Doctor of Philosophy (PhD)


Plant, Environmental Management and Soil Sciences

Document Type



Identification of criteria for predicting soybean [Glycine max (L.) Merril] yield would provide farmers with useful management tools. Such criteria not only help in predicting the yield potential but also aid the farmer in determination of environmental factors limiting crop yield. Since a certain total dry matter (TDM) level is expected to optimize yield and R5 marks the end of the period for vegetative TDM accumulation, TDM(R5) is a good putative criterion for optimal yield. Determination of yield components important in yield formation helps to substantiate TDM(R5) as a criterion for optimum yield, since they are formed during discrete periods and therefore would indicate when TDM accumulation is important. Because TDM(R5) could be an efficient and accurate yield criterion and because little research has been done on this subject, our objectives were to use analyses of relationships between yield components, TDM, and yield to determine if: 1. TDM(R5) can be used as criterion for optimum yield; and 2. What level of TDM(R5) is required to optimize yield. The data for this study were collected from previous studies, that contained a variety of cultural treatments like planting dates, row spacings, plant populations, partial defoliation, and waterlogging stress, conducted near Baton Rouge, LA (300 N Lat) between 1987 to 1996 and combined to make a single data set. The data thus pooled was subjected to correlation, regression and path coefficient analyses to achieve our objectives. The study clearly indicated that use of TDM(R5) as a yield criterion is valid and the critical level of TDM(R5) was found to be 600 g m-2 to achieve optimum yield. The TDM(R5) criterion can be used as a very good management tool by the farmers. Yield components like seed number per area, pod number per area, reproductive node number per area and node number per area, which responded strongly to TDM accumulation, are likely to be affected by the cultural practices of the farmer. The farmer should adjust cultural practices to ensure that length of emergence to R5 period is long enough to achieve the required TDM(R5).



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

James Board