Effect of once-off tillage on soil water, inorganic nitrogen and glomalin contents under conservation agriculture in the Swartland sub-region of the Western Cape

Abstract

Strategic tillage can be regarded as an important management option under conservation agriculture (CA). The effects of tillage practice and cropping sequence on volumetric water (mm mm-1), inorganic N (mg kg-1) and glomalin (mg g-1) content in the 0-300 mm soil layer were studied. Responses after no till (NT), inversion (MP) and non-inversion tillage (DT) treatments on wheat-lupine-wheat-canola (WLWC), wheat-medic (McWMcW and WMcWMc) and lupine-wheat-canola-wheat (LWCW) rotations were studied. Tillage did not influence soil water content (SWC) in WLWC or the wheat-medic sequences. Soil water content in LWCW during year 1 tended to be lower in NT than MP and DT, however not always significantly. During year 2, NT resulted in higher SWC at 20 August as well as 21 September in LWCW. Soil inorganic N was not influenced by tillage practice in the LWCW and WLWC sequences in year 1. During year 2, inorganic N content of NT tended to be lower than MP and DT, although not always significantly. During year 1, DT significantly increased glomalin content. It is concluded that strategic tillage did not negatively influence SWC or mycorrhizal growth and did increase inorganic N content in WLWC and LWCW in year 2 after tillage.