Kor watering (first irrigation): For a rice crop, what is the optimum depth of kor watering (first watering) to establish the crop effectively?

Introduction / Context:
Kor watering is the crucial first irrigation applied soon after sowing or transplanting to ensure proper crop establishment. For paddy (rice), adequate initial depth helps puddled-field conditions, seedling anchorage, and early weed suppression.

Given Data / Assumptions:

• Crop: Rice (paddy).
• We seek a standard, exam-oriented value for kor watering depth.
• Field practices assume puddled conditions and typical soils used for rice.

Concept / Approach:
Rice is water-intensive initially; too small a depth risks poor establishment and weed competition, while too large a depth may cause seedling stress. Empirical guidelines used in irrigation scheduling curricula recommend a kor depth close to 19 cm for rice in many North Indian practices.

Step-by-Step Solution:
Consider crop water needs during establishment.Adopt standard kor depth values commonly used in exam problems and design tables.Select 19.0 cm as the optimum for rice.

Verification / Alternative check:
Field-specific adjustments may be made based on soil texture, rainfall, and transplanting method, but the 19 cm benchmark remains a widely accepted value for objective questions.

Why Other Options Are Wrong:
23.0 cm: Excessive; can stress young plants and waste water.17.5, 13.5, 12.0 cm: Insufficient for typical puddled rice establishment in standardized guidance.

Common Pitfalls:

• Confusing kor depth for rice with that for wheat or other cereals.
• Ignoring local soil percolation rates while applying standard values.

Final Answer:
19.0 cm