20 Soil Management, Planting & Establishment Practice Questions & Answers

1. 1. An arborist explains that a site's soil texture cannot be changed by management, but its structure can be improved. What distinguishes the two?

   • A.Texture is the soil's bulk density; structure is its cation exchange capacity.
   • B.Texture is the organic matter content; structure is the mineral content of the soil.
   • C.Texture is the arrangement of pores; structure is the depth of the topsoil horizon.
   • D.Texture is the proportion of sand, silt and clay; structure is how those particles aggregate.✓ Answer

   Texture is set by the size distribution of the mineral particles, so short of hauling in different soil it cannot be altered on site. Structure is how those particles bind into aggregates, and aggregation is created by organic matter, roots and soil organisms and destroyed by traffic and tillage — which is why structure is the property management actually targets.

   Source: ANSI A300 tree care standard, soil management, and ISA soil management best management practices — soil texture versus soil structureReport a problem with this question

2. 2. Which soil holds the largest amount of water that tree roots can actually take up?

   • A.Loam, because much of the water it stores stays available✓ Answer
   • B.Gravelly subsoil, because its large pores fill during rain
   • C.Coarse sand, because water drains through it quickly
   • D.Heavy clay, because it holds the greatest total water

   Plant-available water is the water held between field capacity and the permanent wilting point, not the total water in the soil. Clay stores the most total water but binds much of it too tightly for roots to remove, and sand drains away most of what it receives, so a loam with a mix of pore sizes gives the largest available fraction.

   Source: Soil physics — field capacity, permanent wilting point and plant-available waterReport a problem with this question

3. 3. In a soil considered ideal for root growth, roughly half the volume is pore space. Why does that matter to the tree?

   • A.Pores are where photosynthesis products are stored for winter
   • B.Pores hold both water and the air that roots need to respire✓ Answer
   • C.Pores store the mineral nutrients that roots absorb directly
   • D.Pores determine the soil texture and therefore its fertility

   Roots are living tissue that respires, consuming oxygen and releasing carbon dioxide, so gas exchange through the larger pores is as necessary as water in the smaller ones. A soil whose pore space is roughly half water and half air supports both functions; when pore space is lost the tree runs short of oxygen long before it runs short of water.

   Source: Soil composition — pore space, soil aeration and root respirationReport a problem with this question

4. 4. Heavy equipment traffic compacts the soil over a mature tree's root zone. Why may the crown look normal for several years afterward?

   • A.The tree draws on stored reserves while the damaged root system slowly declines✓ Answer
   • B.Compaction affects only the top inch of soil, so most roots are untouched
   • C.Compacted soil holds extra water, which offsets the loss of root function
   • D.Roots regenerate into compacted soil as fast as they are lost each season

   Compaction collapses the large pores first, cutting off gas exchange and stopping root extension, but a mature tree has stored carbohydrates and an existing crown that can carry it for years. The visible decline appears only after reserves are drawn down, which is why compaction is diagnosed from the soil and the site history rather than from crown symptoms.

   Source: ISA soil management best management practices — soil compaction and delayed crown responseReport a problem with this question

5. 5. A compacted root zone under an established tree must be loosened. Which approach relieves the compaction with the least damage to existing roots?

   • A.Spreading a layer of topsoil over the compacted surface and seeding turf
   • B.Fracturing the soil with high-pressure air and working amendment into it✓ Answer
   • C.Watering the area to saturation for several days so the soil loosens
   • D.Rototilling the whole root zone to plow depth and raking the surface smooth

   Compressed air fractures the soil along its planes of weakness and flows around roots instead of cutting them, so pore space is restored while the absorbing roots survive. Mechanical tillage inside the root zone severs a large share of those roots, and simply covering the compacted layer with soil leaves the impeding layer and its poor gas exchange in place.

   Source: ANSI A300 tree care standard, soil management — mitigating compacted soil within root zones with pneumatic (air) tillingReport a problem with this question

6. 6. A soil test shows adequate iron but a pH near 8. The tree's newest leaves are yellow between green veins. What best explains this?

   • A.Iron moves freely in the tree, so old leaves would show it first
   • B.At high pH iron becomes insoluble, so the tree cannot take it up✓ Answer
   • C.The yellowing shows nitrogen loss caused by the alkaline reaction
   • D.High pH destroys the iron in the soil, leaving a true deficiency

   Soil pH governs whether a nutrient is available, not whether it is present: as pH rises, iron and manganese form compounds the root cannot absorb. Iron is also immobile once inside the tree, so it cannot be moved out of old leaves, and the interveinal yellowing appears on the youngest foliage first.

   Source: Soil chemistry — soil pH and micronutrient availability; iron chlorosis symptom patternReport a problem with this question

7. 7. A fertilizer is labelled 20-10-10, and the analysis figures are percentages by weight of the product. How much actual nitrogen is in 20 lb (9 kg) of this fertilizer?

   • A.20 lb (9 kg)
   • B.2 lb (0.9 kg)
   • C.10 lb (4.5 kg)
   • D.4 lb (1.8 kg)✓ Answer

   The first figure of the analysis is the percentage of nitrogen by weight, so 20 percent of 20 lb (9 kg) is 4 lb (1.8 kg) of actual nitrogen. Rates for tree fertilization are written in pounds or kilograms of actual nitrogen per unit area, so the analysis must always be converted before a rate is calculated.

   Source: Fertilizer labelling — N-P-K analysis expressed as percent by weight of the productReport a problem with this question

8. 8. A newly planted tree in a compacted, poorly drained bed is losing vigour, and the owner asks for a heavy fertilizer application. What is the sound recommendation?

   • A.Assess the soil and drainage first, because nutrients are probably not the limit✓ Answer
   • B.Water more heavily along with the fertilizer so nutrients reach deep roots
   • C.Fertilize at double rate, because compacted soil ties up all nutrients
   • D.Apply a high-nitrogen product now to push new growth past the problem

   A fertilizer recommendation should rest on soil or foliar analysis, visual assessment and knowledge of local growth, and here the symptoms point to a physical site problem rather than a nutrient shortage. Adding nutrients does not restore pore space or drainage, and forcing shoot growth on a root system that cannot supply water usually makes the stress worse.

   Source: ANSI A300 tree care standard, soil management — basis required for a fertilizer recommendationReport a problem with this question

9. 9. After a week of standing water in a poorly drained bed, a tree wilts even though the soil is saturated. What is happening?

   • A.The saturated soil is holding water too tightly for roots to extract
   • B.Cold wet soil has forced the tree into an early dormant condition
   • C.Roots have taken up so much water that the leaf cells have burst
   • D.Roots are short of oxygen and can no longer move water upward✓ Answer

   Standing water fills the pores that normally hold air, so roots cannot respire and lose the energy needed for water uptake; fine roots then die and the crown wilts exactly as it would in drought. Watering such a tree makes it worse, so the response is to check drainage before assuming a lack of water.

   Source: Soil aeration — waterlogging, root oxygen deficiency and wilt symptomsReport a problem with this question

10. 10. Why is a wide ring of coarse organic mulch over a young tree's root zone considered good practice?

    • A.It supplies all the nitrogen a young tree needs during its first seasons
    • B.It seals the soil surface so rainfall runs off instead of soaking in
    • C.It conserves moisture, moderates soil temperature and shields the trunk✓ Answer
    • D.It raises soil temperature sharply so that roots grow through the winter

    Organic mulch buffers the extremes the surface soil would otherwise see, slows evaporation, suppresses the grass that competes with new roots, and adds organic matter as it breaks down. It also removes the reason to bring a mower or string trimmer near the trunk, which is a common cause of bark injury on young trees.

    Source: ANSI A300 tree care standard, soil management — benefits and placement of organic mulchReport a problem with this question

11. 11. A crew has piled mulch a foot (30 cm) deep against the trunks of street trees. What harm does this cause?

    • A.The pile of mulch makes the trunk grow faster than the roots can support
    • B.Deep mulch at the trunk forces water away from the root ball, drying it
    • C.Bark stays wet and decays, and roots grow up into the mulch and girdle the stem✓ Answer
    • D.Mulch pulls nitrogen out of the bark and starves the trunk of nutrients

    Trunk tissue is not adapted to constant moisture, so bark kept wet under piled mulch softens and decays and becomes an entry court for organisms. At the same time roots turn upward into the moist mulch and circle the buried stem, and years later those stem-girdling roots compress the vascular tissue and the tree declines.

    Source: ANSI A300 tree care standard, soil management — mulch shall not be placed against trunks or cover root flaresReport a problem with this question

12. 12. When a tree is set in the planting hole, where should the bottom of the trunk flare sit relative to finished grade?

    • A.At or slightly above the finished grade of the surrounding soil✓ Answer
    • B.Level with the top of the container media, whatever that depth is
    • C.Deep enough that the top of the root ball is covered with backfill
    • D.About two inches (5 cm) below the finished grade of the soil

    Setting the flare at or slightly above finished grade keeps the trunk in air and the roots in soil, which is the arrangement each tissue is built for. Planting deeper buries bark that then stays wet, starves the deep roots of oxygen and invites stem-girdling roots, and the resulting decline unfolds over years rather than showing up at once.

    Source: ANSI A300 tree care standard, planting and transplanting — bottom of the trunk flare at or above finished gradeReport a problem with this question

13. 13. A container tree has 3 in (8 cm) of media covering the trunk flare. How should the depth of the planting hole be determined?

    • A.From the top of the container media down to the base of the root ball
    • B.From the top of the media plus an extra allowance for later settling
    • C.From the bottom of the trunk flare down to the base of the root ball✓ Answer
    • D.From the base of the root ball plus the height of the container rim

    Excess media above the flare is not part of the usable root ball, so measuring from the top of the container would put the flare below grade once the tree is set. Measuring from the bottom of the flare, and never digging deeper than that measurement, keeps the flare at grade and leaves undisturbed soil beneath the ball so it cannot settle.

    Source: ANSI A300 tree care standard, planting and transplanting — root ball depth measured from the bottom of the trunk flareReport a problem with this question

14. 14. A tree is being planted in heavy, compacted soil. Which planting hole gives the new roots the best chance?

    • A.Narrow and deep, with the ball set low so it cannot blow over
    • B.Wide, with sloping loosened sides, and no deeper than the root ball✓ Answer
    • C.Wide and deep, backfilled with loose soil under the ball for drainage
    • D.Just the width of the ball, so the undisturbed sides hold it firmly

    Most regenerated roots grow outward in the upper soil, so a hole at least one and a half times the ball diameter — wider is better on difficult sites — with loosened, unglazed sides gives them room to leave the ball. Loose fill placed under the ball only lets the tree settle, which sinks the flare below grade and undoes the correct planting depth.

    Source: ANSI A300 tree care standard, planting and transplanting, and ISA tree planting best management practices — planting hole width and loosened sidesReport a problem with this question

15. 15. A container-grown tree shows roots circling tightly around the outside of the root ball. What should be done before planting?

    • A.Plant deeper so the circling roots sit below the root zone
    • B.Wrap the ball in burlap to hold the circling roots in place
    • C.Cut or straighten the circling roots so they can grow outward✓ Answer
    • D.Leave them intact so no root mass is lost at planting time

    A circling root keeps the direction it was trained to take in the container, so left alone it continues around the stem and eventually compresses the trunk and the vascular tissue beneath it. Cutting or redirecting those roots, including shaving the outer face of a badly bound ball, costs a little root mass now and prevents girdling failure later.

    Source: ANSI A300 tree care standard, planting and transplanting — circling and kinked roots straightened or severed at plantingReport a problem with this question

16. 16. A balled-and-burlapped tree in a wire basket has been set at the correct depth in the hole. What is done next with the packaging?

    • A.Retain the entire basket until the tree has been watered in fully
    • B.Cut away the top third of basket, burlap and twine and remove it✓ Answer
    • C.Remove all the twine but leave the basket and burlap fully intact
    • D.Leave everything in place because the materials break down in soil

    The tree is set first so the ball is not broken while it is being moved, and then the upper third of every supporting material is cut off and taken out of the hole before final backfilling. Twine and treated or synthetic burlap left around the upper ball can girdle the trunk and the emerging roots, and material left at the surface also wicks water away from the ball.

    Source: ANSI A300 tree care standard, planting and transplanting — removal of root ball supporting materials from the top thirdReport a problem with this question

17. 17. What should normally be used to backfill around the root ball of a newly planted tree?

    • A.Coarse sand, to guarantee drainage around the root ball
    • B.A rich mix of peat and compost to feed the new roots
    • C.The soil dug from the hole, settled in layers with water✓ Answer
    • D.Bagged potting media, matching the container the tree came in

    Backfill should match the surrounding soil unless an amendment serves a specific, identified objective, and any organic amendment stays a small fraction of the volume. A backfill that differs sharply in texture creates an interface where water perches and roots turn back into the hole, so the tree behaves as though it were still in a pot; settling the native soil in layers with water removes air pockets without packing it hard.

    Source: ANSI A300 tree care standard, planting and transplanting — backfill similar to site soil, settled in layersReport a problem with this question

18. 18. Under current planting practice, when should a newly planted tree be staked?

    • A.Only when the tree is planted in soil that drains very quickly
    • B.Only when the tree is unstable or the site requires support✓ Answer
    • C.Always, since every new tree needs support in its first year
    • D.Always for container stock, but never for balled-and-burlapped

    Support is installed only when it is needed — an unstable root ball, top-heavy stock, a windy, sloping or high-traffic site — because a trunk that is allowed to flex builds taper and anchoring roots. A rigidly staked tree grows a slender, poorly tapered stem that can fail when the support is finally removed, and any support that is used should be attached loosely and taken off once the tree is stable.

    Source: ANSI A300 tree care standard, planting and transplanting — support systems installed only when neededReport a problem with this question

19. 19. During the first months after planting, why is irrigation aimed at the root ball itself rather than only at the surrounding bed?

    • A.The backfill cannot absorb irrigation water until roots reach it
    • B.The root ball must stay saturated to keep new roots from drying
    • C.Watering the bed pushes fertilizer salts down into the root ball
    • D.The root ball holds nearly all the roots and dries out first✓ Answer

    Until roots grow out into the surrounding soil, the small volume of the ball is the tree's entire water supply, and it dries faster than the backfill around it. Frequency and volume are therefore judged from the soil, the weather and the moisture actually found in the ball rather than from a fixed calendar, and the soil is kept moist but never waterlogged.

    Source: ISA tree planting best management practices and university extension guidance — irrigating the root ball during establishmentReport a problem with this question

20. 20. Two trees are planted on the same site, one of 2 in (5 cm) caliper and one of 5 in (13 cm) caliper. What can be expected about establishment?

    • A.Both establish in the same season since the site is identical
    • B.The smaller tree takes longer because its root system is small
    • C.The larger tree takes longer to re-establish its root system✓ Answer
    • D.The larger tree establishes sooner because it has more reserves

    Digging removes most of a tree's root system, and the larger the trunk the larger the crown that the remaining roots must supply, so establishment time rises with caliper — commonly estimated in temperate climates as about a year for every inch of trunk diameter. Until the root system is rebuilt the tree is in water stress, which is why post-planting care must be specified for the whole establishment period rather than a single season.

    Source: Research on transplant establishment — establishment time increases with trunk caliperReport a problem with this question

Practice questions based on the published knowledge domains of the ISA Certified Arborist examination outline and on standard arboriculture references. ISA and Certified Arborist are marks of the International Society of Arboriculture; this site is not affiliated with or endorsed by ISA. Answers here deliberately avoid pesticide products and rates, standard clause numbers and the dimensions recalled from them, regional species recommendations and local ordinances, all of which change and vary by place — always follow the pesticide label and your jurisdiction's applicator licensing, the tree-care safety standards in force, and the requirements of the authority having jurisdiction. Confirm current exam requirements with ISA before testing. About the ISA Certified Arborist credential →