**7. Land suitability**

According to several researchers [90–94], there have been very drastic shifts in land use in West Lampung, Sumatra, Indonesia over the last ten years (2000–2010). Primary forests have declined significantly, while dryland agriculture (coffee-based farming), rice fields, and residential areas have grown. These adjustments cause soil erosion and surface runoff. According to the author's observations in the region, soil depletion resulted in erosion and landslides during the rainy season (see **Figure 9**). Meanwhile, during the dry season, there is drought and soil cracking (**Figure 7**). This phenomenon indicates the occurrence of soil quality issues in the West Lampung

#### *Tropical Volcanic Residual Soil DOI: http://dx.doi.org/10.5772/intechopen.98285*

region. As a result of these issues, it is assumed that the volcanic residual soil of the study area has unique characteristics for specific land use.

Based on our research, using a statistical approach (K-Means Clustering) (**Tables 2** and **3**) and qualitative analysis, the soils of the research area are divided into two clusters (**Figure 10**). The first cluster soils with low plasticity, LL brine value of 50% or less (low to intermediate salt content). This cluster included soils with the inactive soil category (< 1) and contained minerals: despujolsite, hematite, chlorite, montmorillonite (< 0.4%), and quartz. While the second cluster soils with intermediate to high plasticity have LL brine values greater than 50% (intermediate to high salt content), and soils with the normal to active soil category (> 1). Despujolsite, hematite, magnetite, illite, montmorillonite (> 0.4%), dickite, and quartz are the minerals that can be found in this cluster.

The following is an example of soil suitability. The first cluster includes swellshrink features ranging from zero to intermediate. This soil type has well-structured soil, strong consistency, low seepage losses, and a limited pore area [67, 95]. The soils would be ideal for agriculture, building foundations, and earth construction due to their characteristics [67].

The second cluster is distinguished by intermediate to high swell-shrink characteristics [96]. These soils are dispersed because of their high Natrium content. The soils had been heavily eroded, and platy aggregates had formed [95]. These traits contribute to slow seedling emergence and germination [97]. These soils have insufficient soil intensity [98]. Infiltration in these soils can be rapid at first, but they later stay wet for long periods, causing erosion, infrastructure destruction, and trafficability problems [99]. Because of their characteristics, soils in this cluster are well suited for primary forest growth.


#### **Table 2.**

*Tropical volcanic residual soil cluster.*


**Table 3.** *ANOVA.*
