Relationships Among Cottonseed Vigor and Emergence

Better predictive methods of field emergence of cotton (Gossypium spp.) seedlings are needed than are presently available. In this paper we report on two types of relationships for predicting seedling emergence. The first is the association between field emergence and a vigor term of germinating seedlings called % transfer (ratio of plant axis weight to total weight of seedlings). The second is the relationship between time to 50% total emergence (ET₅₀) and total emergence. Seed of diverse origin were germinated in the laboratory at 15 C for 8 days or at 25 C for 4 days and % germination, and % transfer were determined. Several field plantings were made, and periodic counts were made as seedlings emerged. The time course of germination of two lines that responded differentially in germination and field studies was examined by taking weights and seedling axis lengths repeatedly for 4 days at 25 C and 14 days at 15 C. Germination at 15 C for 8 days did not consistently predict field emergence better than germination at 25 C for 4 days. Some improvement occurred when germination parameters were averaged for the two temperatures. Combining % transfer with % germination into a term called “germination index” did not consistently aid in predicting field emergence over use of % germination alone, apparently because seed with high viability generally produced vigorously germinating seedlings. Percent transfer was negatively correlated with ET₃₀. Predictability of the germination parameters was improved by extending the length of the germination period. Total emergence decreased linearly with increase in ET₅₀. The average decrease ranged from just under 2% per day of ET₅₀ to over 4% when the test involved a salt-affected soil. We conclude that incorporation of these seed vigor terms into seed testing will not aid in predicting potential for cottonseed emergence. The relationship between emergence and ET₅₀ should serve as an aid in making early decisions about replanting, although the nature of the relationship will probably depend upon local soil conditions.