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Title: EFFECTS OF CUTTING THE MAIN STEM ON BIOMASS YIELD AND FLOWER PRODUCTION IN SUNN HEMP

Author
item Abdul Baki, Aref
item BRYAN, HERBERT - UNIVERSITY OF FLORIDA
item ZINATI, GLADIS - UNIVERSITY OF FLORIDA
item KLASSEN, WALDEMAR - UNIVERSITY OF FLORIDA
item CODALLO, MERLYN - UNIVERSITY OF FLORIDA
item HECKERT, NOLAN - UNIVERSITY OF FLORIDA

Submitted to: Journal of Vegetable Crop Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: High temperatures, heavy rains, excessive tillage, and continuous use of land all-year-round to produce several crops per year deplete the organic matter and nutrients from south Florida soils, render them infertile and highly dependent on commercial fertilizers that are both costly and contaminants to surface and groundwater. A search for cover crop species adapted to tropical climate resulted in identifying sunn hemp as an excellent cover crop to use as mulch or green manure to improve organic matter content of the soil. However, seed production by sunn hemp in Florida is not economical due to poor yields. We developed a cultural practice that increases flowering by almost 400 percent by cutting the plants at a specific height which forces them to form more branches and more flowers. The approach is simple to apply and allows production of sunn hemp seed as well as seed for export to other regions. Users of this research are growers, seed producers, and extension specialists.

Technical Abstract: A field experiment was conducted at the Tropical Research and Education Center, Univ. of Florida, Homestead, to determine the effects of cutting the main stem of sunn hemp plants at different heights on plant morphology, biomass yield, and flower production. Seeds treated with cowpea-type rhizobium were sown on 15 April 1999. The main stems were cut at 30, 60, and 90 cm above soil surface 100 days after seeding. Control plants were left uncut. Biomass that had been cut from plants was determined and included in the total biomass yield. Seventy days of growth following stem cutting individual plants were evaluated for: plant height; main stem diameter; fresh and dry weights of roots, main stems primary branches, secondary branches, leaves, open flowers, and unopened flowers. The number of primary branches, secondary branches, and open flowers per plant were recorded. Leaf area and nutritional analyses of the plant parts were determined. We conclude that cutting the main stem at 30-cm height and allowing the plants to grow for an additional 70 d, yields the highest quality biomass for use as green manure, windbreaks, and mulch. Cutting at 90 cm produced the largest biomass yield and increased flower production.