Soil Quality Along a Distances Gradient from Shorelines in Samas Coastal Sandy Land, Bantul, Yogyakarta

Kualitas Tanah pada Jarak Garis Pantai di Lahan Pertanian Pasir Pantai Samas, Bantul, Yogyakarta

Abstract

Samas coastal sandy land is characterized as a marginal agricultural area, approximately 4 km from the shoreline. This study was conducted with three primary objectives:  to evaluate its soil characteristics, to calculate its soil quality index (SQI), and to examine the limiting factors for soil quality. This study used a purposive survey method, sampling points were selected at varying distances from the coastline. Soil quality parameters analyzed included root density, weight density, porosity, clay content, C-organic, total N, available N/P/K, pH, and microbial counts (CFU/g). Soil quality was evaluated based on the criteria by Mausbach & Seybold (1998) and scoring function from Karlen et al. (1996), both of which were adapted to local conditions. The results showed that the 1 km from the coastline had the highest sand content (62.041%) but the lowest microbial counts (670×10³ CFU/g), while soils 4 km inland showed the lowest sand content (19.819%) and highest C-organic (1.297%), total N (0.392%), C/N ratio (3.309), and microbial activity (1910×10³ CFU/g). Available N, P, and K were consistently high across all sites. The soil quality index (SQI) increased with distance from the coast, transitioning from "moderate" (SQI 0.472 at 1 km) to "good" (SQI 0.774 at 4 km). The limiting factors identified were porosity, non-capillary porosity (NPD), C-organic, and available N. These findings underscore the critical role of shoreline proximity in shaping soil quality gradients in Samas’ sandy coastal agroecosystems.