The time taken between the sowing and harvesting of crops called 

Explanation :

Crop Period: The time period that elapsed for the instant of the sowing of the crop to the instant of its harvesting is called crop period.

Base Period: The time between the first watering of a crop at the time of its sowing to its last watering before the harvesting is called the base period or the base of the crop.

Crop period is slightly more than the base period, but for all practical consideration, they are taken as one and the same thing, and generally expressed in days.

Important Point:

Duty: It is the number of hectares of land irrigated for full growth of a given crop by a supply of 1 cumec of water continuously during the entire base period of that crop.

Delta: The total water depth required by a crop to attain its full maturity in its base period.

The relation between Duty (D), Delta (Δ) and Base period (B) is given as:

\({\bf{\Delta }}\left( {{\bf{metres}}} \right) = \frac{{8.64B}}{D}\)