Estimation of field capacity and wilting point of some New Zealand soils from their saturation percentages

Abstract

The purpose of this study was to investigate the applicability of the readily measured saturation percentage (SP) as a possible index for estimating field capacity (FC) and wilting point (WP) water contents of some New Zealand soils. Saturation percentages of 39 soil samples from different depths in five different texturally layered soils were determined by the saturation paste method. Undisturbed soil cores from the field were used to determine laboratory-based measurements of the field capacity and wilting point of these samples. The results indicated a strong linear relationship between the mass percentage water contents at field capacity and wilting point, and the saturation percentage. High correlation coefficients suggested that easy and quick estimates of FC and WP of these soils can be obtained from their saturation percentages. However, the lack of correlation between the saturation percentage and available water capacity (AWC) in these soils clearly showed the inability of the SP method to provide good estimates of AWC. The paper also debates the relative value of field and laboratory measurements of “field capacity”, supporting the latter as a useful practical guide for the grower.

Keywords:

• field capacity
• wilting point
• soils
• water content
• saturation percentage
• available water capacity