Soil Fertility and Plant Nutrients

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Questions and Answers

Which nutrients are classified as mobile nutrients in plants?

Nitrogen, manganese, and zinc

Calcium, sulfur, and boron

Phosphorus, potassium, and magnesium (correct)

Iron, copper, and molybdenum

What indicates that a nutrient is immobile within the plant?

Deficiency symptoms appear first in new leaves (correct)

Calcium is strongly held by soil particles

Nutrient can easily leach from the soil

Deficiency symptoms appear first in old leaves

Which nutrient is NOT classified as an immobile nutrient?

Calcium

Zinc

Iron

Phosphorus (correct)

What factor affects nutrient mobility within the soil?

Soil chemical properties like CEC and AEC Signup and view all the answers

Which scenario would lead to greater leaching of nutrients?

Soil with low CEC and high moisture Signup and view all the answers

Why do certain nutrients leach more readily than others in soil?

Their charge properties and strength of soil binding Signup and view all the answers

What are the essential nutrients required by plants expressed in?

Parts per million (ppm) Signup and view all the answers

Which of the following nutrients is typically leached less in comparison to potassium?

Calcium Signup and view all the answers

Which of the following statements correctly describes micronutrients?

Deficiency in any micronutrient can affect overall plant growth. Signup and view all the answers

What is the primary clue for diagnosing nutrient deficiency symptoms?

The location of the first symptoms on the plant Signup and view all the answers

Which group of nutrients are considered macronutrients?

Carbon (C), Hydrogen (H), Oxygen (O) Signup and view all the answers

What can deficiencies in micronutrients lead to, according to the Law of the Minimum?

Overall plant growth failure Signup and view all the answers

Which of the following plants is known to accumulate arsenic and can be toxic?

Astragalus genus Signup and view all the answers

What role does water play for plants aside from being a nutrient?

It provides structural stability. Signup and view all the answers

Which substances can accumulate heavy metals without contributing to plant growth?

Tobacco and Indian mustard Signup and view all the answers

What does the term 'basic nutrients' refer to in the context of plant nutrition?

Essential elements from water and carbon dioxide Signup and view all the answers

What ions must crops absorb from soil pore water to obtain nitrogen?

NH4 and NO3 Signup and view all the answers

What factors can cause variation in nitrogen mineralization potential?

Soil moisture, temperature, soil type, and cropping system Signup and view all the answers

Under what soil moisture condition is nitrogen mineralization optimal?

60% water-filled pore space Signup and view all the answers

Which soil pH range favors bacterial activity and, consequently, nitrogen mineralization?

pH between 6 and 7.5 Signup and view all the answers

What does a high C:N ratio in organic residues indicate regarding nitrogen availability?

Nitrogen will likely be immobilized Signup and view all the answers

What type of organic residues are likely to increase NH4 concentration in soil pore water?

Decomposed animal manure and food-based compost Signup and view all the answers

How do urea fertilizers release NH4 in the soil?

Through microbial hydrolysis by urease enzyme Signup and view all the answers

What is the primary source of NH4 in unfertilized soil?

Nitrogen mineralization Signup and view all the answers

What molecule primarily contributes to the nitrogen content in chicken manure collected from laying facilities without bedding?

Uric acid Signup and view all the answers

Which process is responsible for converting NH₄⁺ to NO₂⁻?

Nitrification Signup and view all the answers

How long does it typically take for uric acid in chicken manure to transform into NH₄⁺ in warm, moist soil?

Several days to a week Signup and view all the answers

What is the C:N ratio of liquid pig slurry?

3 Signup and view all the answers

Which type of manure is considered a 'fast-release' nitrogen fertilizer due to its high moisture content and readily-degradable components?

Liquid pig slurry Signup and view all the answers

What role do ammonia oxidizers play in the nitrogen cycle?

Transforming ammonia to nitrite Signup and view all the answers

What characterizes animal manure mixed with bedding compared to liquid manure forms?

Lower water content Signup and view all the answers

What enzyme catalyzes the conversion of nitrite to nitrate?

Nitrite oxidoreductase Signup and view all the answers

What effect does a higher clay content have on H₄P0₄ adsorption?

It increases H₄P0₄ adsorption. Signup and view all the answers

Which compound is formed as a precipitate with H₄P0₄ in acidic soils?

Iron(III) hydroxide phosphate. Signup and view all the answers

What is the consequence of high phosphorus saturation in soil?

More water-soluble H₄P0₄ remains in pore water. Signup and view all the answers

What factors influence phosphorus loss through erosion and runoff?

Concentration of water-soluble H₄P0₄ and particulate P. Signup and view all the answers

What type of rocks can release elemental sulfur through weathering?

Plutonic rocks, such as pyrite. Signup and view all the answers

Which microorganisms primarily mediate the oxidation of sulfur compounds?

Autotrophic fungi and bacteria. Signup and view all the answers

What is formed when H₄P0₄ precipitates with Ca in neutral to alkaline soils?

Dicalcium phosphate dibydrate. Signup and view all the answers

What role does soil erosion play in phosphorus transport?

It transports both particulate and dissolved phosphorus. Signup and view all the answers

What is a significant factor affecting the conversion of So to SO in soils?

Presence of sulfur-oxidizing microorganisms Signup and view all the answers

From which of the following sources does sulfur enter the soil?

Volcanic eruptions and weathering of crusts Signup and view all the answers

What influences sulfur oxidation reactions to occur rapidly in soil?

Warm temperatures and sufficient moisture Signup and view all the answers

What are some gaseous emissions that can contribute sulfur to the atmosphere?

Hydrogen sulfide and sulfur dioxide Signup and view all the answers

Which of the following is NOT a biogenic source of sulfur?

Atmospheric nitrogen fixation Signup and view all the answers

What effect does moisture content around 60% have on soil in relation to sulfur?

Facilitates sulfur release from minerals Signup and view all the answers

Which gas is produced from the oxidation of sulfur in the atmosphere?

Sulfuric acid Signup and view all the answers

What role does dry and wet deposition play in soil sulfur content?

It introduces sulfur into the soil from atmospheric sources Signup and view all the answers

Study Notes

Soil Fertility

Improving agricultural production leads to decreased soil fertility due to increased nutrient removal by plants.
Soil degradation affects agricultural productivity in many ways, including physical (erosion, crusting, compaction), chemical (acidification, leaching, salinization), and biological (loss of microbial biodiversity).
Offsite land degradation effects include eutrophication of surface water, groundwater contamination, and trace gas emissions.
Soil fertility is the ability of soil to hold plant nutrients and make them available for plant growth.
Soil fertility types include native fertility (natural capacity of the soil) and managed fertility (added nutrients and amendments).

Plant Nutrients

Throughout Earth's history the natural cycling of nutrients occurs through decomposition of biomass.
There are 16 essential nutrients for plants.
12 essential nutrients are typically managed by growers ("mineral nutrients").
Primary nutrients (N, P, K) are required in larger quantities.
Intermediate nutrients (S, Mg, Ca) are intermediate in quantity.
Micronutrients are needed in very small quantities.
The "law of the minimum" applies to any essential nutrient for plant growth that is deficient.

Essential Nutrients for Plants

Macronutrients (e.g., C, H, O, N, K, Ca, P, Mg, S) are needed in larger amounts by plants.
Micronutrients (e.g., B, Cl, Cu, Fe, Mn, Mo, Ni, Zn, Si, Na) are needed in smaller amounts.
Some elements are required for human nutrition but not for plant growth.

Beneficial Nutrients

Non-essential elements are beneficial for some plants, but not all.
Examples include Si, Na, and Se.
Sodium is important in halophilic (salt-loving) plants.

The Forms of Nutrients in Soil

Five forms of plant nutrients in soil include minerals, inorganic cations and anions, nutrient complexes, soluble/soil solution ions, and organic matter.
Mineral examples: feldspar (Ca, K), calcium carbonate (CaCO3).
Nutrients bound to cation and anion exchange sites on soil colloids.
Soluble ions are the nutrients in the soil solution most readily available to plants.

Movement of Nutrients from Soil to Plant Root

Three methods of nutrient uptake: root interception, mass flow, and diffusion.
Root interception: Nutrients come into physical contact with root surface.
Mass flow: Nutrients are transported with water movement.
Diffusion: Nutrients move along a concentration gradient from higher to lower concentration.

Nutrient Uptake into the Root and Plant Cells

Root hairs are major sites of uptake.
Water absorption through osmosis and capillary action.
Nutrient absorption through diffusion and cation exchange.

Nutrient Mobility

Some nutrients are mobile in the plant tissue (e.g., N, P, K, Mg); immobile nutrients (e.g., Ca, S, Fe, Mn, Zn) do not translocate, meaning symptoms first appear in newer growth.
Mobility within soil is related to soil chemistry, conditions, and leaching.

Soil pH

Soil pH is an important chemical characteristic that affects nutrient availability.
Ideal soil pH for nutrient availability is 6.5.
Variations in soil pH require adjusting nutrient management strategies.

Soil Nutrient Cycles

Various cycling processes include nitrogen (N), phosphorus (P), and sulfur (S) cycles.
Nitrogen cycling is crucial for chlorophyll.
Phosphorus is essential for energy storage and transfer.
Sulfur is important for cellular functions.

Factors Controlling Loss of Plant Nutrients

Runoff, erosion, leaching, gaseous losses, and crop removal.
Runoff and erosion remove dissolved or attached soil particles.
Leaching carries nutrients downwards.
Gaseous losses include volatilization and denitrification.
Crop removal takes nutrients from the field.

Soil Fertility Management

Soil testing is a crucial tool in managing soil fertility.
Soil testing helps monitor current nutrient levels and adjust nutrient and lime recommendations.
Soil sampling should follow standard practices to ensure representative samples.

Plant Analysis

Plant analysis can be used to diagnose nutrient deficiencies.
Proper sampling of plant tissues (leaves, petioles) is crucial.
Plant tissue analysis can confirm nutrient deficiencies, help with fertilizer recommendations, and evaluate plant health.

Importance of Measuring Residual Soil Nitrate

Measuring residual soil nitrate (RSN) helps assess N use efficiency and provides data for adjusting future N fertilizer recommendations.
4R nutrient management (right source, rate, time, and place) framework can guide fertilizer application.

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Description

Explore the vital concepts of soil fertility and plant nutrients in agriculture. This quiz covers the effects of soil degradation, types of soil fertility, and the essential nutrients required for plant growth. Test your knowledge on how these factors influence agricultural productivity.