What is "spray drain"

Spray \Spray\ (spr[=a]), n. [Cf. Dan. sprag. See Sprig.]

1. A small shoot or branch; a twig.
   --Chaucer.

   Syn: sprig.

   The painted birds, companions of the spring, Hopping from spray to spray, were heard to sing.
   --Dryden.

2. A collective body of small branches, or cut flowers with long stems; as, the tree has a beautiful spray; many sprays were sent in condolence to teh funeral home.

   And from the trees did lop the needless spray.
   --Spenser.

3. (Founding)

   1. A side channel or branch of the runner of a flask, made to distribute the metal in all parts of the mold.

   2. A group of castings made in the same mold and connected by sprues formed in the runner and its branches.
      --Knight.

      Spray drain (Agric.), a drain made by laying under earth the sprays or small branches of trees, which keep passages open.

n. (context agriculture English) A drain made by laying under earth the sprays or small branches of trees, which keep passages open.