Silvicultural, hydro-orological and economic aspects of a combination ofvegetative(Falcataria moluccana-Vigna cylindrica) and terrace systemsin soils of different slopes

Abstract

Soil and water conservation techniquesinvolving a combination ofvegetative and mechanical systemswill increasethe benefitsfrom both conservation aspect as well as economic aspect. This study wasaimed atanalyzingthesilvicultural, hydro-orological and economic aspects of a combination ofvegetative(Falcataria moluccana-Vigna cylindrica) and terrace system in soils of different slopes(a steep and a very steep slope gradient).The silvicultural parameters examined in this study were the ground coverage of V. cylindricagrowthandsurvival rate, stem diameter and height ofF. moluccana trees. The hydro-orological parameters includederosion rate, erosion hazard index, erosion hazard class, and erosion hazard level. The economic parameters includedtotal cost, total revenue, and profit. The result showed that the survival rate, diameter increment and height increment of F. moluccana, andground coverage ofV. cylindrica in the land with the steep slope(>25-45%) was90%, 2.02 cm year-1,1.54 m year-1, and80-90%, respectively. Theerosion rate, erosion hazard index, erosion hazard class, anderosion hazard level in this steep slope was0.38 ton ha year-1, 0.03(low), I(very low), and very low, respectively. In the steeper ground(>45%), the survival rate of F. moluccanareached 90%, the V. cylindricacoverage was 70-79% and the diameter and height increment of F. moluccanawas1.63 cm year-1and 1.19 m year-1, respectively. Theerosion rate was 1.81 ton ha-1year-1, erosion hazard index of 0.13(low), erosion hazard class wasI(very low), and erosion hazard level was low in the very steep slope land. The profit fromV. cylindricawasRp3,865,000.00 ha-1 cropping season-1and Rp665,000.00 ha-1 cropping season-1 in steep slope and very steep slope, respectively. The application of the proposed combination of vegetativeand terrace system could reduce surface runoff and erosion rate in thelong term, in addition toproviding short termeconomic benefits