Audio Transcript Excerpt:
PROFESSOR: 'In agronomy, excessive soil salinization in arid irrigated valleys is a major cause of cropland desertification.

Question

Audio Transcript Excerpt:
PROFESSOR: 'In agronomy, excessive soil salinization in arid irrigated valleys is a major cause of cropland desertification. When farmers apply surface irrigation in hot desert climates, much of the water evaporates before percolating deep into aquifers. Because river water contains trace dissolved mineral salts, evaporation leaves these minerals behind in the topsoil. If agricultural fields lack subsurface drainage tile infrastructure, repeated irrigation cycles continuously pull groundwater upward via capillary action, concentrating toxic sodium and chloride ions in the root zone and eventually rendering the soil impermeable to plant life.'

How does repeated irrigation lead to soil infertility in arid regions without adequate subsurface drainage?

Accepted Answer

Evaporation and capillary action concentrate dissolved salts in the shallow root zone, poisoning plants and degrading soil permeability.

Answer

It washes away all sand particles, leaving behind bedrock.

Answer

It introduces cold water that permanently freezes soil microbes.

Answer

It stimulates weed seeds to overgrow and choke out agricultural crops.

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More Connecting Content Questions in TOEFL iBT

Practice More TOEFL iBT Connecting Content Questions

More Connecting Content Questions in TOEFL iBT