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Publication Date
1981
Description
The acreage of stargrass and bermudagrass (Cynodon spp.) throughout tropical and subtropical regions has increased greatly. However, many Cynodons have a hydrocyanic acid potential (HCN-p) that may be toxic to livestock. The purpose of this study was to determine the HCN-p in fresh and hay samples of meristematic stem tips from nine Cynodon entries at different physiological stages of growth during the summer (19°-33°C) and autumn (11° -32°C). Two selected entries (Ona and UF-5 stargrass) were also separated into meristematic stem tips, leaves and sheaths, and nodes and internodes at different stages of maturity to monitor HCN-p, dry matter (DM), and percentage of whole plant contributed by plant components. Correlations were determined between HCN-p concentration and total solar radiation. All plant entries were staged at 7.5 cm and received 280, 25, and 93 kg/ha of nitrogen (N), phosphorus (P), and potassium (K), respectively, one week prior to commencement of summer and autumn studies. Significant differences in HCN-p concentration in meristematic stem tips were obtained among the nine Cynodon entries over a 2-year period. The HCN-p concentration basically followed either high or low levels. High-level HCN-p grasses averaged 407 and 529 ppm on a fresh-weight (FW) basis during summer and autumn, respectively; low-HCN-p grasses averaged 121 and 131 ppm FW. Average HCN-p concentrations were lowest for Calli bermudagrass (75 ppm) and highest for Puerto Rico stargrass (506 ppm). Entries decreased with maturity during summer, but during autumn HCN-p remained high until temperatures fell below freezing. After a freeze HCN-p decreased from 92 to 43 ppm and 78 to 25 ppm in high- and low-level grasses, respectively. Meristematic tips dried to 85 % DM decreased in HCN-p by 88 % and 78 % for high- and low-level grasses, when compared with fresh samples. Significant correlations (r = 0.56) were found between HCN-p and total solar radiation. Separating Ona and UF-5 grasses into plant parts for DM and HCN-p revealed similar DM levels in both grasses. However, HCN-p in UF-5 was consistently lower (P < 0.05) than HCN-p in Ona stargrass. The meristematic tips generally contained the highest (P < 0.05) HCN-p regardless of species. These data indicated differences (P < 0.05) in HCN-p concentrations between Cynodon entries that can be beneficial when managing tropical grasses.
Citation
Mislevy, P; Hodges, E M.; and Martin, F G., "Hydrocyanic Acid Potential in Stargrass (Cynodon spp.)" (1981). IGC Proceedings (1977-2023). 24.
(URL: https://uknowledge.uky.edu/igc/1981/section11/24)
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Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Hydrocyanic Acid Potential in Stargrass (Cynodon spp.)
The acreage of stargrass and bermudagrass (Cynodon spp.) throughout tropical and subtropical regions has increased greatly. However, many Cynodons have a hydrocyanic acid potential (HCN-p) that may be toxic to livestock. The purpose of this study was to determine the HCN-p in fresh and hay samples of meristematic stem tips from nine Cynodon entries at different physiological stages of growth during the summer (19°-33°C) and autumn (11° -32°C). Two selected entries (Ona and UF-5 stargrass) were also separated into meristematic stem tips, leaves and sheaths, and nodes and internodes at different stages of maturity to monitor HCN-p, dry matter (DM), and percentage of whole plant contributed by plant components. Correlations were determined between HCN-p concentration and total solar radiation. All plant entries were staged at 7.5 cm and received 280, 25, and 93 kg/ha of nitrogen (N), phosphorus (P), and potassium (K), respectively, one week prior to commencement of summer and autumn studies. Significant differences in HCN-p concentration in meristematic stem tips were obtained among the nine Cynodon entries over a 2-year period. The HCN-p concentration basically followed either high or low levels. High-level HCN-p grasses averaged 407 and 529 ppm on a fresh-weight (FW) basis during summer and autumn, respectively; low-HCN-p grasses averaged 121 and 131 ppm FW. Average HCN-p concentrations were lowest for Calli bermudagrass (75 ppm) and highest for Puerto Rico stargrass (506 ppm). Entries decreased with maturity during summer, but during autumn HCN-p remained high until temperatures fell below freezing. After a freeze HCN-p decreased from 92 to 43 ppm and 78 to 25 ppm in high- and low-level grasses, respectively. Meristematic tips dried to 85 % DM decreased in HCN-p by 88 % and 78 % for high- and low-level grasses, when compared with fresh samples. Significant correlations (r = 0.56) were found between HCN-p and total solar radiation. Separating Ona and UF-5 grasses into plant parts for DM and HCN-p revealed similar DM levels in both grasses. However, HCN-p in UF-5 was consistently lower (P < 0.05) than HCN-p in Ona stargrass. The meristematic tips generally contained the highest (P < 0.05) HCN-p regardless of species. These data indicated differences (P < 0.05) in HCN-p concentrations between Cynodon entries that can be beneficial when managing tropical grasses.
