UNDERSTANDING AGRONOMY

Plant Nutrients and Fertility Objectives Identify essential nutrients for plant growth; Identify essential nutrients for plant growth Distinguish between micronutrients and macronutrients; Distinguish between micronutrients and macronutrients Discuss the nitrogen cycle and its effect on plant nutrition; Discuss the nitrogen cycle and its effect on plant nutrition Discuss the role of pH in plant nutrition; and Discuss the role of pH in plant nutrition 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 C.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 (N 2 ) into ammonium ions (NH 4 +) The Nitrogen Cycle What the heck is that?

The bacteria pull in N 2 while they decompose dead plant matter During that process N 2 is converted into NH 4 + 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 NH 4 + 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 N 2 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

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