4th Meeting

SOIL CHEMICAL PROPERTIES

By Dr. Sumihar Hutapea, MS/

Indah Apriliya, SP, M.Si 4^th Meeting

Introduction

Fertility  The ability of the soil to supply essential plant nutrients and soil water in adequate amounts and proportions for plant growth and reproduction

Nutrient  Nutrients are chemical elements that are essential for the growth and fertility

Deficiency  Plant condition where an essential nutrient is not sufficiently available

Micro Nutrients  Nutrient needed in smaller quantities

Macro Nutrients  Nutrient needed in larger quantities

Chemical Properties of Soil

01 02 03

04 05

Plant Nutrients Soil pH

Base Percentage Saturation

Cation Exchange Capacity

Soil Colloid Properties

Liebig's law of the minimum (Justus von Liebig 1803-1873)

He stated that the

nutrient present in least relative amount is the limiting nutrient.

Plant Nutrients

• Plants have nutritional requirements just like humans in order to grow, develop and complete their life cycle

• Sixteen nutrients are essential for plant growth and living organisms in the soil

• These fall in two different categories namely macro and micronutrients.

• Nearly all plant nutrients are taken up in ionic forms from the soil solution as cations or as anions

Criteria of Essentially of a Nutrient

The need for the nutrient is specific and deficiency of it cannot be corrected by the other element

Element required by plant to complete its life cycle

Elements needs to be directly involved in the nutrition and plants active metabolism

01

02 03

Type of Nutrients

There are two basic type of nutrients that are present in the soil to make it a fertile one :

• Macro nutrients : Macro nutrients are required by the plant in relatively large amounts

• Micro nutrients : Micro nutrients are required only in small amounts

C, H, O, N, P, K, Ca, Mg, S

Fe, Mn, B, Mo, Cu, Zn, Cl

Essential

Elements for

Plant Growth

Sources and Uptake Essential Elements

Mechanisms of Nutrient Uptake of Plant Root Cells from Soil

Mass Flow

1 2 3

Diffusion Root

Interception

Mass Flow

• Mass flow is the movement of plant nutrients along with water to the roots

• It is a convective process in which plant nutrient ions and other dissolved substances are transported in the flow of water to the root due to transpirational water uptake by the plant

• Some mass flow can also occur due to evaporation and percolation of soil water

Diffusion

• Diffusion process operates when an ion moves from an area of high concentration to one of low concentration

• As plant roots absorb nutrients from the surrounding soil solution, a diffusion gradient is set up

• Mainly 3 soil factors which influence the movement of nutrient ions into the root through diffusion namely diffusion coefficient, concentration of the nutrient in the soil solution and buffering capacity of the solid phase of the soil for the nutrient in soil solution phase

Root Interception

• Root interception is the extension (growth) of plants roots into new soil areas where there are untapped supplies of nutrients in the soil solution

• As the root system develops and exploits the soil more completely, soil solution and soil surfaces retaining adsorbed ions are exposed to the root mass and absorption of these ions by the contact exchange phenomenon is accomplised

The movement nutrients in the soil

https://conference.ifas.ufl.edu

2

Soil pH

Soil pH

• Soil pH may be defined as the negative logarithm of H+ concentration of soil solution

• Range of pH value  0-14

 Soil pH < 7  Acidic

 Soil pH = 7  Neutral

 Soil pH > 7  Alkaline

• Below 4.5 and above 8.5 usually is not suitable for plant

• Soil pH 5.5 to 8  Best soil pH

Soil pH

• K, Ca, Mg most available at pH > 6

• P availability is usually greates in the range of 5.5 to 6.8

• Most micronutrients (except Mo and B) are more available in acid than alkaline soils

Cation Exchange 3

Capacity (CEC)

Cation Exchange Capacity (CEC)

• CEC is the maximum quantity of total cations that a soil is capable of holding, at a given pH value, available for exchange with the soil solution

• CEC is used as a measure of fertility, nutrient retention capacity, and the capacity to protect groundwater from cation contamination

• It is exppressed as centi-mol of hydrogen per kg

Cation Exchange Capacity (CEC)

• Generally speaking, a sandy soil with little organic matter will have a very low CEC while a clay soil with a lot of organic matter (as humus) will have a high CEC

• Organic matter (as humus) always as a high CEC, with clay soils, it depends on the type of clay

• The percentage of the CEC that a particular cation occupies is also known as the base saturation percentage, or percent of base saturation.

Source : https://www.slideshare.net/RafiqulIslam293

Cation Exchange Capacity (CEC)

04 05

Base Percentage

Saturation Soil Colloid Properties

Will be continued next week

TASK..!

• Make groups of 3 to 5 people

• Make a power point presentation (Min. 3 pages) consisting of :

1. Choose one essential nutrient in the soil (each group cannot be the same)

2. Describe :

 The source of these nutrients,

 The function of these nutrients for plants,

 The absorption mechanism of these nutrients, and

 Symptoms of nutrient deficiency (with the picture)

3. Assignments are submitted no later than Oct 21, 2020 at 5 pm to email Indahapriliya93@gmail.com with the subject

DDIT_Name of Team Leader

THANK YOU

Stay Safe and Healthy everyone..!!