SOIL QUALITY ASSESSMENT OF TAAL LAKE

The soil is a complex, multifaceted environment. This complexity has prompted the evolution and adaptation of a highly diverse biotic community, which uses the soil as its permanent or temporary habitat or refuge. Many thousand species of animals and micro-organisms live in soils, ranging in size from the almost invisible microbiota (e.g. bacteria, fungi and protozoa) to the more conspicuous macrofauna and megafauna (e.g. earthworms, termites, millipedes, moles and rats). (World Soil Resources Reports June 2002)

Soil quality concise definition includes “fitness for use” and “the capacity of a soil to function. “ Combining these, soil quality is the ability of a soil to perform the functions necessary for its intended use. Soil functions include: sustaining biological diversity, activity, and productivity; regulating water solute flow; filtering, buffering, degrading organic and inorganic materials; storing and cycling nutrients and carbon; and providing physical stability and support. (USDA Soil Quality Indicator)

I had conducted assessment on soil quality of Mud Spring and for Mt. Makiling, the same sampling procedure and test parameters in determining physicochemical properties was followed; , For our field work on Toxicology in the Environment, I collected soil samples from three (3) different stations at Taal Lake area to evaluate soil quality and determine indications of Organic Matter content, soil pH and available nutrients in reference to the capacity of a soil to function within ecosystem, to sustain biological productivity, maintain environmental quality, and promote plant and animal health.  

For soil quality assessment we first identify three stations for soil sampling. First station (S1) was at shores of Kay Liling resort and spa; Second station (S2) was on shores of volcano island (across Taal lake) and Third station (S3) at mountain top near volcanic crate (1 kilometer from Taal Lake basin view point). Since major terrestrial biomes’ geographical distribution is dependent on temperature, precipitation, altitude and latitude; coordinates of each station were determined prior to sampling collection.

Sample 1 (Shores of Kay Liling resort and spa): Three trials were evaluated for each parameters and average reading as follows; Nitrogen (N) content was low, Phosphorous (P) was high, Potassium (K) was sufficient, pH at 7.6, and organic matter was 0.5

A pH range of 6 to 7 is generally most favourable for plant growth because most plant nutrients are readily available in this range. Soil at station has a pH of 7.6 a slight alkaline condition of soil. The most important concept regarding pH is that extreme acid or alkaline conditions affect the availability of virtually all the essential nutrients. Soil pH at station 1 correlates the low availability of Nitrogen (N), sufficient amount of Potassium (K) and High availability of Phosphorous (P); at pH 5.0 (strongly acidic) the amount of calcium, magnesium, potassium, nitrogen, and sulphur available is only half as much as at pH 6.0 (moderately acidic). The availability of phosphorus begins to decline at pH 6.5. Below 6.0, most phosphorous is unavailable. Excessive alkalinity also leads to nutrients imbalance.

Soil at station 1 has a rather alkaline pH, and the soil test report indicated low levels of several of the trace elements such as Nitrogen. Therefore, soil at station 1 is not best for maximizing soil life and plant – available nutrients.   

Organic matter (OM) is a measure of all plant and animal residues, ranging from raw, undecomposed materials to stable humus. Organic material of soil at station 1 has a low organic matter which also explains low Nitrogen availability since OM is a source of nitrogen, the major cations and trace minerals. One thing to be considered is that the site serves commercial purposes as its shore of a resort and spa. Natural setting has frequent human intervention with maintenance required to preserve the area. 

Sample 2 (Shores at Volcanic Island – Taal Lake): Three trials were evaluated for each parameters and average reading as follows; Nitrogen (N) content was low, Phosphorous (P) was high, Potassium (K) was sufficient, pH at 7.6, and organic matter was -0.1

Soil quality of station 2 is much comparable with station one; soil was collected on shores of volcano island with frequent human intervention and serves as commercial area for eco tourism. Furthermore, residential lots were noted near shoreline. Soil was of wet, black and loose with pH of 7.6 has a rather alkaline pH. In correlation with detected amount of low nitrogen (N), sufficient potassium (K) and high availability of phosphorus was due to the alkalinity of soil - at pH 5.0 (strongly acidic) the amount of calcium, magnesium, potassium, nitrogen, and sulphur available is only half as much as at pH 6.0 (moderately acidic). The availability of phosphorus begins to decline at pH 6.5. Below 6.0, most phosphorous is unavailable.

In general, Soil at station 2 has a rather alkaline pH, and the soil test report indicated low levels of several of the trace elements such as Nitrogen. Therefore, soil at station 2 is not best for maximizing soil life and plant – available nutrients.    

Organic material of soil at station 2 has a low organic matter which also explains low Nitrogen availability since OM is a source of nitrogen, the major cations and trace minerals. One thing to be considered is that the site serves commercial purposes for tourist of Taal Lake basin. Natural setting has frequent human intervention with local residents and fishermen maintenance required to preserve the area. 

Sample 3 (Volcanic Island Mountain Top near crater – Taal Lake): Three trials were evaluated for each parameters and average reading as follows; Nitrogen (N) content was low, Phosphorous (P) was high, Potassium (K) was sufficient, pH at 6.4, and organic matter was 1.3

Soil at station 3 was collected on mountain top (near crater), as observed, a man-made pathway was facilitated to serve purpose of horse back riding to view point spot (as part of eco-tourism livelihood). On way by foot, encountered several digestive wastes from horse, grassland, forest, color variation of soil and rock formation. In general, there were different classification and characteristics of ecosystem. Soil pH at station 3 was at 6.4 that are not extremely acidic or alkaline, therefore, best for maximizing soil life and plant-available nutrients.

Organic matter of soil at station 3 has a greater amount at 1.3 as compared to station 1 and 2. Despite low nitrogen availability it is still a normal indication since the amount of nitrogen being released by OM depends heavily on the quality of the organic matter and the soil conditions (texture, temperature, water content). Nevertheless, testing for OM can be useful to observe general trends provided it is measured every year or two.

In general, soil at station 3 has a greater amount of raw residue, which are useful for stimulating soil microbial activity, but do not contribute to nutrient retention. Humus and other more stable decomposed organic matter present at area are very important nutrient sources and contributor.  

Soil quality of Taal Lake was determined using Chemical Indicators (N, K, P and soil pH) and measure of Organic Matter (OM) and data collected lead to conclude that soil quality varied on location with several factors affecting it.

  

Soil quality at station 1 and 2 may not be maximized soil life and plant – available nutrients, yet still can be adjusted and function within the ecosystem. However, soil quality at these areas had not interfere with the ability of locals to promote socio-economic growth through ecotourism, thus, still sustain biological productivity and helped residence maintain environmental quality.

Soil quality at station 3 has much potential and capacity to function well within the ecosystem as evident with diversity of plants within scope of Volcano Island Mountain as contributed with the nutrients and organic matter content of soil. Thus, this support claim that soil in Taal can sustain biological productivity, maintain environmental quality and promote plant and animal health.  

Soil provides a list of services to all users of terrestrial ecosystems and is crucial to our agricultural societies. From an anthropogenic point of view, soil quality may be then measured in terms of the services the soil provides to our society. The value of soil services to human societies has changed during history and thus the value we give to soils has also changed over time as it depends upon the economic and cultural basis of a society for a given context.

Holistically, soil at Taal is of quality that considered gift to provided food security (quality and quantity); environmental quality and biodiversity; human and health welfare.