AS Soil

Question 1

Contour ploughing

Answer 1

A soil erosion control measure where land is cultivated by ploughing horizontal furrows along the contours of the land.

Question 2

Crop rotation

Answer 2

The practice of growing a different crop in a field on a cycle of three, four or five years.

Question 3

Features of fertile soil

Answer 3

Water, soluble nutrients and metals, air, DOM, pH of 5.5 - 7, presence of soil biota, good texture

Question 4

Sandy soils

Answer 4

lots of air space, drain quickly, loses water and nutrients quickly, less water present so less thermal capacity (warm up and cool down quickly), easy root penetration

Question 5

Clay soils

Answer 5

less air space, poorly drained, hold water and nutrients for longer, more water present so higher thermal capacity (warm up and cool down slowly), harder for roots to penetrate

Question 6

Humans activities contributing to soil erosion

Answer 6

removal of vegetation, ploughing, overgrazing, reducing soil biota, soil compaction, cultivating steep slopes

Question 7

How humans affect soil fertility

Answer 7

aeration by ploughing and draining, Increasing and depleting nutrients, Irrigation, soil compaction, adjusting pH

Question 8

Mulch

Answer 8

Material placed on the soil surface to reduce evaporation losses and reduce weed growth.

Question 9

Multicropping

Answer 9

A form of polyculture where two or more different crops are grown in an area at the same time.

Question 10

Ploughing

Answer 10

The cultivation of the soil by turning over the surface layer.

Question 11

Soil erosion

Answer 11

the loss of soil in a location due to wind or water, water erosion includes rain splash, surface runoff and landslides

Question 12

Terracing

Answer 12

The replacement of a sloping landscape by the creation of a series of narrow horizontal stepped strips, often used to reduce soil erosion.

Question 13

Tied ridging

Answer 13

A method of reducing soil erosion by creating a grid of raised ridges that cause rainfall to collect, increasing infiltration and reducing runoff.

Question 14

Tillage

Answer 14

The cultivation by turning the soil eg by ploughing.

Question 15

Universal soil loss equation (USLE)

Answer 15

A formula that can be used to calculate rates of soil erosion.

Question 16

Windbreaks

Answer 16

Hedgerows and rows of trees that reduce wind velocity to reduce soil erosion.

Question 17

Soil Texture

Answer 17

The proportion of minerals in soil ie sand, silt and clay

Question 18

Soil analysis, determining soil texture sedimentation method

Answer 18

1. remove stones, twigs
2. Separate peds/particles,
3. half fill a clear containing with soil
4. Add water and invert/shake
5. Allow to settle (2 minutes for sand, 2 hours for silt, 2 days for clay)
6. Measure the depth of each layer and calculate the proportion/percentage of sand, silt and clay.

Question 19

Soil analysis, determining soil texture soil sieve method

Answer 19

1. Stack the sieves with the coarsest mesh at the top, each sieve size will capture either sand, silt or clay
2. Add a dry, crushed soil sample to the top sieve
3. Shake/agitate the sieve stack for 2 minutes
4. Weigh the contents of each sieve and calculate the proportion/percentage of sand, silt and clay.

Question 20

Soil triangle

Answer 20

used to determine soil texture once percentages of each are known, read the axes as an inverted triangle, clockwise.

Question 21

Soil analysis, determining water content

Answer 21

1. soil must be stored in a sealed container to prevent water loss
2. Remove stones, plant material and living organisms
3. Place soil sample in a preweighed evaporating basin/crucible
4. Soil is placed in an oven at approx 100°C for 24 hours and until a constant mass is reached
5. Soil is reweighed, the mass loss is the original amount of water present in the sample.
6. Calculated % water content, mass of water (lost) divided by original mass of soil multiplied by 100

Question 22

Soil analysis, determining bulk density

Answer 22

mass of dry soil per unit volume. Dry mass over volume. g cm-3

Question 23

Soil analysis, determining organic matter

Answer 23

1. Record the mass of a dry soil sample
2. place the soil sample in an oven at around 450°C until a constant mass is reached
3. The sample is reweighed and the mass loss is the mass of organic matter in the original dry sample
4. Calculate % organic matter, mass of organic matter (lost) divided by dry soil mass multiplied by 100

Question 24

Soil analysis, determining pH

Answer 24

1. use a calibrated electronic pH meter
2. use universal indicator solution (soil sample + barium sulphate + water + shake in test tube)
3. use universal indicator papers
4. never say litmus paper!