Erosion Control in Pineapple Fields on the Island of Ishigaki

Abstract

Two field trials were conducted to evaluate the potential of alternative management practices for the control of soil erosion in pineapple fields on the island of Ishigaki. In the first trial, the effect of cover crops on minimizing soil loss was investigated. Weeping lovegrass (Eragrostis curvula) and a legume plant (Arachis pintoi) were planted on a 1 m strip on the lower edge of plots, each measuring 11 m in length and 5 m in width with a 3° slope. In these plots as well as the control, pineapple seedlings were planted under conventional tillage. After 12 months, soil loss in the plots with E. curvula and A. pintoi was reduced to 1/107 and 1/680, respectively, of that in the control plot. Since A. pintoi is a creeping vine, it inhibited pineapple growth when it encroached upon the adjoining area. In another trial, pigeonpea (Cajanus cajan) was sown, cut down 4 months later, and deliberately left on the soil surface after which pineapple seedlings were planted under no-tillage and minimum tillage. These plots were compared with the control plot where pineapple seedlings were planted under conventional tillage. After 8 months, soil loss in the no-tillage plot was reduced to 1/14 of that in the control plot, whereas soil loss in the minimum tillage plot was almost the same as in the control. Based on these findings, a new management practice involving the use of cover crops and no-tillage planting is recommended to farmers for the prevention of soil erosion in pineapple fields.