Title page for ETD etd-05072001-204551

Type of Document Master's Thesis
Author Johnson, Bryan Fisher
Author's Email Address brjohns4@vt.edu
URN etd-05072001-204551
Degree Master of Science
Department Plant Pathology, Physiology, and Weed Science
Advisory Committee
Advisor Name Title
Wilson, Henry P. Committee Chair
Hagood, Edward Scott Jr. Committee Member
Holshouser, David L. Committee Member
  • soybean maturity group
  • soybean yield
  • leaf area
  • herbicide damage
  • full-season soybean
  • double-crop soybean
  • soybean injury
Date of Defense 2001-05-07
Availability unrestricted
The occasional failure of glyphosate to control all weeds throughout the entire growing season has prompted growers to sometimes use herbicides other than glyphosate on glyphosate-tolerant soybean. Field studies were conducted in 1999 and 2000 to investigate potential crop injury from several herbicides on glyphosate-tolerant soybean, and to determine the relationship between soybean maturity, planting date, and herbicide treatment on soybean injury, leaf area index (LAI), and yield. Three glyphosate-tolerant soybean cultivars representing maturity groups III, IV and V were planted at dates representing the full-season and double-crop soybean production systems used in Virginia. Within each cultivar and planting date, 15 herbicide treatments, in addition to a control receiving only metolachlor preemergence, were applied to cause multiple levels of crop injury. Results of this study indicate that glyphosate-tolerant soybean generally recovered from early-season herbicide injury and LAI reductions; however, reduced yield occurred with some treatments. Yield reductions were more common in double-crop soybean than in full-season soybean. In full-season soybean, most yield reductions occurred only in the early maturing RT-386 cultivar. These yield reductions may be attributed to the reduced developmental periods associated with early maturing cultivars and double-crop soybean that often lead to reduced vegetative growth and limited LAI. Additional reductions of LAI by some herbicide treatments on these soybean may have coincided with yield reductions; however, reduced LAI did not occur with all yield reducing treatments. Therefore, soybean LAI response to herbicide treatments does not always accurately indicate the potential detrimental effects of herbicides on soybean yield. Further, yield reductions associated with herbicide applications occurred, although soybean sometimes produced leaf area exceeding the critical LAI level of 3.5 to 4.0 which is the minimum LAI needed for soybean to achieve maximum yield.
  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
  01_Title.PDF 7.36 Kb 00:00:02 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01
  02_Abstract.PDF 4.80 Kb 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01
  03_Acknowledgements.PDF 5.96 Kb 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01
  04_toc.pdf 9.62 Kb 00:00:02 00:00:01 00:00:01 < 00:00:01 < 00:00:01
  05_Chapter_1.pdf 92.39 Kb 00:00:25 00:00:13 00:00:11 00:00:05 < 00:00:01
  06_Chapter_2.pdf 508.44 Kb 00:02:21 00:01:12 00:01:03 00:00:31 00:00:02
  07_Chapter_3.pdf 49.67 Kb 00:00:13 00:00:07 00:00:06 00:00:03 < 00:00:01
  08_Vita.pdf 47.98 Kb 00:00:13 00:00:06 00:00:05 00:00:02 < 00:00:01

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