Agroecosystems Lab

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Fertilizer phosphorus by weed interactions in rice systems

Herbicide resistance weeds are a major problem confronting the long-term sustainability of California’s rice-based systems. Research is testing stale seed bed and no-till management practices to control these weeds. Initial on-station results have shown that rice yields can be maintained while at the same time affording environmental (water quality) and economic benefits due to reduced tillage and less herbicide inputs. Key issues that need to be addressed before these systems can be extended to growers are: first, for the stale seed bed, it is critical to know the temperature and duration of soil wetness required to induce germination of different weed species. Second, these systems will require a change in the timing and mode of fertilizer application-especially P. In order to address these issues we are proposing a combination of pot experiments followed up with on-farm field validation. Results will be used to develop best management practices for these systems.

Project Goals and Outcomes
The purpose of this project is to address the knowledge gaps in these novel stale seedbed and no-till rice systems which will allow for the extension of these systems to growers fields. The major gaps in these systems are a good understanding of the water and temperature requirements for the germination of specific rice weeds and P management. The specific objectives are as follows:
  1. To develop hydrothermal time models for the major rice weed species in California. This will culminate with a web-based calculator which can be used by growers to determine how long their fields need to be kept moist.
  2. To compare the fall versus spring P applications on soil P availability and access the affect of fall P applications on weed, algae growth, and surface water P concentrations.
  3. Use the information collected to develop the best management practices for these systems and extend the results of project to rice growers.