Alabama has some of the best fields for agriculture in the country due to ample rainfall, long growing season, and proximity to major urban markets. Considering the long-term drought in California, urban development and high land cost in central and south Florida, vegetable acreage in Alabama is projected to rise significantly in the next decade due to low production costs and long growing season for crops. However, one of the biggest problems with expanding vegetable production in Alabama and the Southeast is limited weed control options and tremendous weed pressure as compared to Midwest and northern U.S. Southern crabgrass, goosegrass, pigweed species, lambs quarter and nutsedges can outcompete plant growth early in the season, and reduce yield and harvest efficiency. Moreover, sensitive vegetable varieties can be easily injured by herbicides, and herbicides registered for vegetable production are generally limited as compared to agronomic crops. Considering limited herbicide options, strong market demands, high weed pressure and long growing season, weed control in vegetable production has been challenging in the Southeast, particularly in organic production.
To suppress weeds, increase soil temperature, retain moisture and prevent nutrient leaching, many vegetable farmers utilize plastic mulch in their production. However, initial installation costs, irrigation equipment and annual material costs are high. In some cases, direct seeding without plastic mulch may be easier to operate and more cost-effective as plastic mulch disposal and recycling are both financially and environmentally costly. To increase sustainability, biodegradable mulches have been developed since the 1980s but adoption rate is low due to high cost, inconsistent breakdown time, and lack of knowledge among farmers about the performance of biodegradable mulches. So far, little research and extension work has been done in the Southeast to evaluate the efficacy and economic viability of newer biodegradable mulches and to promote this option to vegetable farmers.
The proposed solutions to address the problems stated above include evaluating high-residue cover crops and biodegradable mulches for weed control in sustainable vegetable production.
- Evaluating high-residue cover crop systems plus reduced tillage for weed suppression and reduction of herbicide usage as compared to bare ground system.
- Assessing the potential of reducing polyethylene mulch usage with adopting high-residue cover crop systems plus biodegradable mulches in organic production.
Research plots have been established at Hornsby farm and Wiregrass research and extension center. Beds were formed last October and plastic was installed immediately afterwards. Beds were kept as 3 ft wide and row spacing was 6 ft wide. Cereal rye, rye + crimson clover, and white clover were spread with battery power spreader. Two termination methods (spraying glyphosate then run over with tractor tire, or only run over with tractor tire) will be used in early April of 2019 to terminate cover crops in these plots. Checks will be managed as 1) non-treated, full of winter weeds, 2) chemical control using glyphosate (Roundup) + flumioxazin (Chateau). During growing season, watermelon and bell peppers will be transplanted into these beds at normal transplant spacing. Cover crop plots will not be sprayed with preemergence herbicide (Chateau). Only chemical control check will receive Chateau + Roundup. Postemergence treatment of Sandea and Select Max will be used on chemical control check around 5 weeks following transplanting. PI will determine if cover crop plots will receive this POST treatment based on weed assessment and field scouting. If cover biomass is sufficient at this timing, PI may not apply any herbicide to the row middles before crop harvest. Weed count and biomass in each plot will be conducted twice during crop growth (4-5 weeks after transplanting and before harvest). Final yield will also be taken in each plot.
This study is conducted in a very simple way that most of vegetable farmers can follow without needing special equipment. Cover crop treatments have good potential to reduce herbicide usage in row middles and they may provide longer weed suppression than chemicals. Cover crops planted in row middles also can increase general soil health, water holding capacity and organic matter content, along with supporting pollinator population (clover), which is important in specialty crop production.
Three types of biodegradable tarps have been purchased and will by installed at Hornsby farm and another location TBD. The goal is to evaluate 1) if they can last one growing season and retain integrity, 2) if they can sufficiently suppress weeds under the tarp. These tarp will be lay in high weed pressure area. Multiple evaluations on tarp integrity and weed control will be conducted through out the season until fall of 2019.
No results is available yet. They will be ready later in 2019 after crops are harvested.
Educational & Outreach Activities
Research study is still in progress. No outreach and educational activities can be scheduled at this point.