I’d long been aware that the process of locating contour lines in sloping agricultural lands is basically the same as that when spots on posts at same vertical elevation are marked using a carpenter's level hose. I in fact wrote in Bamboo Production and Propagation Methods which was published via this website in PDF format in 2010:
“Viewed from the side, an imaginary line that will traverse the points of each contour line will be more or less horizontal, as if a plastic hose filled with water was used by a carpenter in locating two points of the same elevation.”
But it took a brief reunion with Dr. Ariston Calvo at the University of Southern Mindanao in 2011 for me to be enlightened that indeed, a level hose can be used in place of A-Frame. From then on I mentally stretched to formulate a procedure on how exactly would I use the carpenter’s level-hose.
The level hose (or hose level) is a standard tool made of transparent plastic hose preferably slightly thicker than a common pencil, used by carpenters and construction masons. I’ve used it plenty of times, in fact, in carpentry works. In landscaping, I usually start by marking the spots at same elevation on several stake guides sunk around the area to be landscaped.
With a level hose filled near full with water, carpenters and construction masons mark the points on a vertical structure or guide, for example posts, at the same vertical level. Constant atmospheric pressure makes the levels of water at both ends of the hose settle at the same elevation, for example 100 masl.
The same principle applies to contour lines in sloping lands. Therefore, a level hose can be used to mark spots on the ground with the same elevation. We did it in my sister’s farm in 2015.
We produced two stakes (whole bamboo culms) with more or less same length (about 1.5 m). We also marked the same distance (about 1 m) from the base of the stakes. These stakes were our vertical extenders from ground level. Otherwise it will be impossible to use a hose if both ends are to be pressed on the ground.
One worker held one end of the hose filled near-full with
water and another the other end. Each also carried one of the two marked
stakes. To prevent bubbles forming and spillage of water, both ends were folded
until ready for use. A third man also carried spare water for refilling.
One (the First Man) positioned himself where staking was to start while the other (the Second Man) moved forward approximately at same elevation. The First Man placed his extender stake upright from ground level and pressed the end portion of the hose against the stake. The Second Man did the same. Both then opened (unfolded) the hose at their ends. The First Man moved the hose upward or downward (not the stake) to position the level of water at the 1-m mark, at the same time advising the Second Man to move his extension-stake upward or downward.
When the level of water at both ends were at the 1-m marks, that’s it. Both stakes sat on the ground with same elevation.
The first extension-stake was then removed and replaced with a pointed stake sunk into the ground by a Third Man. This stake marked the first spot on the contour line. The First Man moved farther forward while the Second Man remained in place now becoming the First Man. The procedure was repeated until the last spot on the contour line was reached.
The operation can even be expedited by marking only the location of hills for the main crops. If, for example, the planned hill-to-hill distance is 5 meters, a longer hose, like 7-8 meters or more should be used. With the Third Man carrying a measuring tool, for example a bamboo pole cut 5 meters, the ensuing main crops will be spaced properly on the contour line.
This technique also has the advantage of application in farms with thick vegetation. It will not be necessary to clear the land first before the operation. The extender stakes just have to be long enough to allow the workers to see the marks. The permanent stakes marking the points on the contour should likewise be as long as to become visible to the next workers who will do the planting.
Both techniques (use of A-Frame and Level hose) may not be necessary if there is no want of mathematical precision. Traditional corn farmers have in fact practiced contour farming for many generations and they apply it in planting corn and coconut or in plowing the land by instinct and practiced eye. By hiring them, crops can be planted as if contour lines have been previously defined.
If the farm was previously furrowed using a carabao-drawn plow, these furrows if still visible can likewise be used as a guide in the placement of the next crops to be grown, for example coconut or fruit crop or any other perennial crop.