Integrated Agrochemical Characterization of an Agricultural Land through Composite Indices and Statistical Analysis

Abstract

The study summarizes the agrochemical characterization of an agricultural land module, composed of five plots (A1–A5) from the area of ​​Ciacova locality, Timiș County, Western Plain of Romania. The agricultural module studied had an area of ​​137.05 ha, in the arable category. The study was based on 28 soil samples and 16 agrochemical indicators of soil reaction (pH, hydrolytic acidity – HA, sum of base cations – SBC, base saturation degree – V, aluminium – Al), organic matter (humus – H), and supply of macro- and microelements (NI, P, K, Ca, Mg, S, Fe, Mn, Cu, Zn). Descriptive statistics, area-weighted means, standardized indicators, Nutrient Balance Index (NBI), Soil Quality Index (SQI), Pearson’s correlations, multivariate analysis, hierarchical cluster analysis, and effect sizes (η²) for plot differentiation were calculated. The overall average pH was 6.33, in the slightly acidic–neutral range, and the surface-weighted averages confirmed a predominantly slightly acidic reaction. The weighted average SQI was 0.48 and the weighted average NBI was 0.62, indicating an intermediate agrochemical quality, with relatively better nutritional balance than the overall quality score. PCA separated plot A1 from the others of the plots, and cluster analysis confirmed the same differentiation. The key indicators resulting from the combination of the PCA contribution and the relationship with SQI were H, NI, Mg, S, Cu, Mn and HA, which suggested that the land cannot be adequately characterized by a single index, but by a group of indices covering organic matter, soil reaction and cation/nutrient balance.