Nitrogen transformations in wet soils are markedly different from those in drained, aerated soils. These differences affect the prevalent soil microorganisms and microbial activities and the turnover, availabilility, and losses of N.
The document discusses sulfur as a plant nutrient, including its sources, forms in soil, and factors affecting its availability. Sulfur exists in both inorganic and organic forms in soil, and is taken up by plants primarily as sulfate ions. Its availability is influenced by soil properties like texture, pH, organic matter, and redox conditions. Sulfur deficiency can limit plant growth, so fertilization may be needed to maintain sufficient levels for crop production.
Chemistry and physics of submerged soilAnandhan Ctry
This document summarizes submerged soils. It discusses four main types: waterlogged (gley) soils, marsh soils, paddy soils, and subaquatic soils. It describes the characteristics of submerged soils, including the absence of oxygen, chemical changes that occur like reduction, and transformations of carbon, nitrogen, iron, manganese, sulfur, phosphorus, silicon and trace elements. Key points are that submerged soils become anaerobic, chemical elements shift to their reduced forms, and decomposition of organic matter produces gases like methane and hydrogen sulfide.
Characterisation and management of salt affected soils (1)aakvd
Salt affected soils are soils containing soluble salts that negatively impact plant growth. They are classified as saline soils containing neutral salts or alkali soils containing soluble sodium salts. Saline soils occur in arid regions due to insufficient rainfall for leaching salts out of the soil. Alkali soils form due to accumulation of soluble sodium salts that disperse soil particles. Management of salt affected soils involves physical measures like leaching and drainage, chemical amendments like gypsum, and soil management practices like basin irrigation and growing salt tolerant crops.
This document presents a summary of several classical theories on plant growth response to nutrients:
1) Liebig's Law of the Minimum states that plant growth is limited by the scarcest nutrient.
2) Blackman's Law of the Limiting Factor states that the growth rate is determined by the slowest acting growth factor.
3) Willcox's Theory of the Nitrogen Constant found plants absorb about 318 lbs of nitrogen per acre at optimum conditions.
4) Spillman's Equation models the relationship between growth amount, maximum possible yield, growth factor quantity, and a constant.
5) Baule Unit defines the amount of nitrogen, phosphorus, or potassium needed to produce 50% of maximum possible
Definition and introduction of fertilizer use efficiency , Causes for Low and Declining Crop Response to Fertilizers and FUE.Methods to increase fertilizer use efficiency.
This document summarizes the key impacts and management of waterlogged soils. It notes that waterlogging can lead to oxygen depletion, increased bulk density, lowered redox potential, and nutrient toxicity issues like iron and manganese. Crop yields are reduced due to waterlogging, with losses ranging from 40-77% depending on the crop. Management strategies include land leveling, controlled irrigation, use of tolerant crop varieties, raised bed planting, drainage systems, and establishing deep-rooted plants for bioremediation. Rice cultivation can help reclaim waterlogged soils due to its extensive root system and ability to dilute soil salinity.
The document discusses sulfur as a plant nutrient, including its sources, forms in soil, and factors affecting its availability. Sulfur exists in both inorganic and organic forms in soil, and is taken up by plants primarily as sulfate ions. Its availability is influenced by soil properties like texture, pH, organic matter, and redox conditions. Sulfur deficiency can limit plant growth, so fertilization may be needed to maintain sufficient levels for crop production.
Chemistry and physics of submerged soilAnandhan Ctry
This document summarizes submerged soils. It discusses four main types: waterlogged (gley) soils, marsh soils, paddy soils, and subaquatic soils. It describes the characteristics of submerged soils, including the absence of oxygen, chemical changes that occur like reduction, and transformations of carbon, nitrogen, iron, manganese, sulfur, phosphorus, silicon and trace elements. Key points are that submerged soils become anaerobic, chemical elements shift to their reduced forms, and decomposition of organic matter produces gases like methane and hydrogen sulfide.
Characterisation and management of salt affected soils (1)aakvd
Salt affected soils are soils containing soluble salts that negatively impact plant growth. They are classified as saline soils containing neutral salts or alkali soils containing soluble sodium salts. Saline soils occur in arid regions due to insufficient rainfall for leaching salts out of the soil. Alkali soils form due to accumulation of soluble sodium salts that disperse soil particles. Management of salt affected soils involves physical measures like leaching and drainage, chemical amendments like gypsum, and soil management practices like basin irrigation and growing salt tolerant crops.
This document presents a summary of several classical theories on plant growth response to nutrients:
1) Liebig's Law of the Minimum states that plant growth is limited by the scarcest nutrient.
2) Blackman's Law of the Limiting Factor states that the growth rate is determined by the slowest acting growth factor.
3) Willcox's Theory of the Nitrogen Constant found plants absorb about 318 lbs of nitrogen per acre at optimum conditions.
4) Spillman's Equation models the relationship between growth amount, maximum possible yield, growth factor quantity, and a constant.
5) Baule Unit defines the amount of nitrogen, phosphorus, or potassium needed to produce 50% of maximum possible
Definition and introduction of fertilizer use efficiency , Causes for Low and Declining Crop Response to Fertilizers and FUE.Methods to increase fertilizer use efficiency.
This document summarizes the key impacts and management of waterlogged soils. It notes that waterlogging can lead to oxygen depletion, increased bulk density, lowered redox potential, and nutrient toxicity issues like iron and manganese. Crop yields are reduced due to waterlogging, with losses ranging from 40-77% depending on the crop. Management strategies include land leveling, controlled irrigation, use of tolerant crop varieties, raised bed planting, drainage systems, and establishing deep-rooted plants for bioremediation. Rice cultivation can help reclaim waterlogged soils due to its extensive root system and ability to dilute soil salinity.
The document discusses phosphorus and phosphatic fertilizers. It begins with an introduction to phosphorus as a macronutrient for plants and describes how it exists in different forms in soils, including inorganic and organic phosphorus. It then discusses the production processes for common phosphatic fertilizers like single super phosphate (SSP), triple super phosphate (TSP), and ammonium phosphates (MAP and DAP). The document outlines the chemical reactions involved in the manufacture of these fertilizers. It also addresses phosphorus transformations in soil, including mineralization, immobilization, adsorption, and the factors that influence phosphorus availability.
Sulphur-Source, forms, fertilizers, their behaviour in soils, factors affecti...Abhishika John
Sulphur is an essential secondary nutrient for plant growth. It is the 13th most abundant element in the earth's crust and is absorbed by plants primarily as sulfate ions. Several factors affect the availability of sulphur in soils, including soil texture, organic matter content, pH, and the presence of other ions and nutrients. Sulphur exists in soils in both inorganic and organic forms, and the mineralization of organic sulphur by microorganisms makes it available to plants. Fertilizer application may be needed to supplement sulphur in deficient soils.
Nitrogen is an essential nutrient for plants that exists in soil in various organic and inorganic forms. The processes of mineralization and immobilization control nitrogen availability. Mineralization converts organic nitrogen into plant-available inorganic forms like ammonium and nitrate through aminization, ammonification, and nitrification carried out by soil microbes. Immobilization occurs when carbon-rich residues cause microbes to use inorganic nitrogen, decreasing availability for plants. Maintaining a proper carbon-to-nitrogen ratio in soil is important to promote nitrogen mineralization while avoiding immobilization.
Potassium- Forms,Equilibrium in soils and its agricultural significance ,mech...Vaishali Sharma
The slide is conserned with the potassium fertilisers apllied in the soils. When the fertiliser applied in higher amount then it is avail in different form for plant uptake and there exist a equilibrium in soils and it has many agricultural significance and the slide also deal with brief on the mechanism of potassium fixation in the soil.
This document discusses salt-affected soils, including their classification, distribution in India, and properties. It describes saline soils, saline-alkali soils, and alkali soils based on pH, electrical conductivity, and exchangeable sodium percentage. The major causes of salt-affected soils are arid climate, poor drainage, irrigation with saline water, and other factors. Reclamation methods include physical, biological, and chemical approaches like using gypsum. Proper management of these soils requires attention to irrigation, drainage, amendments, and crop choices.
This document discusses potassium (K) in soils. It covers the following key points:
- K exists in soils in various forms including solution, exchangeable, fixed, and structural/mineral forms. Exchangeable K is the most plant-available.
- K is essential for plant growth and plays important roles in processes like photosynthesis and enzyme activation. Deficiency causes burn symptoms on older leaves and reduced yields.
- Common fertilizers containing K include potassium chloride, potassium sulfate, and potassium magnesium sulfate. Fertilizer K can increase various forms of K in soils.
- Factors like clay content, soil pH, wetting/drying, and freezing/thawing can influence K
This document discusses soil chemistry in submerged soils. It explains that submergence leads to a lack of oxygen in the soil, causing a shift from aerobic to anaerobic organisms. Anaerobic respiration causes chemical compounds other than oxygen to be reduced in a predictable sequence from the least to most energetically favorable. This results in changes to the chemical forms of elements like nitrogen, iron, and sulfur in the soil. Submergence also typically causes soil pH to become more neutral. Nutrient availability is highest within this neutral pH range common for submerged soils.
Saline, sodic, and saline-sodic soils occur when rainfall is insufficient to leach salts below the root zone, leaving soils high in salts like sodium, calcium, magnesium, chloride, and sulfate. Saline soils have high salt levels that increase osmotic pressure and reduce water availability to plants. Sodic soils have high sodium levels that disperse soil particles, reducing infiltration and root growth. Saline-sodic soils contain both high salts and sodium but remain flocculated if salt levels stay elevated; management focuses on exchanging sodium for calcium followed by leaching salts. Proper irrigation water quality and sufficient leaching are needed to manage all salt-affected soils for agriculture.
Nitrogen use efficiency is often low for crops, ranging from 30-50% due to nitrogen losses through mechanisms like ammonia volatilization, nitrate leaching, and denitrification. Methods to improve nitrogen use efficiency include proper fertilizer, soil, and crop management practices as well as modifying fertilizers. Slow release fertilizers, urease inhibitors, and nitrification inhibitors can be used to coat or add chemicals to fertilizers to reduce nitrogen losses and allow for more efficient nitrogen uptake by crops.
Fertilizer use efficiency depends on many factors related to the soil, climate, crop, and fertilizer characteristics. Only a fraction of the nutrients in fertilizer may be absorbed by crops, with the rest lost through leaching, volatilization, immobilization, or interactions between fertilizers. Maximum efficiency is obtained when the minimum amount of fertilizer needed is applied based on soil testing. Efficiency varies depending on soil properties like texture, pH, temperature, and moisture as well as the fertilizer type and application method used.
Integrated Nutrient Management and Balanced Fertilization by Bhanumahi (CCSH...MahanteshKamatyanatti
This document discusses integrated nutrient management and balanced fertilization. It defines balanced fertilization as applying nitrogen, phosphorus, potassium, and other nutrients in proper proportions to meet crop demands and avoid nutrient deficiencies or inefficiencies. The key aspects of balanced fertilization are applying the right nutrient type and quantity using the right application method at the right time. This helps maximize crop yields, improve cost effectiveness, enhance crop quality, and maintain soil fertility while avoiding pollution. The document recommends fertilizer application based on soil testing, use of high-yielding varieties, correcting all nutrient deficiencies, and following the 4R nutrient stewardship concept of applying the right source at the right rate, right time, and right place.
Soil fertility evaluation and fertilizer recommendationBharathM64
This document discusses different approaches for evaluating soil fertility and determining fertilizer recommendations, including soil analysis, plant analysis, and visual deficiency symptoms. It describes methods for both rapid tissue tests of fresh plant parts and total laboratory analysis of dried plant materials. Diagnosis and recommendations can be generalized, based on soil test ratings with adjustments, or use the soil test crop response and target yield concept to determine fertilizer doses needed to achieve specific yields.
Unit 1 lecture-1 soil fertility and soil productivityLuxmiKantTripathi
The document discusses the concepts of soil fertility and productivity, outlining key factors that affect each such as parent material, climate, organic matter and crop management practices. It also reviews the history of understanding soil fertility from ancient Greek and Roman scholars to modern scientists who established theories of plant nutrition and developed agricultural experiments. The overall goal is for students to understand essential plant nutrients and their roles in agriculture and crop production.
Lime requirement of acid soil, liming materials, reclamation and management o...MahiiKarthii
The document discusses lime requirement of acid soils and liming materials. It states that lime requirement is the amount of lime needed to raise the pH of an acidic soil to a desired level, as determined by the Shoemaker buffer method. Liming materials include oxides, hydroxides, carbonates, and silicates of calcium and magnesium. Examples given are limestone, dolomite, slags, and wood ash. The efficiency of liming materials depends on their purity, fineness, and neutralizing value. Liming raises the soil pH and reduces aluminum and manganese toxicity, while improving the availability of phosphorus, micronutrients, and nitrogen fixation.
Fertilizers undergo various chemical reactions in soil that determine their availability to plants. Nitrogenous fertilizers like ammonium sulfate and urea release ammonium ions through cation exchange or hydrolysis reactions. These ions can then be further transformed by soil microbes. Phosphate fertilizers like single superphosphate dissolve in soil water but can precipitate or react with soil minerals to form insoluble compounds depending on the soil pH. Potassium fertilizers like potassium chloride and potassium sulfate readily dissolve to release potassium ions for plant uptake. After application, the nutrients in fertilizers may be taken up by crops, react with the soil, leach below the root zone, or be lost through erosion, runoff or gas emission.
The document discusses the effect of chemical composition of plant residues on nitrogen mineralization in soil. It presents findings from several case studies and research papers. The chemical composition of different plant residues like lignin, polyphenols and C:N ratio affects their decomposition rate and impacts nitrogen mineralization. Plant residues high in nitrogen and low in lignin and polyphenols decompose faster, releasing nitrogen for plant uptake. The studies show crop residues and tree leaves with higher lignin and polyphenol content immobilize soil nitrogen during decomposition.
The document summarizes the nitrogen cycle, which is the biogeochemical process by which nitrogen is converted between different chemical forms and moves through ecosystems. Key points include: (1) nitrogen is essential for life but most organisms cannot use atmospheric nitrogen, (2) microorganisms drive five processes - fixation, uptake, mineralization, nitrification, and denitrification - that convert nitrogen into biologically available forms, and (3) human activity such as fertilizer use has increased nitrogen fixation and altered the global nitrogen cycle, with environmental consequences like water pollution and coastal eutrophication.
effect of submergence in soils and its managementpreethi durairaj
Submergence of soils in water leads to several physical, biological, and chemical changes. Oxygen levels decrease as water replaces air in pore spaces, promoting anaerobic conditions. This allows reduction reactions to occur, changing soil properties like pH, redox potential, and nutrient availability. While phosphorus, potassium, iron, and manganese availability increases, nitrogen can be lost through leaching or denitrification if not properly managed, and sulfur, zinc and copper availability decreases overall. Careful water and nutrient management is needed for optimal crop growth in submerged soils.
The document discusses phosphorus and phosphatic fertilizers. It begins with an introduction to phosphorus as a macronutrient for plants and describes how it exists in different forms in soils, including inorganic and organic phosphorus. It then discusses the production processes for common phosphatic fertilizers like single super phosphate (SSP), triple super phosphate (TSP), and ammonium phosphates (MAP and DAP). The document outlines the chemical reactions involved in the manufacture of these fertilizers. It also addresses phosphorus transformations in soil, including mineralization, immobilization, adsorption, and the factors that influence phosphorus availability.
Sulphur-Source, forms, fertilizers, their behaviour in soils, factors affecti...Abhishika John
Sulphur is an essential secondary nutrient for plant growth. It is the 13th most abundant element in the earth's crust and is absorbed by plants primarily as sulfate ions. Several factors affect the availability of sulphur in soils, including soil texture, organic matter content, pH, and the presence of other ions and nutrients. Sulphur exists in soils in both inorganic and organic forms, and the mineralization of organic sulphur by microorganisms makes it available to plants. Fertilizer application may be needed to supplement sulphur in deficient soils.
Nitrogen is an essential nutrient for plants that exists in soil in various organic and inorganic forms. The processes of mineralization and immobilization control nitrogen availability. Mineralization converts organic nitrogen into plant-available inorganic forms like ammonium and nitrate through aminization, ammonification, and nitrification carried out by soil microbes. Immobilization occurs when carbon-rich residues cause microbes to use inorganic nitrogen, decreasing availability for plants. Maintaining a proper carbon-to-nitrogen ratio in soil is important to promote nitrogen mineralization while avoiding immobilization.
Potassium- Forms,Equilibrium in soils and its agricultural significance ,mech...Vaishali Sharma
The slide is conserned with the potassium fertilisers apllied in the soils. When the fertiliser applied in higher amount then it is avail in different form for plant uptake and there exist a equilibrium in soils and it has many agricultural significance and the slide also deal with brief on the mechanism of potassium fixation in the soil.
This document discusses salt-affected soils, including their classification, distribution in India, and properties. It describes saline soils, saline-alkali soils, and alkali soils based on pH, electrical conductivity, and exchangeable sodium percentage. The major causes of salt-affected soils are arid climate, poor drainage, irrigation with saline water, and other factors. Reclamation methods include physical, biological, and chemical approaches like using gypsum. Proper management of these soils requires attention to irrigation, drainage, amendments, and crop choices.
This document discusses potassium (K) in soils. It covers the following key points:
- K exists in soils in various forms including solution, exchangeable, fixed, and structural/mineral forms. Exchangeable K is the most plant-available.
- K is essential for plant growth and plays important roles in processes like photosynthesis and enzyme activation. Deficiency causes burn symptoms on older leaves and reduced yields.
- Common fertilizers containing K include potassium chloride, potassium sulfate, and potassium magnesium sulfate. Fertilizer K can increase various forms of K in soils.
- Factors like clay content, soil pH, wetting/drying, and freezing/thawing can influence K
This document discusses soil chemistry in submerged soils. It explains that submergence leads to a lack of oxygen in the soil, causing a shift from aerobic to anaerobic organisms. Anaerobic respiration causes chemical compounds other than oxygen to be reduced in a predictable sequence from the least to most energetically favorable. This results in changes to the chemical forms of elements like nitrogen, iron, and sulfur in the soil. Submergence also typically causes soil pH to become more neutral. Nutrient availability is highest within this neutral pH range common for submerged soils.
Saline, sodic, and saline-sodic soils occur when rainfall is insufficient to leach salts below the root zone, leaving soils high in salts like sodium, calcium, magnesium, chloride, and sulfate. Saline soils have high salt levels that increase osmotic pressure and reduce water availability to plants. Sodic soils have high sodium levels that disperse soil particles, reducing infiltration and root growth. Saline-sodic soils contain both high salts and sodium but remain flocculated if salt levels stay elevated; management focuses on exchanging sodium for calcium followed by leaching salts. Proper irrigation water quality and sufficient leaching are needed to manage all salt-affected soils for agriculture.
Nitrogen use efficiency is often low for crops, ranging from 30-50% due to nitrogen losses through mechanisms like ammonia volatilization, nitrate leaching, and denitrification. Methods to improve nitrogen use efficiency include proper fertilizer, soil, and crop management practices as well as modifying fertilizers. Slow release fertilizers, urease inhibitors, and nitrification inhibitors can be used to coat or add chemicals to fertilizers to reduce nitrogen losses and allow for more efficient nitrogen uptake by crops.
Fertilizer use efficiency depends on many factors related to the soil, climate, crop, and fertilizer characteristics. Only a fraction of the nutrients in fertilizer may be absorbed by crops, with the rest lost through leaching, volatilization, immobilization, or interactions between fertilizers. Maximum efficiency is obtained when the minimum amount of fertilizer needed is applied based on soil testing. Efficiency varies depending on soil properties like texture, pH, temperature, and moisture as well as the fertilizer type and application method used.
Integrated Nutrient Management and Balanced Fertilization by Bhanumahi (CCSH...MahanteshKamatyanatti
This document discusses integrated nutrient management and balanced fertilization. It defines balanced fertilization as applying nitrogen, phosphorus, potassium, and other nutrients in proper proportions to meet crop demands and avoid nutrient deficiencies or inefficiencies. The key aspects of balanced fertilization are applying the right nutrient type and quantity using the right application method at the right time. This helps maximize crop yields, improve cost effectiveness, enhance crop quality, and maintain soil fertility while avoiding pollution. The document recommends fertilizer application based on soil testing, use of high-yielding varieties, correcting all nutrient deficiencies, and following the 4R nutrient stewardship concept of applying the right source at the right rate, right time, and right place.
Soil fertility evaluation and fertilizer recommendationBharathM64
This document discusses different approaches for evaluating soil fertility and determining fertilizer recommendations, including soil analysis, plant analysis, and visual deficiency symptoms. It describes methods for both rapid tissue tests of fresh plant parts and total laboratory analysis of dried plant materials. Diagnosis and recommendations can be generalized, based on soil test ratings with adjustments, or use the soil test crop response and target yield concept to determine fertilizer doses needed to achieve specific yields.
Unit 1 lecture-1 soil fertility and soil productivityLuxmiKantTripathi
The document discusses the concepts of soil fertility and productivity, outlining key factors that affect each such as parent material, climate, organic matter and crop management practices. It also reviews the history of understanding soil fertility from ancient Greek and Roman scholars to modern scientists who established theories of plant nutrition and developed agricultural experiments. The overall goal is for students to understand essential plant nutrients and their roles in agriculture and crop production.
Lime requirement of acid soil, liming materials, reclamation and management o...MahiiKarthii
The document discusses lime requirement of acid soils and liming materials. It states that lime requirement is the amount of lime needed to raise the pH of an acidic soil to a desired level, as determined by the Shoemaker buffer method. Liming materials include oxides, hydroxides, carbonates, and silicates of calcium and magnesium. Examples given are limestone, dolomite, slags, and wood ash. The efficiency of liming materials depends on their purity, fineness, and neutralizing value. Liming raises the soil pH and reduces aluminum and manganese toxicity, while improving the availability of phosphorus, micronutrients, and nitrogen fixation.
Fertilizers undergo various chemical reactions in soil that determine their availability to plants. Nitrogenous fertilizers like ammonium sulfate and urea release ammonium ions through cation exchange or hydrolysis reactions. These ions can then be further transformed by soil microbes. Phosphate fertilizers like single superphosphate dissolve in soil water but can precipitate or react with soil minerals to form insoluble compounds depending on the soil pH. Potassium fertilizers like potassium chloride and potassium sulfate readily dissolve to release potassium ions for plant uptake. After application, the nutrients in fertilizers may be taken up by crops, react with the soil, leach below the root zone, or be lost through erosion, runoff or gas emission.
The document discusses the effect of chemical composition of plant residues on nitrogen mineralization in soil. It presents findings from several case studies and research papers. The chemical composition of different plant residues like lignin, polyphenols and C:N ratio affects their decomposition rate and impacts nitrogen mineralization. Plant residues high in nitrogen and low in lignin and polyphenols decompose faster, releasing nitrogen for plant uptake. The studies show crop residues and tree leaves with higher lignin and polyphenol content immobilize soil nitrogen during decomposition.
The document summarizes the nitrogen cycle, which is the biogeochemical process by which nitrogen is converted between different chemical forms and moves through ecosystems. Key points include: (1) nitrogen is essential for life but most organisms cannot use atmospheric nitrogen, (2) microorganisms drive five processes - fixation, uptake, mineralization, nitrification, and denitrification - that convert nitrogen into biologically available forms, and (3) human activity such as fertilizer use has increased nitrogen fixation and altered the global nitrogen cycle, with environmental consequences like water pollution and coastal eutrophication.
effect of submergence in soils and its managementpreethi durairaj
Submergence of soils in water leads to several physical, biological, and chemical changes. Oxygen levels decrease as water replaces air in pore spaces, promoting anaerobic conditions. This allows reduction reactions to occur, changing soil properties like pH, redox potential, and nutrient availability. While phosphorus, potassium, iron, and manganese availability increases, nitrogen can be lost through leaching or denitrification if not properly managed, and sulfur, zinc and copper availability decreases overall. Careful water and nutrient management is needed for optimal crop growth in submerged soils.
The nitrogen cycle describes how nitrogen is converted between its gaseous form in the atmosphere and biological and chemically active forms in soils, oceans, and the biosphere. Key processes include nitrogen fixation, nitrification, assimilation, ammonification, and denitrification which convert nitrogen between gaseous, ionic, and organic forms. Through these processes, nitrogen is circulated naturally between the living world and the atmosphere.
Under submerged soil conditions:
1) Oxygen is depleted from the soil as water fills pore spaces, creating oxidized and reduced soil layers. Aerobic microbes die off while anaerobic bacteria proliferate.
2) Nutrient availability is impacted - phosphorus, potassium, iron, and manganese availability increases while nitrogen can be lost through leaching or denitrification.
3) Soil properties change, including increases in acidic soil pH and decreases in alkaline soil pH as redox potential decreases under low oxygen conditions.
This document discusses the transformation of nitrogen, phosphorus, potassium, and sulfur in soils. It describes the key processes involved in each transformation, including mineralization, nitrification, denitrification, immobilization, solubilization, and oxidation/reduction. It notes that microorganisms play a critical role in transforming organic forms of nutrients into plant-available inorganic forms through the secretion of enzymes and organic acids. Specific microbes involved in each transformation are also outlined, such as nitrifying bacteria, phosphate solubilizing bacteria and fungi, potassium solubilizing bacteria, and sulfur oxidizing bacteria.
The document discusses the global nitrogen cycle, including major pools and fluxes of nitrogen in terrestrial and aquatic ecosystems. It describes how biological nitrogen fixation by bacteria, plants, and cyanobacteria introduces new nitrogen into ecosystems. The document outlines the internal cycling of nitrogen in soils through mineralization, immobilization, and nitrification carried out by soil microbes. It discusses how nitrate produced through nitrification can be lost from ecosystems through leaching and denitrification, causing issues like eutrophication and dead zones.
This document provides an overview of the nitrogen and phosphorus cycles. It begins with the student's name, course details, and introduction to the topic. For nitrogen, it discusses the history of discoveries in the cycle. It then defines the steps of the cycle including nitrogen fixation, assimilation, ammonification, nitrification, denitrification, and sedimentation. For both nitrogen and phosphorus, it discusses biological and non-biological processes, important molecules and enzymes involved, and the impacts of human activity on accelerating the cycles.
The document summarizes submerged soils, including paddy soils. It discusses how submergence causes soils to transition from aerobic to anaerobic conditions. This biological transition results in a predictable sequence of chemical reductions. First, oxygen and nitrates are reduced, followed by manganese, iron, sulfur and carbon compounds. The reductions change the soil chemistry, typically making the pH more neutral between 6.5-7, which increases nutrient availability for rice crops.
The nitrogen cycle describes the conversion of nitrogen between its various chemical forms and involves both biological and non-biological processes. Key processes include nitrogen fixation by bacteria and lightning which converts atmospheric nitrogen gas into ammonia; nitrification by bacteria which converts ammonia into nitrites and nitrates; assimilation by plants which use nitrates and ammonium for growth; ammonification by decomposers which converts organic nitrogen waste into ammonia; and denitrification by bacteria which converts nitrates back into nitrogen gas. Human activities like fossil fuel combustion, agriculture, and deforestation have significantly impacted the global nitrogen cycle.
The document discusses biogeochemical cycles, specifically gaseous cycles. It provides details on the nitrogen cycle, including the steps of nitrogen fixation, nitrate assimilation, ammonification, nitrification, denitrification, and sedimentation. It also briefly summarizes the carbon cycle, noting it is a perfect gaseous cycle as carbon transfers and transformations occur quickly between the atmosphere and organisms through photosynthesis, respiration, decomposition and other processes.
Nitrogen and carbon cycle and their effect on global climate change.PriyankaPrakash37
1) The document discusses the nitrogen and carbon cycles, how human activity has altered them, and their effects on global climate change.
2) It describes how the nitrogen cycle involves the movement of nitrogen between the environment and organisms, and how human activities like fossil fuel combustion and fertilizer use have increased reactive nitrogen levels.
3) It also explains the carbon cycle and how carbon is the basic building block of all living things, being present in the atmosphere, soils, oceans, and Earth's crust. However, human activities have disrupted the natural flows of both nitrogen and carbon.
32. soil alkalinity and salinity by Allah Dad Khan Mr.Allah Dad Khan
Saline soils occur where precipitation is less than evapotranspiration, causing cations like sodium, calcium, and magnesium to accumulate. This raises soil pH above 8.5. Salinity hinders plant growth by limiting their ability to take up water. Specific ions like sodium also interfere with potassium uptake.
Phosphorus and nitrogen are often deficient in alkaline soils. Phosphorus reacts with calcium, aluminum, and iron to form insoluble compounds unavailable to plants. Nitrogen is lost through volatilization or leaching. Micronutrients like iron and zinc also have low solubility in alkaline conditions. Maintaining soil organic matter helps buffer these issues.
nitrogen is the most abundant atmospheric gas,yet is a limiting factor. this presentation is a bird's eye view, of nitrogen cycle, its fixation, uptake and assimilation in plants
This document discusses various topics related to soil and water management including land preparation, types of irrigation, mineral nutrition, and soil conservation. It describes the major purposes of land preparation such as leveling land and preparing seed beds. It discusses different types of irrigation like center-pivot, drip, and furrow irrigation. It also outlines the major mineral nutrients needed by plants like nitrogen, phosphorus, potassium, and their functions. Finally, it discusses soil conservation methods to prevent erosion like terracing, contour tillage, strip cropping, and grass waterways.
The soil air contains oxygen, carbon dioxide, nitrogen and water vapor. The composition of soil air is similar to atmospheric air except for higher carbon dioxide levels due to respiration of soil fauna and flora. Factors like soil texture, organic matter content, season, moisture and vegetation affect the composition of soil air. Proper soil aeration is important for plant growth as it supports respiration of plant roots and soil microbes, nutrient availability, and nitrogen fixation.
This document is a short presentation on soil by Md. Galib Ishraq Emran from Jahangirnagar University's Department of Environmental Sciences. It discusses soil aeration, factors that affect soil aeration like organic matter and moisture, and the importance of soil aeration. Soil aeration allows for the exchange of oxygen and carbon dioxide in the soil pore space and affects nutrient availability and root growth. Proper aeration is important for plant respiration, microbial activity, and preventing toxicity from things like excess manganese or hydrogen sulfide under low oxygen conditions.
Nitrogen is an essential element that cycles through various forms in the environment. The nitrogen cycle involves nitrogen fixation, ammonification, nitrification, and denitrification processes carried out by microorganisms. Nitrogen fixation converts atmospheric nitrogen gas into ammonium which can then be used by plants and other organisms. Ammonification and nitrification convert organic nitrogen and ammonium into nitrates. Denitrification returns nitrogen to the atmosphere as nitrogen gas. The nitrogen cycle is crucial for ecosystems as it makes nitrogen available to support primary production.
Nitrogen fixation is a process where nitrogen in the atmosphere is converted into forms usable by living organisms like ammonia. It is carried out by nitrogen-fixing bacteria in soil and symbiotically in legumes. The nitrogen cycle describes how nitrogen circulates between ecosystems through biological and physical processes like fixation, ammonification, nitrification, and denitrification. The carbon cycle similarly exchanges carbon between the biosphere, atmosphere, hydrosphere, geosphere, and pedosphere through chemical, geological, and biological processes. It was key to making Earth habitable but human activities have significantly impacted the global carbon and nitrogen cycles.
Similar to Nitrogen transformations in wet soils (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
Travis Hills' Endeavors in Minnesota: Fostering Environmental and Economic Pr...Travis Hills MN
Travis Hills of Minnesota developed a method to convert waste into high-value dry fertilizer, significantly enriching soil quality. By providing farmers with a valuable resource derived from waste, Travis Hills helps enhance farm profitability while promoting environmental stewardship. Travis Hills' sustainable practices lead to cost savings and increased revenue for farmers by improving resource efficiency and reducing waste.
BREEDING METHODS FOR DISEASE RESISTANCE.pptxRASHMI M G
Plant breeding for disease resistance is a strategy to reduce crop losses caused by disease. Plants have an innate immune system that allows them to recognize pathogens and provide resistance. However, breeding for long-lasting resistance often involves combining multiple resistance genes
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Unlocking the mysteries of reproduction: Exploring fecundity and gonadosomati...AbdullaAlAsif1
The pygmy halfbeak Dermogenys colletei, is known for its viviparous nature, this presents an intriguing case of relatively low fecundity, raising questions about potential compensatory reproductive strategies employed by this species. Our study delves into the examination of fecundity and the Gonadosomatic Index (GSI) in the Pygmy Halfbeak, D. colletei (Meisner, 2001), an intriguing viviparous fish indigenous to Sarawak, Borneo. We hypothesize that the Pygmy halfbeak, D. colletei, may exhibit unique reproductive adaptations to offset its low fecundity, thus enhancing its survival and fitness. To address this, we conducted a comprehensive study utilizing 28 mature female specimens of D. colletei, carefully measuring fecundity and GSI to shed light on the reproductive adaptations of this species. Our findings reveal that D. colletei indeed exhibits low fecundity, with a mean of 16.76 ± 2.01, and a mean GSI of 12.83 ± 1.27, providing crucial insights into the reproductive mechanisms at play in this species. These results underscore the existence of unique reproductive strategies in D. colletei, enabling its adaptation and persistence in Borneo's diverse aquatic ecosystems, and call for further ecological research to elucidate these mechanisms. This study lends to a better understanding of viviparous fish in Borneo and contributes to the broader field of aquatic ecology, enhancing our knowledge of species adaptations to unique ecological challenges.
2. INTRODUCTION
• Nitrogen is one of the most important primary
nutrient non- metal elements which require large
quantity for the plant growth and nutrition
• No other element essential for life takes as many
forms in soil as nitrogen (N),and transformations
among these forms are mostly mediated by microbes.
• It occurs in the atmosphere, lithosphere, and
hydrosphere. The soil accounts for only a small
amount of lithospheric nitrogen, and of this soil
nitrogen, a very minute amount is directly available to
plants.
• Nitrogen takes nine different chemical forms in soil
corresponding to different oxidative states.
• Biological N2 fixation,whereby N2 is transformed to
organic N dominant natural process by which N enters
soil biological pools.
3. NITROGEN TRANSFORMATIONS
• Nitrogen transformations in wet soils are markedly different from those in drained, aerated soils.
• These differences affect the prevalent soil microorganisms and microbial activities and the turnover,
availabilility, and losses of N.
• The forms of N present in wet soils are generally similar to those in aerated soils; but the relative
magnitude of the N forms, particularly nitrate (NO3)and ammonium (NH4
+), and N transformation are
markedly affected by the oxidation status of soil.
• Nitrate is the dominant form of inorganic N in drained, aerated soils; whereas NH4
+ is the dominant and
stable form of inorganic N that accumulates in wet soils.
• The main N transformation processes in submerged soils—as in aerated soils—are mineralization,
immobilization, nitrification, denitrification, ammonia (NH3) volatilization, and biological N2 fixation.
• Soil submergence modifies these processes, and a unique feature of submerged soils is the simultaneous
formation and loss of NO3−, occurring within the adjoining aerobic and anaerobic soil zones.
• Submerged soils as compared with aerated soils are favorable environments for loss of N by nitrification–
denitrification, NH3 volatilization, and for addition of N via biological N2 fixation (BNF).
4. WET SOILS
• Wet soils are soils that are saturated with water for a
sufficiently long time in a year to give the soil the
following distinctive gley horizons resulting from
oxidation-reduction processes:
i. A partially oxidized ‘A’ horizon high in organic matter
ii. A mottled zone in which oxidation and reduction
alternates
iii. A permanently reduced zone which is bluish green in
colour
• They occur in a range of ecosystems including rice
(Oryza sativa L.) fields, wetlands, estuaries, and
floodplains.
5. PROPERTIES OF WET SOILS
• Depletion of oxygen
A unique feature of wet soils, affecting N transformations, is
the depletion of oxygen (O2) throughout most of the root zone.
• Development of aerobic and anaerobic layer
The greater potential consumption of O2 as compared to the
available supply through the flood water results in two
distinctly different layers being formed in wet soil: an oxidized
or aerobic layer where O2 is present and a reduced or
anaerobic layer in which no free O2 is present.
• Change in soil biology
When oxygen in the soil is depleted, aerobic organisms die or
become dormant. They are replaced by two types of
organisms surviving without oxygen called facultative and
obligate anaerobes
6. • Soil depends on oxygen from plants
Some plants like rice are adapted to grow in wet soils and have
porous structures in their stems and roots called aerenchyma
tissues. These tissues provides a passage for the flow of gas
into the plants through leaves and then down to the roots.
• Oxidation-reduction potential
The most striking and easiest-to-measure change occurring in
a soil as a result of submergence is the decrease in oxidation-
reduction or redox potential. Aerated soils have characteristic
redox potentials in the range +400 to +700 millivolts;
waterlogged soils exhibit potentials as low as -250 to -300
millivolts.
7. MINERALIZATION AND IMMOBILIZATION
• In aerated soils NO3- is the inorganic form and all of the nitrogen reactions that follow the decomposition
of organic matter proceed towards the production of NO3-. Thus, organic form of nitrogen undergoes
mineralization to NH4+, oxidation of NH4+ to NO2- and oxidation of NO2- to NO3-.
In aerobic soils:
Organic form of Nitrogen NH3+ NO2- NO3-
But in an anaerobic soil the absence of O2 inhibits the activity of Nitrosomonas microorganisms that
oxidises NH4+ and therefore, nitrogen mineralization stops at the NH4+ form.
In wet soils:
Organic form of Nitrogen NH4+ Stops at this point
• Mineralization, or more specifically ammonification- the conversion of soil organic N to ammonium-
supplies plant- available N in wet agricultural soils.
• This breakdown of organic N in wet soils is characterized by anaerobic decomposition, which involves
different microorganisms and end products than aerobic decomposition.
• Ammonium accumulates in anaerobic decomposition due to the absence of O2, which is required for
conversion of NH4
+ to NO3
−.
Mineralization
Ammonification
Microbial oxidation Microbial oxidation
Mineralization
8. • Microbial decomposition of organic matter in aerated soil is accomplished by a wide range of
microorganisms. Respiration by these organisms is associated with high energy release, and the
decomposition of substrates progresses rapidly with evolution of CO2. As cell synthesis proceeds, there is
a heavy demand for mineral nutrients, particularly N.
• Decomposition in the bulk volume of a submerged soil, on the other hand, depends on a relatively
restricted bacterial micro flora. These anaerobes operate at a lower energy level and are less efficient
than aerobes as a consequence of incomplete decomposition of carbohydrates and synthesis of fewer
microbial cells per unit of organic C degraded.
• The processes of both decomposition and cell synthesis are consequently slower under anaerobic than
aerobic conditions.
• In aerobic soil the main end products of decomposition are CO2,NO3
−, SO4
2−, water, and resistant residues.
The main end products of anaerobic decomposition are CO2, CH4, organic acids, NH4
+, H2S, and resistant
residues.
• The breakdown of SOM and plant residues is typically slower in wet soils than aerobic soil . Hence, a
lower gross N mineralization rate would be expected in wet soils as compared with aerobic soils.
• Gross N immobilization is characteristically lower in submerged soils because of the low metabolic
requirement of anaerobic microorganisms for N. The net effect of the lower gross mineralization and
lower gross immobilization is often a higher net N mineralization in submerged than aerobic soils,
leading to higher rates of inorganic N release in submerged soil.
• Because of the low N requirement of anaerobic metabolism, the net release of inorganic N from
decomposing plant residue would expectedly occur at a higher C/N in submerged rather than aerobic
soil.
9. NITRIFICATION- DENITRIFICATION
• Nitrification is the biological conversion of NH4
+ to NO3
- which requires free O2. It is a two step
process. Bacteria known as Nitrosomonas convert NH4
+ to NO2
-. Next, bacteria called
Nitrobacter finish the conversion of NO2
- to NO3
-. The reactions are generally coupled and
proceed rapidly to the NO3
- form; hence NO2
- levels at any given time are usually low.
• In wet soils it is restricted only in the oxidized zones which include the water column, a small
layer of surface soil, and soil in the root zone of aquatic plants.
• The magnitude of nitrification is regulated by the availability of O2, which determines the
fraction of the total soil volume occupied by aerobic zones, and NH4
+ concentration in these
aerobic zones.
• Ammonium in aerobic zones originates from formation by ammonification within the aerobic
zone, inputs of external N including fertilizer, and diffusion of NH4
+ from adjacent anaerobic
soil zones.
• Nitrate formed by nitrification is stable within an aerobic zone, but it can be readily reduced in
adjacent anaerobic soil zones.
• Oxygen availability is typically the factor most limiting nitrification in submerged agricultural
soils.
10. • Nitrate does not accumulate in the anaerobic zone because of the high demand for NO3
− to serve
as an electron acceptor in the absence of O2.
• Denitrification is the dissimilatory reduction of NO3
−, whereby NO3
− serves as a terminal
electron acceptor and is reduced to gaseous end products of nitrous oxide (N2O) and nitrogen
gas(N2).
• Denitrification is mediated by heterotrophic microorganisms; and its rate is regulated by NO3
−
concentration and available C, which serves as an energy source or electron donor.
• The supply of NO3
− originating from the aerobic zones is typically the factor limiting
denitrification in submerged soils.
• In submerged soils, the demand for NO3
− to serve as an electron acceptor is typically much
greater than the demand for NO3
− as an N source for microbes and plants.
• Assimilatory reduction of NO3
− where NO3
− is used as a nutrient source and incorporated into
cell biomass is consequently not a significant process.
• Anaerobic soil conditions promote the accumulation of NH4
+, which serves as the primary
inorganic N source for microbes and plants.
• Assimilatory reduction of NO3
− would only be expected when NH4
+ levels are low and NO3
−
levels are high.
11. • A characteristic of submerged soils with important implications for N cycling is the adjoining presence of
aerobic zones where nitrification occurs and anaerobiczones where denitrification occurs.
• The environments suitable for the growth of nitrifiers and denitrifiers are mutually exclusive, but the
transport of substrates and products between the aerobic and anaerobic zones couples nitrification and
denitrification.
• Nitrogen loss by coupled processes of simultaneous nitrification and denitrification is consequently a
unique feature of submerged soils
• The addition of fertilizer N, transport of NH4
+ from anaerobic to aerobic zones, and ammonification in
aerobic zones typically supply adequate NH4
+ for nitrifiers. High NH4
+ levels in aerobic zones suggest the
supply ofNH4
+ exceeds the rate at which NH4
+ is converted to NO3
−.
• The loss of N by coupled nitrification–denitrification is usually limited by the formation of NO3
− , and the
supply of NO3
− can consequently control the size and activityof denitrifiers.
• The loss of fertilizer N by nitrification–denitrification can be reduced by controlling nitrification, which
is typically the rate-limiting step in the process leading to N loss.
• The buildup of NO3
- can be reduced by more effective placement of fertilizer N into the anaerobic zone of
soil , amendment of fertilizer with a nitrification inhibitor, and use of controlled release fertilizer.
• The reduction in NO3
− accumulationwith nitrification inhibitors, while effective in controlling N loss by
nitrification–denitrification and leaching, can enhance NH3 volatilization as a result of enhanced buildup
of ammoniacal N in floodwater and surface soil.
12. Figure: A schematic diagram of the processes by which ammonium fertilizer can be lost from a waterlogged soil.
Ammonium nitrogen applied to the oxidized soil surface is nitrified and then leaches down into the reduced
subsurface layer, where it is denitrified and lost from the soil.
13. AMMONIA VOLATILIZATION
• Ammonia volatilization is a major process by which fertilizer N is lost from rice fields with submerged or
saturated soils.
• A substantial portion of the fertilizer N broadcast into the floodwater of rice fields or incorporated into
puddled soils before rice establishment can accumulate in the floodwater as ammoniacal N (NH4
+ + NH3)
within the week after N application.
• Urea, a common fertilizer for rice, is rapidly hydrolyzed within the week after application to submerged
soils. Ammoniacal N originating from the hydrolyzed urea accumulates in floodwater. High concentrations
of ammoniacal N together with high floodwater pH and temperature favor loss of added fertilizer N by
NH3 volatilization.
• The magnitude of NH3 loss from submerged soils is directly related to the content of aqueous NH3 or
partial pressure of ammonia (ρNH3) in water at the interface with the atmosphere.
• Aqueous NH3 as a fraction of total ammoniacal N is directly influenced by water pH and temperature.
Aqueous NH3 is negligible below pH 7.5, but it increases rapidly from pH 7.5 to 10. At pH 9.2 about 50% of
the ammoniacal N in water is present as NH3.
• Aqueous NH3, at a constant ammoniacal N concentration and pH, increases linearly with temperature,
resulting in nearly a fourfold increase with a change in temperature from 10 to 40°C .
• Water pH is, however, a more important factor influencing NH3 loss than temperature.
14. • Ammonia loss from fertilizer N applied to young rice increases linearly with wind speed and ρNH3
Ammonia loss can be reduced with rice establishment practices that reduce wind speed near the
floodwater surface.
• Young broadcast-seeded rice has been reported to have lower wind speed at 3 to 10 cm above floodwater
and lower associated NH3 loss from applied fertilizer N than young transplanted rice .
• The denser plant population and greater surface cover with broadcast seeded rice, which restricted gas
exchange at the floodwater–atmosphere interface, presumably accounted for the lower ammonia loss.
Methods to reduce N loss through volatilization
Incorporating urea before transplanting rather than broadcasting into floodwater at 10 to 21 days after
transplanting often reduces NH3 loss.
The loss of NH3 from basal incorporated urea is reportedly less when floodwater is first removed and urea
is broadcast and incorporated into saturated soil with no floodwater rather than broadcast and
incorporated with standing floodwater.
NH3 loss can be reduced by reducing the ρNH3 in water at the water–atmosphere interface of saturated or
submerged soils. Films of organic compounds, algal scum, and azolla on the surface of floodwater have
been shown to reduce NH3 loss by restricting the transfer of ammonia from floodwater to the overlying
atmosphere.
The application of fertilizer N immediately before rather than 14 days before permanent flooding reduces
NH3 loss during production of dry-seeded rice on non puddled soils .
The buildup of ammoniacal N in floodwater can be reduced by more effective incorporation and
placement of fertilizer N into puddled soils, application of fertilizer N immediately before rather than after
permanent flooding in non puddled soils, controlled release fertilizers, and urease inhibitors.
15. BIOLOGICAL NITROGEN FIXATION
• Biological Nitrogen Fixation is a process by which molecular nitrogen in the air is converted
into ammonia (NH3) or related nitrogenous compounds in soil which is metabolized by most organisms.
• Wet soils are favorable environments for BNF because of their depletion of O2 and ready supply of C
substrate.
• Nitrogen inputs by BNF help sustain SNSC and maintain SOM, and the input of N by BNF has helped
sustain rice yields at low levels without fertilizer N for hundreds of years on wet soils.
• Long-term N balances for rice grown on submerged soils without fertilizer N typically indicate the
maintenance of total soil N content, as a result of BNF by associative and free-living microorganisms
• Nitrogen fixers—diazotrophs—in wet agricultural soils can be broadly grouped into indigenous and
exogenous systems.
• The indigenous (autochthonous) BNF system comprises cyanobacteria and phototrophic bacteria
inhabiting the floodwater and soil surface, and it comprises heterotrophic bacteria in the root zone and
free-living in the soil. These diazotrophs are typically widespread and native in lowland rice ecosystems.
• The exogenous (allochthonous) BNF system comprises diazotrophs such as N2–fixing cyanobacteria
living in symbiosis with Azolla spp. and heterotrophic and phototrophic rhizobia harboured on aquatic
legumes.The exogenous system is not ubiquitous in lowland rice ecosystems, and it must be applied or
inoculated.
16. • The diverse autotrophs and heterotrophs comprising the indigenous BNF system occur in soil and
floodwater during rice growth and between rice crops when the water regime is favorable.
• Estimates of indigenous BNF based on N balances are typically in the range of 15 to 50 kg N ha−1 crop−1
for lowland rice ecosystems with soil submergence.
• Associative BNF in the rice rhizosphere occurs mostly during the heading stage when soil inorganic N is
low. It depends on rice cultivar and environment and it is often estimated at <10 kg N ha−1 crop−1
although it could theoretically achieve a maximum of 40 kg N ha−1 crop−1.
• Estimates of BNF by free-living heterotrophic bacteria are typically <20 kg N ha−1 crop−1 .
• The application of straw enhances heterotrophic and photodependent BNF by an estimated 2 to 4 kg N
ha−1 Mg−1 of applied straw. The straw serves as a C substrate for heterotrophs, and it can create a more
favorable environment for BNF by reducing inorganic N through temporary immobilization.
• A widely studied exogenous BNF system in submerged rice soils is the symbiotic association of the
Anabaena azollae Strasburger with the freshwater fern Azolla spp. The cyanobacterium inhabits the leaf
cavity of azolla, which can grow rapidly in submerged soils before the rice crop and during the early
growth of rice.
• Estimates of BNF under field rather than experimental conditions suggest symbiotic BNF from the azolla–
cyanobacterium association can contribute 10 to 50 kg N ha−1 crop−1.
17. ANAEROBIC AMMONIUM OXIDATION/ ANAMMOX
• Anaerobic ammonium oxidation (anammox), the process of oxidizing ammonium through the reduction of
nitrite, removes N permanently from aquatic ecosystems and returns it to the atmosphere as nitrogen gas
(N2), as does denitrification.
• The proposed reactions for this process are shown below:
5NH4
+ + 3NO3
− = 4N2 + 9H2O + 2H+
NH4
+ + NO2
− = N2 + 2H2O
• The majority of the soil profile in wetlands is anaerobic, resulting in accumulation of high levels of NH4
+. In
the absence of oxygen, it is thermodynamically possible that several other alternate electron acceptors can
potentially oxidize NH4
+–N
• However, this pathway assumes that some anaerobic bacteria are capable of using NH4
+–N as an electron
donor and derive energy through oxidation.
• The significance of these processes has been documented for wastewater lagoons and marine sediments. At
present, this reaction is not reported in submerged agricultural soils, and the significance of the reaction to
overall N loss remains a subject of speculation.
• The reaction is controlled by availability of NO2
− and competition by heterotrophs,which are dominant in
submerged soils.
• Under conditions of limiting available C, it is likely that some autotrophs might use NH4
+ as an energy
source and potentially oxidize it to N2 gas. Submerged soils, however, are typically not limited by C; and
when NO3
− and NO2
− are present in these systems, they will be used by heterotrophic denitrifiers.
18. AMMONIUM FIXATION
• Fixation of the ammonium ion (NH4
+) by clay minerals is an alternate way of building the nitrogen (N)
pool in soil to optimize N crop recovery and minimize losses.
• The accumulation of NH4+ and the anaerobic conditions following soil submergence are favorable for
the temporary fixation of NH4+ in soils with high amounts of expandable 2:1 clay minerals.
• A buildup of exchangeable NH4+ from mineralization following soil submergence could lead to a
concentration gradient favouring NH4+ diffusion into the interlayers of clay minerals.
• Soil submergence can increase NH4+ fixation through the reduction and dissolution of Fe3+ oxide
coatings on the surface of clay minerals thereby reducing obstacles for NH4+ movement in and out of
interlayers of the clay minerals.
• Soil submergence can also increase NH4+ fixation through the reduction of octahedral Fe3+, which
increases the negative charge of interlayers of the clay minerals.
• The temporary fixation of NH4+ could protect N from losses, while still enabling a timely release of the
NH4+ to plants.
• Nonexchangeable NH4+ can be an important source of N to rice on submerged soils rich in vermiculite.
19. LEACHING LOSSES
(A) NITRATE
• Nitrate present in the root zone of a soil which is submerged at the beginning of the
season is almost invariably lost by denitrification or by being leached out of the root
zone before the plants are large enough to utilize the nitrogen.
• The biological activity and the rate of percolation of water through the soil will
determine which of these mechanisms is most important.
• Nitrate produced in the surface oxidized layer of a waterlogged soil can easily move
downward by diffusion and percolation into the underlying reduced layer, where it is
rapidly denitrified.
• This process is one of the most important pathways of nitrogen loss in waterlogged
soil. Nitrate nitrogen can also be lost from a flooded field by runoff, but the nitrate
content of the flood water seldom exceeds a few parts per million.
20. (B) AMMONIUM NITROGEN
• Ammonium nitrogen is much less subject to leaching from the soil than nitrate because
of its adsorption on the cation-exchange complex.
• Nonetheless, loss of ammonium by leaching is more severe in waterlogged soil than in
well drained soil because:
1. Ammonium is not as likely to accumulate in a well drained soil as in a waterlogged
soil.
2. Reduction reactions in a waterlogged soil produce ferrous and manganous ions which
displace ammonium from the exchange complex to the soil solution where it is more
subject to removal.
3. The constant head of water on the soil surface results in greater downward
percolation of the soil solution in a waterlogged soil than occurs in a well drained soil.
• The addition of organic matter increased the amount of ammonium in the soil solution
instead of immobilizing the nitrogen. There is an increase in the leaching loss of
ammonium due to the addition of organic matter.
22. REFERENCES
• Das,D.K.2012.Introductory Soil Science.2nd Edition, Kalyani Publishers New Delhi.
• Sathyanarayana, E., Kumar, M.S. and Hadole,S.S.2019.Soil Science Treatise.2nd Edition, Jaya Publishing
House Pvt. Ltd. New Delhi
• Buresh,R.J., Reddy, K.R. and Kessel, C.V. 2008. Nitrogen Transformations in Submerged Soils. Soil Sci. Soc.
Am. J. 11:401-427
• Biswas, T.D. and Mukherjee, S.K. 2017. Textbook of Soil Science. 2nd Edition, Mc Graw Hill Education.
• Patrick, H.W.M. And Mahapatra, I.C. 1983. Transformation and availability to rice of nitrogen in
waterlogged Soils. 323-339
• Tisdale, S. L., Nelson, W. L., Beaton, J. D., and Havlin, J. L. (1993). “Soil Fertility and Fertilizers.” 5th ed.
Macmillan New York.
• www.researchgate.net
• www.sciencedirect.com
• soils.ifas.ufl.edu