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Harmful algal blooms are increasing in size, duration, and intensity around the globe. For several decades, cereal straws have been recognized as a viable algal control. The objective of this study was to explore the relationship between algal growth in aqueous cultures and total phenolics and flavonoids after the addition of barley (Hordeum vulgare) and rice (Oryza sativa L.) straw decomposition extracts. Results showed significant inhibition by 5.0 g/L rice straw extract on both Microcystis aeruginosa, a cyanobacteria responsible for freshwater harmful algal blooms, and Raphidocelis subcapitata, a green alga. Results also showed that the overall extract concentration of either barley or rice straw might be more important for the inhibition of green algae, whereas the particular compounds released during the decomposition of rice straw may be more important for cyanobacterial inhibition. However, more specific identification of flavonoids and phenolic compounds should be conducted to determine their inhibitory role(s). [ABSTRACT FROM AUTHOR]

In response to increased public scrutiny of rice straw burning after harvest, research was initiated to determine how post-harvest residue management impacts readiness-toplant. The objectives of the study were to: 1) determine how different combinations of burning and/or flooding and nitrogen (N) fertilization impact residue decomposition, and 2) quantify readiness-to-plant the following spring. The study was conducted on two 40-acre fields on a farm near McGehee, Arkansas. The management treatments were: burned/flooded, burned/non-flooded, unburned/flooded, and unburned/non-flooded each with and without additional N fertilizer application. The fertilizer was added to promote decomposition of the residue. Initial findings from the Fall 2017 to Spring 2018 decomposition period suggest that flooding reduces residue by an additional 20% by the spring, but not nearly to the extent that was attained by burning alone. The final residue of the unburned plots were 4.2 and 2.5 times larger than burned plots for nonflooded and flooded treatments, respectively. Our findings suggest that burning straw residue is still the most effective strategy to manage straw residue after harvest. Year 2 of this two-year study is underway. [ABSTRACT FROM AUTHOR]