雅思阅读 186: The Quiet Revolution of No-Till Farming（免耕农业的静悄悄的革命）

改编自 Frontiers in Climate / British Society of Soil Science。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://www.frontiersin.org/journals/climate/articles/10.3389/fclim.2019.00008/full

Reading Passage

A. For ten thousand years, farmers have tilled the soil. Turning the earth over with a plough buries weeds, loosens the seedbed and prepares a clean surface for sowing. It is one of the oldest operations in agriculture, and for most of that history no one questioned it. In the last half-century, however, a small but growing movement has argued the opposite: that the plough is doing more harm than good. No-till farming — sowing seed through undisturbed stubble without any inversion of the soil — has moved from a marginal practice among a handful of innovators to a technique adopted on hundreds of millions of hectares across North and South America, Australia and increasingly China and South Asia. In the United States alone, more than half of cropland is now sown under some form of no-till. The reasons are not ideological. They are written in the soil itself: in erosion rates that fall, in water that stays put, and in carbon that used to escape into the sky. The practice spread from the American Midwest in the 1960s, carried by farmers who noticed that their loess soils were blowing away under conventional tillage.

B. Conventional tillage disrupts the soil in ways that are easy to see and harder to reverse. When the plough slices through the ground, it shatters the crumbs and clumps — called aggregates — that hold the soil together. Exposed to sun and rain, the organic matter bound inside those aggregates oxidises and escapes into the atmosphere as carbon dioxide. Rain strikes bare soil directly, sealing the surface and running off rather than infiltrating. Wind lifts loose particles into dust storms, carrying away the most fertile top layer. No-till inverts none of this. Crop residues remain on the surface like a mulch, shielding the soil from raindrop impact and slowing evaporation. Over years, pores stay continuous, earthworms move freely, and the aggregates that form under undisturbed conditions become larger and more stable. A global synthesis of 89 studies found that no-till consistently increases the proportion of large, water-stable aggregates relative to ploughed fields, with pore continuity and mean aggregate size improving by roughly 20 per cent. Those physical improvements are not cosmetic; they determine whether rain soaks in or runs off, whether roots grow deep or shallow, and whether the soil can withstand a heavy storm without washing away.

C. The carbon implications are the reason no-till has attracted the attention of climate policymakers. Every tonne of carbon retained in the soil is a tonne not released to the atmosphere. Under conventional tillage, soil organic carbon (SOC) is lost rapidly because aggregates are broken and the organic matter inside them is exposed to oxygen and microbes. Under no-till, by contrast, carbon is physically protected inside stable aggregates, where decomposers cannot reach it. Estimates suggest that no-till systems can cut carbon dioxide emissions to roughly 2,900 kilograms of carbon dioxide equivalent per hectare per year, compared with tilled fields. A comprehensive mega-analysis drawing on 24 earlier meta-analyses confirmed that conservation tillage — including no-till, reduced tillage and their combination — substantially raises SOC stocks across a wide range of cropping systems and climates. Reduced tillage emerged as the most effective single practice, with strict no-till close behind. The result has placed soil carbon sequestration at the centre of proposals for "natural climate solutions," although scientists caution that the total amount of carbon the world's croplands can realistically store is small compared with fossil-fuel emissions.

D. Yet the picture is more complicated than "plough bad, no-till good". Long-term experiments in China and India have shown that the benefits of no-till are concentrated in the upper layers of the soil. In the top 15 centimetres, no-till with straw mulch consistently raises organic carbon, nitrogen, phosphorus and potassium, as well as the soil's cation exchange capacity. But in the subsoil layer between 15 and 40 centimetres, only no-till combined with straw cover produced measurable gains; no-till alone without mulch often failed to improve the deeper layers at all. Some studies have even found that strict no-till can cause compaction in the subsoil, because the soil is never loosened by implements. Weed control is another challenge: without the plough to bury weeds, farmers must rely more heavily on herbicides, raising environmental concerns that the carbon benefits alone do not resolve. The most successful systems combine no-till with cover crops, diverse rotations and judicious fertiliser rather than adopting the technique in isolation. A field under strict no-till on its own, without returning crop residues or rotating crops, can look like a failure.

E. The appeal of no-till is that it addresses several problems at once. It reduces erosion, holds water, improves yields in dry years and draws carbon down from the atmosphere. It also lowers fuel costs, because a field that does not need ploughing can be sown in a single pass. But the technique is not a universal panacea. In heavy, poorly drained soils, no-till can delay planting in wet springs. In regions where weeds are strongly adapted to no chemical control, the herbicide burden becomes unsustainable. And the carbon gains, though real, unfold over decades, not seasons — a timescale that sits awkwardly with the pressure farmers feel to maximise next year's harvest. No-till is best understood not as a single innovation but as the core of a broader conservation-agriculture package, whose success depends as much on local knowledge and economic incentives as on the plough itself. The farmers who have thrived under no-till are not ideologues; they are agronomists who watched their topsoil stop washing away and their fuel bills drop, and kept going. Their fields, seen from the air, hold their shape through rainstorms that strip tilled fields bare.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. How tillage damages the soil and what no-till changes ii. The history of the plough in ancient Egypt iii. Carbon sequestration and the evidence for it iv. Why no-till is not a simple solution v. The broader conservation package and its limits vi. How herbicides are manufactured vii. Why organic farms outyield conventional farms

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. What happens when conventional tillage breaks up soil aggregates? A. Organic matter inside them is exposed and lost as CO₂. B. The soil immediately becomes more fertile. C. Earthworms move deeper into the subsoil. D. Water infiltration improves dramatically.

6. What did the mega-analysis of 24 earlier meta-analyses find? A. No-till had no effect on soil carbon. B. Conservation tillage practices substantially raised soil organic carbon. C. Conventional tillage was better in all climates. D. Reduced tillage was the least effective practice.

7. According to long-term experiments in China and India, where are the benefits of no-till concentrated? A. In the subsoil below 40 centimetres. B. In the top 15 centimetres. C. Only in the parent rock layer. D. Equally at all depths.

8. What problem can strict no-till cause without additional measures? A. It increases ploughing costs. B. It can cause subsoil compaction and heavier herbicide use. C. It always reduces crop yields. D. It prevents earthworms from surviving.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. No-till farming has been adopted on hundreds of millions of hectares.
10. No-till systems emit roughly 2,900 kilograms of CO₂ equivalent per hectare per year.
11. No-till alone without straw mulch consistently improves the subsoil layer.
12. No-till farming always produces higher yields than conventional tillage, regardless of climate.
13. No-till reduces fuel costs because sowing requires only one pass over the field.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

Under conventional tillage, soil organic carbon is lost because aggregates are broken and organic matter is exposed to (14) __________; under no-till, carbon is physically protected inside stable (15) __________.

答案与解析

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