Graph with Na on x axis and SS-I on y axis. Points converge tightly around a straight line bisecting the graph at a 45-degree angle. Table showing how soil Na relates to SS-I.

Figure 2. Soluble salts index as predicted by soil test sodium concentrations. Based on this relationship: SS-I = 53.523 (sodium), R² = 0.9798, n = 910.

Graph with Na on x axis and SS-I on y axis. Points converge tightly around a straight line bisecting the graph at a 45-degree angle. Table showing how soil Na relates to SS-I.

Data compiled by David H. Hardy, NCDA&CS, Agronomic Division, 2024.