3.1 Effect of LU on soil organic carbon
With regard to LU, negative effects of SOC were found for LU like BL, CL, GL, HL and PL as when compared to FL (Figure 3). The SOC decreased significantly for BL (-27.3%), CL (-31.1%), GL (-36.1%) and PL (-35.5%) over the FL considered as control for this study but found non-significant changed for HL (-11.5%) in comparison to FL and this might be due to some data points were found with the positive effects but the maximum data points of ranges had come in the side of negative effects as the Figure 3 showed the mean value lied towards the negative effect. These results indicated that conversion of FL towards other land uses (BL/CL/GL/HL/PL) could readily result into decline in SOC content under most conditions. The percent negative change of SOC for all the land uses (BL/CL/GL/HL/PL) over the FL was found to be in greater in range due to variability in vegetation, soil types, climatic conditions, topography, and followed management practices in the different regions of the India.
On depth-wise the overall SOC showed negative effects for other land uses (BL/CL/GL/HL/PL) over the FL (Figure 3). In soil depth 0-15 cm, SOC decreased significantly in BL (-25.5%) and GL (-27.5%) over the FL but found non-significant changed for CL (-21.0%), HL (-17.5%) and PL (-31.1%) in comparison to FL and this might be due to some data points were found with positive effect but the maximum data points of ranges had come in the side of negative effect as the Figure 1 showed the mean value lies towards the negative effect. The majority of management practices are being carried out in soil depth 0-15 cm that could have resulted in buildup of SOC in few cases during long-term studies for the land uses CL, HL, and PL as compared to the newly established FL in the different regions of the country. In soil depth 15-30 cm, SOC decreased significantly in BL (-29.6%), CL (-46.5%), GL (-41.3%) and PL (-40.5%)over the FL but non-significant changed for HL (-12.4%) as compared to FL whereas in soil depth 30-45 cm, SOC decreased significantly in BL (-27.7%), CL (-54.9%), GL (-63.7%) and PL (-36.4%) over the FL and non-significant changed for HL (1.8%) in comparison to FL (Figure 3). The depth-wise results of SOC were in concurrence to the findings of overall SOC and similarly indicated that conversion of FL towards other land uses (BL/CL/GL/HL/PL) could readily result into decline in SOC content.