Questions 22-25 are based on the following text.
 

    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 soild rice fields. In the soil taxonomy system, peat soils are grouped into a separate soil order called hsitosols, which means that the land is predominantly composed of organic soil materials in the form of the remains of plant tissues. The nature and the 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 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.

(adapted from https://freelearningji.wordpress.com)

The purpose of the writer in writing the sentence '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' in paragraph 4 is to ....