Coconut and Mahogany Plants Based Soil Water Conservation at Volcanic Slopes of Central Java-Indonesia

Vegetative based soil and water conservation is most commonly done by the community to contribute to income improvement at the volcanic slopes in Java Island, Indonesia. Coconut and Mahogany plants have been cultivated as intercrops in most dry-land agricultural fields by many people for different purposes of income generation. The differences in canopy characteristics between the two plants significantly affect the production of runoff. Field evidence is needed to support it as a suitable plant for soil and water conservation efforts. The study was conducted using a field survey method equipped with soil characteristic measurements in the laboratory. The data collection process began with a study of the landscape of the research area which was divided into three zones, namely residual, erosion, and deposition. In each zone, coconut and Mahogany plants were selected with the ideal morphology for measurement of interception, throughfall, and stemflow during rain events. Soil sampling under the plant canopy was used to measure texture, bulk density, particle density, porosity, macro pores, initial soil moisture, and organic matter. Coconut plants are considered better for the purpose of vegetative soil and water conservation than Mahogany. However, Mahogany must be arranged at the upper plot and Coconut at the lower plot to enhance runoff reduction. Coconut can reduce the volume of surface runoff significantly so that the erosion rate becomes smaller. Coconut roots function to stabilize the physical properties of soil which can ensure continuous infiltration and percolation processes during rain events so that the amount of water stored in the soil increases. Those two trees may be planted along the natural drainage canal that is usually located at the edge of dry-land agricultural fields.