Soil Fertility and Soil Productivity Flashcards

Flashcards on Soil Fertility & Soil Productivity

Soil Productivity

The capacity of a soil for producing a specified plant or sequence of plants under a specified system of management.

Soil Fertility

The quality of a soil that enables it to provide essential chemical elements in quantities and proportions for the growth of specified plants.

Liebig's Law of Minimum

States that plant growth is limited by the nutrient present below the minimum requirement.

Soil Fertility

The ability of the soil to supply essential nutrients to plants in sufficient and balanced amount.

Soil Productivity

The ability of the soil to produce desired quantities of plant yield.

Plant Nutrition

The supply and absorption of chemical elements or compounds required by the plant.

Nutrients

Chemical elements or compounds required by plants for normal growth.

Metabolic Processes

Mechanisms by which elements are converted to cellular materials or as sources of energy, or to drive reactions.

Essential Nutrient Elements

C, H, O, N, P, K, Ca, Mg, S, Fe, Mn, Cu, Zn, B, Mo, Cl, Ni

Beneficial Nutrient Elements

Cobalt (Co), Sodium (Na), Silicon (Si), Selenium (Se)

Available forms of Nitrogen for Plant Use

NH4 +, NO3 -

Available forms of Phosphorus for Plant Use

H2PO4 -,HPO4 2-

Available forms of Potassium for Plant Use

K+

Available forms of Calcium for Plant Use

Ca2+

Available forms of Magnesium for Plant Use

Mg2+

Available forms of Sulfur for Plant Use

SO4 2-

Available forms of Iron for Plant Use

Fe2+, Fe3+

Available forms of Manganese for Plant Use

Mn2+

Available forms of Boron for Plant Use

H3BO3, BO3 -

Available forms of Zinc for Plant Use

Zn2+

Available forms of Copper for Plant Use

Cu2+

Available forms of Chlorine for Plant Use

Cl-

Available forms of Molybdenum for Plant Use

MoO4 2-

Available forms of Nickel for Plant Use

Ni2+, Ni3+

Criteria of Essentiality of an element in plant nutrition

Element must be directly involved in the nutrition and metabolism of the plant; It should form a component of either a structural or functional molecule in the plant.

Functions of Nitrogen in plants

Constituent of amino acids, proteins and nucleic acids (DNA, RNA); Integral part of chlorophyll molecule; Component of energy-transfer compounds, such as adenosine diphosphate (ADP) and adenosine triphosphate (ATP)

Functions of Phosphorus in plants

Most essential function of P in plants: Energy storage and transfer; ATP and ADP; Essential element in deoxyribonucleic acid (DNA) and ribonucleic acid(RNA); Structural component of nucleic acids, coenzymes, nucleotides, phosphoproteins, phospholipids and sugar phosphates

Main functions of Potassium

Enhancing photosynthesis, transporting sugars, and activating enzymes

Functions of Calcium in plants

Essential for translocation of carbohydrates and nutrients; Essential to cell wall membrane structure and permeability; Important to N metabolism and protein formation by enhancing NO3 - uptake; Essential for cell division and elongation

Functions of Magnesium in plants

Primary constituent of chlorophyll molecule. Structural component in ribosome which are associated with protein synthesis. Associated with energy transfer reactions from AP in metabolic processes like photosynthesis, glycolysis, TCA cycle (or citric acid or krebs cycle), and respiration.

Functions of Sulfur in plants

Needed in synthesis of S–containing amino acids, such as cystine, cysteine and methionine (about 90% of S in plants); Needed in synthesis of coenzyme A, biotin, thiamin (or vitamin B1) and glutathione.

Nutrient Absorption: Mass Flow

movement of nutrients to the roots due to uptake and transpiration of water.

Nutrient Absorption: Diffusion

movement of nutrient ions from an area of high concentration to one of low concentration

Nutrient Absorption: Root interception (Contact exchange)

direct exchange between root surface and colloid surface.

Passive Transport

Simple diffusion through membranes occurs with small, nonpolar molecules (i.e., O2, CO2). For small, polar species (i.e., H2O, ions, amino acids), specific proteins in the membrane facilitate the diffusion down the electrochemical gradient.

Active Transport

Larger, more-charged molecules have greater difficulty in moving across a membrane, requiring active transport mechanisms (i.e., sugars, amino acids, DNA, ATP, ions, phosphate, proteins)

Rationale for the Need of Fertilizers

Amount of available nutrients in the soil is not enough to meet crop management for high yield; The nutrient in the soil is not present in readily available form; Nutrient depletion or loss is continuous.

Fertilizer

Any substance that is applied to the soil or to the plant to supply the elements required for the nutrition and growth of plants.

Single Nutrient Fertilizers

Fertilizers that supply one primary nutrient

Multinutrient Fertilizers

Fertilizers containing two or three primary nutrients e.g., Ammonium phosphate (16-20-0)

Complete Fertilizer

Contains the 3 primary nutrients which are historically known to be deficient in most soils.

Fertilizer Grade

Weight percentage of the nutrients contained in a fertilizer. Guaranteed minimum analysis of the plant nutrient in terms of % total N, % available phosphate (%P2O5) and % soluble potash (%K2O)

Fertilizer Ratio

Relative proportion of each of the primary nutrients N, P2O5 and K2O in a fertilizer material.

Inorganic Fertilizer

Any fertilizer product whose properties are determined primarily by its content of mineral matter or synthetic chemical compounds.

Organic Fertilizers

Any fertilizer product of plant and/or animal origin that has undergone decomposition through biological, chemical and or any other process as long as the original materials are no longer recognizable, soil-like in texture and free from plant or animal pathogens.

Pure Organic Fertilizer

No chemical has been added to the finished product to increase nutrient content.

Fortified or Enriched Fertilizer

Fertilizer that has be enriched with microbial inoculants, hormones or chemical additives to increase nutrient content.

Production of Nitrogen Fertilizers

Nitrogen fertilizers are manufactured in a variety of formulations, each with different properties and uses for crop production systems. These all essentially begin with anhydrous ammonia which is manufactured from air and natural gas by the Haber-Bosch process

Common N formulations

Urea (45 – 46 % N); Ammonium sulfate (20 – 21 % N); Ammonium nitrate (33 % N); Calcium cyanamide (20-22% N); Anhydrous ammonia (82 % N); Ammonium phosphate (11 % N); Ammonium chloride (26 % N)

Phosphorus Fertilizer Expression

Phosphorus in fertilizer materials is usually expressed in the oxide form (P2O5). Although this form does not actually exist in fertilizer materials, it has been adopted as the standard form for comparison among different P fertilizers.

Sulfur (S) fertilizer sources and formulations

Elemental sulfur (0-0-0-90 S); Ammonium sulfate (21-0-0-24 S); Calcium sulfate (Gypsum) (24% S); Single superphosphate (SSP) (0-20-0); (8 to 10% S)

Calcium (Ca) fertilizer sources

The primary Ca sources are liming materials such as CaCO3, CaMg(CO3)2 and Gypsum (CaSO4.2H2O)

Magnesium (Mg) fertilizer sources

Magnesium sulfate, in the forms of Epsom salts (10% Mg) or keiserite (16% Mg), is the common Mg-supplying fertilizer for crops; Magnesium carbonate (dolomitic lime - CaMg(CO3)2).

Broadcast Method (Fertilizer application)

Spread uniformly over the soil surface.

Sidedress Method (Fertilizer application)

Apply fertilizer in between rows of crops.

Band, row, localized Method (Fertilizer application)

Spread on bands or strip along the side of the row of plants.

Topdress Method (Fertilizer application)

Application sometime after plants have emerged

Foliar Method (Fertilizer application)

Spraying of fertilizer on leaves

Fertigation Method (Fertilizer application)

Application of fertilizer dissolved in irrigation water

Fertilizer grade

weight percentage of the nutrients contained in a fertilizer - guaranteed minimum analysis of the plant nutrient in terms of % total N, % P2O5 and % K2O

Fertilizer ratio

relative proportion of each of the primary nutrients N, P2O5 And K2O in a fertilizer material Example: 14-14-14 => 1:1:1