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  THE Keyline plan embraces a system of progressive fertile soil development for all crop and pasture lands as well as for the steeper and rougher lands that have never before been capable of fast, economic improvement.

  Its primary aim is the development of better soil structure, increased soil fertility and greater actual depth of fertile soil. It includes new cultivation techniques; a method of farm subdivision and layout; planning for timber and scrub clearing and water conservation and irrigation. All are planned to facilitate or assist in the production of fertile soil.

  The Keyline plan is based primarily on a particular line or lines called Keylines. These lines and others related to them are used in all land development planning and act as guides for farm working.

  The first aim of Keyline is to provide simple means of conserving all the rain that falls on the land into the soil itself, retard its evaporation. rate and use this conserved moisture for the rapid production of soil, fertility over both small and large areas of land.

  The simplest form of a Keyline is illustrated in Map 1. This shows a valley formation by means of contour lines. The 180-foot contour line is the Keyline of this simple valley area.

  The Keyline conception itself is a little technical, and an explanation of what this basic idea involves is given first.

  A Keyline is a level or sloping line extended in both directions from a certain point in a valley, called the "Keypoint". This marks or divides the two types of relationship, always in the same vertical interval, that a valley bears to its adjacent ridges. In one of these relationships, that above the Keyline, the valley will be narrower and steeper generally than the adjacent ridges on either side of it. In the second relationship, existing below the Keyline, the valley will be wider and flatter than its immediately adjacent ridges, or shoulders.

  The approximate point of this relationship change in the valley is the Keypoint of this valley. A line, either a true contour in both directions from, this point, or a gently sloping line rising in one direction and falling in the other direction (see later chapter)--from this Keypoint is the Keyline of this valley area.

  Any property that includes in its area a watershed or water divide has one or more Keylines.

  In order to understand the full development and uses of this and other Keylines, reference will be made to contour maps and particular contour lines of the maps. Not all readers will have had experience of these maps and their contour lines, but the following description will make the later references clear.

  Contour lines, or contours, are lines on maps or marked on the land itself to show particular levels. Map 1 is a simple contour map and the contour lines on the map mark the levels.

  All points on the lines marked with the various heights are the same height as indicated by the figures. Thus on the 200-foot contour line all points are 200 feet above "datum". Datum is very often mean sea-level, but may be any other permanent point.

  A contour line lies at right angles to the slope of the land; as the slope changes direction the contour lines curve and turn. Contour lines on a contour map are placed at regular vertical heights apart. The distance apart is called the vertical interval. On farm contour maps these range from 25 feet to 2 feet, according to the type of land formation and accuracy desired. On Map 1 they are 10 feet apart vertically. The space or interval between two contour lines is referred to as a contour strip.

  A contour map exhibits the formation of land by means of contour lines.

  The contour Map 1 exhibits a simple valley formation. The centre line of the valley floor is indicated by a dotted line and the downhill slope by an arrow.

  The 220-foot contour is near the top of a watershed or water divide. The valley formation starts between the 210- and 200-foot contours, as indicated by these two contour lines coming closer together near the dotted line of the valley. The actual slope here is steeper than that on either side between the same two contour lines. This is the valley head. The valley steepens a little more between the 200- and 190-foot contours, as indicated by these two lines being closer together than the 210- and 200-foot contours. The slope of the valley then remains constant to the 180-foot contour in the valley. This is indicated on the map by the distances between the 200- and 190-foot contours and between the 190- and 180-foot contour lines at the centre valley point being approximately equal. At this point, where the 180-foot contour line crosses the dotted line of the valley bottom, a change takes place in the character of the valley formation. The valley bottom flattens considerably, as indicated by the greatly increased distance in the valley bottom between contour lines 180 and 170 feet.

  The whole relationship of the valley to its adjacent ridges in each contour strip has also changed.

  Above the 180-foot contour line the valley bottom is steeper and narrower than its adjacent ridges in the contour strips, but below the 180-foot contour line the valley is flatter and wider, in the contour strips, than its adjacent ridges. The slope relationship between this valley and the adjacent ridges continues through the lower contour strips of the map.

  As a general rule, the relationship is constant for the remainder of a valley. The line of this change of relationship between the valley and its adjacent ridges in each contour strip is the Keyline of this valley. The position or point of this change in the valley itself is the Keypoint of the valley.

  My own discovery, study and use of this -peculiar significance, relating to the varying valley and ridge forms, is the basis of the Keyline plan. Its use in farming and general land planning and development is discussed throughout this book. A study of the topographical geography of general land formation will show a remarkable consistency and regularity in this changing relationship between valleys and their adjacent ridges.

  The crucial point of change in the valley floor slope, the Keypoint, may coincide with the confluence of two or more valleys.

  At the Keyline the line of the valley floor and adjacent ridge slope are neutral.

  Various types of land formations lend differing forms to their Keylines, but generally the significant valley and ridge relationship is consistent in the widest variations of land formations.

  It is important to keep in mind that the valley area in the contour strip above the Keyline is narrower generally than the adjacent ridge area and that the valley area in any contour strip below the Keyline is wider generally than the adjacent ridge area of the same contour strip.

  The 180-foot contour line of Map 1 is the simplest form of Keyline--the Keyline of a single valley. Keylines, as discussed here for farm work, are not located on the very small scale contour maps of large land areas, such as inch-to-the-mile land plans. Maps that have sufficient contours to exhibit accurately every valley on a medium size property will, however, enable the Keylines to be located quite clearly.

  Before explaining the full development of Keyline, this simple form is used in the next chapter to illustrate a practical application of the Keyline principle.