Wet-Dry Cycle Effects on Warm-Season Grass Seedling Establishment

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Abstract
A series of 14-day field experiments were conducted to evaluate seedling establishment characteristics of Bouteloua, Eragrostis, and Panicum grass species with controlled wet-dry watering combinations. The objective of the study was to validate previously published greenhouse data of Frasier et al. (1985) on the effects of the first wet-dry watering sequence following planting on seedling emergence and survival. Seedling survival numbers were different between the field and greenhouse experiments but the same general responses to watering sequences were measured. With short wet periods (2 days), seeds generally did not germinate but survived the subsequent dry period as viable seeds. Most seeds germinated with 5 wet days and produced seedlings that were able to survive drought periods of 5 to 7 days. Fewer seedlings survived with 3 days wet than with either 2 or 5 days wet. High rates of soil moisture evaporation in a spring field experiment made it difficult to maintain adequate soil moisture for seed germination, and seeds which germinated failed to produce seedlings. Seedlings were successfully established in 2 experiments conducted later in the summer following the onset of summer rains, which increased the relative humidity and reduced the rate of soil moisture evaporation. This effect was verified in a greenhouse study. In both the greenhouse and field experiments, seedlings were established when the relative humidity exceeded 50% for over one-half of the time during the initial wet-dry period.