Annual Report of Progress
to the
MISSISSIPPI SOYBEAN PROMOTION BOARD
for 1998

Objectives & Significant Accomplishments

The objective of this study was to determine soybean varietal response when planted late on flood-prone soil in the southern portion of the Mississippi Delta. The responses that were measured during the 1998 growing season included stand establishment, plant height, influence of diseases and insects, and yield. The entire test was planted on July 7, 1998. Soil moisture was adequate for germination and emergence of seedlings. Over the next week, over five inches of rain occurred on the plot area. Soybeans in all but two plots emerged to a good stand. The two plots that did not have any seedling emergence were disease check varieties with poor emergence (observed from state-wide soybean variety trials). These two varieties were not included in the analysis of data. The growing season was not ideal for soybean production during 1998. Although total rainfall was sufficient, long periods between rains resulted in drought-like effects on plant growth.

Results from the test are presented in Tables 1-9 (see appendix). Data were analyzed by maturity group, so direct comparisons between maturity groups can not be made statistically. The data were also analyzed separately for the Roundup Ready and Conventional Variety Tests.

Roundup Ready Trial: Group, IV Varieties. Data for the various Maturity Groups are presented in Tables 1-4. Overall the yields were very poor, ranging from just Å bu/acre to a high of almost 12.0 bu/acre. Maturity Group IV (both early and late maturing) shattered immediately upon maturity in late October. By the time the plots were harvested within one week of maturity, most Group IV varieties had shattered from 25-50%. Shattering contributed to low yields among Group IV varieties. Group V Varieties. The Group V varieties were harvested almost three weeks later than the Group IV's. The highest yields were observed in the early-maturing Group V varieties. H5088RR was the highest yielding variety with 11.7 bu/acre. Although yields were poor among the early-maturing Group V varieties, consistently higher yields were observed within this maturity group as compared to the other maturity groups. Early-maturing Group V varieties generally were considered mature in early November but many varieties still retained green leaves and stems although the pods were physiologically mature. Shattering was not a problem within this maturity group. Yield of the late-maturing Group V varieties was extremely poor. About 6.0 bu/acre was the highest yield. The author feels that delayed maturity was the cause of low yields. When harvested on 11/24/98, all varieties within this maturity group still had a few green pods, green leaves and stems, which made harvest difficult.

Conventional Variety Trial: Data for the conventional variety trial is presented in Tables 6-9. When compared to the Roundup Ready test, the conventional varieties generally resulted in higher yield. Yields ranged from about 2.0 bu/acre to 16 bu/acre. Group IV Varieties. Group IV varieties yielded poorly in 1998 (Table 6 and 7). Maturity was reached by mid- to late October. Upon reaching physiological maturity, shattering occurred. Shattering was similar as in the Roundup Ready Group IV test and was estimated to range from 25-50%. Shattering was most likely responsible for such poor yields. Group V Varieties. The Group V varieties generally were the highest yielding Group in the test, with more varieties producing yields in thc range of 12-16 bu/acre (Tables 7 and 8). The early-maturing Group V varieties were harvested almost three weeks in advance of the late-maturing Group V varieties. There was not that much difference in actual physiological maturity between these two groups, but the late-maturing Group V varieties retained some green leaves and stems until harvest on 11/24/98. Group VI Varieties. About 50% of the Group VI varieties produced yields of 10-15 bu/acre (Table 9). Overall, this maturity group resulted in the most consistent higher yielding varieties. Time of maturity was later than all other maturity groups. Plants retained green leaves, stems and a few green pods at harvest on 11/24/98.

Soybean seed quality and yield was extremely poor in 1998. Later maturing varieties never reached full maturity. Although insects were present, insecticide application was made at the appropriate time. Mild aerial web blight was present, which has been suggested to delay maturity. Coupled with the dry, hot summer and mild disease, maturity may have been delayed. Harvesting in late November most likely will not be feasible in most years as rainfall would make harvest difficult or impossible.

Group VI soybeans produced the greatest yields but had the latest maturity. Group V soybeans (either test and maturity group) initially appear to provide suitable yield potential and maturity for soybeans grown on flood-prone soil planted late in the growing season.

Publications

 None in 1998. This test should be repeated in 1999. Two years of data can then be published as an information sheet.

Soybeans in Mississippi Mississippi Agricultural and Forestry Experiment Station  Mississippi State University Extension Service Division of Agriculture, Forestry and Veterinary Medicine

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