Unit 5- Soil Science
Soil Fertility
Nutrient Needs for Plant Growth
Plants need nutrients in order to grow properly.
• Plants receive most of the nutrients that they need from the growing media.
• Plant nutrients can be divided into two groups, macronutrients and micronutrients.
Nutrient Needs for Plant Growth
Macronutrients are those elements that are needed by the plant in the largest amount.
• nitrogen (N)
• phosphorus (P)
• potassium (K)
• calcium (Ca)
• magnesium (Mg)
• sulfur (S)
Primary Nutrients
Nitrogen, phosphorus, and potassium are considered primary nutrients.
• Nitrogen-produce green leafy growth
• Phosphorus- flowers and fruit production
• Potassium- provide disease resistance
Nutrient Needs for Plant GrowthMicronutrients- nutrients needed in smaller amounts
by the plants, but are still essential to plant growth. • boron (B) • copper (Cu) • chlorine (Cl) • iron (Fe) • manganese (Mn) • molybdenum (Mo)• zinc (Zn)
Nutrient Deficiency
A soil test can be performed on the soil to determine which nutrients are present or deficient (absent or lacking).
When nutrients are deficient in the soil, the plant growth is adversely affected.
Signs of Nutrient Deficiency
Oftentimes, plants visibly show a nutrient deficiency by turning colors.
• When nitrogen is deficient in the soil, a plant’s older leaves will start to turn yellow (chlorosis) and eventually die.
• A plant will show purpling in the stem or leaf when phosphorus is deficient in the soil.
Soil pH
Soil pH measures the amount of acidity or alkalinity in the soil. It is based on the amount of hydrogen ions present in the soil.
Nutrient availability is influenced by the pH of the soil.
Soil pHSoil pH can range from 1-14.
• pH readings of 1-6 are acidic
• pH readings of 8-14 are alkaline or basic
• pH reading of 7 is neutral
Amending Soil pH
A soil test can be done to determine the pH of the soil and amendments can be added to modify the pH.
• To raise the pH, limestone can be added to the soil.
• To lower the pH, Sulfur is added to the soil.
Fertilizer
A fertilizer is any material that is provided to plants to supply the nutrients needed for plant growth.
Fertilizers vary in the components they contain, the way they are applied, and the function they serve.
Fertilizer Analysis
The fertilizer analysis states the percentage of primary nutrients (nitrogen, phosphate, and potash) present in the fertilizer.
The analysis is written as 3 numbers, for example, (15-10-26). The numbers, always in this order, represent the percent of nitrogen, phosphorus, and potash, present in the fertilizer.
Fertilizer Analysis
Example: A fertilizer with an analysis of
15-10-6
has 15% nitrogen,10% phosphate, and 6% potash.
Fertilizer analyses do not equal 100%. The rest of the fertilizer composition would be some micronutrients and other filler materials.
Complete/Incomplete Fertilizers
If a fertilizer contains all three primary nutrients, it is called a complete fertilizer.
If a fertilizer is lacking any of the three primary nutrients, it is an incomplete fertilizer.
Fertilization Plan
When growing plants, it is important to use the right type of fertilizer for the end result.
Example
Fertilizer Result
High Nitrogen Green Foliage
High Phosphorus FloweringRoot stimulation
Fertilization Plan
It is equally important to time the fertilizer in a way that is most beneficial to the plants.
The grower should also consider the application method that eliminates the most waste, making the fertilizer most cost effective and least harmful to our environment.
Fertilizer Plan
• Liquid form- sprayed directly onto the foliage
• Granular- slow release fertilizer; slowly dissolves over a period of time
