Soil Erodibility of Several Types of Green Open Space Areas in Yogyakarta City, Indonesia

Abstract

The city development tends to reduce green open space area. This land use change will affect the soil erodibility and then increase the erosion rates. Therefore, the existence of green open space area is very important in preventing soil erosion of the city. In Yogyakarta city, there are several types of green open space area, but there is still lack of data on how far those areas play role in erosion process. The objectives of this research were: a) to measure the value of soil erodibility of several types of green open space areas, and b) to study the soil characteristics related to soil erodibility.The soil erodibility measurement was done at the 11 sites samples of green open space area of Yogyakarta city, including river side, sport field (3 sites), garden (2 sites), office yard, settlement, school yard, and zoo (2 sites). In this research, both disturbed and undisturbed soil samples were taken from the field then analyzed in the laboratory. The K formula of Wischmeier and Smith was used for calculating the soil erodibility.The research results showed that the soil texture was mostly sandy loam; the soil permeability ranged from the lowest of 2.34cm/hr (at the grass of the zoo) up to the highest of 34.88cm/hr (at the city garden). The soil organic matter ranged from the lowest of 1.2% (at the school yard) up to the highest of 5.65% (at the office yard). The soil structure could be classified as granular at all areas. In general, the green open space area had soil erodibility of 0.16 to 0.29 which was considered as low level. It means that the green open space area reduces soil erodibility. Based on this result, it is strongly recommended that in developing the city, the area of green open space must be allocated.