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Weather and Seed Quality Variables to Predict Cotton Seedling Emergence

Univ. of California Coop. Ext., 17053 Shafter Ave., Shafter, CA 93263

S. Johnson

Univ. of California Coop. Ext., Tulare County, County Civic Center, Agric. Bldg., Visalia, CA 93291

^* Corresponding author.

Emergence of cotton (Gossypium hirsutum L.) seedlings was related to seed quality and temperatures following planting in a 3-yr field study at Shafter, CA. Environmental conditions for seed production were selected to provide a broad range in seed quality. Seed quality, as determined by the standard germination test and the cool test, was combined with heat units (HU) after planting for predicting field emergence percentage. A total of 74 seed lots (11 in 1984, 39 in 1985, and 24 in 1986) were planted at two different dates, and emergence of 100 seed from each of four replications evaluated. Warm germination percentage (W%) was measured at 30 °C, and ranged between 25 and 90%, cool germination (C%) was measured at 18 °C, and ranged between 1 and 88%, and field emergence percentage ranged from 5 to 98% in these studies. Multiple regression was used to determine the degree of association between variables. Predicting field emergence with C + W% was better than either component alone (r² = 0.352 for n = 148). The HU (base 60 °F) for 5 or 10 d after planting explained as much variation in field emergence as seed quality (r² = 0.348 and 0.365), but HU 15 d after planting were not related to field emergence. When HU 5 d after planting, C + W% percentage, and the interaction between the two were considered in multiple regression, 68.5% of the variation in field emergence was explained. With 10 HU 5 d after planting there was a linear increase in field emergence percentage as C + W% increased, but at 25 HU, seed with C + W% of 110 had as many seedlings emerge as lots with C + W% of 175. Eliminating seed lots with warm germination percentages less than 80 from these regressions did not alter the predicted values for field emergence within the range of the data, but did reduce the statistical significance of the relationship. The HU for 5 d can be forecast on the National Oceanic and Atmospheric Administration's (NOAA) weather radio with reasonable accuracy in the San Joaquin Valley of California. If temperatures can be forecast accurately in other regions, cotton growers can adjust seeding rates and plant to a desirable stand, if warm and cool germination percentages of planting seed are known.

Received for publication January 25, 1988.

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