Fertilizer Experiment


Certified Procrastinator
5 Years
Jan 14, 2018
Hello! I’m doing a project/testing what types of manure is a better fertilizer (which one will have the highest grown plant (tomato) in 12 weeks?)
I’m using a set weight of fertilizer (currently undecided), if horse and poultry manure. I will then add both manures to its own empty milk jug of water, then water the plants with the water/manure mixture. I have 16 plants. Each manure has 4 plants. 4 for horse, 4 for poultry, and one for regular as a constant.
The last one is one I’m a little lost on. I’ve read that mixing cattle and poultry manure for a fertilizer is too much nitrogen for a veggie? Especially if it isn’t composted/not fresh. Does anyone know ifW this would be the same for horse/poultry mixtures, if it would be good for the plant, or slow down the growth? Or should I just try the mixture to see what happens? I don’t expect to eat these plants, or even get any fruits since I’m growing this late in the year.
(They will be inside, under artificial light until mid December.)

Thanks for any ideas!


8 Years
Apr 6, 2014
Melrose Park Illinois
You are doing an experiment and possibly with your children as a project. :idunno
Here is the outline, guideline to the Scientific method.
Steps in the Scientific Method
  • 1 – Make an Observation. You can't study what you don't know is there. ...
  • 2 – Ask a Question. ...
  • 3 – Do Background Research. ...
  • 4 – Form a Hypothesis. ...
  • 5 – Conduct an Experiment. ...
  • 6 – Analyze Results and Draw a Conclusion. ...
  • 7 – Report Your Results.
Remember that you are experimenting, so your results will be the knowledge you gain.
If you are going to tailor-make your procedure to get GOOD RESULTS, then you are not really experimenting.
I know that Chicken poop un-composted is considered HOT. The result will be a burned plant. That of course depends on the amount of it.
Small (ideal) amounts will promote good growth. At a certain level, the amount is too great, and plant burning and plant dies.
Wishing you well in your experimentation.:highfive:


5 Years
Nov 12, 2017
Western Ohio
Good luck!

Your 4 treatments should be:

1. Horse
2. Chicken.
3. Water (from same source, and not softened water). This is your control.
4. Other manure, such as rabbit, OR a commercial fertilizer. Don’t mix the horse and poultry bc it will not add anything to this experiment.

With your manures, they should be standardized in some way. Weight:add same amount to the test plants. Or do a little research that tells you the Nitrogen content, generally, of these manures is x per weight of manure. Then use that weight (so the nitrogen is standardized or some other component like potassium or phosphorus).

Horse and chicken manure are “hot” and can damage your plants, if added too much at once (small amounts ok). Rabbit poop is not hot, can be added directly. Horse and chicken poop can be disease vectors, another reason they are aged before using with plants (rain splashed into soil, splashing potential disease back into plants).

I don’t know if you are a student doing a school project, or a parent guiding a project. I’ve judged many science fair projects over the years from elementary thru high school, so having a reason for your treatments is important. Having a clear control. Having a good hypothesis that you disproved or “failed to disprove” is also key (along with reasons why). You have 4 plants for each treatment, which is great. You have plans to quantify your results (measurements in cm), rather than qualitative (“looked taller”).

Good luck.

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