Comparing the effects of chemical and organic fertilization on soil quality, plant productivity and insect pest incidence in tomato cropping systems

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Non efficient use of chemical fertilizers can increase the susceptibility of plants to insect pests, cause groundwater contamination due to nitrate leaching, and result in emissions of nitrous oxide, a potent greenhouse gas. On the other hand, organic fertilization practices add organic matter to the soil, improving its structure, aeration and water retention, and promoting soil microbial activity and a slow release of nutrient. As a result organically-fertilized fields show reduced pest populations compared to conventionally-fertilized ones.

The overall goal of this project is to understand how soil fertility management may affect soil quality as well as plant health and may therefore affect insect pest abundance, using tomato as a teste crop in the coastal area of northern California. We are particularly interested in comparing the short-term and long-term effects of chemical versus organic fertilization (composts and compost teas) on soil physico-chemical characteristics, soil microorganisms, plant quality, crop yield and densities of several insect pests and in determining the relationships between soil fertility, crop nutritional status and insect pest incidence. The proposed research will benefit vegetable growers interested in implementing ecologically-based pest management strategies, which will allow them to reduce fertilizer use and costs while keeping high yields, maintaining soil health and fertility as well as minimizing environmental impacts. (Collaboration with M. Altieri, UC Berkeley)

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