Cambridge IELTS 11 · Listening · Test 4 · Part 4

Listening Test 4, Part 4: answers explained

The use of soil to reduce carbon dioxide (CO2) in the atmosphere

The recording and its 10 questions (31–40). Every answer is explained with the words that give it away.

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Part 4 recording

Play it once, as in the exam, and answer the questions below as you listen.

Questions 31–40

Note completion
31 Erosion is more likely in soil that is ______
32 Lal found soil in Africa that was very ______
33 plants turn CO2 from the air into carbon-based substances such as ______
34 some CO2 moves from the ______ of plants to microbes in the soil
35 uses established practices to make sure soil remains fertile and ______
36 e.g. through year-round planting and increasing the ______ of plants that are grown
37 taking place on a big ______ farm
38 uses compost made from waste from agriculture and ______
39 aims to increase soil carbon by using ______ that are always green
40 giving farmers ______ for carbon storage, as well as their produce

Answers explained

Answer the questions first: finding the evidence yourself teaches more than reading it. The answers stay folded until you ask.

Question 31

dry

What you hear

erosion can occur if soil is dry

Why

Erosion can occur ‘if soil is dry’, and the lecturer links dryness to soil short of carbon, so dry completes the note. Carbon-rich soil is dark, crumbly, fertile and holds some water, which describes soil that resists erosion.
Question 32

hard

What you hear

the ground had become extremely hard, like cement

Why

Studying soils in 1970s and ‘80s Africa, Lal found so little organic matter that the ground had become extremely hard, like cement. Hard fits ‘very ______’. Dark and crumbly describe healthy, carbon-rich soil, which is the opposite of what he found.
Question 33

sugar / sugars

What you hear

transform it into sugars

Why

‘Such as’ signals an example, and the lecturer names the first one: plants turn CO2 into ‘sugars and other carbon-based substance’. Sugar or sugars is accepted. Fungi and microbes come in the next sentence as where the carbon goes, not what it becomes.
Question 34

roots

What you hear

some transfer from the roots to fungi and soil microbes

Why

Some carbon stays in the plant, but a share passes ‘from the roots to fungi and soil microbes’, which store it. The gap names the plant part the carbon leaves: roots. Soil is where it ends up, so it cannot fill ‘moves from the ______ of plants’.
Question 35

moist / damp / wet

What you hear

boost the fertility of soil and keep it moist

Why

Regenerative agriculture aims to ‘boost the fertility of soil and keep it moist’, which the note recasts as ‘remains fertile and ______’. Moist, damp and wet are all accepted. The practices listed afterwards, such as year-round planting, belong to the next note.
Question 36

variety

What you hear

increasing the variety of plants being grown

Why

After ‘increasing the’, the lecturer says ‘variety of plants being grown’, the second practice beside keeping fields planted all year. Variety is the exact word. ‘Number’ or ‘range’ might occur to you as paraphrases, but the gap needs what is actually said.
Question 37

cattle

What you hear

a large cattle farm in the state

Why

Silver’s first-of-its-kind study is on ‘a large cattle farm’ in California, and the note’s ‘big’ paraphrases large. The one word before ‘farm’ is therefore cattle. California is the state, not the type of farm.
Question 38

gardens / gardening

What you hear

waste produced in gardens

Why

Her compost is made from waste that is both agricultural, such as manure and cornstalks, and ‘waste produced in gardens’, like leaves and lawn trimmings. So ‘agriculture and ______’ takes gardens, with gardening also accepted. Manure and cornstalks belong to the first half of the pair.
Question 39

grasses

What you hear

cultivating grasses that stay green all year round

Why

Jones and 12 farmers are building soil carbon by ‘cultivating grasses that stay green all year round’, which the note rewords as ‘always green’. The plural grasses is what is said and what the grammar needs after ‘using’. Composting is the other method, covered in the previous note.
Question 40

payment / payments / money

What you hear

farmers should receive payment

Why

Rattan Lal argues that farmers should be paid not only for corn or beef but for the carbon they store in their soil, so they ‘receive payment’. The gap after ‘giving farmers’ needs that noun; payments or money also score. Corn and beef are the produce already in the note.

Part 4 audioscript

Part 4 · audioscript

As we saw in the last lecture, a major cause of climate change is the rapid rise in the level of carbon dioxide in the atmosphere over the last century. If we could reduce the amount of CO2, perhaps the rate of climate change could also be slowed down. One potential method involves enhancing the role of the soil that plants grow in, with regard to absorbing CO2. Rattan Lal, a soil scientist from Ohio Stage University, in the USA, claims that the world’s agricultural soils could potentially absorb 13 per cent of the carbon dioxide in the atmosphere - the equivalent of the amount released in the last 3o years. And research is going on into how this might be achieved.

Lal first came to the idea that soil might be valuable in this way not through an interest in climate change, but rather out of concern for the land itself and the people dependent on it. Carbon-rich soil is dark, crumbly and fertile, and retains some water. But erosion can occur if soil is dry, which is a likely effect if it contains inadequate amounts of carbon. Erosion is of course bad for people trying to grow crops or breed animals on that terrain. In the 1970s and ‘80s, Lal was studying soils in Africa so devoid of organic matter that the ground had become extremely hard, like cement. There he met a pioneer in the study of global warming, who suggested that carbon from the soil had moved into the atmosphere. This is now looking increasingly likely.

Let me explain. For millions of years, carbon dioxide levels in the atmosphere have been regulated, in part, by a natural partnership between plants and microbes - tiny organisms in the soil. Plants absorb CO2 from the air and transform it into sugars and other carbon-based substance. While a proportion of these carbon products remain in the plant, some transfer from the roots to fungi and soil microbes, which store the carbon in the soil.

The invention of agriculture some 10,000 years ago disrupted these ancient soil-building processes and led to the loss of carbon from the soil. When humans started draining the natural topsoil, and ploughing it up for planting, they exposed the buried carbon to oxygen. This created carbon dioxide and released it into the air. And in some places, grazing by domesticated animals has removed all vegetation, releasing carbon into the air. Tons of carbon have been stripped from the world’s soils - where it’s needed - and pumped into the atmosphere.

So what can be done? Researchers are now coming up with evidence that even modest changes to farming can significantly help to reduce the amount of carbon in the atmosphere.

Some growers have already started using an approach known as regenerative agriculture. This aims to boost the fertility of soil and keep it moist through established practices. These include keeping fields planted all year round, and increasing the variety of plants being grown. 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.

One American investigation into the potential for storing CO2 on agricultural lands is taking place in California. Soil scientist Whendee Silver of the University of California, Berkeley, is conducting a first-of-its-kind study on a large cattle farm in the state. She and her students are testing the effects on carbon storage of the compost that is created from waste - both agricultural, including manure and cornstalks, and waste produced in gardens, such as leaves, branches, and lawn trimmings.

In Australia, soil ecologist Christine Jones is testing another promising soil-enrichment strategy. Jones and 12 farmers are working to build up soil carbon by cultivating grasses that stay green all year round. Like composting, the approach has already been proved experimentally; Jones now hopes to show that it can be applied on working farms and that the resulting carbon capture can be accurately measured.

It’s hoped in the future that projects such as these will demonstrate the role that farmers and other land managers can play in reducing the harmful effects of greenhouse gases. For example, in countries like the United States, where most farming operations use large applications of fertiliser, changing such long-standing habits will require a change of system. Rattan Lal argues that farmers should receive payment not just for the corn or beef they produce but also for the carbon they can store in their soil.

Another study being carried out …

Part 4 recording

Questions 31–40

Answers explained

Question 31

Question 32

Question 33

Question 34

Question 35

Question 36

Question 37

Question 38

Question 39

Question 40

Part 4 audioscript