Structure of a Tilled Soil as Influenced by Tillage, Wheat Cropping, and Rainfall

Abstract

AbstractTillage with a tined cultivator (scarifier) and a rotary cultivator was done on Urrbrae fine sandy loam in South Australia. One‐half of the plots were kept bare, while the other one‐half were cropped with wheat (Triticum aestivum L.). Soil macrostructure (voids and aggregates > 0.5 mm) was observed on sections sawed from blocks of the tilled soil which had been impregnated with epoxy resin. Macrostructure was quantified statistically along linear transects on the sections at 0.25, 0.5, and 0.75 of the depth of tillage at the time of tillage and on three subsequent dates when there had been 10, 135, and 395 mm of natural rainfall, respectively. Soil structures are compared and differences between them are presented. Initial differences in soil structure between the tillage treatments had largely disappeared by the second sampling date. Differences in structure due to the presence of the wheat crop were not significant until the final sampling date when the crop was at 0.66 of its final height. Multiple regression equations are presented for the soil macrostructure parameters as functions of cumulative rainfall after tillage and depth in the tilled soil layer.