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Current Master Student's Projects

Effect of Stage of Development of a Sunn Hemp Cover Crop on Decomposition after Soil Incorporation and Physiology and Growth of Papaya in Sunn Hemp Amended Soil

Abdulhakeem Baitsaid, M.S. Student

During the past 2-3 years, the use of sunn hemp (Crotalaria junceae) as a cover crop in south Florida has been increasing rapidly due to recent reductions in the cost of seeds.  Studies at the University of Florida, TREC, have shown that growth of several crops, including papaya, benefit from the use of sunn hemp as a cover crop and then using it a mulch or incorporating it into the soil.  Between crop cycles, instead of allowing fields to remain fallow, growers are increasingly planting sunn hemp, which grows very rapidly during the summer in south Florida.  After sunn hemp reaches a height of about 2.5-3.0 meters, it is mowed and incorporated into the soil to improve soil physical properties and provide a slow-release form of nitrogen.  However, at this late stage of growth, sunn hemp decomposition may be too slow for it to be a good source of nitrogen. Thus, there is a need for in testing the effects of soil incorporation of sunn hemp at different stages of development on the rate of sunn hemp decomposition, and soil nitrogen and organic matter content as well as physiology and growth of crops planted in sunn hemp amended soil.

This study is testing the effects of stage of development of a sunn hemp cover crop for incorporation into the soil on cover crop decomposition, soil nitrogen and organic matter content and physiology and growth of papaya planted in sunn hemp amended soil.

Experiments have been designed to answer the following questions:

  • What are the effects of the stage of development of sunn hemp prior to incorporation into soil on soil nitrogen and organic matter content, and growth and physiology of papaya planted in sun hemp amended soil?
  • What are the minimum rates of inorganic nitrogen required for papaya when sunn hemp is incorporated into the soil prior to crop planting?
  • What is the time needed for decomposition of sunn hemp to achieve maximum release of nitrogen into the soil?
  • Is the lignin content related to nitrogen availability in sunn hemp plant residues?