Contour beds are annual and/or perennial vegetable garden beds that conform to the natural pattern of the landscape. Being on contour means that the paths and beds themselves are level and follow the lay of the land. Not only does this create an attractive pattern on the landscape this technique more importantly allows us to slow, spread, and sink water into our garden beds in a similar way that swales do. This orientation also prevents erosion due to the pacifying of any surface runoff.
To create contour beds one must be able to accurately measure and peg out the contours. This can be done by a number of ways; using a laser level, a water (bunyip) level or an ‘A-frame’. Not having access to a laser level we built an A-frame out of some scrap wood and wire.
An ‘A-frame’ is a simple and easy to build device consisting of 3 pieces of wood/metal, a string and a weight such as a fishing sinker or large fastening nut. It is built by connecting the 3 pieces of wood together to form an ‘A’ shape. They can be fastened together in a number of way: nuts and bolts, wire, or metal can be welded together. The important thing is that the structure is solid and will not move and thus disturb its calibration. A string is then tied to the top of the frame with a weight on the bottom which must hang below the cross member.
To calibrate an A-frame place it on the ground and mark where the string settles on the cross member. Now flip the A-frame around so that the legs of the frame are in exactly the opposite location. Again mark where the string hangs. In-between the two marks make a distinct and solid mark, this mark is your level mark.
Using the A frame is easy, simply walk across the landscape and position the A-frame so that the string hangs over the level mark, place markers such as pegs or sticks at the legs as you go. The imaginary line between all the pegs will give you the contour.
Creating contour beds
Begin digging along the contour creating a path and mounding the soil on the lower side making the bed. Create the beds at a height of 30cm and 120-140cm in width. This width allows for one to reach the middle of the bed by without standing on the bed itself compacting the soil. The paths between the beds should be large enough to accommodate a wheelbarrow (40-60cm) for harvesting and composting, and can be dug out slightly to a depth of 20-30cm. The removed soil is used on the bed and paths filled with woodchips, sawdust or gravel. Woodchips will slowly breakdown and can later be used as compost. Water will always find level, thus for precise levelling flood the paths with water and correct their level using a shovel.
Added into the soil layer should be any organic soil amendments (compost, manure, bone meal, kelp meal, rock dust, etc.) that are needed. In this case we added sifted compost from a 2 cubic meter hot compost pile we started 18 days prior, and guano de isla which were gently mixed into the top 50mm of the beds. Later we drenched the beds with compost tea, and applied the remaining compost. The soil layer should be about .5 m. deep from the bottom of the paths, and watered heavily. Note that in arid climates this technique is inverted with the beds sunken to reduce water loss through evaporation.
Next mulch your beds with pea straw, sugar cane mulch, or composted woody material, and begin planting! We used barley that had been previously used as a substrate for growing oyster mushrooms. It was a pleasant surprise to find large oysters mushrooms growing out of the mulch after heavy rains. The batter or edges of the beds can struggle to retain mulch due to their slope exposing the beds to weed invasion and evaporation due to sun exposure. To combat this we sew a range of annuals including brassicas and coriander from out of date seed we had, which has greatly contributed to the yield of these beds.
Apart from harvesting and the occasional application of worm juice, these beds thanks to the heavy mulch have been maintenance free for months now, and have provided us with an abundance of Tomatoes, Squash, Zucchini, and greens.