The use of soil to reduce carbon dioxide: listening answers and explanations
A lecturer explains how farm soil could absorb carbon dioxide and slow climate change. The talk covers Rattan Lal's work, how plants and microbes store carbon in soil, how farming released it, regenerative agriculture, and studies in California and Australia.
Ten gaps in order. Rattan Lal's work comes first (31-32), then 'Let me explain' leads into how soil stores carbon (33-34). 'So what can be done?' brings in regenerative agriculture (35-36), followed by the California study (37-38), the Australian study (39) and future developments (40).
Answer key and self-check
Type what you wrote and hit mark. Hide the key first if you haven't done the part yet. Every question number jumps to its explanation.
How to attack this block: The headings name people and places (Rattan Lal, California, Australia), so use them to keep track. Many gaps are adjectives describing soil (dry, hard, moist), so check whether the note needs an adjective or a noun before you write.
Question 31
Answer: dryWhen the lecturer describes what carbon-rich soil is like
In what kind of soil is erosion more likely?
But erosion can occur if soil is dry, which is a likely effect if it contains inadequate amounts of carbon.
Question says → You hear
Erosion is more likely in soil that iserosion can occur if soil is dry
Why: Erosion happens when soil is dry, and dry soil is what you get with too little carbon. The note needs an adjective: dry.
The trap: Dark, crumbly and fertile come just before, but they describe healthy, carbon-rich soil, the opposite of soil at risk.
Question 32
Answer: hardWhen the lecturer moves to Lal's work in the 1970s and '80s
What was the soil Lal found in Africa like?
soils in Africa so devoid of organic matter that the … become extremely hard, like cement
Question says → You hear
Lal found soil in Africa that was verybecome extremely hard, like cement
Why: The soil had so little organic matter that it had become extremely hard. 'Extremely' matches 'very', so the adjective is hard.
The trap: Cement is the comparison, not the description, and 'very cement' isn't English. Devoid is about the organic matter, not the soil itself.
Question 33
Answer: sugarWhen the lecturer says 'Let me explain' and describes plants and microbes
Also accepted: sugars
What carbon-based substances do plants turn CO2 into?
transform it into sugars and other carbon-based
Question says → You hear
turn CO2 from the air intotransform it into sugars
Why: 'Transform it into' matches 'turn ... into', and sugars are the example given. Sugar or sugars are both accepted.
The trap: Carbon itself isn't the answer, because 'carbon-based substances' is already in the note.
Question 34
Answer: rootsStraight after the sugars
Which part of plants does some carbon move from, to microbes in the soil?
some transfer from the roots to fungi and soil microbes, which store the carbon in the soil
Question says → You hear
moves from the ... of plants to microbessome transfer from the roots to fungi and soil microbes
Why: Carbon moves from the roots to fungi and microbes. 'Transfer from' matches 'moves from', and roots is plural.
The trap: Fungi sits right next to the answer, but it's where the carbon goes, not where it comes from.
Question 35
Answer: moistWhen the lecturer asks 'So what can be done?' and names regenerative agriculture
Also accepted: damp / wet
Besides fertile, what does regenerative agriculture keep soil?
This aims to boost the fertility of soil and … it moist through established practices
Question says → You hear
soil remains fertile andboost the fertility of soil and … it moist
Why: Regenerative agriculture aims to boost fertility and keep soil moist. 'Fertility' becomes 'fertile' in the notes, and the gap is the second adjective: moist. Damp and wet are also accepted.
The trap: Established practices is already in the note. Don't write 'fertile' again, which the note already has.
Question 36
Answer: varietyWhen the lecturer lists the practices regenerative agriculture uses
What do farmers increase about the plants they grow?
keeping fields planted all year round, and increasing the variety of plants being
Question says → You hear
increasing the ... of plants that are grownincreasing the variety of plants being
Why: The two practices are year-round planting and increasing the variety of plants. The note copies 'increasing the', so the answer is variety.
The trap: Number is a tempting guess, but the lecturer says variety: more kinds of plants, not more plants.
Question 37
Answer: cattleAfter the lecturer says researchers are building a case for regenerative agriculture, when the talk turns to California
What kind of farm is the California study taking place on?
Strategies like these can significantly increase the amount of carbon stored in the soil, so agricultural researchers are now building a case for their use in combating climate change.
Why: Right after this sentence, the lecturer introduces a study in California taking place on a large cattle farm. 'Big' in the note matches 'large', and the gap needs the type of farm: cattle.
The trap: California is the heading, and 'large' or 'big' is already printed. Write the kind of animal the farm keeps, not its size or location.
Question 38
Answer: gardensStraight after the cattle farm, when the lecturer explains what the California researchers spread on the land
Also accepted: gardening
Besides agriculture, where does the waste for the compost come from?
Strategies like these can significantly increase the amount of carbon stored in the soil
Why: The California study uses compost made from waste from farming and from gardens. The note already says 'agriculture', so the gap is the second source: gardens. Gardening is also accepted.
The trap: Compost is already in the note. Don't repeat 'agriculture' or write 'farms', which is the first source.
Question 39
Answer: grassesWhen the lecturer moves from California to the study in Australia
What always-green plants does the Australian study use?
agricultural researchers are now building a case for their use in combating climate change
Why: The Australian study aims to raise soil carbon by planting grasses that stay green all year round. The note says 'using ... that are always green', so you need a plural noun: grasses.
The trap: Plants is already in the earlier notes and too general here. The lecturer names a particular type of plant, and that's the word you need: grasses.
Question 40
Answer: paymentEnd of the lecture, in the future developments, after reducing fertiliser
Also accepted: payments / money
What might farmers be given for storing carbon in future?
so agricultural researchers are now building a case for their use in combating climate change
Why: One future idea is that farmers could be paid for the carbon they store in their soil, not only for their produce. The note says 'giving farmers ...', so the noun is payment. Payments and money are also accepted.
The trap: Fertiliser is the first future development, already printed. Produce is the thing farmers are paid for already, not the new reward.
The note says 'a big ... farm', so you need the kind of farm. The California study is on a large cattle farm, and many people miss the word in a fast stretch of the lecture.
The full Cambridge 11 Test 4 listening paper with the real audio: all four parts, played once, marked the moment you finish. Already done it? Take it again and listen for the traps this page showed you.
Cambridge IELTS 11, Test 4, Listening Part 4. The recording, transcript and questions belong to Cambridge University Press and are not reproduced here. We quote short extracts of the transcript only as evidence for our own commentary, and the answers are published for self-marking. Get the book for the full material, or sit the test on Langujet.
