Spatial and Temporal Variability of Soil Penetration Resistance Transecting Sugarbeet Rows and Inter-Rows in Tillage Systems

Abstract

Abstract. Soil compaction has detrimental consequences on soil quality and plant root growth. Soil compaction is a variable property due to tillage in both space and time. A field study was conducted near Sidney, Montana in 2007 to evaluate spatial and temporal variations of soil penetration resistance (PR) on a 61-cm transect across the rows and inter-rows of sugarbeet on a clay loam in both conventional (CT) and strip tillage (ST) systems. A cone penetrometer was used to measure PR on a grid sampling scheme (5 cm horizontal A— 2.5 cm vertical). The penetrometer was pressed into the soil every 5 cm along a 61-cm transect using a steel template bisecting the rows and inter-rows of sugarbeet. At each transect point, measurements were recorded at 2.5-cm depth increment to a depth of 30 cm. Soil PR measurements were recorded prior to planting (26 April), after the first cultivation (13 June), before harvest (3 October), and after harvest (4 October). Soil water contents were gravimetrically determined at the time of PR measurements. Soil PR was significantly greater in CT than in ST across the rows and inter-rows at the 0 to 30 cm depth for all sampling dates. Generally, soil PR increased with depth at every position on transect for all sampling dates under both tillage systems. Significant temporal variations in soil PR within each tillage system were observed throughout the growing season. Spatial variation data showed that less compaction was observed in crop rows compared to inter-rows under both tillage systems. Soil PR values increased as the growing season progressed and were highest prior to crop harvest, approaching values greater than 3.5 MPa below the soil surface.