Author
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Burke, John |
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Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/8/2002 Publication Date: 5/20/2003 Citation: Burke, J.J. Sprinkler-induced flower losses and yield reductions in cotton. Agronomy Journal. 2003. V. 95, P. 709-714 Interpretive Summary: Cotton pollen is hypersensitive to water and rapidly uptakes water to the point at which the pollen grain ruptures and dies. This study evaluated the effects of sprinkler irrigation on flower shedding and yield reductions of cotton grown in the High Plains of Texas. Evaluations of the timing of sprinkler application on flower losses showed that as the flower opened and pollen dehiscence occurred contact with water from the sprinkler destroyed the pollen and flowers were subsequently shed from the plant. Irrigation between 8 am and 10 am showed no loss in flowers beyond that of cotton irrigated using drag socks to apply the water to the soil surface. Sprinkler irrigation between 10 am and 12 pm showed increasing numbers of flowers shed and sprinkler irrigation between 12 pm and 4 pm resulted in a loss of 80% of open flowers. Approximately 50% of the flowers open on the day of sprinkler irrigation were lost. Sprinkler irrigation application twice a week during peak flowering resulted in a 12% reduction in yield in 2 to 3 bale per acre cotton, and 27% to 36% reductions in 0.5 to 1 bale cotton. If sprinkler application of water is necessary, then applications should occur during the night and early morning hours when flowers are closed. Technical Abstract: Cotton pollen is highly sensitive to water, rupturing within 1-2 minutes of contact. Greenhouse cotton was grown for 120 d under natural light conditions (28 ± 5*C air temperature). Flowers were sprayed with known volumes of water to determine how much was needed to reduce yield. These studies showed that a single spray with 1 ml of water reduced seed set and lint development by 55%. Additional spray applications resulted in further losses and ultimately flower shedding. Field studies in 2000 and 2001 used a center pivot equipped with sprinklers and drag socks to determine the effect of timing and water application methods on flower losses and yield reductions. Treatments included four different times of day applications (8 a.m. to 10 a.m., 10 a.m. to noon, noon to 2 p.m., and 2 p.m. to 4 p.m.) with 77 cubic meters of water. The plots were irrigated 8-times from August 1 to September 1, 2000 and 11 times from July 10 to August 21, 2001. Flowers were tagged immediately before irrigation and tracked for the rest of the season. No significant differences in flower losses between the sprinkler and drag sock treatments were observed in the 8 to 10 a.m. treatment; however, flower losses progressively increased under the sprinkler treatments compared to the drag sock treatments as the day progressed. Maximum flower losses occurred in the 2 p.m. to 4 p.m. treatments. The time course of sprinkler-induced flower losses tracked the opening of the flower and dehiscence of the pollen. Evaluation of seasonal lint yields showed a 21% reduction in 2000 and 11% yield reduction in 2001 under sprinkler irrigation compared with drag sock irrigation. The results of this study emphasize the need to use production practices that limit water contact with open cotton flowers. |
