US EPA

6558721 

Book/Book Chapter 

The Use of Sustainable Soil Management Practices in Fumigated and Non-fumigated Plasticulture Strawberry Production in the Southeastern United States 

Mcwhirt, AL 

2016 

ProQuest Dissertations Publishing 

Conventional strawberry growers in the southeastern United States rely on soil fumigation as a critical component of their annual production cycle as a means to eliminate soil organisms that inhibit plant growth and crop production. This practice limits soil health in strawberry production systems due to the elimination of beneficial soil organisms. Soil health is further limited in these systems by low organic matter inputs and high erosion potential when fields sit fallow during the summer months between cropping seasons. The use of compost, cover crops and soil inoculation with beneficial soil microorganisms has been shown to improve soil health; however, there is a lack of understanding of how these practices might promote soil health within fumigated strawberry production systems. To answer this question a two year strip-plot field study at the Center for Environmental Farming Systems (CEFS) in Goldsboro, NC evaluated soil management practices (compost, summer planted cover crops and the addition of vermicompost and arbuscular mycorrhizal fungi (AMF) to the strawberry plug media (plug inoculation)) applied individually and in various combinations in both Pic-clor 60 fumigated and non-fumigated plasticulture production systems. The effects of these soil management combinations on strawberry yield, fruit quality, plant growth, plant nutrient uptake, arthropod populations in the plant canopy and soil chemical, physical and biological properties were evaluated. Similar marketable yields were observed in the fumigated and non-fumigated main treatments in both years. Fruit shelf life was higher in the fumigated system, but fruit quality attributes including fruit soluble solids (SSC), pH and SSC/titratable acidity were higher in the non-fumigated system during the second year. In both years, AMF introduced via the plug inoculation treatment into the fumigated system failed to establish, which suggests that even after the plant back period introduced live inoculum is impacted by fumigation. At the end of the second year fumigation resulted in higher soil bulk density and reductions to several phospholipid fatty acid (PLFA) soil microbial biomarkers. In both years cover crop treatments had higher total yields in the fumigated system relative to the non-fumigated system, and the combination of compost and cover crops in the non-fumigated plots yielded similarly to the fumigated control. Other effects of soil management practices on yields varied. Marketable yields in the plug inoculation treatment were higher in the non-fumigated system in year 1, but total and marketable yields for this treatment were higher in the fumigated system in year 2. The combination of compost and cover crops supplied sufficient pre-plant nitrogen to the strawberry crop in both years and compost resulted in higher measures of several soil fertility indicators (pH, and cation exchange capacity) across both the fumigated and non-fumigated systems. Within the fumigated system compost also resulted in higher measures of AMF PLFA biomarkers and all soil management practices had higher total PLFA microbial biomass relative to the fumigated control. A separate greenhouse experiment was conducted to compare the live microbial effects of AMF and vermicompost on population growth rates of Tetranychus urticae (two-spotted spider mites), plant growth, and leaf area for three strawberry varieties. Bottom-up effects of the soil microbes present in the inoculants were variable across varieties; in some cases the microbes were shown to suppress mite population growth and in others to promote T. urticae populations. AMF root colonization was lower on plants when T. urticae were present, which suggests a top-down effect of an arthropod on a soil microbial symbiont. Our results demonstrate soil management influence on multiple aspects of the production system, which may help growers evaluate the short-term benefits of sustainable soil management practices based on their system of soil fumigation. 

Horticulture; Soil sciences; (2016)