Hydroponics Notes
1. What is Soil and how does it get there?
a. Soil – a thin layer of earth’s crust that accumulates as a result of weather, wind, water and organisms
i. There are 4 components of soil:
1. Inorganic components (45%)
2. Organic components (5%)
3. Air (25%)
4. Water (25%)
b. Soil accumulates through the weathering of rock
i. Parent material (usually rock) is gradually broken down too smaller and smaller particles by the
climate and organisms
a. roots produce CO2 that turns to acid when it contact water
b. lichens produce acid as a waste product that etch tiny cracks in the parent
material that widen as water freezes and thaws in the cracks
c. Surface water runoff the washes the chipped away finer pieces in lower arias
2. The 4 components of soil
a. Inorganic components
i. Come from weathered rock
ii. Provide anchorage and essential minerals
iii. Made of sediments of various sizes (sand silt and clay)
1. Clay is most important because it has a large amount of negatively charged surface area
that attracts positively charged essential minerals
b. Organic components:
i. Come from, Animal dung and decomposing organisms
ii. Increase the amount of water holding capacity in a soil
iii. Humus – partially organic matter in soil that binds ions and holds water
c. Air spaces and water
i. Same gases as in the atmosphere but more CO2 because of respiration in roots
ii. Water is held in smaller pores of soil whereas air is held in the larger soil pores
iii. Leaching - As water drains through soil it takes with it dissolved minerals away from where they
would be available to plants
d. Different types of soil result from different ratios of these 4 components
i. Loamy soil – ideal agricultural soil (40% sand, 40% silt, and 20% clay)
ii. Peaty soil – soil that is almost completely made of organic components
iii. Chalky soil – a very basic (alkaline) and rocky soil that contains little organic material and air
space
3. Soil layers
a. There are 4 layers to soil:
i. Surface litter – dead leaves and branches on the soils surface
ii. Top soil – the top foot of soil that is most rich in humus with little rock and gravel
iii. Sub soil – layer of soil below the topsoil that contains larger amounts of smaller inorganic
sediment, leaches minerals, and larger sediment like gravel and rocks
iv. Parent material (bedrock) – a solid layer of rock that was biologically and inorganically degraded
to create the above soil
4. Acid in soil
a. The pH of Soil can range from extremely acidic (pigmy forest – pH 2.8) to relatively basic (Death valley =
pH of 8.5)
i. The availability of nutrients changes depending on the pH of the soil
1. In acid soil:
a. Some minerals like Iron and magnesium become soluble to a toxic amount
b. Some essential minerals are dissolved and leached from the soil and therefore
are unavailable to plants
c. Salts begin to accumulate in the soil causing plants to lose water
d. Plants have a hard time absorbing the positively charged minerals they need
because of the amount of positively charged hydrogen ions in the soil
2. In basic soil:
a. minerals essential to plant growth become insoluble and thus unavailable to
plants
b. heavy metals like lead and mercury become more soluble and thus are
accumulated by plants
b. The optimum pH range for most plants is 6.5-7.5.
5. Nutrients in soil
a. There are 19 elements that are essential to all plants
i. Macronutrients – the 10 elements that are required in large amounts for healthy plant growth
ii. Micronutrients – the 9 elements that are required in very small amounts for normal plant
growth
1. Most micronutrients like Chlorine, Iron, and sodium are needed to form plant enzymes
and proteins
iii. Macronutrients gained from air and soil water:
1. Carbon, hydrogen, Oxygen, and Nitrogen (C, H, O) that are used to form virtually every
essential molecule in a plant (carbohydrates, lipids, proteins, and DNA)
iv. Macronutrients gained from the soil
1. Potassium (K) helps plants regulate water movement into and out of the cells
a. Potassium is responsible for improving the overall health of a plant as well as its
disease resistance.
2. Phosphorous (P), used in cell membranes, DNA, and ATP
a. Phosphorus aids in healthy root growth as well as flower and seed production.
3. Nitrogen (N) is used to make proteins, DNA, chlorophyll and enzymes
a. It was thought that nitrogen was put into the soil through the primarily through
the nitrogen cycle however in 2011 it was found that soil nitrogen comes
primarily from soil rock
b. Nitrogen is responsible for stem and leaf growth.
4. Calcium (Ca) helps hold plant cells together and attached to each other
5. Magnesium (Mg) the central ion in chlorophyll (like iron in our blood)
6. Sulfur (S) needed to make certain amino acids and vitamins
6. Getting nutrients into and out of the soil
a. All the macro and micronutrients that plants removed from the soil in nature are put back into the soil
once then plant dies and degrades
b. In agriculture however the parts or all of the plant are removed and sold, therefore nutrients are
constantly lost from the soil and never returned
c. As a result farmed land over time becomes depilated of nutrients and in order to remain fertile the
nutrients must be put back into the soil
i. There are a number of ways to get nutrients back into the soil:
1. Inorganic fertilizers industrial produced concentrated salts that provide a large amount
of immediately available Nitrogen, Potassium and Phosphorous to plants.
a. Although inorganic fertilizers provide everything a plant needs immediately, it is
water soluble and therefore quickly leached from the soil, often is in excess that
contributes to water pollution, and results in accumulating salt levels in soil
2. Organic fertilizers Naturally produced N, P, and K that is in relatively low amounts
a. Organic fertilizers degrade slower in soil providing these nutrients in smaller
amounts over a longer period of time
3. Sustainable methods of farming: Crop rotation and green composting
a. Crop rotation - Not growing the same crop in the same spot year after year to
prevent the soil from becoming overly depleted in nutrients
b. Green composting or manure – allowing cover crops or dead plants to be
directly sown back into the soil mimicking the process that puts nutrients back
into the soil in nature
7. Hydroponics and alternative methods of horticulture
a. Hydroponics – soilless growing where nutrients are provided to the plant roots through a nutrient
solution.
i. Advantages:
1. no herbicides or fungicides, or insecticides
2. plants grow faster and healthier with higher yields because they spend less energy
looking for water and nutrients in the soil
ii. Disadvantages:
1. Plants are slower to start
2. Dependent on inorganic industrial produces fertilizing salts
3. Requires lots of infrastructure
b. Airoponics –soilless growing method that suspends plant roots in air and waters them by misting
nutrient solution
i. Advantages:
1. More nutrient efficient than hydroponics because unused nutrients are recirculated
2. Plant roots receive the most amount of oxygen possible creating the strongest and
healthiest possible plants
3. High crop yields
ii. Disadvantages:
1. Need to keep roots in 100% relative humidity or plant quickly dies
2. Algae and fungus can form on roots killing the plant
3. Requires lots of info structure and relatively controlled sterile environment
c. Vertical gardening - growing container plants in layers vertically instead of horizontally
i. Advantages:
1. Takes less space for much greater increase in yield
2. Most efficient use of water runoff in that many layers of plants have the opportunity to
absorb excess
3. Plants can be grown in soil
ii. Disadvantages:
1. Careful planning needs to be taken to make sure plants get enough water and sunlight
2. Plants generally grow worse as they need to spend lots of energy righting themselves
upwards after growing out of a wall