Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2007
Publication Date: 7/1/2007
Citation: Spencer, D.F., Lembe, C. 2007. Evaluation of barley straw as an alternative algae control method in a northern california rice field. Journal of Aquatic Plant Management. 45:84-90. Interpretive Summary: Algae grow in California rice fields where they may smoother seedlings or cause them to dislodge, resulting in yield loss. Barley straw has been identified as an effective method for reducing algal growth in a variety of aquatic systems in the United Kingdom. It appears to be effective against algal species similar to those that occur in California rice fields. As part of a search for alternative algal management strategies, we sought to determine if barley straw would reduce algal biomass during the crucial 30-day period of seedling establishment. To do this, we conducted field experiments in 2005 and 2006 in which barely straw was evaluated in plots within working rice fields. Measured water temperatures in both experiments were above the threshold for decomposition of the barley straw and production of the hypothesized growth-inhibiting chemical. However, compared to control plots, mean dry weight of algae was not affected by barley straw in either of the experiments. Thus we conclude that adding barley straw to a rice field does not reduce the abundance of algae present within the critical period when algal growth is most troublesome.
Technical Abstract: California rice fields are shallow water systems with depths usually less than 15 cm. Excessive algal growth often characterizes a significant proportion of them. Especially troublesome are species of green algae and cyanobacteria which interfere with rice growth by becoming entangled with the seedlings and subsequently uprooting them when the algal mats dislodge from the sediment. We sought to determine if barley straw would reduce excessive algal biomass during the crucial 30-day period of seedling establishment following initial flooding of the rice field. We conducted experiments in 2005 and 2006 in northern California rice fields. Algae dry weight varied considerably ranging from 0 to 286 g m-2. Relative to controls, mean dry weight of algae was not affected by barley straw in either of the experiments. Measured water temperatures in the 2005 and 2006 experiments were greater than the 20 C threshold for decomposition of the barley straw and production of a hypothesized growth-inhibiting chemical, for a considerable portion of the experimental period.