Can organic amendments harm plants?
Written by
Paul Reynolds
Reviewed by
Prof. Charles Hartman, Ph.D.Organic amendments can have negative effects on your plants if not correctly used. If you do not compost your manure, you can introduce harmful and dangerous microorganisms into your garden. If you over-amend with organic matter or fertilizers, the resulting mineral imbalances may cause nutrient lockouts. I have seen poorly composted and contaminated products wipe out entire crops. Your plants will struggle if organic amendments are not used properly.
The risks of pathogens stem from fresh animal excreta. E. coli and Salmonella remain viable in raw manure, and those pathogens can contaminate both edible crops and groundwater sources. Therefore, always compost manure for 3-4 months at a temperature between 130°F and 150°F. I perform a safety check on manure before applying it in any way.
Mineral imbalances frequently occur when soil amendments overwhelm the soil. For example, an abundance of nitrogen can severely burn the plant roots. An abundance of gypsum can change the pH level beyond the desired pH range. It is important to follow the soil test recommendations exactly. I keep track of everything I apply so that I know never to use it at toxic levels.
Pathogen Contamination
- Compost manure at 130-150°F for 3-4 months
- Avoid raw manure on edible crops
- Test water sources after application
Herbicide Residues
- Conduct bioassays before full application
- Grow beans in sample mix first
- Source from herbicide-free farms
Nutrient Imbalances
- Follow soil test recommendations
- Measure application rates per square foot
- Avoid duplicate nutrient sources
Herbicide contamination can affect even commercial products. Aminopyralid can survive the composting of contaminated plants or products. Once it has contaminated a surface or system, it can remain toxic for years, potentially killing sensitive plants. Always perform bioassays before full-scale application. I test all purchased amendments.
Nutrient burn is a risk with fresh animal waste. Urea concentrations can elevate nitrogen levels to perilous amounts. It will immediately injure plant roots. Age any manure well before application. Personally, I wait a minimum of six months after the application.
Use prevention strategies for safe gardening. Get amendments from trusted sources only. Store them securely in labeled containers. Use gloves and masks when applying them. My safety habits are designed to protect plants and people.
This year, start small. Amend a small portion of your garden. Observe how your plants respond over a two-week timeframe. I changed how I gardened by being watchful. When you watchfully tend to your garden plants, they do well.
Read the full article: 10 Essential Organic Soil Amendments
