Table 1.
Descriptive statistics of all the soil indicators collected from four depths under three soil types used to estimate SQI.
Table 2.
Soil indicators, threshold values, interpretations and scores.
Table 3.
Model of SQI-2.
Figure 1.
Scree plot of principal component analyses.
Table 4.
Results of principal component analyses (PCA).
Table 5.
Pearson correlation coefficients (r) for all soil indicators.
Figure 2.
Overall soil quality index (SQI) values under different soil types.
Different letters indicate significant differences at p<0.05 level for particular indexing method.
Table 6.
Treatment effects on soil quality index (SQI) under three soil types (Ko: Kokomo, CrB: Crosby silty loam, Mc: Muck) and four soil depths.
Figure 3.
Percentage contribution of each soil function in SQI-2 under different soils.
Different letters indicate significant differences at p<0.05 level for particular soil function. Abbreviations: RDC: root development capacity, WSC: water storage capacity, NSC: nutrient storage capacity.
Figure 4.
Percentage contribution of each soil function in SQI-2 under various management practices in different soil.
Different letters indicate significant differences at p<0.05 level for particular soil function. Abbreviations: RDC: root development capacity, WSC: water storage capacity, NSC: nutrient storage capacity; NCC: no cover crop, CC: cover crop, CT: conventional tillage, NT: no tillage.
Table 7.
Pearson correlation coefficients (r) of soil quality index (SQI) versus crop yield and correlations between different SQI values which were averaged up to a certain depth; all numbers are significant at p<0.05 level.