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Common Keylines and Keyline Land Units
FROM the limited application of the Keyline of one valley as illustratedon Maps 1 and 2 and discussed in Chapters 1 and 2, we now consider the next step--theextensions of the Keyline.
Each valley will have its Keypoint and Keyline. Where, by the extensionsof the Keyline levels--either on a true contour or with a slight fall--the one Keylineserves two or more valleys, this line becomes a "Common Keyline". It issimply one line of levels that forms the Keyline of each valley it crosses.
Map 3 illustrates an area of steep country with five major valleysdraining towards a rocky creek.
An examination of the first valley indicates that the 180-foot contour--thebroken line--is the Keyline of this valley. The same contour also serves as the Keylineof the second and third valleys but crosses the fourth valley in a location obviouslynot the Keyline of this valley. The 180-foot contour is the Common Keyline of thefirst, second and third valleys, while the 220-foot contour line is the Common Keylineof the fourth and fifth valleys.
For purposes of cultivation and development these two Common Keylinescontrol two separate areas. A fence line up the centre of the ridge between the thirdand fourth valleys divides the areas according to Common Keylines. These two sectionsare Keyline areas, or complete Keyline cultivation and development units. They includethe areas both above and below the Keyline.
A Keyline area, then, is an area controlled by a Keyline or a CommonKeyline and may include any number of valley areas. The Keyline areas of Map 3 maybe further subdivided into any number of paddocks.
Conversion-year cultivation in the case of crop land or Keyline soildevelopment for pasture improvement is first completed in the area above the Keylineand parallels the Keyline up the slope of the land.
If the Keyline is not to form a gently falling water race--it oftendoes, see "Water Storage", Chapter 7--some other means. of permanentlymarking and preserving the Keyline is necessary.
A row of stakes first marks the Keyline. Leave a narrow strip unploughedon each side of the Keyline stakes. On this, brush or trees will grow along the lineduring the time the area is closed to stock for cropping. This line need only bea few feet wide and it will serve as a permanent marker for the Keyline.
Without the tree growth on the unploughed Keyline strip, a markercan be satisfactorily preserved by carefully following the lines of the previouscultivation.
Another means of permanently marking the Keyline is to use it as afarm roadway.