Tillage Effects on Subsurface Drainage

Abstract

Tillage near the soil surface may greatly influence drainage discharge and pressure head values in the subsurface zone. In this study, a controlled comparative experiment was conducted in the field under natural weather conditions, using a tilled and an untilled column, to evaluate the effects of tillage on subsurface drainage discharge and pressure head values. There were no significant differences between the two columns in subsurface drainage before tillage treatment before the study, as checked by a preliminary experiment. After tilling one column of the two columns, cumulative subsurface drainage discharge was larger and occurred earlier for the tilled column than for the untilled column. The measured drainage discharge and pressure head values were evaluated using the water movement model, HYDRUS version 6.0, which numerically solves the Richards equation. The HYDRUS model reproduced measured values well for subsurface drainage discharge and pressure head values after the tillage, as determined by root mean squared error (RMSE), mean bias error (MBE), and R2 Therefore, it is concluded that the model, which includes the effects of tillage on the hydraulic properties, can explain the reasons for differences in observed drainage in the two columns. Moreover, the effects of tillage depth on subsurface drainage discharge were simulated. The results implied that the effect of tillage on subsurface drainage were induced by the conditions of pressure head just before the first rainfall, and this effect was equal to, or greater than, the effects of changes in hydraulic properties due to tillage.

Approaches for Estimating Soil Water Retention Curves at Various Bulk Densities With the Extended Van Genuchten Model

“…For these 12 soils, different ρ b conditions were achieved by laboratory compaction procedures. The WRC measurements of soils 6, 7, 15, and 16 were made on undisturbed soil samples with different ρ b from various depths in tilled or nontilled field treatments (Gao et al, ; Moroizumi & Horino, ; Or et al, ). For more details about the literature data, please refer to the associated references.…”

Modeling the Relationship between Soil Bulk Density and the Water Retention Curve

“…The model for estimating the effects of bulk density on the WRC was validated by comparing the predicted WRCs of compacted soils with the corresponding data from another experimental data set different from the one used for calibration. The validation data set comprised measured WRCs of (i) mechanically compacted disturbed soil samples of Bet Dagan sandy loam and (ii) undisturbed samples taken from tilled and untilled soil layers of Kitasato sandy loam (Moroizumi and Horino, 2004), Mattapex (fine‐silty, mixed, active, mesic Aquic Hapludults) silt loam (Hill, 1990), and Cotto clay (Or et al, 2000; Snyder et al, 2000). The Bet Dagan soil samples were compacted to various bulk densities by vibrating soil columns that had been filled with air‐dried sieved soil, while their WRCs were measured with a tension table.…”

Effects of artificial land drainage on hydrology, nutrient and pesticide fluxes from agricultural fields – A review

“…Accordingly, lower subsurface drain flows and slightly higher surface runoff have been observed under grassland when compared to a field on which barley was cultivated (Turtola and Jaakkola, 1995). Tilling has been found to accelerate and increase subsurface discharge into drainage pipes due to increased hydraulic conductivity (Moroizumi and Horino, 2004). Especially on clay soils, tilling may substantially enhance the infiltration capacity, thereby leading to enhanced subsurface flow and reduced surface runoff.…”