What is "green fallow"

Fallow \Fal"low\, n. [So called from the fallow, or somewhat yellow, color of naked ground; or perh. akin to E. felly, n., cf. MHG. valgen to plow up, OHG. felga felly, harrow.]

1. Plowed land. [Obs.]

   Who . . . pricketh his blind horse over the fallows.
   --Chaucer.

2. Land that has lain a year or more untilled or unseeded; land plowed without being sowed for the season.

   The plowing of fallows is a benefit to land.
   --Mortimer.

3. The plowing or tilling of land, without sowing it for a season; as, summer fallow, properly conducted, has ever been found a sure method of destroying weeds.

   Be a complete summer fallow, land is rendered tender and mellow. The fallow gives it a better tilth than can be given by a fallow crop.
   --Sinclair.

   Fallow crop, the crop taken from a green fallow. [Eng.]

   Green fallow, fallow whereby land is rendered mellow and clean from weeds, by cultivating some green crop, as turnips, potatoes, etc. [Eng.]

n. Fallow ground which is planted with a different crop, e.g. a pease field planted with turnips.