Effects of Selected Soil Amendments and Mulch Type on Soil Properties and Productivity in Organic Vegetable Production

Abstract

The potential benefits of different types of soil amendments and mulch ground covers on soil chemical and biological properties, crop development and yield, and disease and pest issues in organic vegetable production, as represented by legume (green snap bean), cucurbit (green zucchini squash), and brassicaceous (turnip) vegetable crops, were evaluated in a two-year field trial in Maine, USA. Soil amendments evaluated (following an initial fertilizer base) included a commercial organic fertilizer alone, composted dairy manure, compost plus fish meal, and compost plus Wollastonite, a natural source of silicon (Si). A paper mulch was also compared with a woven polypropylene fabric mulch for their performance and effects as weed barriers within these systems. Mulch type significantly affected soil properties, with the fabric mulch associated with increases in soil moisture, organic matter, and other soil chemical and biological properties relative to the paper mulch. The fabric mulch also resulted in earlier emergence and earlier harvests for bean and zucchini. Soil amendments affected soil properties and crop growth and yield of bean and zucchini, with compost amendments increasing soil pH, organic matter, and several nutrient concentrations, as well as crop emergence and yield relative to a fertilizer-only treatment. Compost treatment also reduced the infestation and damage caused by mites on beans in 2018. Addition of fish meal increased most nutrient element concentrations and microbial respiration, and Si amendment increased emergence of beans, and reduced powdery mildew on squash and late season browning of beans. These results help define specific management practices to improve organic vegetable production and provide useful information and options for growers.