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Using manure in the home garden

Graphic of a bag with a chicken over vegetables.
Many gardeners tout manure’s superiority to synthetic products available today. And if done right, it’ll be a fantastic supply of necessary nutrients to grow a large healthy garden.

Gardening experts often encourage the use of fertilizer. It’s the golden trowel of gardening and an essential source of nutrients for plants. And while there are several types of fertilizers available today, many gardeners like to stick to old faithful: manure.

Manure is packed with nutrients and has had a variety of uses throughout history. Not only is it the oldest fertilizer, it can also be used to generate biofuels and can be turned into fiber to create a number of materials.

Many gardeners tout manure’s superiority to synthetic products available today. And if done right, it’ll be a fantastic supply of necessary nutrients to grow a large healthy garden.

But if you’re a ma-newbie (manure newbie), there are a few things you’ll want to watch out for to avoid contamination risks. Or, put another way: you don’t want poop to get in your food.

Don’t eat sh*t

It’s important to avoid the risk of contamination of your edible crops. Otherwise, you put yourself and others at risk of contracting a food-borne illness. To best avoid unintended contamination, there are a few things to keep in mind.

Timing is key

Manure should be applied at least 120 days before your target harvest date for any vegetables for which the edible part comes in direct contact with the soil, such as root crops or lettuces, and at least 90 days ahead for vegetables that don’t contact the soil, like corn.

The time constraint means spring application likely won’t fit on your garden’s timeline in Iowa. Instead, aim to apply manure after you’ve harvested the last of your vegetables this fall.

Not willing to wait? Alternatively, you could spread manure about a foot away from the base of your plants, giving your greens some breathing room while still being able to incorporate last-minute manure.

If you do apply manure in the fall, cover your targeted area with a tarp or leaves to help the manure break down further and avoid nutrient leaching (when the nutrients go below root level).

Either way, you also - always - need to clean your crops. Washing, peeling and cooking all help to remove potential pathogens.

How to apply manure to your home garden

Alright - health considerations out of the way. Let’s say you’re committed to fertilizing with poop. To begin, get a well-composted manure. It’ll smell less, weigh less and be safer to use.

From there, spread your manure in your target area and incorporate it into the top 6 - 8 inches of soil.

Avoid fertilizer plant burn

You can have too much of a good thing. In this case, that’s too much animal byproduct.

Nutrient excess can damage or kill your plants. Using too much manure - or also manure that’s too fresh - can throw off phosphorus levels and lead to nitrate leaching, nutrient runoff and other issues.

This is another reason to hold the manure to the fall. Planting in the off season helps avoid burning, as it allows ammonia (byproduct) to be released into the atmosphere instead of coming in direct contact with your growing plants.

Additionally, different types of manure will have different levels of nutrients and variable effects on your garden. If you’re going to go all in on manure, see what your space needs by doing a general soil test.

A few more things to keep in mind

  • Avoid manure from dogs, cats and pigs in vegetable gardens or compost piles. 
  • Top off your application area with mulch or some cover crop to avoid it washing away or leaching into non-targeted areas. 
  • If you use very fresh manure, remember, you’re bringing the farm - and its extra stink - to you and your neighbors. Maybe give them some of your produce next season to make up for the extra smell. 

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Madeleine Charis King (she/her) manages and writes Iowa Public Radio’s newsletters. She also takes photos in support of IPR's news and music teams.