Department of Plant and Soil Sciences

Bhoumik, Didhiti and Lewis Edwards. 2000. Soybean Research at OSU 1999. p. 10-11. OSU/DASNR/OAES/OCES. P-976

Ms. Didhiti Bhoumik completed her Masters of Science degree in July 1999.
  .  Delayed harvest produced a drop in yield for some varieties.
  .  Delayed harvest did not always produce a drop in yield for some varieties.

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This study evaluated the yield and seed quality of five Group IV and five Group V varieties (Table 1) harvested at maturity, two,weeks after maturity, four weeks after maturity, and six weeks after maturity. Group IV varieties included:
Manokin, Chesapeake, Delsoy4710, Stressland, and OK916005. GroupV varieties included: Holladay, Hutcheson, Graham, Delsoy 5500, and OK896001. The research was conducted at two locations (Bixby and Chickasha).

Manokin and OK916005 (Essex/Oksoy) produced better yields at both locations each year than the other three varieties at all four harvest dates. These two varieties also produced better seed quality than the other three varieties especially at the later harvest dates.
 

Tabel 1. Cultivars/Germplasm for Delayed Harvest Study

MG IV	MG V
Manokin	Holladay
Chesapeake	Hutcheson
Delsoy 4710	Graham
Stressland	Delsoy 5500
OK916005, Essex/Oksoy	OK896001, Essex/Gail

Yields of Group IV varieties (averaged over all varieties) was highest at harvest date one as expected (Table 2). However, harvest date three yielded more than harvest date two or four. Shattering was not a problem at any of the harvest dates. Date two produced lower yields than date three because of poor harvest conditions at date two (i.e.,a rain occurred just prior to harvest). In 1997 at Bixby yields of Group V varieties declined at harvest dates two and four (Table 3). Likewise in 1998 at Chickasha, yields declined at harvest dates two and four. In 1997 at Chickasha and 1998 at Bixby, there was no decline in yields at any delayed harvest date. Harvest date one always gave the best results for yield. However, harvest date four did not always give the lowest yields as expected. Yields of some of the varieties remained fairly high even with delayed harvest, Seed quality was often better at one or more of the delayed harvests.

 Table 2. Mean Yields (G/plot) at Each Harvest Date Combined Over MG IV Cultivars at Each Location.
 

	Harvest Date One	Harvest Date Two	Harvest Date Three	Harvest Date Four	LSD
Bixby, 1997	1342 a*	1113 c	1246 ab	1151 bc	101
Chickasha, 1997	841 a	698 bc	741 ab	609 c	105
Bixby, 1998	530 a	512 a	427 b	365 c	48

*Means at each row with the same letter are not significantly different at the 5%,Ievel of probability according to LSD.
 

Table 3. Mean Yields (G/plot) At Each Harvest Date Combined Over MG V Cultivars At Each location.
 
 

	Harvest Date     One	Harvest Date      Two	Harvest Date      Three	Harvest Date  Four	LSD
Bixby, 1997	1377 ab*	1417 a	1398 b	803 c	76
Chickasha, 1997	1200 a	1102 a	1128 a	1178 a	105
Bixby, 1998	742 ab	719 b	786 a	787 a	64
Chickasha, 1998	1335 a	1050 b	1108 b	892 c	155

*Means at each row with the same letter are not significantly different at the 5% level of probability according to LSD.

Germination percentages often declined from harvest date two to harvest date three, then leveled off with little or no additional decline. Among Group IV varieties, Manokin and OK916005 appeared to produce the best quality seed (highest germinations) with delayed harvest. All Group V varieties appeared to exhibit good seed qu4litiy with delayed harvest. A large decrease in germination percentage of the harvested seed resulted when there was a rain just prior to harvest. Yields of Group V varieties remained good even with the delayed harvest.