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Combining Compost Application and Soil Solarization for Control of Soilborne Plant Pathogens

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  032264,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.14969) @2003
Authors:   Megan N. Marshall, Jean S. VanderGheynst
Keywords:   Bioreactors, composts, microbial activity, oxygen, organic farming, pest control, plant pathogens, plastic film, self-heating, soil solarization, waste utilization

In soil solarization, moist soil is covered with transparent plastic tarps, resulting in passive solar heating of the soil and a pasteurization effect, which reduces plant pathogen populations without the use of chemical pesticides. By combining compost application and soil solarization, there is the added benefit of utilizing organic wastes and the potential for decreasing the duration of solarization treatments. Compost stimulates microbial activity in the soil, which may lead to heat generation by aerobic microorganisms, higher soil temperatures, and thus more rapid thermal inactivation of pathogen populations.

The objective of these initial laboratory studies was to assess the potential for compost incorporation to produce higher soil temperatures during solarization. These studies were carried out using insulated 1-L bioreactors, which were placed in an incubator to approximate diurnal soil temperature fluctuations typically achieved during solarization. Bioreactors were filled with soil mixed with compost substrates at various loading rates (0, 2% (v/v), or 10% (v/v)). Oxygen was supplied to bioreactors through humidified airflow or by diffusion through a piece of solarization plastic. Temperatures in aerated bioreactors with compost substrates were up to 3-10 C higher than bioreactors with soil alone. Increased respiration in aerated bioreactors with compost substrates suggested that increased temperatures were related to increased aerobic microbial activity.However, the temperature of bioreactors receiving oxygen by diffusion through solarization tarp was not greater when soil was amended with compost substrates.

These results show the potential for compost addition to increase soil solarization temperatures by increasing aerobic microbial activity, if sufficient oxygen is available. Future experiments will focus on variables that influence soil oxygen content during solarization, such as soil moisture content, compost loading rate, and compost stability. New bioreactors are under construction that will provide oxygen to the soil only by diffusion through solarization plastic, will measure temperature more accurately using thermistor probes, and will characterize the oxygen limitation by measuring redox potential in soil and oxygen concentration in headspace.

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