Facilitating Integrated Weed Management in California Rice: Predicting E. spp. and C. difformis emergence across heterogeneous growing environments
The overarching goal of the proposed research is to develop a geographically and temporally sensitive decision support tool that predicts the minimum time required to achieve control of Echinochloa spp. and Cyperus difformis populations using alternative establishment management methods in California rice systems. Coupled with effective outreach, this tool will facilitate the planning and execution of weed control via management and enable wider adoption of alternative establishment approaches.
During the 2010-2011 season, we will conduct experiments at the farm scale in the Sacramento Valley that will produce in-field observations of weed emergence and temperature. These observations will be used to validate empirical emergence predictions and the accuracy of the spatially interpolation of temperatures across the region.
Our objectives for the upcoming field season are to:
1) Characterize the spatial distribution of physiological temperatures (thermal units) in the Sacramento Valley during the early season, using historical temperatures;
2) Test whether thermal units vary between locations as predicted by historical temperatures;
3) Test whether emergence models with lab-derived parameters can adequately predict weed emergence, using location-specific temperatures; and
4) Determine whether location-specific air temperatures predict weed emergence as effectively as block-specific temperatures recorded at the soil surface.
At this point we have identified three growers with historical populations of Echinochloa spp. and Cyperus difformis in their fields who are using alternative stand establishment techniques and will allow us to take temperature and emergence observations during the critical period for weed emergence.
We have begun to create maps of the distribution of physiological temperatures across the Sacramento Valley that are based on historical temperatures and lab-derived cardinal temperatures. These have guided our experimental design such that our field sites are at locations where predicted differences in physiological temperatures are most extreme. The temperatures recorded during the field season will allow us to validate these distribution predictions.
Impacts and Contributions/Outcomes
Most of the impacts of this project will depend on our ability to test and support the hypotheses that physiological temperatures are spatially and temporally heterogeneous in the Sacramento Valley, and that spatially and temporally explicit temperatures will improve the accuracy of an empirical emergence model. We are in the process of designing and preparing the experiments that will test and support these hypotheses.
In the meantime, the physiological temperature distribution map, produced from historical temperatures, is already providing useful information (see attached figure). For example, it appears from the historical distribution of temperatures that a grower south of the Sutter Buttes (a cooler region) might experience a one – two days delay in E. spp. emergence and four – five days delay in C. difformis emergence compared to a grower northwest of the Sutter Buttes (the warmest region).
- Spatially interpolated average thermal unit accumulation for a base temperature of 8.85C during the rice establishment period in the Sacremento Valley