Study Guide 7 - Soil Fertilization
What is the difference between macronutrients and micronutrients? Know if the following
nutrients are macronutrients or micronutrients: nitrogen (N), phosphorus (P), potassium (K), iron
(Fe), and zinc (Zn).
●90 elements ranging from hydrogen, carbon, nitrogen, potassium, iron, phosphorus,
calcium, sulfur, magnesium, etc.
●Plants are autotrophic
●13 naturally occurring mineral nutrients from soil are required by plants to survive
●Macronutrients - required in higher amounts in plants
○Nitrogen (N)
○Phosphorus (P)
○Potassium (K)
○Calcium (Ca)
○Magnesium (Mg)
○Sulfur (S)
○Required in higher amounts
○2% to 4% of its tissue by weight comprised nitrogen
●Micronutrients - required in lower amounts in plants to function and grow
○Iron (Fe)
○Zinc (Zn)
○Manganese (Mn)
○Boron (B)
○Copper (Cu)
○Molybdenum (Mo)
○Nickel (Ni)
How is the term soil defined and how does the definition depends on the context of the person
using the term? In what ways does soil support plant growth? What are the five components
which make up soil? Why can soil be described as “living”?
●Soil is the weathered surface portion of the earth’s crust through various weathering
processes such as wind, sunlight, ice, snow, rain, etc.
●Large parent rock material broken down into small particles of less than 2 mm in
diameter
●Where terrestrial life exists
●Soil is not dirt
●5 Component Parts of Healthy Soil
○Weathered mineral particles
○Macro - and micro - organisms (fungi is the most prevalent)
○Decomposing organic matter (both large and small organisms)
○Water
○Air
●Substance that is full of life with its own unique ecology of biological processes and
organisms interactions
What percentage of soil is made up of water and air? Where is water and air located in soil? Why
is it important not to overwater your plants?
●Layers are called “soil horizons”
●Arrangement of horizons is known as the “soil profile”
●3 main soil horizons
○O horizon (organic)
○A horizon (surface)
○B horizon (subsoil)
○C horizon (substratum)
○R horizon (bedrock)
●Desert soil horizons are:
○Highly variable
○Shallow
○Limited to non - existent surface layer of organic material/matter
Why is organic matter an important component of soil? What is the difference between sand, silt
and clay? Why is a loam soil often considered ideal for growing plants?
●Recycling of dead organisms (primarily plants)
●Largest particles include sand
●Medium particles include silt
●Smallest particles include clay
●Soil inPhoenix usually lacks organic material
●Loam soils have a mixture of sand, silt, and clay particles
○Best for plant root growth and development
○Diverse texture
How can you determine the texture of your soil? Why is it important to know the texture of the
soil in which you are growing plants? Does a sandy or clay soil need to be irrigated more
frequently for optimum plant growth?
●To know how to better manage soil
●Soil texture
○Classifying soils by the size of the dominant soil particles
○“Feel test”
●Sand (2.00 - 0.05 mm) BIG
●Silt (0.05 - 0.002 mm)
●Clay (less than 0.002 mm) SMALL
●Sandier dries out quicker as water runs through
○Must be irrigated more frequently
●Rhizosphere
○The immediate soil environment in which a plant’s root system is growing
○3 important functions
■Support and anchor the plant
■Reservoir for water, oxygen, and essential mineral nutrients
■Substrate for interactions with other living organisms, including bacteria
and fungi (symbiotic relationships)
●Organic amendments will improve soil aeration and drainage
What are symptoms in plants of nitrogen and iron deficiencies? Why are plants often nitrogen
and iron deficient in the southwest? How would you prevent or treat nitrogen or iron
deficiencies?
●Nitrogen and iron are typically in short supply in the desert garden soils
●Plant deficiency symptoms and low plant tissues
●Can be very different
●First symptom that appears is slow growth or lack of growth (nitrogen is essential with
protein and enzymes that allow for growth)
●General yellowing or reddening of older leaves on the lower parts of the plant
○Older leaves portray symptoms first since plants are able to mobilize and move
nitrogen throughout the plant to points of greatest needs, which are mostly young
and developing plant tissues, and not necessarily older leaves
●Iron is essential to the formation of the green pigment chlorophyll
●Yellowing of new and younger leaves on the upper parts of the plant
○Plants are unable to mobilize and move iron
○Opposite symptoms than that of nitrogen deficiency
○Yellowing between the leaf veins (interveinal yellowing or chlorosis or netting)
○Zinc and Manganese nutrient deficiency looks very similar to iron deficiency in
appearance
●Iron, Zinc, and Manganese deficiencies are common in garden plants in desert alkaline
soils
○Alkaline soils bind these elements, making the soil unavailable to plant roots for
uptake or absorption
○Especially silt or clay
Are the soils in the Phoenix area generally acid or alkaline? How can you change the pH of a
soil? Should lime typically be added to soil in our area?
●Phoenix soils are typically more alkaline and range between a pH of 7.5 to 8.5
●Very little organic matter
●Acid forming fertilizers
○Elemental sulfur
○Ammonia fertilizers or urea
○Increase hydrogen ion concentration
●Gypsum is calcium sulfate that cannot lower pH
○Slowly dissolves in water
○No ability to increase hydrogen ions
○Although it can be used as a valuable soil amendment
What is the difference between an organic and inorganic fertilizer? A simple and complete
fertilizer?
●Organic means any fertilizer product derived as a byproduct of living organisms
●Organic may contain the element carbon
●Organic fertilizer/matter amendments added to vegetable and fruit gardens release humic
acids into the soil slowly lowering the soil pH (sustainable)
○Slowly decomposes by bacteria and fungi
○Humic acids are weak organic acids that help reduce the harmful effect of soil
alkalinity by slowly lowering the pH (acidifying the soil)
●Ornamental and desert native gardens DO NOT need regular amendments or fertilizers
●Rototilling or cultivating of the soil is NOT necessary
●Home vegetable and fruit gardens need regular amendments or fertilizers
Know the difference between the following types of fertilizers and how they would be used: a
slow or controlled release fertilizer, a liquid fertilizer, granular fertilizer. What do the numbers
on a fertilizer bag stand for? Why is it important to follow the directions on the fertilizer
container concerning rate when applying fertilizer?
●Governed by law due to commerce
●The Arizona law defines fertilizers as “any substance or mixture of substances intended
to be used for promoting or stimulating the growth of plants, increasing the
productiveness of plants, improving the quality of crops, or producing any chemical or
physical change in the soil”.
○Products must be accompanied by a product label
○Label must include chemical content, proper use, handling, storage, health and
safety precautions, etc.
○Read the product label and instructions
●The 3 numbers indicates the analysis of grade
○Approximate percentages of content
○Total nitrogen
○Available phosphorus
○Soluble potassium or potash
○And percent by dry weight of product
○The higher the numbers are, the more concentrated the element is in the fertilizer
product that are in the bag
○Other products such as calcium, magnesium, sulfur, iron, zine, manganese, etc.
are labeled/listed separately on the product label
●Synthetic/Inorganic fertilizers
○More concentrated (higher numbers)
●Natural and Organic fertilizers
○Less concentrated (lower numbers)
●Fertilizers are classified by their origin and chemistry
●Origin
○Natural
○Manufactured
○Synthesized
●Chemistry
○Inorganic
○Organic
●Slow or controlled release fertilizer
○Slow release over many months
○Synthetic
○Mimic natural and organic fertilizers in the release rate
○Best for long term soil health
●Liquid fertilizer
○Dissolves in water
○Quickly available for plant root uptake
○Present in the soil at high concentrations for relatively short periods of time
●Granular fertilizer
○Dissolves in water
○Quickly available for plant root uptake for relatively short periods of time
○Present in the soil at high concentrations
●Dry formulations fertilizers
○Natural and organic types
○Break down and dissolve very slowly in water
○Available to plants in lower concentrations over longer periods of time
●All fertilizers when dissolved in the soil fraction for root uptake are a form of salt, and as
such interact with other chemical elements in the soil
●Excess fertilizer can “burn” plants (always add less and not more)
Can the normally alkaline pH of a desert garden soil be lowered to a slightly acidic to neutral pH
to increase the availability of Fe, Zn, and Mn for root uptake?
●Yes
●Acid forming fertilizers
○Elemental sulfur
○Ammonia fertilizers or urea
○Increase hydrogen ion concentration
●Gypsum is calcium sulfate that cannot lower pH
○Slowly dissolves in water
○No ability to increase hydrogen ions
○Although it can be used as a valuable soil amendment
●Always wear non - absorbing, water resistant gloves when handling fertilizer
○Ammonium sulfate concentrations can irritate and burn skin
○Organic fertilizers derived from animal by products, manures, bone meal, blood
meal, fish emulsions, etc. can contain pathogens that can infect the skin
●Wear a mask to prevent from inhaling smaller particles such as gypsum or bone
meal
●Always stored unused fertilizers in a dry area and in separate containers (do mix
different fertilizers)
