--- title: "Command area, crop rotation, necessity" subject: "Irrigation and Drainage Engineering" chapter: 1 key: "semester_6/irrigation_and_drainage_engineering:command-area-crop-rotation" source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/command-area-crop-rotation site: BCT Engineering --- # Command area, crop rotation, necessity Irrigation and Drainage Engineering · Chapter 1: Introduction - Asked in: 2078 Chaitra, 4 marks - Video: [Crop season, Crop Ratio, Paleo Irrigation, Kor Watering, Cash Crop and Crop Rotation](https://www.youtube.com/watch?v=oSh63fljApo) — Civil Engineering & Stuff - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/command-area-crop-rotation - Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-1 ## Question What do you mean by command area, cropping pattern, crop intensity and crop rotation? Write down the necessities of crop rotation practice. ## Short answer Command area: gross and culturable area under gravity irrigation. Cropping pattern: yearly crop arrangement. Intensity: ratio of gross cropped to net sown area. Crop rotation: growing different crops in planned sequence, e.g. rice-wheat-pulses. Necessities: improves soil fertility, breaks pest cycles, prevents nutrient exhaustion, spreads water demand, and uses labour/machinery better. ## Answer #### Command area The area that can be irrigated by gravity from a canal or project. **Gross command area (GCA)** is the total area; **culturable command area (CCA)** is the part fit for cultivation. #### Cropping pattern The yearly sequence and arrangement of crops grown in an area (e.g. rice-wheat-fallow). #### Crop (cropping) intensity The percentage ratio of gross cropped area to net sown area in a year. #### Crop rotation Growing different crops one after another on the same land in a planned order, e.g. rice - wheat - pulses. #### Necessity of crop rotation 1. Maintains and improves soil fertility: legumes fix nitrogen, deep-rooted and shallow-rooted crops use different soil layers. 2. Controls pests, diseases and weeds, since their life cycles are broken. 3. Prevents exhaustion of the same nutrients. 4. Improves soil structure and organic matter. 5. Reduces waterlogging and salinity and spreads the water demand over the year. 6. Gives better use of labour and machinery, risk spreading and higher income. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is command area? A. Area under a reservoir B. Area of rainfed farms C. The area irrigable by gravity from a canal or project D. Area of the farmer's house Answer: C. GCA is the total, CCA the part fit for cultivation. (Key point: Command area) 2. Crop rotation means: A. Growing one crop every year B. Growing many crops mixed in one season C. Leaving land fallow permanently D. Growing different crops one after another on the same land in a planned order Answer: D. For example rice - wheat - pulses. (Key point: Crop rotation) 3. How does crop rotation improve fertility? A. Legumes fix nitrogen and crops with different root depths use different layers B. All crops remove the same nutrients C. Rotation adds chemical fertilizer D. It dries out the soil Answer: A. This prevents exhaustion of the same nutrients. (Key point: Soil fertility) 4. Why does crop rotation reduce pests and diseases? A. It kills all insects with water B. Their life cycles are broken C. It floods the field D. It increases weeds Answer: B. Pests are specific to crops, so changing crops breaks their cycles. 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