Morphophysical and Nutrient Characteristics of Degraded Soils in Sta. Rita, Samar, Philippines

Abstract

The productivity of degraded soils greatly depends on a good understanding of their characteristics. Hence, the study was conducted to determine the morphological, physical and chemical characteristics of degraded soils in Sta. Rita, Samar, Philippines. Four representative soil profiles located in different physiographic positions were examined, characterized and sampled. The examination was conducted using a pit measuring approximately 1-m wide and 1-m depth. Soil samples were collected from each horizon, processed and subjected to field and laboratory analyses. Results showed that the soils were derived from sedimentary rocks (i.e., shale). Well-developed soils were found on the summit and foot slope position (horizon sequence: Ap-Bt-BC-C), while moderately developed soils were obtained in the middle slope position (horizon sequence: Ah-Bt-C). Soils had a clayey texture with moderate bulk density, porosity and water holding capacity. They were friable to firm when moist, but plastic and sticky when wet. The soils were highly acidic (soil pH close to 5.0). They had a moderate amount of organic matter, low total nitrogen (N) and low available phosphorus (P); all of which had decreased amounts with soil depth. Exchangeable bases (calcium, magnesium, potassium and sodium) were high in most soil profiles. Thus, N and P fertilization and organic matter addition are highly recommended to increase the productivity of these degraded soils. Moreover, the soils were classified as Typic Hapludalfs or Haplic Luvisols because of their development degree. They were mature with the presence of an argillic horizon (B horizon with high clay accumulation) and high base saturation.

Soil Physicochemical Characteristics and Spore Density of Indigenous Arbuscular Mycorrhizal Fungi (AMF) in Different Vegetation Patches of a Marginal Upland in Central Philippines

“…This study observed no clear trend (p > 0.05) in WHC values between the different vegetation patches (Figure 3). Although WHC ranged from 41.88 to 46.68%, and within the WHC range of clayey (Moody and Cong, 2008) and degraded soils (Asio et al, 2015;Sabijon and Asio, 2022), results corroborated the observation of Asio et al (2015) as WHC being not a desirable indicator of soil degradation due to its dependence to soil texture and a stable soil property.…”

“…Navarrete et al (2013) also reported pH levels of 5.12 and 5.48 from the studied degraded soils in Ormoc and Baybay, Leyte, respectively. Calubaquib et al (2016) and Sabijon and Asio (2022) reported a pH range of 4.5 to 5.4 and 5.0 to 7.0 in the studied degraded soils in Luzon and Samar, respectively. The moderate to strong acidity condition means that this degraded upland had soil fertility problems regarding nutrient availability, micronutrient toxicity and microbial activity (Bohn et al, 2001).…”

“…These values suggest the moderate to extreme compaction of the soils in the studied area. Asio et al (2015) and Sabijon and Asio (2022) reported comparable ranges of Db values (1.35 to 1.66 g cm -3 and 1.30 to 1.50 g cm -3 , respectively) of selected degraded soils in Samar Island. Soil compaction may not be well studied in the Philippine soils (Asio et al, 2009); these values indicate pressing concerns since, at this condition, it will favor surface run-off, exacerbating soil erosion that removes fertile topsoil and decreasing the soil fertility and productivity (Lal, 1990) worth noting compared with the A. aciculatus patches.…”