Agriculture Reference
In-Depth Information
An additional factor contributing to weed suppression could be weed seed
predator populations, which have also differed by system (Menalled et al. 2007).
Populations of seed-predating carabid ground beetles (Coleoptera: Carabidae),
which are sensitive to soil disturbance, were over three times higher and seed preda-
tion rates over two times higher in the No-till system compared to the Biologically
Based system. Taken together, these results are consistent with herbicide use and
soil disturbance as key determinants of weed suppression services. However, given
that both herbicide use and soil disturbance are associated with a host of potential
ecosystem disservices, there is a clear need for research into alternative weed man-
agement practices that improve pest suppression services without incurring signifi-
cant trade-offs in the form of soil or water degradation.
Ecosystem Service Trade-offs
Three of the more important ecosystem services associated with different manage-
ment systems—yield, nitrate loss, and soil C gain—are summarized in Table 15.3.
Table 15.3. Evaluation of yield reductions and environmental gains associated with
alternative systems relative to conventional management.
a
Experiment/
System
Average
Crop
Yield
b
(kg grain
ha
−1
)
Nitrate
Leaching Loss
c
(kg NO
3
−
-N
ha
−1
yr
−1
)
Soil C Gain
d
(kg C ha
−1
yr
−1
)
Yield Trade-off—
Nitrate
Mitigation
(kg NO
3
−
-N kg
−1
grain)f
e
Yield Trade-off—
Soil C
Accumulation
(kg C
kg
−1
grain)f
f
Main Cropping System Experiment (MCSE): Corn-Soybean-Wheat
Conventional
3511
62
0
No-till
3853
42
330
-0.06
0.96
Reduced Input
3597
24
200
-0.44
2.33
Biologically
Based
2765
19
500
0.06
-0.67
Living Field Lab Experiment (LFL): Continuous Corn
Integrated
Conventional
6420
74
80
Organic
5050
32
900
0.03
0.59
a
All values expressed on an annual basis, based on yield reductions or enhancements associated with alternative
management relative to conventional management vs. reductions in nitrate (NO
3
−
) leached and gains in soil carbon (C).
b
MCSE grain yield average for corn-soybean-wheat rotations from 1996 to 2007 (Syswerda and Robertson 2014);
LFL continuous corn grain yield average from 1994 to 2000 (Snapp et al. 2010a).
c
MCSE leaching losses monitored from 1995 to 2006 (Syswerda et al. 2012); LFL leaching losses monitored from
1994 to 2000 (Snapp et al. 2010a).
d
MCSE soil C gain in the A/Ap horizon from 1989 to 2001 (Syswerda et al. 2011); LFL soil C gain in the 0- to 20-cm
horizon from 1993 to 2008 (Snapp et al. 2010a).
e
Trade-off relative to conventional management, where the change in leached nitrate-N is reported as a ratio to change
in grain yield. A negative value implies less N leaching per unit of change in yield, indicating a desirable trade-off
with respect to that ecosystem disservice.
f
fTrade-off relative to conventional management, where the change in soil C sequestered is reported as a ratio to
change in grain yield. A positive value implies more C sequestration per unit of change in yield, indicating a desirable
trade-off with respect to that ecosystem service.
