface of
the land to conserve soil and water resources. Thus, during
the growing season, the conventional system had no more
exposed soil than in either the organic animal-based or the
organic legume-based systems. However, it did not have cover
crops during the nongrowing season.
Organic animal-based cropping. This system represented a typ-
ical livestock operation in which grain crops were grown for
animal feed, not cash sale. This rotation was more complex
than the rotation used in the conventional system. The grain-
rotation system included corn, soybeans,corn silage, wheat,
and red cloveralfalfa hay, as well as a rye cover crop before
corn silage and soybeans.
Aged cattle manure served as the nitrogen source and was
applied at a rate of 5.6 metric tons (t) per ha (dry), 2 years out
of every 5, immediately before plowing the soil for corn.
Additional nitrogen was supplied by the plow-down of
legumehay crops. The total nitrogen applied per hectare
with the combined sources was about 40 kilograms (kg) per
year (or 198 kg per ha for any given year with a corn crop).
The system did not use herbicides for weed control; it relied
instead on mechanical cultivation, weed-suppressing crop
rotations, and relay cropping, in which one crop acted as a
living mulch for another.
Organic legume-based cropping. This system represented a
cash grain operation, without livestock. Like the conven-
tional system, it produced a cash grain crop every year; how-
ever,it used no commercial synthetic fertilizers, relying instead
on nitrogen-fixing green manure crops as the nitrogen source.
The final rotation system included hairy vetch (winter cover
crop used as a green manure), corn, rye (winter cover crop),
soybeans, and winter wheat. The hairy vetch winter cover crop
was incorporated before corn planting as a green manure. The
initial 5-year crop rotation in the legume-based system was
modified twice to improve the rotation. The total nitrogen
added to this system per ha per year averaged 49 kg (or 140
kg per ha for any given year with a corn crop).Both organic
systems (animal based and legume based) included a small
grain, such as wheat, grown alone or interseeded with a
legume. Weed control practices were similar in both organic
systems, neither of which used herbicides for weed control.
Measurements recorded in the
experimental treatments
Cover crop biomass, crop biomass, weed biomass, grain
yields, nitrate leaching, herbicide leaching, percolated water
volumes, soil carbon, soil nitrogen,and soil water content were
measured in all systems. In addition, seasonal total rainfall,
energy inputs and returns, and economic inputs and returns
were determined.
A lysimeter,a steel cylinder 76 centimeters (cm) long by 76
cm in diameter,was installed in four of the eight replications
in each cropping system in fall 1990 to enable the collection
of percolated water. The top of each lysimeter was approxi-
mately 36 cm below the soil surface to allow normal field op-
erations to be carried out directly over the lysimeters. Water
574 BioScience • July 2005 / Vol. 55 No. 7
could not escape from the lysimeter system, and leachate
samples were collected throughout the year.
Levels of nitrogen as nitrate in leachate samples were de-
termined by the Soil and Plant Nutrient Laboratory at Michi-
gan State University in East Lansing. Herbicides in leachate
samples were analyzed by M. J. Reider Associates, Reading,
Pennsylvania. Total soil carbon and nitrogen were deter-
mined by the Agricultural Analytical Services Laboratory at
Pennsylvania State University in University Park. Soil water
content was determined gravimetrically on sieved soil (par-
ticles 2 mm in diameter). Statistical analyses were carried
out using SPSS version 10.1.3 General Linear Model Univariate
Analysis of Variance.
We examined the data from the 22-year experiments carried
out at the Rodale Institute, which compared the organic
animal-based, organic legume-based, and conventional
systems. The following data were considered for all three
systems: crop yields for corn and soybeans, impacts of drought
on crop yields, fossil energy requirements, economic costs and
benefits, soil carbon (organic matter) changes over time,and
nitrogen accumulation and nitrate leaching.
Crop yields under normal rainfall. For the first 5 years of the
experiment (19811985), corn grain yields averaged 4222,
4743, and 5903 kg per ha for the organic animal, organic
legume, and conventional systems, respectively, with the
yields for the conventional system being significantly higher
than for the two organic systems. After this transition period,
corn grain yields were similar for all systems: 6431, 6368,
and 6553 kg per ha for the organic animal, organic legume,
and conventional systems,respectively (Pimentel et al.2005).
Overall, soybean yields from 1981 through 2001 were 2461,
2235, and 2546 kg per ha for the organic animal, organic
legume, and conventional systems, respectively (Pimentel et
al. 2005). The lower yield for the organic legume system is at-
tributable to the failure of the soybean crop in 1988, when cli-
mate conditions were too dry to support relay intercropping
of barley and soybeans. If 1988 is taken out of the analysis, soy-
bean yields are similar for all systems.
Crop yields under drought conditions. The 10-year period from
1988 to 1998 had 5 years in which the total rainfall from
April to August was less than 350 mm (compared with 500
mm in average years). Average corn yields in those 5 dry
years were significantly higher (28% to 34%) in the two or-
ganic systems: 6938 and 7235 kg per ha in the organic animal
and the organic legume systems, respectively, compared with
5333 kg per ha in the conventional system. During the dry
years, the two organic systems were not statistically different
from each other in terms of corn yields.
During the extreme drought of 1999 (total rainfall be-
tween April and August was only 224 mm compared with the
normal average of 500 mm), the organic animal system had
significantly higher corn yields (1511 kg per ha) than either
the organic legume (421 kg per ha) or the conventional
system (1100 kg per ha). Crop yields in the organic legume
system were much lower in 1999 because the high biomass of
the hairy vetch winter cover crop used up a large amount of
the soil water (Lotter et al. 2003).
Soybean yields responded differently than the corn during
the 1999 drought. Specifically, soybean yields were about
1800, 1400, and 900 kg per ha for the organic legume, the
organic animal, and the conventional systems, respectively.
These treatments were significantly different (p= 0.05) from
each other (Pimentel et al. 2005).
Over a 12-year period, water volumes percolating through
each system (collected in lysimeters) were 15% and 20%
higher in the organic legume and organic animal systems, re-
spectively, than in the conventional system. This indicated an
increased groundwater recharge and reduced runoff in the or-
ganic systems compared with the conventional system. Dur-
ing the growing seasons of 1995, 1996, 1998, and 1999, soil
water content was measured for the organic legume and con-
ventional systems. The measurements showed significantly
more water in the soil farmed using the organic legume sys-
tem than in the conventional system (Pimentel et al. 2005).
This accounted for the higher soybean yields in the organic
legume system in 1999 (Pimentel et al. 2005).
Energy inputs. The energy inputs in the organic animal,
organic legume, and conventional corn production systems
were assessed. The inputs included fossil fuels for farm ma-
chinery, fertilizers, seeds, and herbicides. About 5.2 million
kilocalories (kcal) of energy per ha were invested in the pro-
duction of corn in the conventional system. The energy
inputs for the organic animal and organic legume systems
were 28% and 32% less than those of the conventional
system, respectively (figure 1). Commercial fertilizers for the
conventional system were produced employing fossil energy,
whereas the nitrogen nutrients for the organic systems were
obtained from legumes or cattle manure, or both. The in-
tensive reliance on fossil fuel energy in the conventional corn
production system is why that system requires more overall
energy inputs than do organic production systems. Fossil
energy inputs were also required to transport and apply the
manure to the field.
The energy inputs for soybean production in the organic
animal, organic legume, and conventional systems were sim-
ilar: 2.3 million kcal, 2.3 million kcal, and 2.1 million kcal per
ha, respectively (figure 1).
Economics. Two economic studies of the FST were com-
pleted, evaluating its first 9 years (Hanson et al.1990) and first
15 years of operation (Hanson et al. 1997). These two stud-
ies captured the experiences of organic farmers as they develop
over time a rotation that best fits their farm.With the devel-
opment of the final rotation, a third evaluation was completed
comparing this rotation with its conventional alternative
(Hanson and Musser 2003). Many organic grain farmers in
the mid-Atlantic region have been adopting this Rodale
July 2005 / Vol. 55 No. 7 BioScience 575
rotationon their farms, and there was strong interest in an
economic evaluation of this rotation alone (i.e., without the
transition period or learning curve).
The third economic comparison of the organic corn
soybean rotation and conventional cornsoybean systems
covered the period 1991 to 2001 (figure 2). Without price
premiums for the organic rotation, the net returns for both
rotations were similar. The annual net return for the con-
ventional system averaged about $184 per ha, while the
organic legume system for cash grain production averaged
$176 per ha. The annual costs per ha for the conventional
versus organic rotations, respectively, were (a) seed, $73
versus $103; (b) fertilizers and lime, $79 versus $18; (c) pes-
ticides, $76 versus $0; (d) machinery costs,$117 versus $154;
and (e) hired labor,$9 versus $6. Similar revenue comparisons
are $538 per ha and $457 per ha (conventional versus organic).
The net returns for the conventional rotation were more
variable (i.e., risky). The standard deviation for net returns over
the 10-year period was $127 for the conventional rotation and
$109 for the organic rotation.
When the costs of the biological transition for the organic
rotation (19821984) were included, the net returns for the
organic rotation were reduced to $162 per ha,while the con-
ventional net returns remained unchanged. Including the
costs of family labor for both rotations reduced the net returns
of conventional farming to $162 and organic farming to
$127. However, even with the inclusion of the biological
transition and family labor costs, the organic price premium
required to equalize the organic and conventional returns was
only 10% above the conventional product. Throughout the
1990s, the organic price premium for grains has exceeded this
level, and premiums now range between 65% and 140%
(New Farm Organization 2003).
The organic system requires 35% more labor, but because
it is spread out over the growing season, the hired labor costs
per ha are about equal between the two systems. Each system
was allowed 250 hours of freefamily labor per month.
When labor requirements exceeded this level, labor was hired
at $13 per hour.With the organic system,the farmer was busy
throughout the summer with the wheat crop, hairy vetch
cover crop, and mechanical weed control (but worked less than
250 hours per month). In contrast, the conventional farmer
had large labor requirements in the spring and fall, planting
and harvesting, but little in the summer months. This may
have implications for the growing number of part-time farm-
ers for whom the availability of family farm labor is severely
limited. Other organic systems have been shown to require
more labor per hectare than conventional crop production.
On average, organic systems require about 15% more labor
(Sorby 2002, Granatstein 2003), but the increase in labor in-
put may range from 7% (Brumfield et al. 2000) to a high of
75% (Karlen et al. 1995, Nguyen and Haynes 1995).
Over the 10-year period, organic corn (without price pre-
miums) was 25% more profitable than conventional corn
($221 per ha versus $178 per ha). This was possible because
organic corn yields were only 3% less than conventional
yields (5843 kg per ha versus 6011 kg per ha), while costs were
15% less ($351 per ha versus $412 per ha). However, the or-
ganic grain rotation required a legume cover crop before the
corn. This was established after the wheat harvest. Thus, corn
was grown 60% of the time in the conventional rotation,
but only 33% of the time in the organic rotation. Stated in an-
other way, the yields per ha between organic and conventional
corn for grain may be similar within a given year; however,
overall production of organic corn is diminished over a mul-
tiple-year period because it is grown less frequently. On the
other hand, the reduced amount of corn grown in the organic
rotation is partly compensated for with the additional crop
of wheat.
576 BioScience July 2005 / Vol. 55 No. 7
Figure 1. Average energy inputs for corn and soybeans
(in millions of kilocalories per hectare per year) in the
three systems used in the Rodale Institute Farming Sys-
tems Trial from 1991 to 2000: organic animal-based crop-
ping, organic legume-based cropping, and conventional
Figure 2. Average net returns per hectare (ha) for a 400-
ha farm for the organic legume and conventional grain
rotations in the Rodale Institute Farming Systems Trial
from 1991 to 2001. NR I = revenue minus explicit costs;
NR II = NR I minus transitional costs; NR III = NR II minus
all labor costs. Source: Hanson and Musser (2003).
Soil carbon. Soil carbon, which correlates with soil organic
matter levels, was measured in 1981 and 2002 (figure 3). In
1981, soil carbon levels were not different (p= 0.05) be-
tween the three systems. In 2002,however, soil carbon levels
in the organic animal and organic legume systems were sig-
nificantly higher than in the conventional system: 2.5% and
2.4% versus 2.0%, respectively (figure 3). The annual net
aboveground carbon input (based on plant biomass and ma-
nure) was the same in the organic legume system and the con-
ventional system (about 9000 kg per ha) but close to 12%
higher in the organic animal system (about 10,000 kg per ha).
However, the two organic systems retained more of that car-
bon in the soil, resulting in an annual soil carbon increase of
981 and 574 kg per ha in the organic animal and organic
legume systems, compared with only 293 kg per ha in the con-
ventional system (calculated on the basis of about 4 million
kg per ha of soil in the top 30 cm). The increased carbon was
also associated with higher water content of the soils in these
systems compared with the conventional system. The higher
soil water content in the organic systems accounted for the
higher corn and soybean yields in the drought years in these
systems compared with the conventional system (Lotter et al.
Soil nitrogen. Soil nitrogen levels were measured in 1981
and 2002 in the organic animal, organic legume, and con-
ventional systems (figure 3). Initially the three systems had
similar percentages of soil nitrogen, or approximately 0.31%.
By 2002, the conventional system remained unchanged at
0.31%, while nitrogen levels in the organic animal and organic
legume systems significantly increased to 0.35% and 0.33%,
respectively. Harris and colleagues (1994) used 15N (nitrogen-
15) to demonstrate that 47%, 38%, and 17% of the nitrogen
from the organic animal, organic legume, and conventional
systems, respectively, was retained in the soil a year after
Nitrate leaching. Overall, the concentrations of nitrogen as
nitrate in leachates from the farming systems varied between
0 and 28 parts per million (ppm) throughout the year (Pi-
mentel et al. 2005). Leachate concentrations were usually
highest in June and July, shortly after applying fertilizer in the
conventional systems or plowing down the animal manure
and legume cover crop. In all systems, increased soil micro-
bial activity during the growing season appears to have con-
tributed to increased nitrate leaching.
Water leachate samples from the conventional system
sometimes exceeded the regulatory limit of 10 ppm for nitrate
concentration in drinking water.A total of 20% of the con-
ventional system samples were above the 10-ppm limit, while
10% and 16% of the samples from the organic animal and
organic-legume systems, respectively, exceeded the nitrate
Over the 12-year period of monitoring (19912002), all
three systems leached between 16 and 18 kg of nitrogen as
nitrate per ha per year.These rates were low compared with
the results from other experiments with similar nitrogen in-
puts, in which leaching of nitrogen as nitrate ranged from 30
to 146 kg per ha per year (Fox et al.2001, Power et al. 2001).
When measuring these nitrogen losses as a percentage of the
nitrogen originally applied to the crops in each system, the or-
ganic animal, organic legume, and conventional systems lost
about 20%, 32%, and 20%,respectively, of the total nitrogen
as nitrate.
The high nitrate leaching in the organic legume system was
not steady over the entire period of the study; instead, it oc-
curred sporadically,especially during a few years of extreme
weather. For example, in 1995 and 1999, the hairy vetch
green manure supplied approximately twice as much nitro-
gen as needed for the corn crop that followed, contributing
excess nitrogen to the soil and making it available for leach-
ing. In 1999, the heavy nitrogen input from hairy vetch was
followed by a severe drought that stunted corn growth and
reduced the corns demand for nitrogen. In both years,these
nitrogen-rich soils were also subjected to unusually heavy fall
and winter rains that leached the excess nitrogen into the lower
soil layers. Monitoring of soil nitrogen and cover crop pro-
duction is needed to manage the potential for excessive nitrate
in all systems.
July 2005 / Vol. 55 No. 7 BioScience 577
Figure 3. Percentage of soil carbon (above) and nitrogen
(below) for the three systems of the Rodale Institute
Farming Systems Trial in 1981 and 2002 (organic animal-
based cropping, organic legume-based cropping, and con-
ventional cropping). Different letters indicate statistically
significant differences according to Duncan’s multiple
range test; p< 0.05. NSD = not significantly different.
These data contrast with the results of experiments in
Denmark, which indicated that nitrogen leaching from the
conventional treatments was twice that in the organic agri-
cultural systems (Hansen et al. 2001). Overall, nitrogen leach-
ing levels were lower in the FST rotation study than in those
reported by Hansen and others.
Herbicide leaching. Four herbicides were applied in the con-
ventional system: atrazine (to corn), pendimethalin (to corn),
metolachlor (to corn and soybeans),and metribuzin (to soy-
beans). From 2001 to 2003,atrazine and metolachlor were only
detected in water leachate samples collected from the con-
ventional system. No metribuzin or pendimethalin were de-
tected after application (Pimentel et al. 2005).
In the conventional plots where corn was planted after
corn, and atrazine was applied two years in a row, atrazine in
the leachate sometimes exceeded 3 parts per billion (ppb), the
maximum contaminant level (MCL) set by the US Environ-
mental Protection Agency (EPA) for drinking water. These
atrazine levels were higher than those in the corn-after-
soybean treatment (Pimentel et al. 2005). In the conven-
tional system, metolachlor was also detected at 0.2 to 0.6
ppb. When metolachlor was applied two years in a row in a
corn-after-corn treatment,it peaked at 3 ppb (Pimentel et al.
2005). The EPA has not yet established an MCL for meto-
lachlor in drinking water.
Soil biology.Among the natural biological processes on which
the organic rotations depend is symbiosis of arbuscular my-
corrhizae, and this aspect was investigated in the FST exper-
iments. Arbuscular mycorrhizal (AM) fungi are beneficial and
indigenous to most soils. They colonize the roots of most crop
plants, forming a mutualistic symbiosis (the mycorrhiza).
The fungus receives sugars from the root of the host plant, and
the plant benefits primarily from enhanced nutrient uptake
from the fungus. The extraradical mycelia of the AM fungi act,
in effect, as extensions of the root system, more thoroughly
exploring the soil for immobile mineral nutrients such as phos-
phate (Smith and Read 1997).Arbuscular mycorrhizae have
been shown to enhance disease resistance, improve water re-
lations, and increase soil aggregation (Miller and Jastrow
1990, Hooker et al. 1994, Wright et al. 1999, Augé 2000).
Efficient utilization of this symbiosis contributes to the
success of organic production systems.
Soils of the Rodale Institute FST have been sampled to study
the impact of conventional and organic agricultural man-
agement on indigenous populations of AM fungi. Soils farmed
with the two organic systems had greater populations of
spores of AM fungi and produced greater colonization of plant
roots than in the conventional system (Douds et al. 1993).
Most of this difference was ascribed to greater plant cover
(70%) on the organic systems compared with the conventional
cornsoybean rotation (40%). This was due to overwinter-
ing cover crops in the organic rotation (Galvez et al. 1995).
In addition to fixing or retaining soil nitrogen, these cover
crops provide roots for the AM fungi to colonize and main-
tain the fungis viability during the interval from cash crop
senescence to next years planting. Though levels of AM fungi
were greater in the organically farmed soils, indices of eco-
logical species diversity were similar in the farming systems
(Franke-Snyder et al.2001).
Wander and colleagues (1994) demonstrated that soil res-
piration was 50% higher in the organic animal system, com-
pared with the conventional system,10 years after initiation
of the Rodale Institute FST. Microbial activity in the organic
soils may be higher than in the conventional systems soils and
hence could explain the higher metabolism rates in the organic
systems (Lavelle and Spain 2001).
The crop yields and economics of organic systems, com-
pared with conventional systems,appear to vary based on the
crops, regions, and technologies employed in the studies.
However, the environmental benefits attributable to reduced
chemical inputs, less soil erosion, water conservation, and
improved soil organic matter and biodiversity were consis-
tently greater in the organic systems than in the conventional
Soil organic matter and biodiversity.Soil organic matter pro-
vides the base for productive organic farming and sustainable
agriculture. After 22 years of separate management, soil car-
bon (soil organic matter) was significantly higher in both the
organic animal and the organic legume systems than in the
conventional system.Soil carbon increased 27.9%, 15.1%, and
8.6% in the organic animal, organic legume, and conventional
systems, respectively (figure 3).
The amount of organic matter in the upper 15 cm of soil
in the organic farming systems was approximately 110,000
kg per ha. The soil of the upper 15 cm weighed about 2.2 mil-
lion kg per ha. Approximately 41% of the volume of the or-
ganic matter in the organic systems consisted of water,
compared with only 35% in the conventional systems (Sul-
livan 2002). The amount of water held in both of the organic
systems is estimated at 816,000 liters per ha. The large
amount of soil organic matter present in the organic systems
aided in making the systems more tolerant of droughts,
such as those that occurred in 1999 and other drought
Large amounts of biomass (soil organic matter) are ex-
pected to significantly increase soil biodiversity (Pimentel et
al. 1992, Troeh and Thompson 1993, Lavelle and Spain 2001,
Mader et al. 2002). The arthropods per ha can number from
two million to five million,and earthworms from one million
to five million (Lavelle and Spain 2001,Gray 2003). The mi-
croarthropods and earthworms were reported to be twice as
abundant in organic versus conventional agricultural sys-
tems in Denmark (Hansen et al. 2001). The weight of the
earthworms per ha in agricultural soils can range from 2000
to 4000 kg (Lavelle and Spain 2001). There can be as many as
1000 earthworm and insect holes per m2of land. Earth-
worms and insects are particularly helpful in constructing large
578 BioScience July 2005 / Vol. 55 No. 7
holes in the soil that increase the percolation of water into the
soil and decrease runoff.
Soil organic matter is an important source of nutrients and
can help increase biodiversity, which provides vital ecologi-
cal services, including crop protection (Pimentel et al.2005).
For example, adding compost and other organic matter re-
duces crop diseases (Cook 1988, Hoitink et al. 1991) and in-
creases the number of species of microbes in the
agroecosystem (van Elsen 2000). In addition,in the organic
systems, not using synthetic pesticides and commercial fer-
tilizers minimizes the harmful effects of these chemicals on
nontarget organisms (Pimentel 2005).
In conventional crop management in New Zealand, Nguyen
and Haynes (1995) did not report any adverse effect on soil
microbial activity.These conventional systems,however, were
part of a rotation pastoralarable system with a relatively
high level of soil organic matter (carbon content of the soil
ranged from 2.9% to 3.5%).
Overall, environmental damage from agricultural chemi-
cals was reduced in the organic systems because no com-
mercial fertilizers or pesticides were applied to the organic
systems. As a result, overall public health and ecological in-
tegrity could be improved through the adoption of these
practices, which decrease the quantities of pesticides and
commercial fertilizers applied in agriculture (BANR/NRC
2003, Pimentel 2005).
Oil and natural gas inputs. Significantly less fossil energy
was expended to produce corn in the Rodale Institutes organic
animal and organic legume systems than in the conventional
production system (figure 1). There was little difference in en-
ergy input between the different treatments for producing soy-
beans. In the organic systems, synthetic fertilizers and
pesticides were generally not used. Other investigators have
reported similar findings (Karlen et al. 1995,Smolik et al. 1995,
Dalgaard et al. 2001, Mader et al. 2002, Core 4 2003, Pi-
mentel et al. 2005). In general, the use of less fossil energy by
organic agricultural systems reduces the amount of carbon
dioxide released to the atmosphere, and therefore the prob-
lem of global climate change (FAO 2003).
Crop yields and economics. Except for the 1999 drought
year,the crop yields for corn and soybeans were similar in the
organic animal, organic legume, and conventional farming sys-
tems. In contrast, Smolik and colleagues (1995) found that
corn yields in South Dakota were somewhat higher in the con-
ventional system, with an average yield of 5708 kg per ha, com-
pared with an average of 4767 kg per ha for the organic
legume system. However, the soybean yields in both systems
were similar at 1814 kg per ha. In a second study comparing
wheat and soybean yields, the wheat yields were fairly simi-
lar,averaging 2600 kg per ha in the conventional system and
2822 kg per ha in the organic legume system. Soybean yields
were 1949 kg per ha and 2016 kg per ha for the conventional
and the organic legume systems, respectively (Smolik et al.
1995). In the Rodale experiments,corn, soybeans, and wheat
yields were considerably higher than those reported in South
Dakota. These results might be expected, given the shorter
growing season (146 days) and lower precipitation (460 mm)
in South Dakota.
European field tests indicate that yields of organically
grown wheat and other cereal grains average from 30% to 50%
lower than conventional cereal grain production (Mader et
al. 2002). The lower yields for the organic system in these ex-
periments, compared with the conventional system, appear
to be caused by lower nitrogen-nutrient inputs in the organic
system. In New Zealand, wheat yields were reported to aver-
age 38% lower than those in the conventional system, a find-
ing similar to the results in Europe (Nguyen and Haynes
1995). In New Jersey, organically produced sweet corn yields
were reported to be 7% lower than in a conventional system
(Brumfield et al. 2000). In the Rodale experiments, nitrogen
levels in the organic systems have improved and have not lim-
ited the crop yields except for the first 3 years.In the short term,
organic systems may create nitrogen shortages that reduce crop
yields temporarily, but these can be eliminated by raising
the soil nitrogen level through the use of animal manure or
legume cropping systems, or both.
In a subsequent field test in South Dakota, corn yields in
the conventional system and the organic alternative
system were 7652 and 7276 kg per ha, respectively (Dobbs
and Smolik 1996). Soybean yields were significantly higher
in the conventional system, averaging 2486 kg per ha,
compared with only 1919 kg per ha in the organic alterna-
tive system.
The Rodale crop yields were similar to the results in the con-
ventional and organic legume farming system experiments
conducted in Iowa (Delate et al. 2002). In the Iowa experi-
ments, corn yields were 8655 and 8342 kg per ha for the
conventional and organic legume systems, respectively.
Soybean yields averaged 2890 kg per ha for the conventional
farming system and 2957 kg per ha for the organic legume
Although the inputs for the organic legume and conven-
tional farming systems were quite different, the overall eco-
nomic net returns were similar without premiums (figure 2).
Comparative net returns in the Rodale experiments differ from
those of Dobbs and Smolik (1996), who reported a 38%
higher gross income for the conventional than for the organic
alternative system. However, Smolik and colleagues (1995) re-
ported higher net returns for the organic alternative system
in their study with alfalfa and nearly equal returns in the green
manure treatment.
Prices for organic corn and soybeans in the marketplace
often range from 20% to 140% higher than for conventional
corn, soybeans,and other grains (Dobbs 1998, Bertramsen and
Dobbs 2002, New Farm Organization 2003).Thus, when the
market price differential was factored in, the differences
between the organic alternative and conventional farming
would be relatively small,and in most cases the returns on the
organic produce would be higher, as in the results here for the
July 2005 / Vol. 55 No. 7 BioScience 579
In contrast to these results for corn and soybeans,the eco-
nomic returns (dollar return per unit) for organic sweet corn
production in New Jersey were slightly higher (2%) than for
conventional sweet corn production (Brumfield et al. 2000).
In the Netherlands, organic agricultural systems producing
cereal grains, legumes, and sugar beets reported a net return
of EUR 953 per ha, compared with conventional agricul-
tural systems producing the same crops that reported EUR 902
per ha (Pacini et al. 2003).
In a California investigation of four crops (tomato,soybean,
safflower, and corn) grown organically and conventionally,
production costs for all four crops were 53% higher in the or-
ganic system than in the conventional system (Sean et al.
1999). However, the profits for the four crops were only 25%
higher in the conventional system compared with the or-
ganic system. If the 44% price advantage of the four organ-
ically grown crops were included, the organic crops would be
slightly more profitable than the conventional ones (Sean et
al. 1999).
One of the longest-running organic agricultural trials (on-
going for more than 150 years) is the Broadbalk experiment
at Rothamsted (formerly the Rothamsted Experimental
Station) in the United Kingdom. The trials compared a
manure-based organic farming system with a system based
on synthetic chemical fertilizer. Wheat yields were slightly
higher on average in the manured organic plots (3.45 t per ha)
than in the plots receiving chemical fertilizers (3.40 t per
ha). The soil quality improved more in the manured plots than
in those receiving chemical fertilizer,based on greater accu-
mulations of soil carbon (Vasilikiotis 2004).
Challenges for organic agriculture. Two primary problems
with the organic system in the California study were nitrogen
deficiency and weed competition (Sean et al. 1999).This was
also noted for the organic faming systems in the US Midwest.
Although the Rodale experiment overcame nitrogen defi-
ciency challenges through legume cover crop management,
other researchers have been less successful in maintaining and
improving soil fertility levels in organic systems. Rodales re-
sults could also be influenced by geographical soil charac-
teristics and may not be universally applicable.
In organic production systems, pest control can be of
heightened importance and impact. Weed control is fre-
quently a problem in organic crops because the farmer is
limited to mechanical and biological weed control, whereas
under conventional production mechanical, biological, and
chemical weed control options often are employed. Also,
weather conditions can limit the efficacy of weed control.
Mechanical weed control is usually more effective than chem-
ical weed control under dry conditions, while the reverse
holds true under wet conditions. In the Rodale experiments,
only the organic soybeans suffered negative impacts from
weed competition.
Insect pests and plant pathogens can be effectively con-
trolled in corn and soybean production by employing crop
rotations. Some insect pests can be effectively controlled by
an increase in parasitoids; reports in organic tomato pro-
duction indicate nearly twice as many parasitoids in the or-
ganic compared with the conventional system (Letourneau
and Goldstein 2001). However, increased plant diversity in
tomato production was found to increase the incidence of
plant disease (Kotcon et al. 2001). With other crops, like
potatoes and apples, dealing with pest insects and plant
pathogens that adversely affect yields is a major problem in
organic crop production.
Adoption of organic technologies. Several organic technolo-
gies, if adopted in current conventional production systems,
would most likely be beneficial. These include (a) employing
off-season cover crops; (b) using more extended crop rota-
tions, which act both to conserve soil and water resources and
also to reduce insect, disease, and weed problems; (c) in-
creasing the level of soil organic matter,which helps conserve
water resources and mitigates drought effects on crops; and
(d) employing natural biodiversity to reduce or eliminate
the use of nitrogen fertilizers, herbicides, insecticides, and
fungicides. Some or all of these technologies have the potential
to increase the ecological, energetic, and economic sustain-
ability of all agricultural cropping systems, not only organic
Various organic agricultural technologies have been used for
about 6000 years to make agriculture sustainable while con-
serving soil, water,energy, and biological resources.The fol-
lowing are some of the benefits of organic technologies
identified in this investigation:
Soil organic matter (soil carbon) and nitrogen were
higher in the organic farming systems, providing many
benefits to the overall sustainability of organic agricul-
Although higher soil organic matter and nitrogen levels
were identified for the organic systems, similar rates of
nitrate leaching were found to those in conventional
corn and soybean production.
The high levels of soil organic matter helped conserve
soil and water resources and proved beneficial during
drought years.
Fossil energy inputs for organic crop production were
about 30% lower than for conventionally produced
Depending on the crop, soil, and weather conditions,
organically managed crop yields on a per-ha basis can
equal those from conventional agriculture, although it
is likely that organic cash crops cannot be grown as
frequently over time because of the dependence on cul-
tural practices to supply nutrients and control pests.
Although labor inputs average about 15% higher in
organic farming systems (ranging from 7% to 75%
higher), they are more evenly distributed over the
580 BioScience July 2005 / Vol. 55 No. 7
year in organic farming systems than in conventional
production systems.
Because organic foods frequently bring higher prices in
the marketplace, the net economic return per ha is
often equal to or higher than that of conventionally
produced crops.
Crop rotations and cover cropping typical of organic
agriculture reduce soil erosion, pest problems, and pes-
ticide use.
The recycling of livestock wastes reduces pollution
while benefiting organic agriculture.
Abundant biomass both above and below the ground
(soil organic matter) also increases biodiversity, which
helps in the biological control of pests and increases
crop pollination by insects.
Traditional organic farming technologies may be adopt-
ed in conventional agriculture to make it more sustain-
able and ecologically sound.
We thank the following people for reading a draft of this ar-
ticle and for their many helpful suggestions: Robin G.Brum-
field, Rutgers, The State University of New Jersey; Wen
Dazhong, Institute of Applied Ecology, Academia Sinica,
Shenyang, China; Tomek De Ponti, Visiting Fulbright Scholar,
Cornell University; Andrew R. B. Ferguson, Optimum Pop-
ulation Trust, Oxon, United Kingdom; Long Nguyen, National
Institute of Water and Atmospheric Research,Auckland, New
Zealand; Maurizio Paoletti,Università di Padova, Italy; James
Smolik, South Dakota State University; Chris Wien, Cornell
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582 BioScience July 2005 / Vol. 55 No. 7
Organic fertilizers are alternative to chemicals used in agriculture which enhance soil quality, prevent harmful chemicals entering into food chain, improve health and contribute to sustainable future socially, economically and ecologically. Vermicompost is a nutrient-rich organic fertilizer which promotes plant growth and improves soil quality. Vermicomposting is an economically feasible and environment friendly technology in which organic wastes are bio-converted into value added product and various organic wastes are used in this process. Terrestrial weeds are the plant species which grow on land and invasive in nature. These plants are responsible for various nuisances in the environment, agriculture and society. The weed biomass generated after various management methods are considered as organic waste. The terrestrial weed biomass is a possible option for the production of vermicompost. In this chapter scope of vermicompost for sustainable agriculture, the vemicomposting mechanism and the bioconversion of terrestrial weed biomass into vermicompost have been discussed.
Satisfying the demand for agricultural products while also protecting the environment from negative impacts of agriculture is a major challenge for crop management. We used an ecophysiological model of plant-pest interaction and multi-criteria decision analysis to optimize crop management when considering two contrasting objectives: (1) maximizing crop production and (2) minimizing environmental impact related to fertilization, irrigation and pesticide deployment. The model provides an indicator of crop production for 27 management scenarios, obtained combining three levels of fertilization, irrigation and pesticide use, respectively. We computed the environmental impact relevant to each management scenario by means of a weighted sum of costs assigned to fertilization, irrigation and pesticide use. We identified the optimal scenarios with respect to the considered objectives analysing the Pareto front. These scenarios were mostly characterized by high fertilization and no pesticide use. We evaluated the multi-functionality of the optimal scenarios by mean of the Gini coefficient: the scenario better assuring the equality between the two objectives was characterized by high fertilization, intermediate irrigation and no pesticide. Although our results remain qualitative and not immediately transferable to agronomic practices, our analytical framework provides a useful tool to evidence trade-offs among two contrasting objectives and provide solutions to act in an efficient way by leaving a certain degree of freedom to the decision maker.
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The use of rain shelters and reflective groundcovers has been shown to improve the economic and environmental sustainability of organic fruit crops prone to rain-driven epidemics of phytopathogens. Here, we tested whether these structures affect communities of epigean species. To this end, we studied rain shelters and white, synthetic reflective groundcovers placed in a red raspberry organic cropping system in New Brunswick, Canada, during two subsequent summers to assess their independent and combined effects on ground beetles (Coleoptera: Carabidae). 18,445 ground beetles belonging to 54 species were collected. Rain shelters and reflective groundcovers altered patterns of ground beetle species richness, activity density and functional diversity compared to the control, but to a limited extent. Thus, this study suggests that these structures, which have known benefits against phytopathogens, have no detrimental impact on epigean fauna.
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Invasive alien species (IAS) are a major driver of global biodiversity loss, hampering conservation efforts and disrupting ecosystem functions and services. While accumulating evidence documented ecological impacts of IAS across major geographic regions, habitat types and taxonomic groups, appraisals for economic costs remained relatively sparse. This has hindered effective cost-benefit analyses that inform expenditure on management interventions to prevent, control, and eradicate IAS. Terrestrial invertebrates are a particularly pervasive and damaging group of invaders, with many species compromising primary economic sectors such as forestry, agriculture and health. The present study provides synthesised quantifications of economic costs caused by invasive terrestrial invertebrates on the global scale and across a range of descriptors, using the InvaCost database. Invasive terrestrial invertebrates cost the global economy US$ 712.44 billion over the investigated period (up to 2020), considering only high reliability source reports. Overall, costs were not equally distributed geographically, with North America (73%) reporting the greatest costs, with far lower costs reported in Europe (7%), Oceania (6%), Africa (5%), Asia (3%), and South America (< 1%). These costs were mostly due to invasive insects (88%) and mostly resulted from direct resource damages and losses (75%), particularly in agriculture and forestry; relatively little (8%) was invested in management. A minority of monetary costs was directly observed (17%). Economic costs displayed an increasing trend with time, with an average annual cost of US$ 11.40 billion since 1960, but as much as US$ 165.01 billion in 2020, but reporting lags reduced costs in recent years. The massive global economic costs of invasive terrestrial invertebrates require urgent consideration and investment by policymakers and managers, in order to prevent and remediate the economic and ecological impacts of these and other IAS groups.
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Agriculture faces many challenges. In both public discourse and the scientific literature debates about the future are increasing framed in terms of ‘alternative’ versus ‘conventional’ agriculture. In this paper we critically examine this framing, and seek to understand how the term conventional has been and is being used. We argue that the category conventional agriculture has little analytical purchase, and that its use is part of a strategy of homogenising, normalising and othering. In effect, the term conventional agriculture has been weaponised. This helps explain the sterile and unproductive nature of much debate about future agricultures. A more productive approach is to focus on where and how different farming systems can contribute to the sustainability of agriculture.
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A number of excellent textbooks on general ecology are currently available but‚ to date‚ none have been dedicated to the study of soil ecology. This is important because the soil‚ as the ‘epidermis’ of our planet‚ is the major component of the terrestrial biosphere. In the present age‚ it is difficult to understand how one could be interested in general ecology without having some knowledge of the soil and further‚ to study the soil without taking into account its biological components and ecological setting. It is this deficiency that the two authors‚ Patrick Lavelle and Alister Spain‚ have wished to address in writing their text. A reading of this work‚ entitled ‘Soil Ecology’‚ shows it to be very complete and extremely innovative in its conceptual plan. In addition‚ it follows straightforwardly through a development which unfolds over four substantial chapters. Firstly‚ the authors consider the soil as a porous and finely divided medium of b- organomineral origin‚ whose physical structure and organisation foster the development of a multitude of specifically adapted organisms (microbial communities‚ roots of higher plants‚ macro-invertebrates).
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Production costs have been analyzed in several studies using such normative approaches as budgeting and mathematical programming, and positive approaches as estimation of production, cost, or profit functions. This study used budgeting methods to analyze the costs and benefits of adopting integrated crop management (ICM) or organic methods versus conventional agriculture for tomatoes (Lycopersicon esculentum Mill.), sweet corn (Zea mays L. var. saccharada), and pumpkins (Cucurbita pepo L.). Data were collected using field studies conducted at the Rutgers University Snyder Research and Extension Farm, Pittstown, N.J. Time and motion study techniques were used to record machinery use and labor quantities. Records of production inputs and yields were also collected. These records were then converted to a 1.0-acre (0.4-ha) basis to constructed crop budgets. Results show that ICM systems are more profitable than conventional and organic systems. Organic systems had the lowest net returns. However, because of the organic price premium, the net returns were fairly close to those for conventional and ICM systems.
Arbuscular mycorrhizal (AM) symbioses can affect the water balance of amply watered and droughted plants. The mycorrhizal influence most often examined within the field of water relations has been alteration of stomatal behavior. This review summarizes possible biophysical and biochemical mechanisms, discussing how AM fungus-induced changes in tissue hydration, plant size, tissue elemental concentrations and nonhydraulic root-to-shoot signaling may affect stomatal regulation. The review also provides a brief catalog of published mycorrhizal effects on stomata behavior.
The roots of most plants are colonized by symbiotic fungi to form mycorrhiza, which play a critical role in the capture of nutrients from the soil and therefore in plant nutrition. Mycorrhizal Symbiosis is recognized as the definitive work in this area. Since the last edition was published there have been major advances in the field, particularly in the area of molecular biology, and the new edition has been fully revised and updated to incorporate these exciting new developments. . Over 50% new material . Includes expanded color plate section . Covers all aspects of mycorrhiza . Presents new taxonomy . Discusses the impact of proteomics and genomics on research in this area.
In the hierarchical model of soil aggregate formation proposed by Tisdall and Oades (1982), a major mechanism involved in the binding of microaggregates into macroaggregates is physical entanglement by roots and mycorrhizal fungus hyphae. Using data collected from soils of a chronosequence of tallgrass prairie restorations and an adjacent prairie soil cultivated to row crops for at least 100 yr. it was found that root lengths by diameter size class, the lengths of roots colonized by mycorrhizal fungi within each root-size class, and extraradical hyphal lengths of mycorrhizal fungi were all highly correlated with the geometric mean diameter (GMD) of water-stable soil aggregates. To better understand the relative contributions of roots and mycorrhizal fungi to water-stable aggregation, a conceptual model emphasizing the interrelationships between roots of differing size classes, mycorrhizal fungi and aggregate-size distribution was developed and evaluated using path analysis. From path analysis, it was found that extraradical hyphal length followed by fine (0.2–1 mm dia) root length had the strongest direct effects on GMD. It was expected that a physical entanglement mechanism would involve the very finest roots; however, the direct path between very-fine (<0.2 mm dia) root length and GMD was not significant. Although both root-size classes exhibited significant indirect effects on GMD via the relationships between their colonized lengths and xtraradical hyphal length, the overall effect of fine root length on GMD was much stronger than the effect of very-fine root length. To determine the relative influences of plant lifeforms on root morphology and estimate the effects of various lifeforms on GMD, data on aboveground standing crops associated with the root and fungus data were added to the path model. Prairie grasses were associated with both fine and very-line root lengths and exhibited the strongest effects on GMD; whereas, non-prairie grasses were most strongly associated with very-fine root length and only weakly affected GMD. Perennial species of Compositae were associated with line root length and also had a fairly strong influence on GMD. This study supports the conceptual model developed by Tisdall and Oades and suggests that a better understanding of soil aggregate development may be achieved by considering the interactions between roots and mycorrhizal fungi in relationship to plant community composition.
A “Conventional” and an “Alternative” farm located on the western edge of the Corn Belt were compared for relative productivity and profitability over the 8-year time period from 1985 through 1992. Although earnings on both farms were respectable for the area, the Conventional farm was more profitable, on average, than the Alternative farm when organic premiums for the Alternative farm were excluded. This was due in part to higher soybean and com yields and a greater proportion of acreage in corn and soybeans on the Conventional farm. Federal farm program support payments were higher for the Conventional farm in the first 5 years, but not in the last 3 years.