Effects of selected soil amendments and mulch type on soil properties and productivity in organic vegetable production

Authors: Larkin, Robert - Bob

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2020
Publication Date: 6/3/2020
Citation: Larkin, R.P. 2020. Effects of selected soil amendments and mulch type on soil properties and productivity in organic vegetable production. Agronomy. 10:795. https://doi.org/10.3990/agronomy10060795.
DOI: https://doi.org/10.3390/agronomy10060795

Interpretive Summary: Successful sustainable organic vegetable farming faces many production challenges, from maintaining adequate soil health and fertility, and management of weeds, pests, and diseases, to balancing multiple different vegetable crops. Compost amendments provide needed organic matter and nutrients for improving soil and crop health, but additional organic sources of readily-available nutrients needed by crops may be useful for optimizing vegetable production. Weed management is also critical and alternatives to the use of plastic mulch are needed. In this research, the potential benefits of different types of soil amendments and mulch ground covers on soil properties, crop development and yield, and disease and pest issues in organic vegetable production, as represented by green snap bean, zucchini squash, and turnip vegetable crops, were evaluated. Soil amendments 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. Fabric mulch provided improvements over paper mulch for soil moisture, organic matter, and nutrient concentrations, as well as earlier emergence and harvests. Compost amendments improved soil pH, organic matter, and nutrient concentrations, as well as crop emergence and yield compared to fertilizer-only treatments. Fish meal increased soil nutrient concentrations and Si reduced powdery mildew and browning on beans. These results help define specific management practices to improve organic vegetable production and provide useful information and options for growers.

Technical 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 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. 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.