Tillage Depth Effects on Soil Physical Properties, Sugarbeet (Beta vulgaris L.) Yield and Quality.

Tillage depth influences soil-water-plant ecosystem, thereby affects crop yield and quality. The effects of tillage depth were evaluated on soil physical properties and sugarbeet (Beta vulgaris L.) yield and quality. A field study comprises of two tillage depths: shallow (ST) of 10-cm and deep (DT) of 20-cm was conducted on a Lihen sandy loam soil in spring of 2007 at the ARS irrigated research farm near Williston, ND. Soil properties including bulk density (BD), gravimetric water content (GWC), and saturated hydraulic conductivity (Ks) were measured three times during the growing season in four increments to 40 cm depth, approximately 0.5 m apart within the crop row of irrigated sugarbeet. Soil air-filled pore volume (APV) 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. Root’s 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 BD and Ks were significantly affected by the depth of tillage. Soil BD 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 GWC and APV were slightly greater in DT than those under ST. Although tillage depth had no significant effect on sugarbeet population, root yield, sucrose content, or sucrose yield, the small differences in sugarbeet yield and sucrose yield between two depths of tillage may be attributed to reduce BD, 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 no effect on sugarbeet yield or quality.