Question

what are fallow lands? define it's types

Answer 1

There are two types of fallow land: true fallow and occupied fallow. ... Green manure fallow is landcultivated with herbaceous plants, such as lupine and serradella, which are turned under

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Answer 2

A fallow field is land that a farmer plows but does not cultivate for one or more seasons to allow the field to become more fertile again.

There are two types of fallow land: true fallow and occupied fallow. 
True fallow includes bare fallow (tillage begins in thesummer or autumn after harvesting the previous crop), early fallow (the soil is plowed in the spring of the next year), and stripfallow (with strips of corn, sunflower, mustard, and other tall-stalked plants planted in the field to retain snow). 
Occupied fallowis land cultivated during the first half of the summer with plants having a short growing period. Green manure fallow is landcultivated with herbaceous plants, such as lupine and serradella, which are turned under.