Progress 10/01/02 to 09/30/07
Outputs
OUTPUTS: The effects of two tillage methods and six weed control tactics compatible with national organic standards were compared by measuring crop yield, weed pressure, and soil health over four consecutive years on land in transition to organic production. Main crops were sweet corn (2004 & 2006) and edamame soybean (2005 & 2007) with winter cover crop mixtures of winter rye and hairy vetch. Weed-free control plots, maintained by regular hand-weeding, were compared to plots maintained with weekly passes of a rolling cultivator, spring tine weeder, or flame weeder between crop emergence and row closure; and to plots treated with corn gluten meal or flaming before crop emergence. Weed species, counts, and dry weight were recorded. Soil health was measured by assessing changes in soil organic matter, soil compaction, soil nutrient analysis, and extracellular enzyme activity activity (as indicated by catalysis of fluorescein diacetate hydrolysis). In parallel studies, corn gluten meal
was applied to soil at 0, 50, 100, and 200 g per square meter in three consecutive years to test for a dose response in inhibition of weed seed germination; and watermelons were grown in a variety of mulches over two consecutive years to assess the potential of alternatives to plastic mulch on weed pressure and yield. Five African-American high school interns and one Kentucky State University undergraduate student gained hands-on experience in crop production, and experimental design, maintenance, analysis and presentation during the course of these studies. These interns worked closely with the Principal Investigator and Co-Investigator mentors. Findings were incorporated into materials developed for a new "Introduction to Sustainable Agriculture" class, co-taught by the Principal Investigator to more than 40 students over three semesters. Findings were incorporated into more than 30 presentations, farm tours, field days, and workshops, directly reaching more than 1,000 people in six
states in 2005-07. Details of these studies are featured on the website of KSU's Organic Agriculture Working Group (http://organic.kysu.edu), which attracted 7,440 page views from 3,376 unique visitors between its launch in April 2006 and the end of 2007.
PARTICIPANTS: Gary Cline and Karen Kaul shared the role of Principal Investigator until 2004, when Michael Bomford assumed the Principal Investigator responsibilities. Anthony Silvernail was a co-investigator, and doctoral student throughout the study. Study funds supported Silvernail through several graduate-level courses; he was given the opportunity to use the data from this study for a doctoral dissertation. Three researchers at the University of Kentucky collaborated on this study by serving on Silvernail's committee: Mark Williams (chair), Elisa d'Angelo and Herb Strobel. Five high school interns worked on this project through KSU's Research and Extension Apprenticeship Program: Seth Detenber, Bryant Harvey, Akree Peterson, Aminata Kalley and Cole Goodrich. Marion Simon supported this study by coordinating numerous outreach opportunities as part of KSU's Third Thursday program.
TARGET AUDIENCES: Organic farmers; farmers transitioning to organic production; small and limited-resource farmers; farmers seeking sustainable weed and soil management tactics.
PROJECT MODIFICATIONS: The original proposal called for the primary crops to alternate between sweet corn and potato. Potato was removed from the rotation and replaced with edamame soybean after the second year, due a potato crop failure and concerns that repeated potato harvests would mask the cultivation tool effects that the project was intended to evaluate. After the second year a stronger emphasis was placed on evaluating treatment effects on soil health.
Impacts
Differences were found between weed management tactics, but not between cultivation methods. Although the moldboard plow and roto-tiller combination commonly used by Kentucky vegetable growers has been criticized for its negative effect on soil quality, we found no soil quality or yield advantage to using a more expensive, and less widely-available, articulated spading machine, sold as a conservation tillage implement. The rolling cultivator offered the best weed control among the tools tested, giving higher yields than any other treatment except the hand-weeded controls. Pre-emergence treatments with corn gluten meal (CGM) and flaming offered the poorest weed control, reducing crop yield by >70%, relative to hand-weeded controls. CGM inhibited germination of <50% of weeds at the label rate, which could not justify its high application cost (10 cents per square meter). Differences between weed management tactics grew more pronounced and weed diversity declined over the
course of the study: By the study's termination a single weed species (smooth pigweed, Amaranthus hybridus), accounted for >98% of weed biomass. Soil enzyme activity, as indicated by the rate of fluorescein diacetate hydrolysis, was positively related to weed biomass, suggesting a trade-off between yield and soil microbial activity. The parallel study evaluating the effect of different mulches for weed management in watermelon showed a layer of newsprint covered with hay to be the most effective alternative to plastic mulch. Our findings are helping to save organic farmers' money. We have demonstrated that readily-available low-cost weed management and cultivation techniques can work as well as, or better than, much more expensive alternatives. The rolling cultivator, one of the least expensive weed management tools we tested, proved to be the most effective. Its use saves organic growers more than $400 per acre over hand weeding, or over the much less effective tactic of applying CGM
as an organically-approved herbicide. An articulated spading machine costs $5-8,000, and requires a larger tractor than is commonly found on small farms in Kentucky. Our results have allowed us to recommend that vegetable growers transitioning to organic production save their money, and continue to use equipment that they generally already own. Two surveys of conventional growers attending our workshops found that approximately half planned to seek organic certification: The number of certified organic growers in Kentucky quadrupled during the last two years of this study. We expect continuing rapid growth in organic vegetable production in the southeast, and in Kentucky, in particular. This will allow southeastern growers to access a market which has grown by 20% each year for more than a decade, bringing premium prices to organic producers.
Publications
- Bomford, M.K. and Silvernail, A.F. (2008). Effectiveness of Corn Gluten Meal Herbicide for Organic Production in High Weed Pressure Soil. HortTechnology (pending).
- Silvernail, A.F. and Bomford, M.K. (2008). Fluorescein Diacetate Assay: A Tool in Determining the Response of Soil Microbial Activity to Tillage and Weed Control Treatments. Abstracts of Some Papers Presented at the 2007 Annual Meeting of the Kentucky Academy of Science. Journal of the Kentucky Academy of Science 69 (in press).
- Silvernail, A.F. and Bomford, M.K. (2007). Mulch effects on weed pressure and organic watermelon yield (abstract). HortScience 42(4): 954.
- Bomford, M.K. (2006). Organic Research and Demonstrations at Kentucky State University. Page 161-162 in Proceedings of the 4th National Small Farm Conference, October 16-19, 2005, Greensboro, NC.
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Progress 01/01/06 to 12/31/06
Outputs
The effects of two tillage methods and six weed control tactics were compared by measuring crop yield, weed pressure, and soil health after four consecutive years of use. Weed-free control plots, maintained by regular hand-weeding, were compared to plots maintained with weekly passes of a rolling cultivator, spring tine weeder, or flame weeder between crop emergence and row closure; and to plots treated with corn gluten meal or flaming before crop emergence. Significant differences were detected between these weed management tactics. No differences were found between plots cultivated with the tillage implement most commonly used by Kentucky vegetable growers (a moldboard plow) and a more costly conservation tillage alternative, commonly used in Europe (an articulated spading machine). The main crop in 2006 was sweet corn, following a winter cover crop of winter rye and hairy vetch, and the 2005 crop of edamame soybean. For the fourth consecutive year, crops were grown
without inputs prohibited by national organic standards. The effectiveness of each combination of weed management tactic and tillage regime was compared through a) weed identification, b) above-ground weed biomass measurements, c) weed seed bank analysis d) sweet corn yield measurements, e) soil life abundance measurements, and f) a range of soil nutrient analyses. A single weed species (smooth pigweed, Amaranthus hybridus), accounted for 98% of weed biomass, demonstrating a decline in weed diversity since the study's inception. As with sweet corn in 2004 and edamame soybean in 2005, the rolling cultivator offered the best weed control, giving significantly higher sweet corn yields than any other treatment except the hand-weeded controls. Pre-emergence treatments with corn gluten meal and flaming offered the poorest weed control, reducing crop yield by 72 and 90%, respectively, relative to weed-free plots. Regular passes with a flame weeder and spring tine weeder gave inadequate weed
control and some crop damage, depressing yields by 67 and 55%, respectively. Soil enzyme activity, as indicated by the rate of fluorescein diacetate hydrolysis, was positively related to weed biomass. In a related study, corn gluten meal was applied to trays of field soil in the greenhouse at 0, 50, 100, and 200 g/m2, and weeds were allowed to germinate and grow for four weeks. Corn gluten meal applications at the recommended rate (100 g/m2) and at the highest rate (200 g/m2) reduced weed counts by 35 and 50%, respectively, but this response was highly variable. These reductions do not justify the high cost of corn gluten meal applications at the recommended rate (10 cents/m2). The differences between weed management tactic effects were much more pronounced in the sweet corn crop grown in 2006 than in 2004, allowing for clear recommendations to be made to organic vegetable farmers. The results were presented to at least 250 farmers and extension agents interested in organic vegetable
production through demonstrations and workshops at grower conferences and field days.
Impacts
Our results will save organic farmers money. After four years, we have consistently found that some low-cost weed management and cultivation techniques work better than more expensive alternatives. The rolling cultivator, one of the least expensive weed management alternatives tested, proved to be the most effective. Its use will save organic growers more than $400 per acre over hand weeding, or over the much less effective tactic of applying corn gluten meal as an organically-approved herbicide. Similarly, we have shown that an articulated spading machine does not offer a sufficient soil conservation advantage to justify its high cost. Through numerous workshops, we have presented our results to more than 250 southeastern growers interested in organic production. 48% of those who attended one of our workshops in 2005 planned to start growing organically; some of them contributed to the tripling of certified organic farm numbers in Kentucky in 2006. We expect
continuing rapid growth in organic vegetable production in the southeast, and in Kentucky, in particular. This will allow southeastern growers to access a market which has grown by 20% each year for more than a decade, bringing premium prices to organic growers.
Publications
- Anthony Silvernail and Michael K. Bomford. 2006. Weed control in organic edamame soybean production. HortScience 41(4): 1031.
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Progress 01/01/05 to 12/31/05
Outputs
The effects of two tillage methods and six weed control tactics were compared by measuring crop yield, weed pressure, and soil health after three consecutive years of use. Weed-free control plots, maintained by regular hand-weeding, were compared to plots maintained with weekly passes of a rolling cultivator, spring tine weeder, or flame weeder between crop emergence and row closure, and to plots treated with corn gluten meal or flaming before crop emergence. Significant differences were detected between these weed management tactics. No differences were found between plots cultivated with the tillage implement most commonly used by Kentucky vegetable growers (a moldboard plow) and a more costly conservation tillage alternative, commonly used in Europe (a spader). The main crop in 2005 was edamame soybean, following a cover crop of winter rye and hairy vetch, and the 2004 crop of sweet corn. Edamame soybean was used instead of the potato crop called for in the
original proposal, to avoid the soil disturbance characteristic of a potato harvest, and the pest problems that led to potato crop failure at this site in 2003. For the third consecutive year, crops were grown without substances prohibited by national organic standards. The effectiveness of each combination of weed management tactic and tillage regime was compared through a) weed identification, b) above-ground weed biomass measurements, c) weed seed bank analysis d) soybean yield measurements, e) soil life abundance measurements, and f) a range of soil nutrient analyses. Four species -- pigweed (Chenopodium album), goose grass (Eleusine indica), green foxtail (Setaria viridis), and crabgrass (Digitaria sanguinalis) -- accounted for 98% of the weed biomass. As with sweet corn in 2004, the rolling cultivator offered the best weed control, giving edamame soybean yields as high as weed-free control plots. Pre-emergence treatments with corn gluten meal and flaming offered the poorest weed
control, reducing crop yield by 94 and 75%, respectively, relative to weed-free plots. Regular passes with a flame weeder and spring tine weeder gave inadequate weed control and some crop damage, depressing yields by 46 and 55%, respectively. Measurements of soil life abundance were related to sample depth, but not to weed management tactic or tillage regime. In a related study, corn gluten meal was applied to cultivated outdoor plots at 0, 50, 100, 200, and 400 g/m2, and weeds were allowed to germinate and grow for six weeks. Corn gluten meal applications at the recommended rate (100 g/m2) and at the highest rate (400 g/m2) reduced weed counts by 47% and 66%, respectively. These reductions do not justify the high cost of corn gluten meal ($1/kg). The differences between weed management tactic effects were much more pronounced in the edamame soybean crop grown in 2005 than in the sweet corn crop grown in 2004, allowing for clear recommendations to be made to organic vegetable farmers.
The results were presented to at least 250 farmers and extension agents interested in organic vegetable production through demonstrations and workshops at grower conferences and field days.
Impacts
Our results will help fuel growth in organic vegetable production in the southeast by providing research-based recommendations to growers entering the expanding organic marketplace. We have identified the rolling cultivator as a practical component of a successful organic weed management regime. Through numerous workshops, we have presented our results to more than 250 southeastern growers interested in organic production. A survey conducted at one of these workshops found that 48% of attendees plan to start growing organically. We expect rapid growth in organic vegetable production in the southeast, and in Kentucky, in particular. This will allow southeastern growers to access a market which has grown by 20% each year for more than a decade, bringing premium prices to organic growers.
Publications
- Silvernail, A.F. 2005. Weed Management in Organic Sweet Corn. HortScience 40(4): 1071
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Progress 01/01/04 to 12/31/04
Outputs
Two methods of tillage and four weed control tactics were compared in research plots growing organic sweet corn. The effectiveness of each combination of weed management tactic and tillage regime was compared through weed identification and above-ground weed biomass estimates, corn yield, and post-season weed seed bank analysis. Significant differences were detected between some weed management tactics, but not between plots cultivated with a moldboard plow and those cultivated with a spader. The rolling cultivator consistently offered excellent weed control, producing yields equivalent to weed-free control plots. Corn gluten, flame cultivation, and a Williams tool bar fit with spring tine weeders, sweeps and spyders all offered adequate weed control, resulting in corn yields approximately 18% lower than in weed-free control plots. Four species -- pigweed (Chenopodium album), goose grass (Eleusine indica), green foxtail (Setaria viridis), and crabgrass (Digitaria
sanguinalis) -- accounted for 98% of the weed biomass. Weed seed bank and soil microbial analyses are ongoing.
Impacts
Results of this research should be of benefit to organic vegetable growers for control of weeds,which pose a major problem.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
Experimental plots on Kentucky State University's Research Farm were prepared by moldboard or spader tillage. Plots were fertilized with Nature safe 10-2-8 coarse grade turfgrass fertilizer. Organic white potatoes were planted during the first week of June. Plots in each tillage treatment were maintained as untreated controls or weeds were controlled by one of the following methods: Williams toolbar, Rolling cultivator + Buddingher finger weeder, flamer, and corn gluten. From each experimental plot, data on potato yields, weed number, weed identity, and weed biomass were collected at the end of the growing season. Soil samples were collected from the experimental plots for determining the seed population in the plots at the beginning of the current study. These soil samples were kept in plastic trays in a greenhouse and were irrigated daily. Weed seedlings were identified and counted as they emerged. Soil samples were again collected from the experimental plots for
determining the seed population in the plots at the end of the first growing season.
Impacts
Results of this research should be of benefit to organic vegetable growers for control of weeds,which pose a major problem.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Experimental plots on Kentucky State University's Research Farm were plowed in October, 2002. However, vetch cover crop could not be planted due to unusually wet weather. A flame cultivator and a spader were ordered and have been received. Experiments will be done with organically grown potatoes during the 2003 growing season. We are currently planning the experiments for the 2003 growing season with appropriate input from the Farm Manager. Weed seeds were collected in fall, 2002. These seeds will be used for preliminary greenhouse experiments to determine the rate at which corn gluten should be applied for inhibition of weed seed germination.
Impacts
Results of this research should be of benefit to organic vegetable growers for control of weeds, which pose a major problem.
Publications
- No publications reported this period
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