Helen Atthowe, Biodesign Farm
Alex Stone, Oregon State University
This article is part of the Biodesign Farm Organic System Description
Biodesign Farm evolved management strategies that optimized soil organic matter and soil fertility while implementing good cultural practices to minimize the need for pesticides (Table 1). Practices included:
The semiarid climate of Biodesign Farm also contributed to low disease risk. Precipitation is only 13–16 inches and occurs mainly in winter, fall, and early spring.
According to Helen, yield and quality losses to disease declined over 17 years, especially those resulting from tomato bacterial speck. This observation is supported by crop quality monitoring records (1994–2010).
No pesticides were used to manage diseases at Biodesign Farm.
Biodesign Farm's rotation developed around market opportunities and emphasized solanaceous crops. Table 2 and Table 3 show the rotation history. The main focus was a rotation of plant families and crop nutrient needs. The general 3-year rotation for each row was as follows:
Because the field was small, solanaceous crops often abutted and occasionally overlapped. The clover row middles rotated from year to year and also figured into the rotation, but not in a carefully planned manner.
Biodesign also utilized practices targeted to specific crops and disease life cycles (Table 4):
Biodesign's soil-building system was designed to build high organic matter soils with a diverse and healthy soil microbial community. High-nitrogen (N) and lower carbon (C) soil amendments were applied in early years in Old field (1993–1996); higher C amendments were applied in later years. By 1999, manure-based compost rates had been reduced significantly, as mowed living mulch residues became more important (Table 2). In New field, Helen used higher C/lower N amendments from the start (Table 3).
Soil test records indicate a rise in soil organic matter (Soil Fig. 1) and, after 1996 in Old field, a decreasing trend in soil nitrate-N (Soil Fig. 3). Analysis of soil microbial population density in 1995 and 2007 showed relatively high levels of total microbial biomass and arbuscular mycorrhizal fungi. Some level of biological control may have been generated by the farm's soil amendments and soil-building practices, since damage from disease decreased over time.
In the beginning (Old field), drip irrigation was used almost exclusively to avoid wetting tomato foliage and minimize the environmental conditions that favor tomato bacterial speck. Some sprinkler irrigation was used to keep the living mulch row middles irrigated. By 2000, Biodesign was using both sprinkler and drip irrigation in Old field to irrigate all crops, including tomatoes. In New field (2005–2010), mostly sprinkler irrigation was used because the source was a gravity-flow, surface-water system (thereby eliminating energy costs). In New field, disease pressure was low, so disease avoidance was not the main priority when making irrigation decisions.
Disease may have been suppressed by Biodesign's design and soil/habitat-building practices, since in later years diseases occurred at relatively low levels. See the eOrganic video: Organic No-Till Living Mulch Disease: Weed Em and Reap.
Biodesign's goal was to build high organic matter soils with a diverse and healthy soil microbial community. Analysis of microbial population density in Biodesign soils during on-farm experiments in 1996 and 2007 showed relatively high levels of total microbial biomass and arbuscular mycorrhizal fungi. There is some evidence to support Biodesign's hypothesis that microbes in healthy soil increase resistance to cucumber mosaic virus (Zehnder et al., 2000; Ryu et al., 2004; Elsharkawy et al., 2012). Aphid suppression may also have played a role. See Insect Management System.
This article was developed with support from USDA's National Institute of Food and Agriculture through the Western Sustainable Agriculture Research and Education program under grant number SW13-017.
This article is part of the Biodesign Farm Organic Systems Description.
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