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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Publications at this Location » Publication #388974

Research Project: Integrated Weed Management and Restoration Strategies to Protect Water Resources and Aquatic and Wetland Ecosystems of the Far Western U.S.

Location: Invasive Species and Pollinator Health

Title: Toward understanding the impact of nuisance algae bloom on the reduction of rice seedling emergence and establishment

item OHADI, SARAH - University Of California, Davis
item LAGUERRE, GUELTA - University Of California, Davis
item Madsen, John
item AL-KHATIB, KASSIM - University Of California, Davis

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2021
Publication Date: 1/1/2022
Citation: Ohadi, S., Laguerre, G., Madsen, J.D., Al-Khatib, K. 2022. Toward understanding the impact of nuisance algae bloom on the reduction of rice seedling emergence and establishment. Weed Science. 70(1):95–102.

Interpretive Summary: Elevated levels of either nitrogen or phosphorus in the water supporting sprouting rice seedlings will cause increased algal growth, resulting in a bloom. The presence of an algal bloom will reduce rice seedling emergence up to 90% and delay the time to seedling emergence. Uncontrolled algae growth will reduce rice yield and provide gaps in rice coverage that may allow other weed infestation.

Technical Abstract: California rice production has been recently challenged by the early season bloom of nuisance algae. The algal community in rice is a complex of green algae and cyanobacteria species that could develop a thick algal mat on the surface of the water and interfere with the emergence and establishment of rice seedlings. The objective of this research was to determine the impact of algae infestation level on rice seedling emergence. A mesocosm study was conducted in 57 L tubs. Three levels of algae infestation (low, medium, and high) were produced by adding fertilizer N:P amount into the tubs including 0:0, 75:35, and 150:70 kg-1ha. Sixty rice seeds (M-206) were soaked for 24 hours and spread into tubs filled with water. Photosynthetic Active Radiation (PAR), Chlorophyll a concentration as the quantitative measure of algae, number of emerged rice seedlings, and their dry biomass were studied during the experiment. Results showed that algae infestation can directly change the amount of light received into the water. Minimum, maximum and mean percentage of PAR inside the water declined by the increase of algae infestation level. As a consequence, rice seedling emergence dropped under the high algae pressure. At very high algae infestation (i.e. chlorophyll a concentration of above 500 ugml-1), rice seedling emergence reduced up to 90%. Furthermore, rice seedling emergence was delayed under algae infestation. When algae infestation was low, time to 50% of rice seedling emergence (t50) ranged between five and ten days, while at high algae infestation t50 ranged between twelve and twenty days. Moreover, individual rice seedling biomass reduced from one gram to 0.01 gram by the increase of algae infestation. The results from this study indicate that uncontrolled algae at the beginning of the rice-growing season could reduce rice seedling emergence, establishment, and rice stand. Given that algae infestation in field has a patchy pattern, loss of rice stand in these patches could provide empty niches for other weeds to grow.