Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/1/2010
Publication Date: 1/31/2011
Citation: Yates, S.R., Ashworth, D.J., Yates, M.D., Luo, L. 2011. Active solarization as a nonchemical alternative to soil fumigation for controlling pests. Soil Science Society of America Journal. 75(1):9-16. Interpretive Summary: The concern over fumigant emissions and toxicological risks has led investigators to search for non-chemical pest control alternatives. For example, soil heating (e.g., solarization), is based on observations showing that many pests are sensitive to prolonged exposure to high temperatures. Several studies indicate that soil temperatures in excess of 40oC for several tens of hours are required to achieve adequate control. Current solarization methods can be classified as passive possesses since soil heating is accomplished from direct input of solar energy and the energy is then transported into the soil via passive thermal diffusion. Success using this approach relies heavily on factors that affect soil heating, such as soil structure, color, soil moisture, air temperature and solar radiation. A new method to improve soil heating, termed here solar heat pulsing, uses solar energy to heat recirculated irrigation water prior to delivery to the soil via a drip irrigation system. This approach is analogous to solar heating systems for residential pools. The method uses common agricultural materials and technology, requires negligible additional energy and has the ability to provide soil heating in a targeted manner. A pilot study was conducted to test the effectiveness of solar heat pulsing to heat soil. The cumulative environmental heat stress index was used to measure pest-control performance. While preliminary, the results are encouraging and indicate that solar heat pulsing might provide an additional non-chemical pest control methodology that would be more suitable for cool weather climates than standard solarization. Users: Strawberry commission, vegetable commodity croups, growers, scientific community.
Technical Abstract: Deterioration of soil, water, and air resources by soil fumigants represents a serious threat to agricultural production in semiarid 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 nonchemical alternative to soil fumigation but has not found wide acceptance due to limitations in soil temperatures and heating depth, especially in cooler environments. We have developed a new soil heating method, termed active solarization, to increase the 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 d of heating, passive solarization increased at the 10- and 20-cm depths by 263 and 65°C h, respectively, compared with leaving the soil bare. For active solarization, CHT30 increased by 387 and 105°C h,respectively, compared with bare soil. After 30 d of passive solarization, CHT30 at 10 and 20 cm was 345 and 66°C h, respectively, and for active solarization CHT30 was 755 and 252°C h. The results indicate that active solarization increases soil temperatures and heat stress on plant pests. Based on published pest survival information, observed CHT30 aft er active solarization would provide better control of a plant pest (nematode) than passive solarization. Active solarization may offer a suitable nonchemical alternative to soil fumigation.