Physical and hydraulic properties of a sandy loam soil under zero, shallow and deep tillage practices

The effect of tillage depth on physical properties in sandy soils under sugarbeet (Beta vulgaris L.) is not well understood and documented. A 4-yr study was conducted to investigate the effect of zero tillage (ZT), shallow tillage (ST), and deep tillage (DT) practices on soil bulk density (BD), saturated hydraulic conductivity (Ks), and moisture content (MC) in a sandy loam. Undisturbed soil cores were collected at 0- to 10, 10- to 20, 20- to 30, and 30- to 40 cm depths to measure BD and MC under each tillage practice. Soil Ks for the surface and subsurface layers were measured using a single head pressure ring infiltrometer and a constant head well permeameter, respectively. Soil BD was not significantly influenced by tillage in the 0- to 10, 10- to 20, 20- to 30, and 30- to 40 cm layers when averaged for four years. When averaged across the 0- to 40 cm depth, soil BD did not differ significantly among three tillages in 2008, 2009 and 2010; however, BD was significantly lower in DT (1.50 Mg m-3) than in ZT (1.61 Mg m-3) and ST (1.59 Mg m-3) in 2011. Soil BD averaged over all years and layers resulted in nonsignificant differences among three tillage practices. Soil Ks did not differ significantly among three tillage practices in 2008, 2009, and 2011 for the 0- to 40 cm depth. Similarly, soil Ks averaged across four years and four layers was not affected by tillage. In 2010, Ks was significantly greater in ST (27.60 mm h-1) than in ZT (17.21 mm h-1) and DT (12.46 mm h-1). Soil MC was not significantly influenced by tillage in any of the four depths when averaged across four years and when also averaged across four depths for each year. Across four years and four depths, averaged MC was not influenced by tillage. Large variations in Ks among ZT, ST and DT were likely caused by soil variability among replications within each tillage treatment. We concluded that tillage did not significantly affect BD, Ks and soil MC most likely due to the unchanging total porosity in sandy loam soil regardless of tillage type.