July 2020

A soil amendment is any chemical, biological or physical material added to the soil to support crop growth, as well as providing other potential benefits like erosion control. And why are biological soil amendments of concern? They can carry pathogens from fecal matter or other animal origins. Understand and manage risks when applying manure, compost, fish emulsion and agricultural teas, and feather, bone and blood meal to crops that are typically consumed raw.

Below are tips for handling biological soil amendments in crops that are typically eaten raw (such as lettuce, tomatoes, radishes, etc.) to reduce risks to human health.

First, generally assess the soil amendments in use on your farm:

• What type of amendment(s) are you using and where do you keep them?
• Which crops receive amendments? Are the crops typically consumed raw?
• When and how are amendments applied?
• How much is applied and is it according to the label?

Then, put practices in place to minimize risks:

1. Ensure biological soil amendments have been treated and tested to meet the requirements in the Produce Safety Rule – and keep records. Make sure to ask suppliers for records on treatment and testing (DFI gets great info from Full Circle Compost and Organic Gem!). If you are preparing your own soil amendments, here is a resource for properly curing your own compost and understanding requirements.
2. If applying raw soil amendments (ex. raw manure), wait the recommended 90-120 days to harvest from treated areas (length of time depends on if the crop is in contact with the soil – so 90 days for tomatoes and 120 days for carrots, for example).
3. Follow product labels for application rates and store amendments safely (protected from the elements and away from seeds, tools and equipment that could be contaminated). Be aware of the potential for raw manure to runoff, blow or be tracked to other areas of the farm – choose pile locations thoughtfully!
4. Apply soil amendments so that they do not come into contact with the harvestable portion of a crop, such as applying fish emulsion via a drip irrigation system.
5. Wash and sanitize shared tools that come into contact with soil amendments.
6. Be aware of pathogens from soil amendments being carried by wind or water from the field to adjacent areas, and plan accordingly (consider a hedgerow! – see below).
7. Keep a record of when and where amendments were applied.

Published by: Moe, J., 2020, Using Soil Amendments Safely, Desert Farming Initiative, University of Nevada, Reno

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