Transcript Nitrogen Cycle

UNDERSTANDING AGRONOMY
Plant Nutrients and Fertility
•Objectives
• Identify essential nutrients for plant growth;
• Distinguish between micronutrients and
macronutrients;
• Discuss the nitrogen cycle and its effect on plant
nutrition;
• Discuss the role of pH in plant nutrition; and
• Explain the use of fertilizers
Essential Nutrients for Plant Growth
•Nutrients are substances that living organisms
require for life and growth
• There are 16 nutrients required by growing plants
•Some are gathered from the air while others
are found in the soil
Essential Nutrients for Plant Growth
•Stomata are the pores found on plant leaves
• They help with nutrient uptake and cooling
•Elements obtained through stomata are
carbon, hydrogen, and oxygen
•Roots are used to acquire nutrients like
nitrogen, phosphorus, potassium, calcium, and
sulfur
• What has to happen before these elements can
be absorbed by the roots?
•They must be dissolved in water first
Essential Nutrients for Plant Growth
•16 essential nutrients
• Carbon – C
• Boron – B
• Hydrogen – H
• Oxygen – O
• Phosphorus – P
• Potassium – K
• Nitrogen – N
• Sulfur - S
• Calcium – Ca
• Iron – Fe
• Magnesium – Mg
• Chlorine – Cl
• Manganese – Mn
• Molybdenum – Mo
• Copper – Cu
• Zinc - Zn
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Distinguish between micronutrients
and macronutrients
•First, there are two major nutrient categories
• Mineral and Non-Mineral
•Carbon, hydrogen, oxygen, and nitrogen are
all non-mineral nutrients
Distinguish between micronutrients
and macronutrients
•How are micro and macro nutrients different?
• It is based on how much plants need
•Macronutrients are needed in larger quantities
•Micronutrients are needed in smaller amounts
Distinguish between micronutrients
and macronutrients
•Macronutrients:
• Primary
• Nitrogen, Phosphorus, Potassium (N-P-K)
• Secondary
• Calcium, Magnesium, Sulfur
Distinguish between micronutrients
and macronutrients
•Micronutrients
• The remaining 10 elements
The Nitrogen Cycle
•Nitrogen Cycle is the movement of nitrogen
from the atmosphere to soil to organisms and
back
•Nitrogen can be put into the soil in various
ways
• Chemical and organic fertilizers
• Decomposing organisms
• Aerating
• Lightning strikes
The Nitrogen Cycle
•What do legumes do that is so special?
• Fix nitrogen from air in the soil
•Symbiotic relationship with bacteria
• They
nitrogen
Whatconvert
the heck
is that?gas (N2) into ammonium ions
(NH4+)
The Nitrogen Cycle
•The bacteria pull in N 2 while they decompose
dead plant matter
•During that process N2 is converted into NH4+
•The ammonium ions become available to the
plant when the bacteria dies
The Nitrogen Cycle
•Are we actually putting down N 2 when we
fertilize with ‘nitrogen’?
• No
•We are either putting down NH 4+ or nitrate
•Usually NH4+ is converted to another form of
nitrogen called nitrite by Nitrosomas Bacteria
•Nitrite cannot be utilized by plants
The Nitrogen Cycle
•Nitrite must be converted
• There’s a bacteria for that
•Nitrobacter Bacteria convert nitrite into nitrate
• That is called nitrification
The Nitrogen Cycle
•To finish the nitrogen cycle we need
denitrification
• Happens when soil is saturated with water.
• Bacteria convert nitrate into N2 and it escapes into
the atmosphere.
•Nitrogen can also be lost when
• The plant uses it
• Leaching occurs
pH and Plant Nutrition
•How can pH affect a plant’s nutrition?
•Certain nutrients become unavailable to a
plant when the pH gets too high or low
• It greatly affects N-P-K
•Most plants want a soil pH between
5.5 and 8.0
pH and Plant Nutrition
•How can you increase pH? (more basic)
• Add limestone
•How can you decrease pH? (more acidic)
• Add sulfur or gypsum
Using Fertilizers
•Fertilizers are materials added to the soil to
provide a plant with needed nutrients
• Two categories
•Complete 12-12-12
• Contain all three primary macronutrients
• What are they? Nitrogen – Phosphorus -- Potassium
•Incomplete 18-46-0
• Do not contain all three primary macronutrients
Using Fertilizers
•Do the N-P-K numbers always have to add up
to 100%?
• No
•The remainder is filler
•Filler will provide for more even coverage of
the fertilizer
•It is composed of other macro and
micronutrients
Using Fertilizers
•Selecting your fertilizer
•First, determine which nutrients are not readily
available
• How?
•Three different methods
Using Fertilizers
•Visual observation
• You look at the plant
• Pale leaves – nitrogen deficient
• Stunted growth, purplish spots on leaves –
phosphorus deficient
Using Fertilizers
•Soil Testing
• Which nutrients are really in your soil?
• Some simple tests
• Send to a lab for more precise results
Using Fertilizers
•Tissue testing
• Which nutrients are really available to the plant?
• Sometimes nutrients are in the soil, but not
available