Effects of Calcium-Based Surface Amendments on the Penetration Resistance of Subsurface Drained Sodic Soils

摘要

In the saline/sodic and sodic soils of the northern Great Plains, subsurface drainage can inadvertently result in clay particle dispersion if the surface soils are leached with rainwater. Under these conditions, penetration resistance (PR) in wet soilcan be used to examine the effectiveness of free drainage (FD) vs. no drainage (ND) treatments and surface amendments consisting of a high rate of gypsum (GH), a low rate of gypsum (GL), spent lime (SL, a byproduct from the processing of sugarbeets), and no amendments [or check plots (CK)J on improving soil trafficability. The PR and soil moisture contents were determined from 0 to 45 cm depth for sodic soil plots near Wyndmere, North Dakota, during June 2015. The effects of drainage and surface amendments on PR were evaluated using analysis of variance, with gravimetric moisture content incorporated as a covariate. Significant differences were considered at p < 0.05. The mean PR values of ND (450 and 936 kPa) and FD (428 and 917 kPa) for the 0 to 15cm and 15 to 30 cm layers, respectively, were not significantly different. The PR value for the surface 15 cm was higher for GH (485 kPa) than for the other surface amendments. In the 15 to 30 cm layer, the PR for GH (1050 kPa) was significantly higher than for GL (954 kPa), which was in turn higher than for SL (866 kPa) and CK (839 kPa). Benefits from the combined effects of drainage and surface amendments were more evident in the 15 to 30 cm layer than in the 0 to 15 cm layer. In the 0 to 15 cm layer,NDGH had PR means (498 kPa) that were similar to all other treatments but higher than forFDSL (384 kPa). In the 15 to 30 cm layer, FDGL had PR means (1007 kPa) similar to FDGH (1074 kPa) and NDGH (1027 kPa), which showed that drainage coupled with a lower gypsum rate achieved similar results as the higher rate of gypsum application.