Revegetation strategies for Kaho'olawe Island, Hawaii.
Field experiments initiated in 1988 sought to identify effective, economical techniques to revegetate the barren and severely eroded portions of the island of Kaho'olawe caused by the ravages of war, slash-and-burn agriculture, and overgrazing over the past 2 centuries. Treatments included direct sowing plus several rates of fertilizer application with monoammonium phosphate. Some treatments also included jute netting for soil moisture conservation and erosion control. The effect of windbreak fencing was evaluated across all treatments. Direct sowing plus broadcast application of at least 62 kg N/ha plus 291 kg P2O5 was the most cost-effective treatment. Jute netting and windbreak fencing increased plant production, but the high cost of materials and maintenance limits their use to critical areas. The sown species with greatest promise for the windy, semiarid conditions on Kaho'olawe were Cenchrus ciliaris, Cynodon dactylon and Eragrostis curvula. Although not included in the seed mixture, Australia saltbush (Atriplex semibaccata), a naturalized species, responded favourably to fertilizer application. A subsequent, larger-scale revegetation project using a specially modified chisel plough drill to scarify, sow and apply in-furrow fertilizers in a single-pass operation reduced the cost and improved the results of the revegetation process.