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Humic Acid and the Optimum Soil for Plants

Difficulty
Time Required Very Long (1+ months)
Material Availability Readily available
Cost Low ($20 - $50)

Abstract

Humic acid is touted as an organic soil additive to improve plant growth by multiple means. Does it really work? Here's how you can find out.

Objective

The purpose of this project is to determine which soils will yield the greatest plant growth, root length, and root weight: soil without additives, soil with dry humic acid, soil with liquid humic acid, or soil with a combination of dry and liquid humic acid.

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MLA Style

Science Buddies Staff. "Humic Acid and the Optimum Soil for Plants" Science Buddies. Science Buddies, 20 June 2014. Web. 29 July 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_p003.shtml>

APA Style

Science Buddies Staff. (2014, June 20). Humic Acid and the Optimum Soil for Plants. Retrieved July 29, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_p003.shtml

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Last edit date: 2014-06-20

Introduction

Organic matter is an important component of fertile soil. Many different types of organic matter can be used as fertilizers to enhance plant growth, such as manure, compost, etc... Humic acid is believed to be a good organic fertilizer for certain plants. Does humic acid really work to improve plant growth?

Terms and Concepts

You should have an understanding of humic acid and humate, how they are produced and what their impact is on soil.

Cation exchange capacity is an important term to understand how humic acid impacts soil.

Bibliography

Basic explanation of Humic Acid: Similar studies looking at benefits of humic acid on growth of different varieties of plants:

Simple explanation of cation exchange capacity http://www.extension.umn.edu/distribution/horticulture/components/1731-06.html

Impact of organic matter on soil productivity (includes brief discussion of humic acid) http://www.agronomy.lsu.edu/courses/agro2051/Chapter%2012.pdf

Materials and Equipment

  • Pots
  • Potting soil
  • Dry humic acid
  • Liquid humic acid
  • Plants

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Experimental Procedure

  • Fill pots with potting soil.
  • Add dry humic acid to half of the pots.
    *See note below.
  • Make sure you have a good location for the plants so that they will all be exposed to the same conditions and they will not be disturbed during the course of the experiment.
  • Over the next two months water half of the pots that contain humic acid with plain water and the other half with liquid humic acid. Water half of the plain pots with plain water and the other half with liquid humic acid. This process will ensure that you have the following groups of experiments:
    • plain potting soil treated with plain water
    • plain potting soil treated with liquid humic acid
    • humic acid added to potting soil and treated with plain water
    • humic acid added to potting soil and treated with liquid humic acid
    *See note below.
  • Two months later pull the plants and begin gathering data. Some things to measure are: root and plant growth, weight of the roots, weight of the plants.

*Experimental Note
Commercial humic acid products are too concentrated to apply to plants straight from the bottle.
Recommended amounts of dry humic acid powder in the ranges of:

  • 1/4 teaspoon per pot
  • 1/2 teaspoon per pot
  • 1 teaspoon per pot
Recommended amounts of dry humic acid powder in the following ranges:
  • 2 tablespoons liquid humic acid per gallon of water
  • 5 tablespoons liquid humic acid per gallon of water
  • 10 tablespoons liquid humic acid per gallon of water
Select one of the dry and liquid humic acid mixtures mentioned above for your experiment and then use that dilution to test the dry and liquid humic acid variables.

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Variations

Try different types of plants, vegetables, fruits, houseplants...

Try humic acid vs. fertilizer

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