Relationship Between Laboratory Indices of Soybean Seed Vigor and Field Emergence1

Abstract

There have been few comparisons of the relationship between laboratory estimates of soybean [Glycine max (L.) Merr.] seed vigor and field emergence under adverse soil conditions. These studies were conducted in 1973‐75 to compare the results of standard germination, two vigor tests (accelerated‐aging germination and 4‐day germination), and several vigor indices to field emergence in varying soil environments. Each vigor index was computed by converting the results of each laboratory test into a vigor rating ranging from 0 to 10. The three vigor indices evaluated and the tests used in each were: VR‐1 (standard germination, 4‐day germination, and accelerated‐ aging germination), VR‐2 (standard germination and accelerated‐aging germination) and VR‐3 (standard germination and 4‐day germination). The prediction accuracy (those seed lots that emerged in the same performance level in the field as predicted in the laboratory) was determined for each laboratory test and index. All laboratory tests consistently overpredicted field emergence when seed was planted in adverse soil conditions (severe crusting and cold soil temperatures). The prediction accuracy for all seed lots averaged across years with adverse field conditions was very low (8.3%) for standard germination and improved to 46.7% for accelerated‐aging germination and 56.9% for 4‐day germination. The prediction accuracy increased to 65.0% and 68.3% for the VR‐3 and VR‐1 vigor indices for the same comparisons. The VR‐1 index, using all three laboratory tests provided a better estimate of field emergence than either vigor index (VR‐2 and VR‐3) when only two tests were used. The prediction accuracy of the VR‐1 vigor index was approximately 25% higher than averaging the results of the same three tests. The vigor index concept offers the possibility of combining additional laboratory parameters that relate to seed and seedling vigor.