Explanations for Decreased Harvest Index with Increased Yield in Soybean

Yield in soybean [Glycine max (L.) Merr.] is controlled by total dry matter (TDM) accumulation and partition of that TDM into yield as measured by harvest index (HI). Previous research indicated that yield responded to TDM at R5 (seed initiation) [TDM(R5)] in an asymptotic relationship that plateaued at about 600 g m -2 . As yield rose with TDM(R5), HI declined, thus acting as a yield limiting factor. Explanation for the inverse relationship between yield and HI would help develop research strategies for yield improvement. Our objective was to determine if this negative relationship resulted from an inverse relationship between node production efficiency [node no. per gram TDM(R5)] with TDM(R5). Data for this study were collected from previous studies containing a variety of cultural treatments (planting dates, row spacings, plant populations, and waterlogging) conducted near Baton Rouge, LA (30° N lat), between 1987 and 1996 and combined into a single data set. Regression analyses between yield, TDM(R5), yield components, and production efficiencies of yield components [yield component level per gram TDM(R5)] were conducted. Results indicated that the inverse relationship between HI and yield (R 2 = 0.54; b 1 = P < 0.0001, b 2 = P < 0.05) resulted mainly from a negative relationship between node production efficiency and TDM(R5) (R 2 = 0.81; b 1 = P < 0.0001, b 2 = P < 0.05), which resulted in less efficient production of pods and seeds (the main yield components controlling yield) as TDM(R5) increased. In conclusion, reduced node production efficiency with increased TDM(R5) created the inverse relationship between Hl and yield.

[1]  E. J. Kamprath,et al.  Selection for Aluminum Tolerance in Soybeans Based on Seedling‐Root Growth1 , 1979 .

[2]  Manjit S. Kang,et al.  Path Analyses of the Yield Formation Process for Late‐Planted Soybean , 1999 .

[3]  D. Egli,et al.  Dry Matter Accumulation Patterns in Determinate and Indeterminate Soybeans 1 , 1973 .

[4]  J. Board,et al.  Growth Dynamics during the Vegetative Period Affects Yield of Narrow-Row, Late-Planted Soybean , 1996 .

[5]  O. Krober,et al.  Response of Soybeans to Leaf and Pod Removal1 , 1958 .

[6]  R. C. Muchow,et al.  Response of Leaf Growth, Leaf Nitrogen, and Stomatal Conductance to Water Deficits during Vegetative Growth of Field‐Grown Soybean 1 , 1986 .

[7]  J. Board,et al.  Dry matter accumulation predictors for optimal yield in soybean , 2005 .

[8]  Mark W. Schonbeck,et al.  Effect of Pod Number on Dry Matter and Nitrogen Accumulation and Distribution in Soybean 1 , 1986 .

[9]  E. J. Kamprath,et al.  Effect of Soil pH and Liming on Growth and Nodulation of Soybeans in Histosols1 , 1978 .

[10]  R. B. Curry,et al.  Accumulation and Distribution of Mineral Nutrients, Carbohydrate, and Dry Matter in Soybean Plants as Influenced by Reproductive Sink Size1 , 1974 .

[11]  J. Board,et al.  Assimilatory Capacity Effects on Soybean Yield Components and Pod Number , 1995 .

[12]  Edgar E. Hartwig,et al.  Effects of Morphological Characteristics Upon Seed Yield in Soybeans1 , 1970 .

[13]  J. Board.  Light Interception Efficiency and Light Quality Affect Yield Compensation of Soybean at Low Plant Populations , 2000 .

[14]  M. W. Adams,et al.  A Path Coefficient Analysis of Some Yield Component Interrelations in Field Beans (Phaseolus vulgaris L.)1 , 1972 .

[15]  A. Saxton,et al.  Narrow-row seed-yield enhancement in determinate soybean. , 1990 .

[16]  J. E. Board,et al.  Branch Yield Components Controlling Soybean Yield Stability across Plant Populations , 1997 .

[17]  J. E. Board,et al.  Temporal Importance of Greater Light Interception to Increased Yield in Narrow-Row Soybean , 1992 .

[18]  J. Board,et al.  Waterlogging effects on growth and yield components in late-planted soybean. , 1998, Crop science.