Australian Soil

Soil properties are the result of the five soil forming factors; parent rock, climate, topography, organisms and time (Bockheim, et.al., 2014). This is why there is a wide variety of soil types throughout Australia, but are there systematic differences between different regions? This essay will determine whether Australian tropical soils are different from soils of the rest of the country. The tropics are the regions between the latitude lines of the Tropic of Cancer and the Tropic of Capricorn (Seidel, et.al., 2008). The tropics are warm all year, averaging 25 to 28 degrees Celsius, as they don’t experience the kind of seasons the rest of the Earth does (Seidel, et.al., 2008). The tropical seasons are broken up into the wet season and the
There are three main variables in parent material which affects the soil properties: grain size, composition and degree of consolidation (Alexander, 2013). Parent material is the dominant factor over texture (Alexander, 2013). The parent material provides the basic mineralogy for the soil, thus soils formed from granites tend to be sandy and infertile, while those formed from basalts will have a higher clay content and have an increased fertility (Alexander, 2013). Within each region, such as the tropics, the parent material varies significantly throughout and is not one consistent type. Therefore the variety of parent material in the Australian tropics and the rest of the country is not consistently different. The rest of the world had their surfaces wiped clean around 10,000 years ago, Australia as a whole did not experience this, so we have very old weathered soils compared to the rest of the world (Alexander, 2013). While this may make Australian soils different it does not make the soils of the tropics any different to the rest of the country. The topography of the Australian tropics is not different to the rest of the country, there are plains and mountains all around the country and are not influentially different by climatic zones. Therefore, topography, parent material and time are not significant soil forming factors in determining the distinction between tropical and non-tropical
Hence climate is the main soil forming factor that could possibly make any distinguishable characteristic change to soil properties between the regions. Climate, as both temperature and rainfall, has major effects on organic matter, chemical composition, base saturation and contents of carbonates and soluble salts (Young, 1976). The tropics of Australia consistently experience warmer annual temperatures. Warm temperatures coupled with high moisture, will increase the rate of reactions in the soil and therefore increases the weathering process (Stonestrom, et.al., 1998). Therefore in the wet tropics, it is typical to have well-developed, highly weathered soils. The shorter the dry season the higher the percentages of clay, although this effect is frequently masked by the stronger influence of parent material (Mohr, et.al., 1972). The silt: clay ratio tends to decrease with an increased rainfall (Mohr, et.al., 1972). Soils of rainforest climates are frequently high in clay and very low in silt under slower chemical weathering of while in semi-desert and desert soils much material remains as sand or silt particles (Young, 1976). The problem here is that the tropical belt of Australia does not have one consistent type of vegetation or consistent rainfall throughout, and hence not one consistent soil