A field experiment was conducted at the Tropical Research and Education Center, University of Florida, Homestead, to determine the effects on plant morphology, biomass yield, and flower production. of cutting the main stem of sunn hemp (Crotalaria juncea Aref A. Abdul-Baki is Plant Physiologist with the United States L.) plants at different heights. Seeds treated with cowpea (Vigua unguicalata)-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 when the plants were about 1.5 m tall. Control plants were left uncut. Biomass that had been cut from plants was included in the total biomass yield. Seventy days 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. Leaf area and nutritional analyses of the plant parts were determined. Cutting the main stem at 30 and 60 cm above soil surface reduced total plant biomass, whereas cutting at 90 cm height increased biomass yield. Cutting at 30 cm produced the highest quality of biomass by increasing the leaf yield and reducing the weights of root and main stem both of which are low in N and high in C/N. Cutting the main stem at 90 cm produced the highest biomass yield, increased the number and weight of primary and secondary branches and, consequently, increased the number of flowers per plant. Nitrogen was highest in flowers and lowest in roots and main stems. Flowers were highest in K, P, Zn and Cu, whereas roots were highest in Fe content. We conclude that cutting the main stem at 30 cm height and allowing the plants to grow for an additional 70 d result in 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.

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The effects of municipal solid waste (MSW) materials on growth, yield, and mineral element concentrations in tomato (Lycopersicon esculentum Mill.) (1991 and 1992) and squash (Cucurbita maxima Duch. Ex Lam.) (1992 and 1993) were evaluated. Agrisoil compost (composted trash), Eweson compost (co-composted trash and sewage sludge), or Daorganite sludge (chemically and heat-treated sewage sludge) were incorporated into calcareous limestone soil of southern Florida. The control had no MSW material added to the soil. The effect of MSW on crop growth, yield, and mineral element concentrations varied considerably between years for tomato and squash. In 1991, tomato plants grown in soil amended with Eweson or Daorganite had a greater canopy volume than plants in the control treatment. Tomato plants grown in Daorganite had greater total fruit weight (1991) than plants in Agrisoil and more marketable fruit (1992) than control plants. In both years, tomato plants in Agrisoil had higher root Zn concentrations than plants in the other treatments. In 1992, tomato plants in Eweson had lower root Mn concentrations than plants in the other treatments, whereas Mg concentrations in the roots were higher in the Daorganite treatment than in Eweson. Tomato plants in Agrisoil had higher Pb concentrations in the roots than plants in all other treatments. In 1991, leaves of tomato plants in Agrisoil had lower Ca concentrations than leaves of plants in the control treatment. In 1992, leaf Zn concentrations were greater for tomato and squash in Agrisoil than in the control or Daorganite. In 1992, canopy volume and yield of squash were greater for plants in Daorganite than for plants in the control and other MSW treatments. Although canopy volume and total squash fruit weight did not differ among treatments in 1993, plant height was greater for squash plants in the MSW treatments than for those in the control. In 1993, leaf Mg concentrations were greater for squash grown in Daorganite than for plants in the control or Agrisoil. In 1993, fruit Cd concentration was higher for plants with Eweson than for plants in the control or Agrisoil. However, the fruit Cd concentration in squash grown in Eweson compost (1.0 mg/kg dry weight) was far below a hazardous level for human consumption. Our results indicate that amending calcareous soils with MSW materials can increase growth and yield of tomato and squash with negligible increases in heavy metal concentrations in fruit.

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