Time of Planting and Diurnal Soil Temperature Effects on Cotton Seedling Field Emergence and Rate of Development
- J. J. Steiner * and
- T. A. Jacobsen
Cotton (Gossypium hirsutum L.) is often planted in early spring before climatic conditions are optimum for seed germination and seedling development. The objective of this study was to determine, in the field, the effect of time of day and cool-temperature stress from naturally varying soil temperature at a time of planting and following planting on seedling emergence (EMER) and seedling rate of development index (SRDI) for cotton. Seeds of two cultivars (GC-510 SJ-2) were planted at 0800 and 1600 h three days a week for 9 wks beginning 24 Feb. 1988 and ending 13 April. Emerging seedlings were counted and ranked according to their stage of development three times a week for 14 wk. Regression analysis was used to determine the time periods when EMER and SRDI were most sensitive to soil temperature. EMER was more sensitive to cool temperature stress when planted at 0800 than at 1600 h during the initial 100 h after planting. The most critical periods of stress for the two cultivars were the same (0800 and 1600 h planting times = +53 and +143 h from planting, respectively. GC-510 EMER was more sensitive to cool soil temperatures during the initial 100 h after planting than SJ-2. for both cultivars planted at 1600 h, EMER was similarly sensitive to cool soil temperature at 160 h after planting, a sensitive period not previously described. For neither cultivar was EMER influeced by day-of-planting heat units. Time of planting had no effect on SRDI values. GC-510 SRDI was less-tolerant of cool soil temperature than SJ-2 during the initial 30 h from planting (most sensitive at +2 and −6h from planting for 0800 and 1600 h plantings, respectively), but then relatively unaffected by soil temperature. SJ-2 SRDI was sensitive to cool soil temperature for nearly the entire 160-h period from the time of planting (most sensitive to cool soil temperature at + 91 and + 138 h after planting for 0800 and 1600 h plantings, respectively). There was no relationship between EMER and SRDI. Cultivars differed in response to cool soil conditions at planting. When cool soil temperature conditions are expected, rapid and high cotton emergence in the field may be achieved by choosing a suited cultivar and by planting in the afternoon.
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