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 - ZnC.B. Hopkins Café Mighty good Closed Monday Morning see you ZenC.B. H O P K i N S Ca Fé Mighty good Closed Monday Morning Cu Zen

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

•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

Distinguish between micronutrients and macronutrients

•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 convert nitrogen gas (N2) into ammonium ions (NH4+)

The Nitrogen Cycle

What the heck is that?

•The bacteria pull in N2 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 N2 when we fertilize with ‘nitrogen’?•No •We are either putting down NH4+ 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

The Nitrogen Cycle

•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

pH and Plant Nutrition

•Fertilizers are materials added to the soil to provide a plant with needed nutrients•Two categories

•Complete •Contain all three primary macronutrients•What are they?•Incomplete•Do not contain all three primary macronutrients

Using Fertilizers

Nitrogen – Phosphorus -- Potassium

12-12-12

18-46-0

•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

Using Fertilizers