Explanation

• Phosphorus (P) is most available to plants in slightly acidic to neutral soils (pH 6–7.5).
• At low pH (4–5), phosphorus reacts with iron and aluminum, forming insoluble compounds.
• At high pH (8–9), it reacts with calcium, also becoming unavailable.

Last verified on 01-02-2026

Explanation

• Deela (Echinochloa colona / Echinochloa crus-galli) is a common weed in rice fields.
• Competes with rice for nutrients, water, and sunlight, reducing yield.
• Controlled through manual weeding, herbicides, or proper water management.

Last verified on 01-02-2026

Explanation

• Cotton (Gossypium spp.) is a C3 plant, meaning it uses the C3 (Calvin cycle) pathway for photosynthesis.
• In C3 plants, CO₂ is fixed directly into a 3-carbon compound (3‑phosphoglycerate).
• Examples of other C3 crops: wheat, rice, soybean, and potato.

Last verified on 01-02-2026

Explanation

• A wind vane (also called a weather vane) shows the direction from which the wind is blowing.
  • Usually installed on rooftops or meteorological stations.
  • Works with a rotating pointer that aligns with the wind direction.

Last verified on 01-02-2026

Explanation

• Restorative crops improve soil fertility by adding nutrients, especially nitrogen.
• Soybean, being a legume, fixes atmospheric nitrogen through Rhizobium bacteria in root nodules.
• Helps reduce the need for chemical nitrogen fertilizers in subsequent crops.

Last verified on 01-02-2026

Explanation

• Under submerged soil conditions, oxygen is low, so nitrate (NO₃⁻) quickly converts to gases (denitrification).
• Ammonium (NH₄⁺) is more stable in anaerobic (waterlogged) soils like paddy fields.
• Common ammonium fertilizers for rice: Urea, Ammonium sulfate, Ammonium chloride.

Last verified on 01-02-2026

Explanation

• Cotton (Gossypium spp.) belongs to the Malvaceae family.
• This family also includes okra (bhindi), hibiscus, and cacao.
• Plants usually have showy flowers and mucilaginous tissues.

Last verified on 01-02-2026

Explanation

• Wheat (Triticum aestivum) belongs to the Poaceae (Gramineae) family — the grass family.
• This family includes major cereals like wheat, rice, maize, barley, sorghum.
• Members have narrow leaves, hollow stems, and fibrous roots.

Last verified on 01-02-2026

Explanation

• Recommended seed rate of wheat is 50–60 kg per acre.
• Proper seed rate ensures optimal plant population and yield.
• Helps in uniform germination and strong crop stand.

Last verified on 30-01-2026

Explanation

• Herbicides are chemicals used to control unwanted plants (weeds).
• A selective herbicide targets specific parts of a plant, such as roots, without harming other parts or neighboring plants.

Additional information:

• Example of selective herbicide: 2,4-D, which kills broadleaf weeds but not grasses.
• Selective herbicides are widely used in agriculture to protect crops.

Last verified on 23-01-2026