Location: Contaminant Fate and Transport Research2010 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.
3. Progress Report
Deterioration of soil, water and air resources by soil fumigants represents a serious threat to agricultural production in semi-arid regions due to their high volatility and high emission rates. New pest control methods are needed that do not rely on fumigant chemicals. Soil heating via solarization has been proposed as a non-chemical alternative to soil fumigation, but has not found wide acceptance due to limitations in soil temperatures and heating depth, especially in cooler environments. A new soil heating method is proposed, termed active solarization, to increase soil temperature and heating depth in the root zone. An experiment was conducted to compare heating for bare soil, standard (i.e., passive) solarization and active solarization methodologies. A cumulative heat stress index, CHT30, was computed and has been shown to be related to plant–pest survival. After 15 days of heating, passive solarization increased CHT30 at 10 and 20 cm depths by 263 and 65 oC h, respectively, compared to leaving the soil bare. For active solarization, CHT30 increased, respectively, 387 and 105 oC h compared to bare soil. After 30 days of passive solarization, CHT30 at 10 and 20 cm was 345 and 66 oC h, respectively, and for active solarization CHT30, was 755 and 252 oC h. The results indicate that active solarization increases soil temperatures and heat stress on plant pests. Based on published pest survival information, observed CHT30 after active solarization would provide better control of a plant pest (nematode) compared to passive solarization. Active solarization may offer a suitable non-chemical alternative to soil fumigation and may help growers in areas where restrictive regulations on soil fumigation are being adopted. Research progress was monitored throughout the year from regular individual and group meetings, phone conversations, laboratory visits and email correspondence.