The following text is for questions 81 to 85

The word gambut (peat) is taken from the name of a village, Desa Gambut (now Gambut sub-district), which is located about 10 km east of Banjarmasin, South Kalimantan. It is at this place that for the first time, rice has been successfully cultivated in peat soiled rice fields. In the soil taxonomy system, peat soils are grouped into a separate soil order called histosis, which means that the land is predominantly composed of organic soil materials in the form of the remains of plant tissues. The nature and characteristics of peat soils can be determined based on their physical and chemical properties.

Gambut has dark brown to blackish colors. Although its basic materials are gray, brown, or reddish, after decomposition, the dark humic compounds will appear. Furthermore, based on the weight of the contents, peat soil or gambut, which has undergone further decomposition, has a content weight ranging from 0.2 to 0.3 g/cm³. Due to the low content weight, peat has a large capacity as water storage, about 2-4 times its dry weight. In fact, moss peat that has not been decomposed can store up to 12 or 15 even 20 times more water than its own weight. In addition, peat soil has a large absorption area, which is up to 4 times greater than montmorillonite clay.

Next, peat soil has acidic reaction properties. Decomposition of organic matters will produce organic acids that accumulate in the body of the soil hence increasing the acidity of the peat soil. Generally, peat soil shows real resistance to changes in pH when compared to mineral soils.  As a result, peat soil requires more limestone to increase the pH at the same level of the value of mineral soil. Thus, peat soil requires a higher dose of fertilizers than mineral soil.

Furthermore, based on the nutrients contained in it, peat soil is a type of nutrient-poor soil. High level of N and organic matters in peat soils are also accompanied by a high N nitrification process so that the activity of heterotrophic organisms is not well stimulated and the organisms active in the nitrification process can carry out their activities. Therefore, the levels of P (phosphorus) and K (potassium) of peat soils are generally lower than that of the mineral soils. Also, the plants cultivated on the peat soil are very responsive to the fertilization using P and K.

The following text is for questions 86 to 90

Floods are second only to fire as the most common of all natural disasters. They occur almost everywhere  in the world, resulting in widespread damage and even death. Consequently, scientists have long tried to perfect  their ability to predict floods. So far, the best that scientists can do is to recognize the potential for flooding in  certain conditions. There are a number of conditions, from deep snow on the ground to human error, that cause  flooding. 

 When deep snow melts, it creates a large amount of water. Although deep snow alone rarely causes floods,  when it occurs together with heavy rain and sudden warmer weather, it can lead to serious flooding. If there is  a fast snow melting on top of frozen or very wet ground, flooding is more likely to occur than when the ground  is not frozen. Frozen ground or ground that is very wet and already saturated with water cannot absorb  additional water created by the melting snow. Melting snow also contributes to high water levels in rivers and  streams. Whenever rivers are already at their full capacity of water, heavy rains will result in the rivers  overflowing and flooding the surrounding land.  

 Rivers that are covered in ice can also lead to flooding. When ice begins to melt, the surface of the ice cracks  and breaks into large pieces. These pieces of ice move and float down the river. They can form a dam in the river,  causing the water behind the dam to rise and flood the land upstream. If the dam breaks suddenly, lage amount  of water held behind the dam can flood the areas downstream, too. 

 Broken ice-dams are not the only dam problems that cause flooding. When a large human-made dam  breaks or fails to hold water collected behind it, the results can be devastating. Dams contain such huge amounts  of water behind them that, when sudden breaks occur, the destructive force of the water is like a great tidal  wave. Unleashed dam waters can travel tens of kilometers, cover the grounds in meters of mud and debris, and  drown and crush everything and creature in their path. 

 Although scientists can not always predict exactly when floods will occur, they know a great deal about  when floods are likely, or probably, going to occur. Deep snow, ice-covered rivers, weak dams are all strong  conditions for potential flooding. Hopefully, this knowledge of why floods happen can help us reduce the damage  they cause.