Determining minimum data set for soil quality assessment of typical salt-affected farmland in the coastal reclamation area

The need for understanding and assessing soil quality is getting increasingly important because of growing public interest in determining the effect of management practices on the sustainability of the soil resource base. Our objectives were to investigate the effect of consecutive cultivation and different rotation systems on potential soil quality indicators, to identify effective soil quality indicators and to establish a minimum data set that discriminate different rotation systems. This study was conducted in a typical coastal salt-affected farmland in north Jiangsu Province, China. A pool of 22 measured variables representing soil chemical and physical properties (0–10 cm) and groundwater features at 60 sampling sites and 10 representative soil profiles were used. A specific emphasis was given to the impact of crop rotation systems on measured soil and groundwater properties because of the importance of cultivation to the sustainability of soil quality. One-way analysis of variance (ANOVA) showed that measured variables of SOM, SOCD, TN, AP, CEC, AK, ECe, Na and Cl were positively impacted by cultivation. In contrast to cotton–barley rotation, rice–rape rotation had significantly positive influence on SOM and SOCD, but adverse impact on AK, pH, ρb, Ks, WTg and ECg. Factor analysis grouped all measured variables into seven principal components explaining 78.5% of total variance: salinity (PC1), organic matter (PC2), water permeability (PC3), soil texture (PC4), ion exchange (PC5), soil alkalinity (PC6) and available nutrients (PC7). Discriminant analysis indicated that PC1 (Cl, Na and ECg), PC2 (SOM and SOCD) and PC7 (WTg) were the most powerful factors (indicators) to distinguish the two rotation systems. SOCD (SOM) and Cl offered the greatest potential for monitoring soil quality under different management practices. SOM not only had the strongest positive influence on crop biomass, but also contributed the greatest to distinguishing the effect of rotation systems on soil quality. Our study suggested that SOM may be considered as an indispensable factor to determine the sustainability of soil productivity for the salt-affected farmlands in coastal reclamation area.

► Cultivation and crop rotation system have influence on some soil quality properties.
► The 22 measured variables are categorized into seven principal components.
► SOCD (SOM) and Cl offer the greatest potential for monitoring soil quality.
► SOM influences crop yields and contributes to differentiating the rotation system.