Waterfowl break down straw: Study


Your story on rice straw and duck clubs is full of interesting detail, and I really enjoyed reading it.

Something not mentioned in the article is that migratory waterfowl are quite effective at breaking down rice straw. A few years ago, a graduate student at UC Davis under the supervision of me and Dr. John Eadie (an expert on migratory birds) conducted a study at our campus rice facility with mallard ducks following rice harvest.

We set up small flooded basins with and without ducks. The birds were placed in the basins each day over a period of several weeks at stocking densities (birds per acre per season) similar to what has been observed in the Sacramento Valley. The birds acted like little roto-tillers and quickly pulverized the straw. In the basins from which the ducks had been excluded, the straw was slow to break down, even though presumably the same microbes and insects were present in the soil.

We were not very surprised at the result, nor were any of the rice farmers who learned of this. But the effect had not been quantified before due in part to the difficulty of conducting this kind of study in a natural setting. It took a couple of Aggie soil scientists to think of doing it with captive birds (raised for us by two 4-H families) in plots such as one would use to test fertilizers.

This work was reported in the Journal of Applied Ecology. (J.A. Bird, G.S. Pettygrove, and J.M. Eadie. 2000. The impact of waterfowl foraging on the decomposition of rice straw: Mutual benefits for rice growers and waterfowl. J. Applied Ecology 37(5):728-741)

The student's name is Jeff Bird. He has gone on to fame in the field of soil science.

G. Stuart Pettygrove, Ph.D.
Cooperative Extension Soils Specialist
Department of Land, Air & Water Resources
University of California

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