2012 Annual Report
1a.Objectives (from AD-416):
Conduct research to develop new and improved methods to manage pesticides and other organic agricultural chemicals to maintain healthy agricultural systems. Study the fate and transport of agricultural chemicals and investigate the effect of various soil and environmental processes that affect chemical movement in soil. Conduct research that provides "real-world" solutions to improve efficacy, reduce cost and foster a healthy environment. Develop new low-cost management approaches that minimize volatile emissions to the atmosphere, and transport to surface water and ground water.
1b.Approach (from AD-416):
An experimental site will be developed in Field 2B (UC-Riverside AgOps) to test the effectiveness of using solar heat pulsing to sterilize soils in preparation for planting various specialty crops. The experimental design will include standard 40” raised beds and have a bare-soil control and three solarization treatments with three replicates. Soil temperatures and heat flux throughout the raised-bed will be measured for several weeks. Various meteorological measurements will be made to allow determination of the solar energy input to the experiment. Several plant pests will be placed in the beds, be subjected to solarization for 4-6 weeks and then assayed for survival. After the solarization period, the plots will be fumigated with approximately 40% and 70% of the standard rate of Telone Inline to determine if pest control improvement occurs. The experiment will also include a negative control (no solarization, no fumigation) and standard fumigation treatments. Once the data is available, a modeling study will be conducted to investigate the heat transport and fate and transport of fumigant chemicals in the soil beds.
Soil fumigation is an important component of U.S. agriculture but excessive emissions can be problematic. The objective of this study, which is related to objective 1 of the parent project, "Measure and model mechanisms and processes that affect exchange of pesticides between soil, water, plants and air", was to determine the effects of agricultural films (e.g., tarps) on atmospheric emissions of soil fumigants, the soil distribution, and plant pathogen control in the field using plastic films with varying permeability and thermal properties. A reduced-rate of 70% Telone Inline (61% 1,3-dichloropropene and 33% chloropicrin) was applied via drip irrigation to raised soil beds covered with standard high-density polyethylene film (HDPE), thermic film (Thermic), or virtually impermeable film (VIF). Fumigant emission rates were determined using dynamic flux chambers and the concentrations in soil were measured using a gas sampler. The pest control efficacy for the three treatments was determined using bioassay muslin bags containing soil infested with citrus nematodes (Tylenchulus semipenetrans). The results show that the Thermic treatment had the highest emission rates, followed by the HDPE and VIF treatments and the soil concentrations followed the reverse order. In terms of pest control, covering the beds with Thermic film led to sufficient and improved efficacy against citrus nematodes compared to standard HDPE film. For the HDPE treatment, more than 20% of nematodes survived in the soil at 30 cm depth. The VIF treatment substantially reduced the emission loss (2% of the Thermic and 6% of the HDPE treatments) and eliminated plant parasitic nematodes because of its superior ability to entrap fumigant and heat within soils. The findings imply that not only the film permeability but the synergistic ability to entrap heat should be considered when developing new improved films for fumigation.