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ACS CCN1 practice questions

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Question 1Soil Fertility and Plant Nutrition Fundamentals

Which soil pH range is generally considered optimal for the availability of most plant nutrients?

  1. 8.0 to 9.0
  2. 1.0 to 2.0
  3. 6.0 to 7.0 Correct answer.
  4. 3.5 to 4.5

Explanation

Most essential nutrients show their greatest combined availability in slightly acid to neutral soils, roughly pH 6.0 to 7.0. Strongly acid or strongly alkaline conditions reduce the solubility of several nutrients and can increase toxicity of others.

Question 2Soil Fertility and Plant Nutrition Fundamentals

Which of the following is classified as a macronutrient that plants obtain primarily from the soil?

  1. Copper
  2. Boron
  3. Molybdenum
  4. Potassium Correct answer.

Explanation

Potassium is one of the primary macronutrients required in large quantities for enzyme activation, water regulation, and osmoregulation. Molybdenum, boron, and copper are micronutrients needed only in trace amounts.

Question 3Soil Fertility and Plant Nutrition Fundamentals

A soil test reports a cation exchange capacity (CEC) of 25 cmol(+)/kg. What does this value most directly indicate about the soil?

  1. The soil has a high capacity to retain exchangeable cations Correct answer.
  2. The soil is strongly acidic
  3. The soil has a low capacity to hold exchangeable cations
  4. The soil contains no clay minerals

Explanation

CEC measures the total quantity of exchangeable cations a soil can retain per unit mass. A value of 25 cmol(+)/kg is relatively high and indicates substantial capacity to hold nutrients such as calcium, magnesium, and potassium against leaching.

Question 4Soil Fertility and Plant Nutrition Fundamentals

Which process converts atmospheric nitrogen gas into plant-available forms through the action of symbiotic bacteria in legume root nodules?

  1. Denitrification
  2. Biological nitrogen fixation Correct answer.
  3. Nitrification
  4. Ammonification

Explanation

Biological nitrogen fixation is carried out by bacteria such as Rhizobium that reduce atmospheric N2 to ammonia inside legume root nodules. This makes nitrogen available for plant uptake and contributes to soil nitrogen reserves.

Question 5Soil Fertility and Plant Nutrition Fundamentals

Which soil textural class typically has the greatest water-holding capacity?

  1. Clay Correct answer.
  2. Sandy clay loam
  3. Sandy loam
  4. Loamy sand

Explanation

Clay particles have the largest surface area and abundant micropores, giving clay soils the greatest total water-holding capacity. However, much of that water may be tightly held and not fully available to plants.

Question 6Soil Fertility and Plant Nutrition Fundamentals

Legumes are commonly rotated with cereal crops primarily because legumes can do which of the following?

  1. Increase soil pH
  2. Add fixed nitrogen to the soil Correct answer.
  3. Reduce soil organic matter
  4. Eliminate the need for phosphorus

Explanation

Legumes form symbiotic associations with nitrogen-fixing bacteria and can contribute fixed nitrogen to the cropping system. This reduces the nitrogen fertilizer requirement for a following cereal crop.

Question 7Soil Fertility and Plant Nutrition Fundamentals

Which nutrient deficiency commonly produces interveinal chlorosis on younger leaves because the nutrient is relatively immobile in the plant?

  1. Iron Correct answer.
  2. Magnesium
  3. Nitrogen
  4. Potassium

Explanation

Iron is largely immobile within the plant, so a deficiency appears first on new growth as interveinal chlorosis. Mobile nutrients such as nitrogen, magnesium, and potassium typically show symptoms first on older leaves.

Question 8Soil Fertility and Plant Nutrition Fundamentals

Which practice most directly increases soil organic matter and improves nutrient retention over time?

  1. Burning of crop residues
  2. Continuous bare fallow
  3. Regular additions of compost Correct answer.
  4. Intensive tillage

Explanation

Adding compost supplies stabilized organic carbon that builds soil organic matter and increases cation exchange capacity. Organic matter improves nutrient retention and overall soil structure.

Question 9Soil Fertility and Plant Nutrition Fundamentals

A fertilizer analysis is listed as 18-46-0. What does the 46 represent?

  1. Percent calcium carbonate equivalent
  2. Percent phosphorus expressed as P2O5 Correct answer.
  3. Percent potassium expressed as K2O
  4. Percent nitrogen

Explanation

In fertilizer grades, the three numbers represent percent nitrogen, available phosphorus expressed as P2O5, and soluble potassium expressed as K2O, in that order. The middle value of 46 therefore indicates 46 percent P2O5.

Question 10Soil Fertility and Plant Nutrition Fundamentals

Why is ammonium-based nitrogen fertilizer sometimes associated with acidification of the soil?

  1. Ammonium uptake releases hydrogen ions and nitrification produces acidity Correct answer.
  2. Ammonium converts directly to nitrogen gas
  3. Ammonium reacts with phosphorus to form gypsum
  4. Ammonium raises the CEC of the soil

Explanation

When plants take up ammonium, they release hydrogen ions, and bacterial nitrification of ammonium to nitrate also generates hydrogen ions. Over time these processes lower soil pH, so long-term ammonium use can acidify soils.

Question 11Soil Fertility and Plant Nutrition Fundamentals

Which soil condition most limits phosphorus availability to plants in many acid soils?

  1. Excess nitrate
  2. Low CEC
  3. Fixation by iron and aluminum Correct answer.
  4. High organic matter

Explanation

In acid soils, dissolved phosphate reacts with iron and aluminum to form insoluble compounds, reducing its availability. Liming to a suitable pH reduces this fixation and improves phosphorus availability.

Question 12Soil Fertility and Plant Nutrition Fundamentals

A grower wants to determine whether a field needs potassium before planting. Which approach provides the most reliable site-specific basis for the decision?

  1. Estimating from the color of the soil
  2. Collecting a representative soil sample for laboratory analysis Correct answer.
  3. Relying on the previous year's yield alone
  4. Applying a fixed rate regardless of soil test

Explanation

Laboratory soil testing of a representative sample gives a quantitative measure of plant-available potassium and supports calibrated fertilizer recommendations. Yield history and appearance are indirect indicators that do not quantify soil supply.

Question 13Soil Fertility and Plant Nutrition Fundamentals

Which form of nitrogen is most readily leached from soils because it carries no positive charge and is not held on cation exchange sites?

  1. Organic nitrogen in humus
  2. Urea
  3. Ammonium
  4. Nitrate Correct answer.

Explanation

Nitrate is an anion and is repelled by the negatively charged exchange complex, so it moves freely with drainage water. Ammonium is a cation and is held on exchange sites, while urea and humus are not the leachable ionic form.

Question 14Soil Fertility and Plant Nutrition Fundamentals

Which nutrient is most commonly deficient in calcareous, high-pH soils and causes interveinal chlorosis of new leaves?

  1. Nitrogen
  2. Iron Correct answer.
  3. Sulfur
  4. Magnesium

Explanation

In calcareous soils with high pH, iron forms insoluble compounds and becomes largely unavailable, producing interveinal chlorosis on young leaves. This is a classic pH-related micronutrient deficiency.

Question 15Soil Fertility and Plant Nutrition Fundamentals

Which statement best describes the role of cation exchange in supplying potassium to plant roots?

  1. Potassium is only available after soil pH falls below 5
  2. Potassium is held by covalent bonds that roots must break
  3. Potassium is taken up only as a gas through leaves
  4. Potassium is held on exchange sites and released into solution as roots take up other cations Correct answer.

Explanation

Potassium is held as an exchangeable cation on negatively charged soil surfaces. As roots absorb potassium, other cations replace it on exchange sites, replenishing the soil solution and buffering supply.

Question 16Soil Fertility and Plant Nutrition Fundamentals

A soil has a pH of 5.2 and a low base saturation. Which amendment is most appropriate to raise the pH toward the target range for most agronomic crops?

  1. Agricultural lime Correct answer.
  2. Elemental sulfur
  3. Gypsum
  4. Ammonium sulfate

Explanation

Agricultural lime (calcium carbonate) neutralizes soil acidity and raises pH while supplying calcium. Elemental sulfur and ammonium sulfate acidify soil, and gypsum supplies calcium without raising pH.

Question 17Soil Fertility and Plant Nutrition Fundamentals

Which of the following best explains why sandy soils generally require more frequent potassium fertilization than clay soils?

  1. Sandy soils have lower cation exchange capacity and lose potassium more readily Correct answer.
  2. Sandy soils have a higher pH than clays
  3. Sandy soils have higher organic matter than clays
  4. Sandy soils fix potassium more strongly than clays

Explanation

Sandy soils have a low cation exchange capacity because they contain little clay and organic matter, so exchangeable potassium is easily leached. This requires more frequent, smaller potassium applications.

Question 18Soil Fertility and Plant Nutrition Fundamentals

Which process in the nitrogen cycle converts ammonium to nitrate and is carried out by soil bacteria?

  1. Nitrogen fixation
  2. Nitrification Correct answer.
  3. Denitrification
  4. Ammonification

Explanation

Nitrification is a two-step microbial oxidation of ammonium to nitrite and then nitrate. It makes nitrogen available as nitrate but also increases the potential for leaching and denitrification losses.

Question 19Soil Fertility and Plant Nutrition Fundamentals

A plant shows stunted growth with purple discoloration on older leaves and poor root development. Which nutrient deficiency is most consistent with these symptoms?

  1. Phosphorus Correct answer.
  2. Iron
  3. Calcium
  4. Boron

Explanation

Phosphorus deficiency often causes stunted growth, dark green to purplish older leaves, and poor root development because phosphorus is mobile and redistributed from older tissue. These symptoms indicate inadequate phosphorus supply.

Question 20Soil Fertility and Plant Nutrition Fundamentals

Which practice is most effective for reducing nitrate leaching into groundwater after a nitrogen application?

  1. Flood irrigating immediately after application
  2. Leaving the soil bare between seasons
  3. Splitting nitrogen applications to match crop uptake Correct answer.
  4. Applying all nitrogen in a single large dose in autumn

Explanation

Splitting nitrogen applications synchronizes nitrogen supply with crop demand, reducing the amount of nitrate present in the soil when drainage occurs. This limits leaching losses and improves nitrogen use efficiency.

Question 21Soil Fertility and Plant Nutrition Fundamentals

Which soil property is increased most directly by raising soil organic matter content?

  1. Erosion susceptibility
  2. Soil crusting
  3. Water-holding capacity Correct answer.
  4. Bulk density

Explanation

Organic matter increases porosity and aggregation, which raises the soil's ability to retain water. It also improves structure and reduces bulk density and erosion.

Question 22Soil Fertility and Plant Nutrition Fundamentals

A soil test shows adequate total soil nitrogen but plants display nitrogen deficiency symptoms. Which explanation is most plausible?

  1. The nitrogen is present but largely in organic forms not yet mineralized Correct answer.
  2. The plants are deficient in phosphorus instead
  3. The soil pH must be above 9
  4. Nitrogen is always unavailable when total nitrogen is high

Explanation

Total nitrogen includes organic forms that must be mineralized to ammonium and nitrate before plants can take them up. If mineralization is slow, plants can show deficiency even when total nitrogen is high.

Question 23Soil Fertility and Plant Nutrition Fundamentals

Two soils have the same CEC, but soil A has a base saturation of 40 percent and soil B has a base saturation of 85 percent. Which conclusion is best supported?

  1. Soil B has proportionally more exchange sites occupied by basic cations Correct answer.
  2. Soil A holds more total cations than soil B
  3. Soil B has no exchangeable hydrogen
  4. Soil A has a higher pH than soil B

Explanation

Base saturation is the percentage of exchange sites occupied by basic cations such as calcium, magnesium, and potassium. A higher base saturation means a larger proportion of sites is occupied by these cations, which usually corresponds to a higher pH.

Question 24Soil Fertility and Plant Nutrition Fundamentals

A grower applies urea to the soil surface on a warm, moist day without incorporation. Which nitrogen loss pathway is most likely to increase?

  1. Nitrate leaching
  2. Cation exchange
  3. Ammonia volatilization Correct answer.
  4. Phosphorus fixation

Explanation

Urea hydrolyzes to ammonium and, at the soil surface, can raise localized pH and lose nitrogen as ammonia gas. Incorporation or irrigation moves urea into the soil and reduces volatilization.

Question 25Soil Fertility and Plant Nutrition Fundamentals

Which combination of soil conditions would most strongly limit the availability of both phosphorus and micronutrients such as zinc and iron?

  1. Neutral pH with balanced fertility
  2. High pH and calcareous conditions Correct answer.
  3. Slightly acid pH with high organic matter
  4. Low CEC with moderate organic matter

Explanation

High pH, especially in calcareous soils, promotes precipitation of phosphorus with calcium and renders iron and zinc largely insoluble. These conditions reduce the availability of all three nutrients simultaneously.

Question 26Soil Fertility and Plant Nutrition Fundamentals

Which essential plant nutrient is taken up primarily as the negatively charged ion H2PO4- and is most available to plants in soils near pH 6.5?

  1. Sulfur
  2. Phosphorus Correct answer.
  3. Magnesium
  4. Calcium

Explanation

Phosphorus is absorbed mainly as the primary orthophosphate anion H2PO4-, and its solubility is greatest in the slightly acidic range around pH 6.5. Below that range it is fixed by iron and aluminum, and above it by calcium.

Question 27Soil Fertility and Plant Nutrition Fundamentals

A soil test reports a cation exchange capacity of 20 cmol/kg and a base saturation of 50 percent. Approximately how much of that exchange capacity is occupied by basic cations such as calcium, magnesium, and potassium?

  1. 10 cmol/kg Correct answer.
  2. 5 cmol/kg
  3. 20 cmol/kg
  4. 15 cmol/kg

Explanation

Base saturation is the percentage of the cation exchange capacity occupied by basic cations. Multiplying 20 cmol/kg by 50 percent gives 10 cmol/kg of exchange sites held by basic cations, with the remainder occupied largely by acidic cations such as hydrogen and aluminum.

Question 28Soil Fertility and Plant Nutrition Fundamentals

A legume cover crop is terminated and left on the soil surface, and several weeks later the following crop shows nitrogen deficiency. Which explanation best accounts for this?

  1. The residue raises soil pH sharply and locks up all nitrogen as ammonia gas
  2. The residue has a high carbon-to-nitrogen ratio, so microbes immobilize soil nitrogen as they decompose it Correct answer.
  3. The residue releases nitrogen too slowly because legumes contain almost no nitrogen
  4. The residue repels water and prevents nitrogen from moving into the root zone

Explanation

When residue has a high carbon-to-nitrogen ratio, soil microbes need additional nitrogen to build their own biomass and draw it from the soil solution. This immobilization temporarily reduces nitrogen available to the crop until decomposition balances out.

Question 29Soil Fertility and Plant Nutrition Fundamentals

Soil test results show a pH of 7.8 with free lime present, and a crop is showing interveinal chlorosis on the newest leaves. Which nutrient is most likely deficient?

  1. Boron
  2. Molybdenum
  3. Manganese
  4. Iron Correct answer.

Explanation

In calcareous, high-pH soils iron forms insoluble compounds and becomes poorly available, producing interveinal chlorosis on young leaves because iron is not mobile within the plant. Molybdenum availability actually increases at high pH, so it is not the limiting nutrient here.

Question 30Soil Fertility and Plant Nutrition Fundamentals

Two soils have identical cation exchange capacity and organic matter, but soil A is dominated by kaolinite clay while soil B is dominated by smectite clay. Which statement best explains why soil B generally holds more exchangeable cations?

  1. Smectite holds cations only through pH-dependent edge charges, which are always stronger than permanent charges
  2. Kaolinite has a larger specific surface area because of its 1:1 layer structure
  3. Smectite has a higher surface charge density from isomorphic substitution and interlayer swelling, giving more exchange sites per unit mass Correct answer.
  4. Kaolinite retains cations by fixing them permanently between layers, removing them from exchange

Explanation

Smectite is a 2:1 clay with substantial isomorphic substitution and an expanding interlayer, which produces a high permanent negative charge and a large specific surface area. Kaolinite is a 1:1 clay with little substitution and low surface area, so it holds far fewer exchangeable cations per unit mass.

Question 31Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which fertilizer material is a single-nutrient source that supplies only nitrogen?

  1. Potassium chloride
  2. Ammonium nitrate
  3. Monoammonium phosphate
  4. Anhydrous ammonia Correct answer.

Explanation

Anhydrous ammonia (82-0-0) contains only nitrogen, so it is a straight nitrogen fertilizer. Monoammonium phosphate also supplies phosphorus, and potassium chloride supplies potassium.

Question 32Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which material is commonly used as a liming agent to raise soil pH?

  1. Calcium carbonate Correct answer.
  2. Elemental sulfur
  3. Ammonium sulfate
  4. Gypsum

Explanation

Calcium carbonate neutralizes soil acidity and raises pH. Gypsum and elemental sulfur do not raise pH; ammonium sulfate is an acid-forming fertilizer.

Question 33Nutrient Sources, Fertilizer Materials, and Soil Amendments

What does the grade designation 18-46-0 on a fertilizer label indicate?

  1. 18% ammonium, 46% P2O5, 0% K2O
  2. 18% nitrogen, 46% elemental phosphorus, 0% potassium
  3. 18% nitrate, 46% phosphate, 0% potash
  4. 18% nitrogen, 46% phosphorus pentoxide, 0% potassium oxide Correct answer.

Explanation

Fertilizer grades express the percentages of total nitrogen, available phosphorus expressed as P2O5, and soluble potassium expressed as K2O. The grade 18-46-0 therefore means 18% N, 46% P2O5, and 0% K2O.

Question 34Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which of the following is a natural organic soil amendment that improves water-holding capacity in sandy soils?

  1. Sand
  2. Vermiculite
  3. Perlite
  4. Sphagnum peat moss Correct answer.

Explanation

Sphagnum peat moss is an organic material that absorbs and holds water, improving water retention in sandy soils. Perlite and vermiculite are inorganic minerals, and sand does not increase water holding.

Question 35Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which fertilizer material is a common source of both nitrogen and sulfur?

  1. Urea
  2. Ammonium sulfate Correct answer.
  3. Muriate of potash
  4. Triple superphosphate

Explanation

Ammonium sulfate contains 21% nitrogen and 24% sulfur, supplying both nutrients. Urea supplies only nitrogen, triple superphosphate supplies phosphorus and calcium, and muriate of potash supplies potassium and chloride.

Question 36Nutrient Sources, Fertilizer Materials, and Soil Amendments

What is the primary purpose of adding compost to soil?

  1. To increase soil salinity
  2. To improve soil structure and add organic matter Correct answer.
  3. To supply readily available nitrogen
  4. To raise soil pH

Explanation

Compost is a source of stabilized organic matter that improves soil aggregation, water retention, and biological activity. It is not a primary liming material or a high-analysis nitrogen fertilizer.

Question 37Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which material is classified as a synthetic chelate used to supply micronutrients such as iron?

  1. EDTA Correct answer.
  2. Gypsum
  3. Blood meal
  4. Dolomite

Explanation

EDTA (ethylenediaminetetraacetic acid) is a synthetic chelating agent that binds metal ions like iron, zinc, and copper, keeping them soluble and available to plants. Gypsum and dolomite are mineral amendments, and blood meal is an organic nitrogen source.

Question 38Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which fertilizer is considered a slow-release nitrogen source because it requires microbial decomposition?

  1. Urea
  2. Ammonium nitrate
  3. Sulfur-coated urea
  4. Blood meal Correct answer.

Explanation

Blood meal is an organic material that must be mineralized by soil microbes before its nitrogen becomes available, making it a slow-release source. Ammonium nitrate and urea are quickly available, and sulfur-coated urea is a controlled-release fertilizer but not dependent on microbial decomposition in the same way.

Question 39Nutrient Sources, Fertilizer Materials, and Soil Amendments

A soil test recommends 60 lb of P2O5 per acre. How many pounds of triple superphosphate (0-46-0) are needed to supply this amount?

  1. 130 lb Correct answer.
  2. 46 lb
  3. 60 lb
  4. 276 lb

Explanation

Triple superphosphate is 46% P2O5, so the amount needed is 60 lb ÷ 0.46 = 130.4 lb per acre. The other values result from incorrect calculations.

Question 40Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which nitrogen fertilizer has the highest percentage of nitrogen by weight?

  1. Ammonium sulfate (21-0-0)
  2. Ammonium nitrate (34-0-0)
  3. Urea (46-0-0)
  4. Anhydrous ammonia (82-0-0) Correct answer.

Explanation

Anhydrous ammonia contains 82% nitrogen, the highest concentration among common nitrogen fertilizers. Urea is 46%, ammonium nitrate is 34%, and ammonium sulfate is 21%.

Question 41Nutrient Sources, Fertilizer Materials, and Soil Amendments

Why is dolomitic lime preferred over calcitic lime on soils deficient in magnesium?

  1. Dolomitic lime neutralizes acidity faster
  2. Dolomitic lime contains magnesium carbonate in addition to calcium carbonate Correct answer.
  3. Dolomitic lime is more soluble and moves quickly through the soil
  4. Calcitic lime contains more calcium than dolomitic lime

Explanation

Dolomitic lime contains both calcium carbonate and magnesium carbonate, so it supplies magnesium as well as raising pH. Calcitic lime contains primarily calcium carbonate and little magnesium.

Question 42Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which of the following is a commercial source of potassium?

  1. Superphosphate
  2. Ammonium phosphate
  3. Calcium nitrate
  4. Potassium sulfate Correct answer.

Explanation

Potassium sulfate (0-0-50) is a potassium fertilizer that also supplies sulfur. Superphosphate supplies phosphorus, ammonium phosphate supplies nitrogen and phosphorus, and calcium nitrate supplies nitrogen and calcium.

Question 43Nutrient Sources, Fertilizer Materials, and Soil Amendments

What is the main advantage of using a chelated micronutrient fertilizer compared with a sulfate salt?

  1. Chelates are rapidly leached from the soil
  2. Chelates supply more micronutrient per pound
  3. Chelates are less expensive
  4. Chelates remain available to plants over a wider pH range Correct answer.

Explanation

Chelating agents protect metal ions from precipitation and adsorption, keeping them soluble and available across a wider pH range than simple sulfate salts. Chelates are generally more expensive and do not necessarily supply more nutrient per pound.

Question 44Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which material is used as a soil amendment to improve drainage in heavy clay soils?

  1. Perlite Correct answer.
  2. Peat moss
  3. Compost
  4. Gypsum

Explanation

Perlite is a lightweight, porous mineral that improves drainage and aeration when mixed into heavy soils. Compost and peat moss increase water retention, and gypsum is used primarily to supply calcium and sulfur or to improve sodic soil structure, not as a drainage amendment.

Question 45Nutrient Sources, Fertilizer Materials, and Soil Amendments

A grower wants to supply 30 lb of actual nitrogen per acre using urea (46-0-0). How many pounds of urea are required?

  1. 138 lb
  2. 65 lb Correct answer.
  3. 46 lb
  4. 30 lb

Explanation

The amount of fertilizer needed is the desired nutrient rate divided by the fertilizer analysis: 30 lb ÷ 0.46 = 65.2 lb of urea per acre. The other values represent common calculation errors.

Question 46Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which of the following is a natural mineral amendment that supplies both calcium and sulfur without raising soil pH?

  1. Lime
  2. Gypsum Correct answer.
  3. Wood ash
  4. Dolomite

Explanation

Gypsum (calcium sulfate) supplies calcium and sulfur and has a neutral effect on soil pH. Lime and dolomite raise pH, and wood ash is alkaline.

Question 47Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which fertilizer material is a byproduct of the steel industry and is used as a liming agent?

  1. Rock phosphate
  2. Gypsum
  3. Epsom salt
  4. Basic slag Correct answer.

Explanation

Basic slag is a byproduct of steel production that contains calcium silicate and other compounds and is used as a liming material. Gypsum, Epsom salt, and rock phosphate are not primarily liming agents.

Question 48Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which of the following statements about urea is true?

  1. Urea is a source of both nitrogen and sulfur
  2. Urea is a phosphorus fertilizer
  3. Urea is a slow-release nitrogen source
  4. Urea is hydrolyzed to ammonium carbonate, which can raise soil pH temporarily Correct answer.

Explanation

Urea hydrolyzes in soil to ammonium carbonate, which temporarily raises pH around the granule. Urea is a quickly available nitrogen fertilizer (46-0-0) and does not contain sulfur or phosphorus.

Question 49Nutrient Sources, Fertilizer Materials, and Soil Amendments

What is the primary role of sphagnum peat moss in a potting mix?

  1. To supply nitrogen
  2. To increase bulk density
  3. To increase pH
  4. To improve water retention and aeration Correct answer.

Explanation

Sphagnum peat moss holds water and improves aeration and structure in potting mixes. It is acidic and low in nutrients, and it lowers bulk density.

Question 50Nutrient Sources, Fertilizer Materials, and Soil Amendments

Which micronutrient fertilizer is commonly applied as a foliar spray to correct iron chlorosis?

  1. Ferrous sulfate Correct answer.
  2. Zinc sulfate
  3. Manganese sulfate
  4. Copper sulfate

Explanation

Ferrous sulfate (iron sulfate) is a water-soluble iron source used in foliar sprays to correct iron deficiency. Copper, zinc, and manganese sulfates supply different micronutrients.