Root abundance of maize (Zea mays L.) in conventionally-tilled and zero-tilled soils of Argentina

TABOADA, M. A.; ALVAREZ, C. R.

REVISTA BRASILEIRA DE CIêNCIA DO SOLO

Año: 2007

0100-0683

Maize root growth is negatively affected when soil has shallow (e.g. agricultural traffic) and subsoil (e.g. claypans) compacted layers. Both kinds of soil mechanical impedances often coexist in field maize crops, but their combined effects on root growth were seldom studied. Soil physical properties and maize root abundance were determined in three different soils of the rolling Pampa of Argentina, which were cropped to maize under nearby conventionally-tilled (CT) and zero-tilled (ZT) plots. In the soil with a light Bt horizon (loam Typic Argiudoll, Chivilcoy site), induced plough pans were detected in CT plots at 0.12 m depth through significant increases in bulk density (1.15 to 1.27 Mg m-3) and cone (60º tip angle) penetrometer resistance, PR (7.18 to 9.37 MPa in summer) from CT to ZT plots. This caused maize root abundance to be 40 % - 80 % lower in CT than in ZT plots below the induced pans (“shadow” effect). Two of studied soils had hard structured Bt horizons (clay pans), but only one of them (silty clay loam Abruptic Argiudoll, Villa Lía site) showed expected PR increases (up to 9 MPa) with depth. In the other clay pan soil (silty clay loam Vertic Argiudoll, Pérez Millán site), PR did not increase with depth but reached 14.5 MPa at 0.075-0.2 m depth in both CT and ZT plots. However, maize root abundance was stratified within the first 0.2 m in both Villa Lía and Pérez Millán sites. In them, the hard Bt horizons did not represent an absolute but a relative mechanical impedance to maize roots, as root clumping through desiccation cracks were detected in them.