The effect of surface applied soil amendments on barley root growth in an acid subsoil

Abstract

The root growth of an A1 sensitive barley (H. vulgare L.) was used to evaluate the influence of surface applied amendments on the properties of an acid subsoil. Soil columns were packed with 10 cm of A horizon over 45 cm of an acidic Bt horizon from a Gilpin silt loam. Prior to planting of the barley the columns received surface treatments of dolomitic lime (8.4 Mg .cntdot. ha-1), hog manure (44.8 Mg .cntdot. ha-1) with and without lime, cow manure (44.8 Mg .cntdot. ha-1) with and without lime, gypsum (14.6 Mg .cntdot. ha-1), and EDTA (5.1 Mg .cntdot. ha-1) with lime. The columns were leached twice weekly over a 6 wk period with 5 cm additions of water. Lime alone did not significantly increase subsoil pH or reduce exchangeable A1 at depths below 15 cm. The EDTA plus lime treatment caused significant increases in soil pH and reductions in exchangeable A1 throughout the column. Gypsum treatments also reduced exchangeable A1 but neither gypsum nor EDTA plus lime treatments resulted in improved barley root growth or rooting depth in the acid subsoil when compared to check columns. Maximum root growth and rooting depths were found in the columns receiving manure treatments with and without lime. Soluble organic components from the manures may have complexed part of the A1 and reduced its toxicity. Bulk density values in the manure treated columns were lower than those in the non-manure treated columns at the end of the experiment. This may have contributed to the improved barley root growth in the manure treatments.