The Downside of Using Manure in the Greenhouse

Using manure on plants growing in a greenhouse environment can be bad, if done in an improper manner.


This guide will help you learn all about the basic and advanced techniques on how to use manure inside greenhouse gardens, and find the top universities and college agriculture resources, on the subject.

Manure fertilizer Farming Truck Spreading Fertilizer


Plant Burn

The roots of delicate greenhouse plants, particularly very young plants, can be burned from the high ammonia present in fresh farm manure. Ammonia is classified as a base, but its chemical composition can be too strong for the fragile leaves and roots of immature plants still growing in a greenhouse environment.


Manure from PoultryManure made from the poultry farming, category of animals are especially high in ammonia

  1. Hens
  2. Chicks
  3. Roosters


If too much fresh poultry manure is applied to the soil, young plants will burn quickly. Compared to aged manure, the ammonia content in fresh poultry manure is higher.

  • Adding large amounts of manure to greenhouse soil may seem to increase nutrients and aid in plant growth, but growth can actually be reduced because of excessive amounts of ammonia.



Adding fresh manure to greenhouse soil can increase the risk of gastrointestinal illness in humans. The human pathogen E. coli is present in fresh animal manure. If this manure is used to nourish the soil in which greenhouse fruits and vegetables are going to be grown, the gardener should add the manure several months before the fruits and vegetables will be harvested, getting your greenhouse plants schedule correct can make all of the difference.

  • For carrot, potato or beet crops, this should be a time period of at least four months.
  • For other edible plants, the manure should be added at least three months before the plants are ready for harvesting.


A good rule of thumb to follow is:

Add fresh manure in the fall.

  • Do not add it prior to planting, in the spring or at any time during the growing season.
English: Manure for mushroom compost
English: Manure for mushroom compost (Photo credit: Wikipedia)


Slow Release of Nutrients

Small amounts of micro-nutrients and plant nutrients is contained in fresh manure. Depending on the bedding material, such as sawdust, the moisture in the manure, its age and exposure to the elements, the levels of nutrients can differ from one batch to another. In addition, the release of nitrogen may not take place quickly enough for young plants in the greenhouse.


Specifically, when manure is added to soil on a regular basis, that soil will contain sufficient amounts of potassium, phosphorus and micro nutrients such as zinc. The soil should also contain potash, which helps nourish greenhouse plants.


Compost Food Waste Only Sign
Compost Food Waste Only Sign (Photo credits:




Nutrient Contents in Different Manures


1. Manure from Beef with Bedding

  • Beef manure with bedding contains about 1.1 percent nitrogen, 1.3 percent potassium and 0.9 percent phosphorus.
  • Without bedding, the potassium measures 1.2 percent and phosphorus measure 0.7 percent.


2. Manure from Dairy Cattle with Bedding

  • The manure produced by dairy cattle – with bedding – has 0.5 percent nitrogen, 0.5 percent potassium and 0.2 percent phosphorus. Without bedding, the numbers are the same.


3. Manure from Horses with Bedding

  • Horse manure with bedding has 0.7 percent nitrogen, 0.7 percent potassium and 0.2 percent phosphorus.


4. Manure from Poultry with Litter

  • Poultry manure with litter has 2.8 percent nitrogen, 1.7 percent potassium and 2.3 percent phosphorus; without, the numbers are different: nitrogen is 1.7 percent, potassium 1.7 percent and phosphorus 2.4 percent.


5. Manure from Rabbits

  • Rabbit manure contains 2.0 percent nitrogen, 1.2 percent potassium and 1.3 percent phosphorus. Sheep manure, with bedding, contains 0.7 percent nitrogen, 1.3 percent potassium and 1.3 percent phosphorus.


6. Manure from Swine with Bedding

  • Swine manure, with bedding, contains 0.4 percent nitrogen, 0.4 percent potassium and 0.4 percent phosphorus.
  • Without bedding, 0.5 percent nitrogen, 0.4 percent potassium and 0.5 percent phosphorus.


7. Manure from Turkey with Litter

  • Turkey manure, with litter, contains 1.0 percent nitrogen, 0.7 percent potassium and 0.8 percent phosphorus.
  • Without litter, it contains 1.4 percent nitrogen, 0.9 percent potassium and 1.0 percent phosphorus.
  • All of these percentages are as of the time of land application.

Norpro GRIP EZ Stainless Steel Compost Buckets


Weed Seeds

Fresh manure, because it has been recently produced, may still have weed seeds in it, bringing the risk of sprouting weeds for the gardener.

  • The weeds can choke out and kill young plants unless the gardener is in his greenhouse every day to look for weeds and pull them.
  • Horse manure, in particular, can cause a significant weed issue for the gardener.
  • The most efficient way of reducing the risk of weed seeds and weeds is for the gardener to compost the manure, allowing it to heat to temperatures higher than 145 degrees F.
  • He must also turn the compost during the heat processing so all of the manure composts.


The composting process can take between six weeks and three months, so the gardener should begin this process, turning the manure every week to continue the composting process. Decomposition can be sped up (and the odor can be reduced) by adding high-carbon material to the manure.

A homeowner sifts soil made from his compost b...
A homeowner sifts soil made from his compost bin in background. Composting is an excellent way to recycle household and yard wastes. (Photo credit: Wikipedia)


Salt Build-Up


As fresh manure is exposed to the elements, especially moisture, snow and rain, the salt in the manure leaches out and into the ground.

  • If the greenhouse gardener applies manure heavily and frequently, salt can build too high into the soil in the greenhouse starter pots.
  • For this reason, he should only apply one inch of manure per year.
  • If he cultivates the manure less than 6 or 8 inches into the soil, he needs to adjust the rate of application, then test the soil for salt content before adding more.


Learning How to Compost Manure Correctly

Composting Manure

The greenhouse gardener can use composted manure or bagged composted manure. The second variety is available in nurseries or garden centers. Because salts can concentrate in manure as it composts, this is a disadvantage. The salt content increases as the manure dries out and its volume goes down.


Basics of the Use of Manure in a Greenhouse Garden


Manure is a natural, organic method of adding nutrients to soil.

For the greenhouse gardener, manure comes with its own considerations and downsides, from too much ammonia and salt content to the very real potential of transmitting a potentially dangerous E. coli germ to young plants being grown for food. The release of nitrogen, a needed nutrient for young plants, can also be slow when manure has been applied to the soil.


If you’re garden is causing additional problems, get in touch with an expert greenhouse gardener, to get the opinion of a licensed professional.


Nutrient Rich Garden Poultry Manure with Red Worms




References Used:


  1. Guides: Using Manure Safely and Effectively – (
  2. Forums: Can You Use Too Much Cow Composted Manure? – (
  3. Forums: Using Composted Manure from Lowes – (


Recycling Soil and Manure to Use in Greenhouses






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