One plant that is ideal for the chop-n-drop system is pigeon pea. Pigeon pea is a fast-growing, nitrogen-fixing legume frequently used as a cover crop for bare soils, such as newly-established swales. Pigeon pea not only makes excellent mulch, but it can be used as food for both animals and humans.
Like other nitrogen-fixing plants, pigeon pea captures atmospheric nitrogen and stores it in its root nodules. When the plant dies or is pruned, the nitrogen is released into the soil in a form that can be used by other surrounding plants. Since pigeon pea grows fast, it can be pruned often.
Our local Molokai, Hawaii Permablitz group recently performed a chop-n-drop on a 5-month old swale located at Alu Like’s Ho`ala Hou Program site in Hoolehua. The swale was designed by Geoff Lawton during a Permaculture Research Institute USA Earthworks course in December 2010. The swale is approximately 80 meters long, two meters wide and 1/2 meter deep. It can hold 80,000 liters of water during a rain event.
Students planted the swale with a variety of trees and plants with the intention of establishing a food forest. They scattered seeds, cuttings, plant starts and keiki (baby) trees throughout the top and bottom mounds along the entire length of the swale. A simple line of micro-drip tape irrigation and a couple of good rains quickly turned the swale from a dry barren landscape into a lush strip of jungle.
As would be expected with ideal watering and weather, 5 months later, plants such as pigeon peas and invasive grasses grew so fast they were smothering some of the keiki trees. In order to give the trees more room to grow, a chop-n-drop was needed. The goal of the chop-n-drop was to thin out the areas around the keiki trees, remove some of the invasive grasses and chop-n-drop pigeon pea and other nitrogen-fixers to feed and mulch beneficial plants.
The chop-n-drop went relatively quick. In about 2 hours, 6 people with pruning shears "cleared" over half the swale. After the group finishes the rest of the swale, they plan to interplant additional species such as malabar chestnut, papaya and garden greens such as okinawa spinach. Although a chop-n-drop requires a bit of labor, like other smart Permaculture techniques a little bit of work yields a whole lot of benefit.