Tillage Effects on Physical Properties in Two Soils of the Northern Great Plains

Abstract

Tillage practices profoundly affect soil physical and hydraulic properties. It is essential to select a tillage practice that sustains the soil physical properties required for successful growth of agricultural crops. We evaluated the effects of conventional (CT) and strip (ST) tillage practices on bulk density (rho(b)), gravimetric water content (theta(w)), and saturated hydraulic conductivity (K(s)) at the soil surface and at 10- to 15-cm depth in two soils of the Northern Great Plains (NGP). Soil cores were collected from each plot at 0- to 10- and 10- to 20-cm depths under each tillage practice at both sites to measure rho(b) and theta(w). In-situ K(s) measurements at the soil surface and at 10- to 15-cm depth were determined using a pressure head infiltrometer (PHI) and a constant head well permeameter (CHWP), respectively, at two sites, one in North Dakota (Nesson, mapped as Lihen sandy loam) and one in Montana (EARC, mapped as Savage clay loam). The K(s) measurements were made approximately 1 m apart in the center of crop rows within CT and ST plots of irrigated sugarbeet ( Beta vulgaris L.). Tillage treatments significantly affected soil rho(b) and theta(w) in clay loam soil at the EARC site, while rho(b) and theta(w) did not differ between CT and ST in sandy loam at the Nesson site. The log-transformed K(s) at the soil surface did not differ significantly between CT and ST practices at either site. The effect of tillage on log-transformed K(s) at the 10- to 15-cm depth was significant in both sandy loam and clay loam soils at P < 0.10 and 0.05 levels, respectively. The K(s) values at 10- to 15-cm depth were 23% and 138% greater for ST than for CT at Nesson and EARC sites, respectively. Differences in soil compaction as evaluated through rho(b) data at 10- to 20-cm depth explain K(s) variations between the CT and ST systems at both sites. It was concluded that the CT operations increased soil compaction, which consequently altered rho(b), thereby reducing K(s) in the soil.