Revegetation strategies for Kaho'olawe Island, Hawaii

Abstract

Over the past 2 centuries, the island of Kaho'olawe has suffered the ravages of war, slash-and-burn agriculture, and overgrazing. Today, much of the island is barren and severely eroded. A research project initiated in 1988 has sought to identify effective, economical techniques to revegetate portions of the island. Treatments included drill seeding plus several rates of fertilization with monoammonium phosphate (11-52-0). Some treatments also include jute netting for soil moisture conservation and erosion control. The effect of windbreak fencing was evaluated across all treatments. Drill seeding plus broadcast application of at least 62 kg ha-1 N plus 291 kg h-1 P205 was the most cost-effective treatment. Jute netting and windbreak fencing significantly enhanced plant production, but the high cost of materials and maintenance limits their use to critical areas. The planted species with greatest promise for the windy, semiarid conditions on Kaho'olawe were buffelgrass (Cenchrus ciliaris L.), bermudagrass [Cynodon dactylon (L.) Pers.] and weeping lovegrass [Eragrostis curvula (Schrad.) Nees]. Although not included in the seed mixture, Australian saltbush (Atriplex semibaccata R. Br.), a naturalized species, responded favorably to fertilization. A subsequent, larger scale revegetation project using a specially modified chisel plow seeder to scarify, plant, and apply in-furrow fertilization in a single-pass operation reduced the cost and improved the results of the revegetation process.