Sulfur Oxidation in Soil

Questions and Answers

What role does sulfur play in protein synthesis?

It is necessary for the synthesis of amino acids like cysteine and methionine. (correct)

It inhibits enzyme activity during translation.

It acts as a primary energetic molecule.

It serves solely as a structural component of proteins.

In what form does the majority of sulfur exist in non-calcareous surface soils?

Airborne gaseous sulfur

Organic forms (correct)

Inorganic sulfates only

Insoluble sulfate compounds

What is the significance of SO42- in anaerobic conditions within waterlogged soils?

It increases nitrogen fixation rate.

It reduces soil acidity.

It acts as an electron acceptor during the anaerobic decay of organic matter. (correct)

It aids in the persistence of organic matter.

Which compounds are synthesized with the help of sulfur?

Glucosides and pungency compounds in certain vegetables Signup and view all the answers

Which statement about the similarities between nitrogen and sulfur cycles is true?

Both have gaseous components and are affected by soil properties. Signup and view all the answers

What is the consequence of anaerobic decay of organic matter in terms of sulfur?

Formation of H2S as a by-product. Signup and view all the answers

How does sulfur affect oil content in certain crops?

It increases oil content in crops like soybean and linseed. Signup and view all the answers

What happens to H2S in normal submerged soils with adequate iron supply?

It is completely removed by reacting with Fe2+ to form FeS. Signup and view all the answers

What is the effect of larger hydrated cations such as Na+, Ca2+, and Mg2+ on the crystal lattice of clay?

They escape fixation and cannot fit in between the layers. Signup and view all the answers

In humid regions, what can the application of lime lead to regarding potassium (K) fixation?

Increase in K fixation in certain soils. Signup and view all the answers

Which condition may result in undesirable effects on potassium availability due to liming?

Soils with pH-dependent negative charge. Signup and view all the answers

What is the primary factor influencing the availability of Ca2+ in soil solutions?

Exchangeable calcium percentage. Signup and view all the answers

What happens to K in well-drained soils compared to acid soils?

K is less likely to be leached out in well-drained soils. Signup and view all the answers

What may happen if calcium carbonate levels are excessive in soil?

Reduction of potassium uptake by plants. Signup and view all the answers

Which soil condition may necessitate supplemental calcium for sufficient Ca2+ availability?

Low CEC in sandy or acid soils. Signup and view all the answers

What is the result of alternate wetting and drying, and freezing and thawing on potassium in soils?

Results in potassium fixation in nonexchangeable forms. Signup and view all the answers

What role does boron play in plants during the reproductive phase?

Regulates the development of reproductive organs Signup and view all the answers

How does boron affect carbohydrate metabolism in plants?

Aids in the translocation of photosynthates Signup and view all the answers

In what condition is boron most soluble for plant uptake?

Acidic soils Signup and view all the answers

What effect does over liming have on boron availability in plants?

Results in boron deficiency Signup and view all the answers

Why do plants experience greater boron deficiency during dry weather?

Plant roots can only access lower soil horizons Signup and view all the answers

What consequence does an imbalance of boron cause in plants?

Causes sterility and malformation of reproductive organs Signup and view all the answers

What is a primary function of chloride in plants?

Aids in the evolution of oxygen during photosynthesis Signup and view all the answers

Which statement about chloride in soils is true?

It is primarily found as simple, soluble chloride salts Signup and view all the answers

Which nutrient group is classified as macronutrients?

Nitrogen, Phosphorus, Potassium Signup and view all the answers

What percentage of total dry matter of plants is made up of carbon and oxygen combined?

96% Signup and view all the answers

Which non-ionic form is associated with nitrogen?

CO (NH2)2 Signup and view all the answers

What is the ionic form of potassium in plants?

K+ Signup and view all the answers

Which of the following is a basic nutrient contributing to the structural composition of plants?

Carbon Signup and view all the answers

Which mineral element has both ferrous and ferric ionic forms?

Iron Signup and view all the answers

Which of the following nutrients is considered a micronutrient?

Zinc Signup and view all the answers

What nutrient group does not include sulfur?

Basic Nutrients Signup and view all the answers

What is formed during the oxidation of amorphous FeS precipitates?

SO42- ion Signup and view all the answers

Which factor is NOT affecting the rate of biological S oxidation in soils?

Soil pH level Signup and view all the answers

What is the approximate C/N/S ratio in most well-drained, non-calcareous soils?

120/10/1.4 Signup and view all the answers

In what form is most sulfur present in the surface horizons of well-drained agricultural soils?

Organic forms Signup and view all the answers

What accounts for over 90% of the total S in most non-calcareous surface soils?

Organic S Signup and view all the answers

What relationship exists between organic C, total N, and total S in soils?

They are positively correlated. Signup and view all the answers

What is one of the broad groups of S compounds recognized in soils?

HI reducible S Signup and view all the answers

Which of the following factors is related to variations in the C/N/S ratio among soils?

Parent material Signup and view all the answers

Study Notes

Plant Nutrients Overview

Essential nutrients contribute to crop growth regardless of concentrations in plants.
Nutrient data assist in effective fertilizer management and recommendations.

Forms of Mineral Elements

Key minerals and their forms:
- Nitrogen (N): Ionic - NH4+, NO3-; Non-ionic - CO(NH2)2
- Phosphorus (P): Ionic - H2PO4-, HPO42-; Non-ionic - Nucleic acids, phytin
- Potassium (K): Ionic - K+
- Calcium (Ca): Ionic - Ca2+
- Magnesium (Mg): Ionic - Mg2+
- Sulfur (S): Ionic - SO42-; Non-ionic - SO2
- Iron (Fe): Ionic - Fe2+, Fe3+; Non-ionic - FeSO4 with EDTA
- Manganese (Mn): Ionic - Mn2+; Non-ionic - MnSO4 with EDTA
- Zinc (Zn): Ionic - Zn2+; Non-ionic - ZnSO4 with EDTA
- Copper (Cu): Ionic - Cu2+; Non-ionic - CuSO4 with EDTA
- Boron (B): Ionic - B4O72-, H2BO3-, HB032-
- Molybdenum (Mo): Ionic - MoO42-
- Chloride (Cl): Ionic - Cl-

Macronutrients and Micronutrients

Basic Nutrients: Carbon, hydrogen, and oxygen comprise 96% of plant dry matter.
- Rice yields around 12 t/ha, consisting of 5.4 t each of carbon and oxygen.
Macronutrients: Needed in large quantities include Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, and Sulfur.
- Nutrient fixation and soil conditions affect nutrient availability and cation exchange capacity (CEC).

Bioavailability and Role of Nutrients

Calcium (Ca): Availability influenced by total supply, soil pH, CEC, and exchangeable Ca2+.
- Sandy or acidic soils may require supplemental calcium.
- High NO3- nutrition enhances Ca2+ accumulation in plants.
Sulfur (S): Crucial for protein synthesis, amino acids, enzymes, and oil content in certain plants.
- Exists in organic and inorganic forms, primarily as SO42- in non-calcareous soils.
- The interaction with microbial populations and soil conditions influences sulfur oxidation and availability.

Micronutrients in Plant Growth

Boron (B): Vital for vascular tissue development, carbohydrate metabolism, and overall reproductive health.
- Soluble in acid conditions and often leached in sandy soils; high pH reduces availability.
Chloride (Cl): Important for photosynthesis, particularly in oxygen evolution and protein synthesis.
- Predominantly found in simple, soluble chloride salts in soil.

Environmental Interactions

Conditions like wetting and drying cycles and soil pH adjustments can significantly impact nutrient availability, affecting overall plant health and nutrient uptake.

Understanding Nutrient Dynamics

Organic and inorganic interactions in soils determine the bioavailability of nutrients crucial for crop development.
Nutrient cycling, redox potentials, and soil microbial populations must be taken into consideration for effective soil management strategies.

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Description

This quiz explores the oxidation processes of sulfur in soil, focusing on the conversion of amorphous FeS precipitates and the formation of SO42- ions. It also examines the bioavailability and role of nutrients in plant growth, particularly the intermediate formation of elemental sulfur during sulfur compound reduction. Test your knowledge on sulfur dynamics in reduced soils, oxidation factors, and environmental impacts.