Annual Report of Progress
to the
MISSISSIPPI SOYBEAN PROMOTION BOARD
for 1995

Significant Accomplishments

All cultivars in MG's early IV, late IV, V, and VI were planted in area with a historic iron chlorosis problem at the Blackbelt Prairie Station, Brooksville. Visual walk throughs and visual ratings were taken on the early IV and late IV cultivars until it was determined that an early to mid podfill rating gave the most separation of the cultivars. Visual ratings were made on all of the early IV, late IV and V cultivars. The symptoms on the MG VI cultivars did not reach a level that would allow ratings to be made. The rating scale was 1 =no yellowing to 5=severe yellowing. The yield results and the ratings were included in the 1995 Variety Test Publication.

Correlation coefficients (significant at P=0.05) between final yield and visual ratings were -0.68, -0.72, and-0.41 for the early IV, late IV, and V cultivars, respectively. These values indicate that on the average as the level of yellowing increased, the yield decreased.

Meter readings using the Minolta SPAD-502 chlorophyll meter were made on all of the MG V cultivars. As the readings were made in the field it became evident that factors such as leaf thickness, pubescence color, and the cultivars natural variations in col or had an effect on the readings. When the meter readings were analyzed with the visual ratings and the yields it was found that the correlation coefficients were nonsignificant with both measurements. It was felt that a base reading for each cultivar wou ld have to be established to determine if the reading was measuring iron chlorosis or the natural differences in color between cultivars.

The area around the test was planted in a solid stand of soybean. Observations made throughout the growing season allowed us to determine the area most severely effected by iron chlorosis. Plans have been made to reposition the test in attempt to make rat ings on all cultivars from MG early IV to VI. After a base line of information is developed for each cultivar only the new entries along with a series of check cultivars would to be screened. This will eventually allow a reduction in the amount of time a nd funding needed to maintain information on this problem.

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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