PARENT SESSION
Oral Session #60: Agroecology- Sustainable Agriculture.
Presiding: R. Bohanan
Wednesday, August 7. 8:00 AM to 11:30 AM. Mesquite Room, Radisson.
Integrating water fowl activity and rice straw management .
van Kessel, Chris*,1, van Groenigen, Jan-Willem1, Burns, Ed2, Eadie, John2, Horwath, William3, 1 Dept. of Agronomy and Range Science, Davis2 Dept. of Wildlife, Fish and Conservation Biology, Davis3 Land, Air and Water Resoures, Davis
ABSTRACT- Conversion of natural wetlands into agricultural lands has considerably reduced important waterfowl habitat in many regions of the world. Rice fields that are winter flooded to increase residue decomposition may offer valuable substitute foraging habitat. This study quantifies the agronomic benefits of foraging waterfowl in winter flooded rice fields in the Sacramento Valley in California. Fifteen winter flooded rice fields were selected along a 105 km long transect throughout the rice-growing region. In each field, 5 pairs of waterfowl exclosures and control plots were established. Residue decomposition was measured in spring, weed pressure in mid-season, and weed biomass and grain yield at harvest. The presence of waterfowl resulted in a significant decrease in remaining residue in spring from 1233 to 1014 kg per ha across the transect. At the seven sites with highest observed waterfowl activity, remaining residue decreased from 1549 to 836 kg per ha. Midseason weed ratings for the seven sites with highest waterfowl activity showed an increase of weed coverage from 20 to 30% in the presence of waterfowl. At harvest, average grassy weed biomass increased from 44 to 91 kg per ha over the whole transect in absence of waterfowl. For the seven sites with the highest waterfowl activity the grassy weed biomass more than doubled, from 89 to 204 kg per ha. During this study, no significant yield effect could be detected. We conclude that winter flooding rice fields results in mutual benefits for waterfowl and agriculture. Foraging waterfowl increase residue decomposition and decrease weed pressure, decreasing the cost of farmer operations. These advantages could be of particular significance in organic farming systems, where use of pesticides is prohibited. Winter flooding rice fields might lead to similar mutual benefits in other temperate-zone rice systems, such as in the Mediterranean and Japan.
KEY WORDS: waterfowl foraging, waterfowl habitat, rice sustainability, conservation