Tillage Depth Effects on Soil Physical Properties, Sugarbeet Yield, and Sugarbeet Quality

Tillage depth influences the soil-water-plant ecosystem, thereby affecting crop yield and quality. The effects of tillage depth on soil physical properties and sugarbeet (Beta vulgaris L.) yield and quality were evaluated. A field study composed of two tillage depths [10 cm, referred to as shallow (ST), and 20 cm, referred to as deep (DT)] was conducted on a Lihen sandy loam soil in spring 2007 at the Agricultural Research Service (ARS) irrigated research farm near Williston, North Dakota. Soil bulk density (ρ(b)), gravimetric water content (theta(w)), and saturated hydraulic conductivity (Ks) were measured three times during the growing season at four depth increments to 40 cm deep. Samples were taken approximately 0.5 m apart within the crop row of irrigated sugarbeet. Soil air-filled pore volume ((epsilon)a) was calculated from soil bulk density and water content data. Soil penetration resistance (PR) was also measured in 2.5-cm increments to a depth of 35 cm. Roots were hand-harvested from each plot, and each sample consisted of the roots within an area consisting of two adjacent rows 1.5 m long. Soil ρ(b) was greater in ST than in DT, whereas Ks was greater with DT than with ST. Soil PR was significantly greater in ST than in DT at the 0- to 20-cm depth. Soil theta(w) and epsilon(a) were slightly greater in DT than those under ST. Although tillage depth had no significant effect on sugarbeet population, root yield, or sucrose content, a small difference in sucrose yield between two depths of tillage may be attributed to reduced ρ(b), increased water intake, improved aeration, and increased response to nitrogen uptake under DT than under ST. It was concluded that tillage depth enhanced soil physical quality and had little effect on sugarbeet yield or quality.