Among the following crops, which one is the most important anthropogenic source of both methane and nitrous oxide ?

Defines 'wet padi cultivation' (rice grown in flooded lowlands) — a distinctive wet, waterlogged practice.

A student can connect flooded/wet soils to anaerobic microbial activity (like in wetlands) that produces CH4, suggesting rice fields are plausible CH4 sources among these crops.

States methane is emitted by natural wetlands and similar sources.

By analogy, flooded rice paddies resemble wetlands; combining this with (3) supports suspecting rice fields emit substantial CH4 compared with dryland crops.

Gives rice's very large global area and central role as a staple crop (about 150 million ha).

Large cultivated area implies a proportionally large potential contribution to any per-area greenhouse-gas emission (CH4 or N2O) relative to crops with smaller area.

Notes heavy irrigation of rice in major producing states and that about one-fourth of cropped area in the country is under rice.

High irrigation/waterlogging prevalence increases the relevance of wet-soil methane processes and also indicates rice's dominance in cropped area locally, informing comparisons with cotton, sugarcane, and wheat.

Explains that human activities including agriculture are increasing atmospheric N2O.

A student could combine this with knowledge that N2O arises from fertilized soils and that rice fields are intensively managed/irrigated to assess whether rice (vs. the other listed crops) likely contributes more N2O per area or in total.

Gives a general rule that methane (CH4) is emitted by natural wetlands and also by human activities (example: livestock), linking CH4 to wet/anaerobic systems and certain anthropogenic practices.

A student could combine this with knowledge that some crops (e.g., flooded rice paddies) create wet/anaerobic soils to judge which crop is likeliest CH4 source.

States that nitrous oxide (N2O) has natural sources but is increased by human activities such as agriculture, implying crop management (fertiliser use, soils) can make crops important N2O sources.

One could compare typical fertilizer and soil-management intensity among cotton, rice, sugarcane and wheat (using external agronomic data) to assess which crop likely emits more N2O.

Defines 'wet padi cultivation' (rice) as a dominant crop grown in flooded lowlands whenever rainfall is high, highlighting rice as a crop associated with permanently wet soils.

Combine this with the methane-wetland link (snippet 2) to infer rice paddies are plausible major anthropogenic CH4 sources compared with non‑flooded crops like cotton.

Reports that India has the largest area under cotton and lists major cotton-producing countries, indicating cotton's large global area in some regions.

A student could weigh crop area (cotton vs rice etc.) together with per‑area emission tendencies (from external sources) to assess whether cotton could be the largest anthropogenic emitter.

Describes common cropping rotations (rice–wheat, sugarcane–wheat, cotton–wheat), indicating which crops are grown intensively/irrigated and thus may have distinct management and input regimes.

Use knowledge of how intensive irrigation and rotations affect soil redox and fertiliser application to infer relative CH4 and N2O emission potential among these crops.

States India has the largest area under sugarcane cultivation in the world and lists many major producing states, implying large overall extent of this crop.

A student could combine large cultivation area with emission factors (CH4/N2O per ha) to judge whether sugarcane could dominate agricultural emissions among the listed crops.

Notes India is the second largest producer (after Brazil) and that sugarcane occupies only a small share of cropped area yet contributes large production—indicating both high yields and significant production footprint.

Using this production/area information together with typical management practices (irrigation, residue use) a student could estimate relative emissions per crop.

Explains sugarcane is largely an irrigated crop concentrated in tropical/sub‑humid zones (Indo‑Gangetic plain, Maharashtra, Gujarat), indicating specific water/soil conditions and management intensity.

A student could relate irrigated/anaerobic field conditions (from basic agronomy knowledge) to potential methane or N2O production pathways to compare crops.

States that human activities — agriculture among them — are increasing atmospheric N2O, linking crop management to N2O emissions generally.

A student could take this general rule and check which crop practices (fertilizer use, irrigation, residue handling) among the four tend to produce more N2O to evaluate the statement.

Notes that rice is the most important staple and that irrigation water is extensively used in major rice-producing countries, highlighting rice's association with flooded/irrigated systems.

Using basic external knowledge that flooded/rice paddies are strong CH4 sources, a student could contrast rice's known methane risk against sugarcane's conditions to test which crop is likely the largest CH4 source.