Submitted to: Applied Soil Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/8/2007
Publication Date: 9/24/2007
Citation: Carrera, L.M., Buyer, J.S., Vinyard, B.T., Sikora, L.J., Teasdale, J.R. 2007. Effects of cover crops, compost, and manure amendments on soil microbial community structure in tomato production systems. Applied Soil Ecology. 37:247-255. Interpretive Summary: Conventional vegetable production requires intensive tillage and expensive off-farm inputs such as pesticides, herbicides, fertilizer, and black plastic mulch. Pesticides and herbicides can contaminate the environment while fertilizer may contribute to excessive nutrient levels in nearby watersheds. Black plastic mulch can only be used once and then becomes a waste disposal problem. Alternative vegetable production systems have been developed that minimize tillage and depend, as much as possible, on on-farm inputs. A tomato production system developed at the USDA Beltsville Agricultural Research Center uses a hairy vetch cover crop to suppress weeds and provide nitrogen to the tomato plants. This system produces larger tomato plants, higher yields, and a longer growing season. Sustainable agriculture depends not just on inputs to feed the plants but on also the bacteria and fungi that naturally grow in the soil. Soil microbes provide essential ecosystem services, including nutrient recycling, suppression of disease-causing organisms, degradation of crop residues, and degradation of excess chemicals such as pesticides and herbicides. Unfortunately, we know very little about how agricultural management systems affect soil microbes. In this study we analyzed the soil microbes in a conventional tomato production system and in a number of alternative systems that used hairy vetch cover crop, poultry manure, or poultry manure compost. All systems used black plastic mulch except the hairy vetch system. Soil microbes were not affected by manure or compost, but all black plastic systems were significantly different from the hairy vetch systems. Apparently cover cropping and black plastic mulch produce different soil microbial communities. This work may lead to agricultural management systems with enhanced soil quality.
Technical Abstract: Soil microbial community structure was investigated in field tomato production systems that compared black polyethylene mulch to hairy vetch mulch and inorganic N to organic N. A randomized complete block design with four replicates was used. Treatments consisted of ammonium nitrate, hairy vetch cover crop, hairy vetch cover crop and poultry manure compost (10 t/ha), three levels of poultry manure compost (5, 10, 20 t/ha), and two levels of poultry manure (2.5 and 5 t/ha). Black polyethylene mulch was used in all treatments without hairy vetch. Soil samples were taken at five different periods during the growing season. Fatty acid analysis was used to characterize the total soil microbial community structure while two substrate utilization assays were used to investigate the community structure of culturable bacteria and fungi. In all cases, the seasonal effect was greater than the treatment effect. Soil microbial communities under hairy vetch and vetch plus compost were distinct from all treatments under black polyethylene mulch. There were no statistically significant effects due to nitrogen source.