Soil Fertility and Soil Quality

Introduction to Soil Fertility

• Soil fertility refers to the soil quality that enables it to supply the right compounds in the right amounts and proportions for proper plant growth, when all other growth factors are favorable.
• Soil productivity is the soil's ability to produce a specified plant under a specified management system.
• A soil must be fertile to be productive, but a fertile soil is not automatically productive (e.g., fertile soils in arid regions need irrigation).

Importance of Soil Fertility and Soil Quality

• Increasing world population and conversion of agricultural lands into residential/commercial areas necessitates balanced soil for food and fiber production.
• Soil fertility is a key factor for successful crop production and is a measure of a soil’s capacity to supply plant nutrients.
• Intensive fertilizer use and cropping have increased food production but caused soil problems and environmental pollution, leading to over-exploitation of nutrients.
• "Soil quality" emphasizes the socially valued functions of soil and is mainly determined by soil functions.
• Soil production function - soil serves as a medium for plant growth, by assuring the supply of food, feeds, fiber, and fuel.
• Soil transformation function - nutrients are taken up by plants, transformed, distributed, and efficiently converted into yield.
• Soil habitat function - providing a living space for flora and fauna, supporting a diverse range of organisms.
• Soil degradation function - the breakdown and transformation of plant and animal residues into nutrients by microorganisms, closing the nutrient cycle.
• Soil self-regulation function - maintenance of ecosystem functions, acting as a filter, buffer, and storage, while cycling nutrients, retaining/breaking down harmful substances, and storing carbon dioxide.

Factors Affecting Soil Productivity

• Include all physical, chemical, and biological conditions of the soil and practices affecting fertility, water/air relationships, and biological agents activity.
• Internal factors: Genetic or hereditary factors that aren't managed.
• External factors: Factors regulated to a certain extent.
• Climatic factors: precipitation, solar radiation, atmospheric gases (CO2, NO2, N2O, O2), wind velocity.
• Edaphic/Soil factors: soil moisture/air/temperature, mineral matter, inorganic/organic components, microorganisms, soil reaction.
• Biotic factors: interactions of plants (competitive and complementary), weeds, parasitic plants and symbiotic/free-living bacteria.
• Animals: like earthworms, small and large animals affect soil.
• Physiographic factors: geological strata, topography.
• Anthropogenic factors: human skills and cultivation efficiency.

Historical Development of Plant Nutrition and Soil Fertility

• Cultivation of plants marked the dawn of agriculture.
• Mesopotamia (now Iraq) shows evidence of early civilization with agriculture, located between the Tigris and Euphrates rivers.
• Ancient Athens canals were built to move sewage from cities to farmland.
• Ancient Egyptian murals show agricultural practices such as tillage, planting, irrigation, and harvesting, but not fertilization.
• In the golden age of Greeks (800-200 BC) manure increased productivity, green manure crops (legumes) enriched the soil, marl increased productivity (liming), wood ashes, and saltpeter (KNO3) are beneficial to plants and saline soils could be detected via a taste test.
• The Roman god of manure Stercutius, was worshipped by old women and children.
• Agricultural practices may date back 8,000-10,000 years ago in the Nile Valley (Egypt) and Indus (India) regions.

Important People in the Development of Soil Fertility

• Theophrastus (327-287 B.C.) suggested plants with high nutrient needs also have high water requirements and emphasized green manure crops' value.
• Pietro de Crescenzi (1233–1320) published a farming book.
• Francis Bacon (1561–1624) thought main plant nourishment was water and soil's purpose was to keep plants erect, each plant got a unique substance from the soil.
• Jan Baptiste van Helmont (1577–1644), a Flemish chemist, his willow tree experiment "proved" water was plants' sole nutrient.
• Robert Boyle (1627-1691) confirmed van Helmont's findings and stated plants contained formed salts, spirits, earth, and oil from water.
• J.R. Glauber (1604–1668), a German chemist, suggested saltpeter (KNO3), not water, as the "principle of vegetation".
• Jethro Tull (1674–1741) theorized plants ingested small particles, cultivating the soil eased soil particle uptake and wrote "Horse Hoeing Husbandry" / developed the horseshoe and seed drill.
• John Woodward (1700's) believed plant growth depended on something else than water.
• Albrecht Thaer (1752-1829) believed in the Humus Theory: plants live on humus-derived extracts (C, H, O, N) then rebuild complex plant tissue. Plants can generate other vital nutrients from four elements in humus.
• Philip Carl Sprengel (1787-1859), Thaer's student, concluded salts in humus extracts were real plant nutrients that discussed the idea of fertilizers.
• Theodore de Saussure (1800s) believed the soil provides few nutrients, plants get C from air, growth could not be due to the CO2 uptake, but also to H2O. Plants convert CO2 and water to glucose reaction.
• Justus von Liebig (1802–1873), a German chemist, stated the Law of the minimum in 1862 for predicting crop response to fertilization, /plant growth proportional to fertilizer mineral availability. The modern phosphate fertilizer industry began in 1840 when Leibig demonstrated bones' fertilizer value increase from sulfuric acid.
• J.B. Bousingault (1802-1882), French chemist experimented and maintained a balance sheet, also considered the father of experiments.
• J.B. Lawes and J.H. Gilbert (1843) established an agricultural experiment station at Rothamsted, England. After 12 years, discovered crops required both phosphorus and potash, non-legume crops require nitrogen, /soil fertility could be maintained using using fertilizers /fallow increases nitrogen availability.
• John B. Lawes patented phosphate rock acidulation in 1842 and commercial superphosphate production in England in 1845.

Soil Fertility Research During the Twentieth Century

• The Haber-Bosch process for ammonia synthesis led to a Nobel Prize for Haber /one of the most discoveries of the early twentieth century.
• Soil science (Pedology) was recognized as an agricultural science faculty during the early to mid-20th century.
• Soil fertility scientists used extraction media (water, organic acids, or mineral acids) to assess soil nutrient and crop yield levels/crop response curves (Mitcherlich, 1923; Naubauer, 1932).
• Extraction solutions (Trougs, Brays, Mehlichs, Olsen, etc.) were used to assess available soil nutrients.
• Kjeldahl (1879) devised one of the most used techniques in soil and plant analysis.
• Plant essential nutrients are now routinely estimated using automated spectrocolorimetry, mass spectroscopy, radioisotope techniques, X-ray fluorescence, atomic absorption, emission spectroscopy.

Soil-Plant Relationships - Learning Outcomes

• Determine essential elements' role in plant growth.
• Know the functions of each nutrient in the plant.
• Understand how plant roots absorb nutrients.
• Know mobility of nutrients in the soil.
• Understand the deficiency symptoms of elements.
• Understand the transformation of nitrogen, phosphorus, potassium, and sulfur in soils and related processes.
• Identify the causes of soil fertility decline.

Introduction to Soil-Plant Relationships

• A plant needs nutrients essential for nourishment and metabolic processes so that producers determine what nutrients needed to maximize crop production.
• Understanding how plants absorb/move nutrients are important for determining plant deficiency symptoms.
• Beneficial elements, why only 17 are needed of the periodic table's 100+ elements, element distribution in the soil and element cycle are also discussed to understand transformation of elements, available forms/reasons for fertility decline.

Definition of Terms

• Nutrient: Substances required by an organism's normal growth and reproduction.
• Plant Nutrient: A food composed of chemical elements essential for plant growth and development.
• Nutrition: The supply and absorption of chemical compounds needed for an organism’s growth and metabolism development.
• Deficient: An essential element's low concentration in a plant severely limits growth, produces distinct deficiency symptoms, or lowers yield/product quality.
• Insufficient: Essential nutrient concentration in a plant/available amount inadequately affects plant development and growth.
• Toxic: High element concentration in plants, affects plant growth severely + causes toxicity.
• Excessive: Safely high essential nutrient concentration, results in other nutrients shortage.

Essential Elements in Soils and Their Forms

• There are only seventeen of the 100(+) elements in the periodic table considered essential.
• Arnon and Stout (1939) suggested three criteria for plant nutrient essentiality: deficiency makes plant unable to complete life cycle; deficiency specific and irreplaceable; directly involved in plant nutrition.
• Beneficial elements are needed by specific plants only, ie: cobalt (Co) required by legumes for nitrogen (N) fixation/silica (Si) is beneficial to help plants with multiple stresses. Other beneficial elements include sodium (Na) and vanadium (V).
• Essentiality is determined by growing plants in a nutrient.
• Beneficial elements with their specific functions:
  • Silicon (Si) strengthens cell walls, transfers energy, drought resistance, reduces water loss and prevents fungal infection.
  • Cobalt (Co) is essential in N fixation.
  • Sodium (Na) can replace K in the functions for halophytes, it is needed for plants/C4 plants with dicarboxylic photosynthetic pathway.
  • Vanadium (V) is essential for green algae.
• Plants need 17 elements found in nature to grow/develop. Elements plants use large termed macronutrients.
• Macronutrients: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S).
• Micronutrients are essential elements in smaller amounts: iron (Fe), boron (B), copper (Cu), chlorine (Cl), manganese (Mn), molybdenum (Mo), zinc (Zn), and nickel (Ni).
• Essential Elements and their available forms:
  • Non-mineral Macronutrients:
    • Carbon (C): CO2, H2CO3
    • Hydrogen (H): H+, OH-, H2O
    • Oxygen (O): O2.
  • Primary Macronutrients:
    • Nitrogen (N): NO3- (nitrate), NH4+ (ammonium)
    • Phosphorus (P): H2PO4-, HPO4-2 (phosphate)
    • Potassium (K): K+.
  • Secondary Macronutrients:
    • Calcium (Ca): Ca2+
    • Magnesium (Mg): Mg2+
    • Sulfur (S): SO42- (sulfate).
  • Micronutrients:
    • Boron (B): H3BO3 (boric acid), H2BO3- (borate)
    • Copper (Cu): Cu2+
    • Iron (Fe): Fe2+ (ferrous), Fe3+ (ferric)
    • Manganese (Mn): Mn2+
    • Zinc (Zn): Zn2+
    • Molybdenum (Mo): MoO4- (molybdate)
    • Chlorine (Cl): Cl- (chloride)
    • Nickel (Ni): Ni2+.

Profile Distribution of Elements

• Soil nutrients distribution from the soil/location and profile horizon.
• Soil nutrients varying within the soil profile is due to an intense vertical exchange of materials from the atmosphere, biosphere, and lithosphere.
• Changes in soil-profile nutrient distributions influence productivity, ecology, degradation, and nutrient availability.
• The type, thickness, and position of horizons can yield information about forming such as climate, topography, and vegetation type.
• Weathering, atmospheric deposition, leaching, and biological cycling mechanisms shape the vertical distribution of soil nutrients.
• Weathering dissolution and atmospheric deposition determine nutrient input depth.
• Leaching and biological cycling influence vertical nutrient transport in opposite ways.

Role of Essential Elements in Plant Nutrition

• Carbon (C), hydrogen (H), oxygen (O) are within the plant structure obtained from air (CO2) and water (H2O) are the basis sugars and starch.
• Macronutrients= Primary nutrients: nitrogen (N), phosphorus (P), and potassium (K) that helps supply essential nutrients. Secondary nutrients are calcium (Ca), magnesium (Mg), and sulfur (S).
• Minute amounts of micronutrients necessary for plant survival and are enzyme activators include: Fe, B, Cu, Cl, Mn, Mo, Zn, Co, and Ni.
• Essential elements, its available forms, and functions in plants:
• Non-mineral Macronutrients:
  • Carbon (C) is a constituent of carbohydrates; necessary for photosynthesis.
  • Hydrogen (H) maintains osmotic balance + carbohydrate constituent and important in many reactions.
• Primary Macronutrients:
  • Oxygen (O) is a carbohydrate constituent necessary for respiration.
  • Nitrogen (N) helps proteins, nucleic acids and chlorophyll.
  • Phosphorus (P) a constituent of proteins, enzymes, nucleic acids, metabolic substrates, energy.
  • Potassium (K) is involved with photosynthesis/carbohydrate and protein.
• Secondary Macronutrients:
  • Calcium (Ca): A component of cell walls; plays a role in the structure and permeability.
  • Magnesium (Mg) is an enzyme activator, a component of chlorophyll.
  • Sulfur (S) is also a part of plant proteins.
• Micronutrients:
  • Boron (B) sugar translocation and carbohydrate metabolism.
  • Copper (Cu) A respiration catalyst + component of enzymes.
  • Iron (Fe) is in chlorophyll synthesis + enzymes used for transferring electrons.
• Manganese (Mn) Controls several oxidation-reduction systems and photosynthesis.
• Zinc (Zn) is involved with enzyme systems.
• Molybdenum (Mo) is involved with nitrogen fixation.
• Chlorine (Cl) is for the oxygen production.
• Nickel (Ni) is in the enzyme and helps seed germination.
• Nitrogen, phosphorus, and sulfur are the most likely to limit plant growth. Nutrient deficiencies most commonly occur when the element isn't at a sufficient natural level in the soil.
• Inadequate element quantity, unavailable due high/low pH, low temperatures, or too little/too much water cause deficiencies.
• Deficiencies indicated by plant changes, that differs based on mobility of the mineral. For nitrogen, potassium, and magnesium first show in older leaves mobilized then to younger leaves.
• One element deficiency can have multiple symptoms/same symptoms can be caused by multiple deficiencies elements.
• List of essential elements, their effects.
  • Carbon Air- Not often deficient.
  • Hydrogen - water, not often deficient.
  • Oxygen Air/Water - Not often deficient.
  • Nitrogen shows light leaves in the older leads/Mobile. -Phosphorus colorizes the Leaves purplish to red/Mobile-Soil
  • Potassium-scorching of leaf/Mobile/Soil.
  • Calcium-Mid leaf issues immobile, the other magnesium/ mobile.
  • Sulfer/mobile/Soil. -Boron-immobile.
  • Copper- Immoble Soil.
  • Iron, immobile soil.
  • Manganease Immobile Soil.
• Zinc, immobile Soil.
• Molybdenum, mobile soil.
  • chlorine , mobile Soil.
  • Nickel, mobile Soil.

Biochemical Classification of Elements

• Classification of Nutrients
• Plants divide nutrient based on these.
• Macronutrients: large amounts Primary Nutrients-nitrogen ,phosphorus, and calcium.
• See primary level nutrients. smaller than nitrogen and calcium magnesium, and sulfer.
• Micronutrients -Very small amounts.

Classification of elements based on biochemical behavior.

• Group 1- c h o
• Group 2- p and s
• Group 3- k ca mg
• Group 4- fe mn
• Group 1 contains structural elements.
• They are a major and constitute fats and carbs. Used in enzymes.
• Provides energy.
• Group 2 is accessory structural elements.
• Amino acids and non protestants.
• Involve a storage energy-and phosphate.
• Group 3- translocation. They use translocation and synthesize in carbs and enzymes activation.
• Group 4- catalyst these elements uses in oxidation and exists in plants.

Availablity of Nutrients

• Affectef greatly by the effect of soil PH affected by phosphors which is range 6.0,7.5
• phosphrus binds with iron, al while also forming with calcium making the plant unavailable. While on the manganese is soulable in an alkaline ph. The condition of soduim are soluble. However at low ph the micro are avialable ect molybedmun. Zinc decreases as problem. Micronutrinces supplemes with fertilizers. The availability og nutrines decreases at ph belo6.0.
• The soil ph- test and manage plant and yeild of crops.

Mechanisms of Nuetrient Uptake

• Nuterins must each surph of uptake og essenial
• root or ontace exchage-occurs when mutren contact surface. Other is a exchange . area surph of soirl and enbling.
• soil are are sume less that soil
• root are higher than contence.

Mass flow

• flow - the surface area of plant of the amoutn or soil mass that transpire .flow of soil is decrese. - The moevmeent of on the rpoots are achied by mass an difusio - other substance are transported. Dificusion- difusion long gradient. In the concentration gradient.

Law of the minimum

• • plants need heat light , air , the plants growth is limited by the light is affect plant production.
• Justs was explaned by Jutus

Mitchelich;s equation

• Michehlich's law is an application of effect on yeild cropis. It was created by 19O9. DEsribes this productio as limits are raised the yeilda re proportion of diffenac a= maximun
• A -x - y=- cx. where cx constnt Yield is called diminishing law. Mainain soil and a level is hiher to a ceria limits. Correspondimg to 98 percent. The values varies.

Nitrogen

• Primary Micro use of amino to protein and ezymes. Important component, Herediat.
• Essential of Carbs. Stimaltis is also sufficnt dark green. involved and essential. Is constituientof and form
• Deficicny - defcent in are yellow leaves of and nitrogen. Leaves at the yellow appears on lower plants or mobile, or nitrogen. are to promentnt clorsis sugar content is ,high carbon is desnd .
• toxcicty
• leadsto high leaves attcks the plant in excesss also reduces suagr, the period phase.
• Frosm of n taken by Plants
• dynymac transfrom the respect nutrition bulkls in organic. 2 in inorganic continouse. The utilize is inoranich.

Nitrogien Cycles

• 1.Mineralization conversion nitrogen 2, ismmbilztion- is opporite of mirilizato in
• 3- nitification
• 4-volitization- is loss of amounia-nitrgenthrogough
• 5 dterification-
• plants to the to posons of n under condiitons majority has some greenhouse gas.
• 6. Symbiotic F of nitrogen
• 7 Leaching - ratie occire
• 8 Plant uptake - is anerobi.

phosphous

• roles to inplant

• second after most is dnx and Rna. The system energy in adenosine.

• stimulate energy

• Deficiency phos deficent spindlie and thin with dark is leaves plants ususla s symptoms except for general is recongzed is may take,

• may the to shwo if phosos is defcent. They stem becomes.

• Toxitiy - is easly flows river. Excessive. Zine dficient. Forms of p

• The forms of p is present forms. Phos take is h2hpo throgh mass flow. mostly the solutions phos is s very small the source soils of phos are mineral fertitliers organic in soil few milgrm soil totalp depends climate vegetation irrigation etc.

Pottassium

• roles in pln
• is esstia plant d is is classfied the takes up - of during The it present of earth potassium Thehectart clayyAlmost The profile surface -toleaee winteriness of develop
• iseasy in addition , spcfic assiatied to ofpotassium is plant form to olde is it In on TheSomein casethe is to - reduced the tip brown of blades are rice
• Toxty -The of manganease does effcte that be to it and calcium potassium soils form the is.