Characterizing the soil physical condition in reduced tillage systems for winter wheat on a fine sandy loam using small cores

Abstract

A tillage study was conducted in Prince Edward Island with winter wheat (Triticum aestivum L.) over two seasons on a Gowanbrae light fine sandy loam, a Humo-Ferric Podzol. One-pass mouldboard ploughing, shallow tillage using a rotary harrow, and direct drilling were evaluated for their effects on crop productivity and soil physical properties. Direct drilling increased plant survival but not grain yield in the first year compared to the other tillage systems. Leaf diseases significantly reduced crop performance under shallow tillage and direct drilling in the second year. None of the tillage systems had adverse effects on soil strength at field capacity over the 0- to 350-mm soil profile depth, as penetrometer resistance values were < 1.5 MPa. Differences in soil macro-aggregation and organic carbon distribution between tillage systems were noted in the Ap horizon. Sequential measurements on soil cores equilibrated at 6 kPa tension for macropore volume, air permeability at low air pressure (0.25 kPa), oxygen diffusion rate (ODR) at 0.65 mV, and shear strength indicated that the soil physical condition was within the optimum range for root growth, over the 0- to 240-mm depth, in each tillage system. In addition, relative compaction was maintained at a low level in all systems. The quotient of air permeability and macropore volume, as an index of pore continuity, indicated that the relatively large macropore volumes under mouldboard ploughing were less efficient in conducting air than the macropores under direct drilling. These differences in pore continuity were most prevalent at the lower soil depth.Key words: Soil physical properties, soil compaction, Podzolic soil, winter cereals