START: 01 JUL 2003 TERM: 30 JUN 2006 FY: 2004 GRANT YR: 2003
GRANT AMT: $147,671
INVESTIGATOR: Gallandt, E. R.; Reberg-Horton, C.; Curran, W. S.; Mortensen, D. A.; Barbercheck, M. E.
PERFORMING INSTITUTION:
PLANT, SOIL AND ENVIRONMENTAL SCIENCES
UNIVERSITY OF MAINE
ORONO, MAINE 04469
THRESHOLD-BASED COVER CROPPING STRATEGIES FOR WEED MANAGEMENT
NON-TECHNICAL SUMMARY: To manage weeds with reduced reliance on, or without herbicides, cropping systems require intervals during which rapid and significant reductions in the germinable portion of the weed seed bank occur or, if already small, seed banks should be managed to maintain a low equilibrium population density. Integrating tillage system and cover cropping practices, this project aims to develop management strategies that will lower the equilibrium density of the weed seed bank.
OBJECTIVES: This project aims to evaluate the intensity of cover cropping to directly or indirectly reduce the density of germinable seeds in the weed seed bank. Objective 1. Evaluate the impact of increasing cover cropping system intensity on weed seed bank dynamics. Hypothesis 1-1. Decline in the germinable weed seed bank will be proportional to the intensity of cover cropping. Hypothesis 1-2. Activity-density of invertebrate weed seed predators will be positively correlated with the amount of time live cover crop biomass is present in a system, and negatively correlated with the frequency of disturbance, i.e., tillage and mowing. Objective 2. Determine the effect of varying germinable seed bank densities on the efficacy of weed control and yield loss in a subsequent test crop. Hypothesis 2-1. To preserve acceptable levels of weed control with minimal herbicide and cultivation inputs, the intensity of cover cropping must increase as the density of germinable seeds increases. Hypothesis 2-2. Incorporated green manure residues will impact the weed seed bank to a greater extent than nonincorporated residues, i.e., no-till. With uniform weed management across treatments this will be manifest in lower weed densities and less crop yield loss where residues are incorporated. Objective 3. Assemble innovative cover cropping systems concepts or techniques into case studies and conduct on-farm research that demonstrates key pest and soil management benefits.
APPROACH: Objective 1. Evaluate the impact of increasing cover cropping system intensity on weed seed bank dynamics. To evaluate the contribution of green manuring practices to the management of the weed seed bank, three objectives and four associated hypotheses will be addressed in field experiments conducted at the University of Maine Rogers Farm in Stillwater, Maine and the Russell E. Larson Agricultural Research Center near University Park, Pennsylvania. The experiments will be established in the spring of 2004 and 2005. Main plot treatments will include four cover crop systems representing different levels of intensity and a fallow control. The second factor is method of handling the cover crop residue when the cash crop is planted the following year, either incorporated or left as a surface mulch for no-till or zone tillage. The intensity of cover cropping is determined by multiple factors including the length of time a field is kept in a living cover crop, the biomass production of the cover crop, and finally, the number of tillage or mowing events before the next cash crop. Back-to-back cover cropping involves more soil disturbance and is therefore hypothesized to decrease the soil seed bank faster. The influence of weed seed bank size will be assessed by establishing a range of seed bank densities at the start of the experiment in the areas to be planted to the cover crop systems. Setaria sp., Chenopodium album, and Abutilon theophrasti will dispersed at specific densities the fall prior to cover crop establishment. The change in seed bank density will be assessed at several critical times over a period of 18 months. Objective 2. Determine the effect of varying germinable seed bank densities on the efficacy of weed control and yield loss in a subsequent test crop. In May of 2005 and 2006, prior to planting the sweet corn test crop, above ground cover crop biomass will be measured in each plot. Prior to planting the sweet corn test crop, the cover crops will either be tilled under with an appropriate tillage implement or killed with a burndown herbicide. Weeds will be suppressed in all treatments by cultivation or with a nonresidual postemergence herbicide. Weed escapes will be quantified at the end of the season. Marketable ears will be collected from the center 8 rows of corn at harvest. The economic performance of the contrasting crop and cover crop-tillage systems will be assessed using partial budgeting methods. Objective 3. Assemble innovative cover cropping systems concepts or techniques into case studies and conduct on-farm research that demonstrates key pest and soil management benefits. This project will develop case studies featuring farmers who are using innovative cover cropping systems. The case studies will focus on the impact of cover crops on weed, insect and disease management, soil quality, and their utility for managing animal manure. Case-study farms will then serve as on-farm sites to demonstrate the concepts and techniques underpinning the practices.
PROGRESS: 2003/10 TO 2004/09
Objective 1. Evaluate the impact of increasing cover cropping system intensity
on weed seed bank dynamics. Field experiments were established in the fall of
2003 at the University of Maine Rogers Farm in Stillwater, Maine (ME) and the
Russell E. Larson Agricultural Research Center near University Park, Pennsylvania
(PA). The experiments are a split-plot, randomized complete block design with
four replications; main plot treatments are a factorial cross of four (ME) or
six (PA) cover crop systems representing different levels of intensity and a
fallow control. The second factor is method of handling the cover crop residue
when the cash crop is planted in 2005, either incorporated or left as a surface
mulch for no-till or zone tillage. Plots (13.4 by 13.4 m) were flagged and,
within each tillage system split-plot, synthetic weed seed banks (1.5 by 2.7
m), comprised of a mixture of common lambsquarters (Chenopodium album), yellow
foxtail (Seteria lutesens) and velvetleaf (Abutilon theophrasti), were established
at four densities (0, 60, 450, and 2100 seeds m-2) on December 4, 2003 (PA)
and March 11, 2004 (ME). Each synthetic seed bank also included ceramic beads,
sized to match the diameter and density of common lambsquarters, sown at 2100
beads m-2. The beads will serve as an internal standard to quantify our efficiency
of seed recovery. To establish the baseline values for the germinable portion
of the synthetic seed banks ten soil cores (9 cm diam. by 10 cm deep) were taken
from each synthetic seed bank location on April 16, 2003 and May 10-13, 2004,
in PA and ME, respectively. To quantify seed bank losses due to establishment,
densities of the synthetic seed bank species, and the most abundant resident
species, was measured on April 21, 2004 and May 12, 2004 in PA and May 14, 2004,
ME. Subsequently, primary and secondary tillage were performed to initiate the
fallow treatment, and the cover cropping systems were planted. To determine
the potential pool of invertebrate weed seed predators at the sites, pitfall
trapping will occur in July and in late summer. Further component studies are
in progress in ME to determine the effects of disturbance and vegetation of
the contrasting cover cropping systems on the behavior of Harpalus rufipes,
an abundant ground beetle known to prey on weed seeds. Objective 2. Determine
the effect of varying germinable seed bank densities on the efficacy of weed
control and yield loss in a subsequent test crop. This will be addressed in
May of 2005 and 2006 when a sweet corn test crop will be planted over each cover
crop system. Objective 3. Assemble innovative cover cropping systems concepts
or techniques into case studies and conduct on-farm research that demonstrates
key pest and soil management benefits. We have collected and reviewed regionally
relevant grower case studies to ensure an optimal design and to avoid redundancy
with prior efforts. In January, 2005, a meeting of the ME and PA PIs and Project
Participants will prioritize cases which will be developed in the 2005 and 2006
growing seasons.
IMPACT: 2003/10 TO 2004/09
To manage weeds with reduced reliance on, or without herbicides, cropping systems
require intervals during which rapid and significant reductions in the germinable
portion of the weed seed bank occur or, if already small, seed banks should
be managed to maintain a low equilibrium population density. Integrating tillage
system and cover cropping practices, this project aims to develop management
strategies that will lower the equilibrium density of the weed seed bank. This
systems approach promises an effective means for managing weed seed banks while
maintaining or improving soil health.
PUBLICATIONS: 2003/10 TO 2004/09
No publications reported this period
PROJECT CONTACT:
Name: Gallandt, E. R.
Phone: 207-581-2933
Fax: 207-581-2999
Email: gallandt@maine.edu