**5.3 Increasing below-ground inputs**

Below ground OC inputs, which includes roots and associated inputs, contribute more to SOC compared with above ground inputs [59, 63, 64] (**Figure 5**). For example, Kätterer et al., [63] reported long-term experimental results which indicated that root derived C was 2.3 times higher than that derived from above ground plant residue. Rasse et al. [64] estimated that mean residence time in soils of root derived C is 2.4 times compared with that of shoot derived C, indicating that root C has a longer residence time in soil compared to the shoot C.

#### **Figure 4.**

*Soil carbon content with depth. Shaded areas represent standard error of the mean. Data from long-term field experiment in Ultuna. Modified from [59].*

#### **Figure 5.**

*Mean annual carbon inputs through above-ground crop residues, roots including rhizodeposition to equivalent topsoil depth (1957–2008), and organic amendments (1956–2008). Modified from [63].*

**Figure 6.**

*Topsoil carbon concentrations over time in the Ultuna long-term soil organic matter experiment. Modified from [63].*

#### **5.4 Organic amendments**

Organic amendment inputs can promote a buildup of SOM and hence SOC [65] (**Figure 6**). Menichetti et al. [59] reported that application of organic amendments affected SOC in the topsoil resulting in fourfold increases in C stock. Organic residues and wastes can be applied to soil, as fresh organic matter, after composting, methanisation, or pyrolysis [12]. However, the effects of residue quality on long term SOC is still a matter of debate [12]. Previous studies have indicated that the most labile and easily degradable compounds contribute more to SOM in the long term than recalcitrant materials such as lignin, this is especially common in clayey soil [66]. There are three explanations to this finding, which include: 1) long lasting SOM are mainly derived from microbial materials [67, 68]; 2) substrates that are easily degradable are processed with a high microbial C use efficiency [69], and 3) soluble compounds could be protected between mineral surfaces [12].

#### **5.5 Integrated, and diverse cropping/farming systems**

Compared with monoculture, introduction of crop diversity increases SOC which improves soil health [70]. Whereby, a combination of diversification within a cropping system and no-till soil management can help to improve SOC [71]. Increased plant diversity can enhance positive soil feedbacks on residue decomposition and soil SOM stabilization and may contribute to C accumulation in soils with rotated crops [72]. Further, Maiga et al. [71] demonstrated that use of diverse 4-year crop rotations for longer duration (>24 years) enhanced SOC, overall C and nitrogen fractions, and soil aggregation in comparison with those under 2-year corn–soybean rotations.

### **6. Conclusion**

Soil organic C is an important indicator of soil health. Soil health is a major component of one health, which encompasses human, animal, and environmental health [73].

### *Land Use Change Affects Soil Organic Carbon: An Indicator of Soil Health DOI: http://dx.doi.org/10.5772/intechopen.95764*

Soil organic C promotes land productivity and provides ecosystem services. Since SOC content influences almost all soil functions and is easily measurable, it can be a suitable indicator of the soil capacity to supply ecosystem services. This hypothesis reinforces the suitability of SOC as an appropriate indicator for soil management decisions, land use planning, and regulation. However, the rapidly increasing global human population is exerting enormous pressure on natural resources, as a result of the need to provide food and fiber to supply demands from this growing population. Consequently, there has been conversion of natural land areas to agricultural land globally in pursuit of meeting the human demand for food and fiber. This land use change has resulted in losses of SOC, which negatively affects productivity and diminish ecosystem services. Previous work has demonstrated that conversion of agricultural land to its natural cover provides positive feedback in terms of increasing soil C stocks. This finding highlights the importance of increasing agricultural production by increasing crop yields per unit area rather than expanding cropland and/or pasture to natural areas for long-term sustainability. In addition, there is need to invest in technological options that enhance SOC stocks in agricultural land. These options include no-tillage/conservation agriculture, irrigation, increasing below-ground inputs, organic amendments and integrated, diverse cropping/farming systems.
