Effect of soil structure on wheat germination in a red-brown earth

Abstract

Physical properties of soil have been measured on two experimental plots which showed high compaction and poor germination of wheat under very wet conditions. The plot treatments were a two-course and a four-course rotation, and formed part of a permanent rotation trial at the Waite Institute. Similar physical properties were measured for thick crusts formed on these cultivated soils. Under the wet conditions pore space available for air was low in both plots, and within the crust itself was almost zero. Significant differences were found in bulk density and water-stable aggregation between treatments. Waterstable aggregation was very low under both treatments compared with that in virgin soil. All physical measurements point to an oxygen deficiency for a period of 2-3 weeks, and this could account for the poor germination and poor early growth, particularly in the two-course rotation plots. The bad structure conditions leading to this are probably due to pulverizing by implements and dispersion over the years by heavy rain, rather than to decrease in organic matter.