The question asks for the definition of Crop ratio. Crop ratio is a term used in agriculture, specifically concerning irrigation practices and cropping patterns across different seasons.

Crop Ratio Definition

Crop ratio is commonly defined based on the area of land irrigated during different cropping seasons. It provides insight into the intensity of irrigation use across the year.

A key definition of Crop ratio relates the irrigated area during the Rabi season to the irrigated area during the Kharif season. These are the two major cropping seasons in many regions.

• The Kharif season typically starts with the onset of the monsoon (around June/July) and ends around September/October. Crops grown are usually rain-fed but may also receive supplementary irrigation.
• The Rabi season starts after the monsoon (around October/November) and ends around March/April. Crops in this season heavily rely on irrigation as rainfall is scarce.

The Crop ratio, in this context, is calculated as:

\( \text{Crop Ratio} = \frac{\text{Area Irrigated in Rabi Season}}{\text{Area Irrigated in Kharif Season}} \)

This ratio helps agricultural planners understand the relative dependence on irrigation during the dry (Rabi) versus wet (Kharif) seasons and plan water resource allocation accordingly.

Analyzing the Options

Let's examine the provided options in light of this definition:

• Option 1: Ratio of area irrigated under perennial crop to total area. This relates perennial crops to the total cultivated area, not specifically focusing on seasonal irrigation patterns or defining a standard crop ratio.
• Option 2: Ratio of area irrigated under non-perennial crop to perennial crops. This compares irrigated areas of different crop types (perennial vs. non-perennial), which is not the standard definition of Crop ratio based on cropping seasons.
• Option 3: Ratio of area irrigated under perennial crop to non-perennial crops. Similar to Option 2, this focuses on crop types rather than seasonal irrigation patterns.
• Option 4: Ratio of area irrigated in rabi season to kharif season. This aligns with the common definition of Crop ratio as discussed above, comparing the irrigated area in the dry Rabi season to the irrigated area in the wet Kharif season.

Based on the common agricultural definition concerning seasonal irrigation, the ratio of the area irrigated in the Rabi season to the area irrigated in the Kharif season is considered the Crop ratio.