Optimizing buckwheat use as a weed suppressive cover crop for sustainable cropping systems in Florida

Optimizing buckwheat use as a weed suppressive cover crop for sustainable cropping systems in Florida

Summary

Buckwheat was planted on Mar. 13, Mar. 27, Apr. 10, Apr. 24, May 8 and May 22 to determine the optimal planting date. Buckwheat planted from April to early May grew better than earlier and later planting dates. Weed suppression was more effective with buckwheat planted at earlier dates than at later dates. Total and monocot weed biomass with buckwheat and a harrowed control was similar, but lower than with a weedy control. These preliminary results suggest that buckwheat for weed suppression in north central Florida should be planted prior to May 8.

Objectives/Performance Targets

1. To determine the optimal environmental conditions and range of effective planting dates for buckwheat as a weed suppressive cover crop in Florida. To determine the optimal incorporation practice for buckwheat grown as a cover crop in Florida.

Accomplishments/Milestones

The optimal environmental conditions and range of effective planting dates for buckwheat as a cover crop to suppress weeds in spring with planting dates of Mar. 13, Mar. 27, Apr. 10, Apr. 24, May 8 and May 22, 2007 were evaluated in spring 2007 and some of the results are presented below. A second trial was conducted in Fall 2007 using planting dates of Sep. 20, Oct. 4, Oct. 18, Nov. 1, Nov. 15, and Nov. 29, 2007. Data collection for the Fall trial will be completed in February, 2008.

The results of the spring trial showed that maximum biomass (247 g/m2), buckwheat height (66 cm), leaf area index (LAI) (2.15), and cover percentage (89%) occurred with buckwheat planted on Apr. 24. Both biomass and LAI responded in a similar manner to planting date, increasing when planted after Apr. 10 and then decreasing with May planting dates. Buckwheat height and cover percentage were lowest with March planting dates, increased with April planting dates, then declined with May planting dates. Before buckwheat was terminated by mowing, weed biomass was lower with earlier planting dates than later planting dates, and monocots were the predominant weed species. The rate of increase in total weed biomass and monocot weed biomass was greater in the weedy control than in the buckwheat cover crop. Therefore, with the planting date of May 22 weed biomass in weedy control was 3.7 and 3.3-fold more, respectively, than buckwheat control. Dicot weed biomass was 3.1-fold less with buckwheat than with the weedy control when averaged over planting dates. After mowing, however, suppression of dicot weed biomass was not consistent with the result before mowing. Conversely, buckwheat reduction of total weed biomass and monocot weed biomass was similar to the harrowed control, but significantly better than weedy control. Total weed biomass and monocot weed biomass were more effectively suppressed with buckwheat planted in March and April than planted in May. These preliminary results suggest that when used as a cover crop for weed suppression in north central Florida, buckwheat should be planted prior to May 8.

The data from the Fall 2007 trial will be analyzed in summer 2008. Spring and fall trials will be repeated in 2008. Optimal planting dates will be used to conduct trials in Spring and Fall 2008 to address objective 2. This study will evaluate the effects of four termination practices (rolling, flail mowing, light tillage, and flail mowing + light tillage) on residue decomposition and weed suppression.

Impacts and Contributions/Outcomes

Because of its rapid growth and establishment, buckwheat will be a useful short-term cover crop for weed suppression in spring and fall seasons. It will need to be terminated by 35 to 40 days after planting to prevent seed maturity leading to volunteers in the subsequent crop. Depending on the method of termination of the cover crop, weed suppression is expected to persist for several weeks after termination.

This project will contribute to the training of a Masters level graduate student. The student’s thesis will be based on this research. The student presented a poster based on the research at the Southern Weed Science Society meeting in January 2008 and will present another poster at the American Society for Horticultural Science meeting in July 2008. Journal articles based on each objective also will be used to disseminate the results.

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