Field Guide. cropping and pastoral grazing on flat to rolling country.

SOIL INDICATORSSoil colour under pasture Compare the colour of a h<strong>and</strong>ful of soil from the soil structure testwith soil taken from under the nearest fence line. Using the three photographs below, compare the relative change insoil colour that has occurred.As topsoil colour can vary between soil types, the photographsillustrate the trend rather than the absolute colour of the soil.THE COLOUR OF THE SOIL is a useful indication of soil drainage <strong>and</strong>aeration, soiI wetness from late autumn to early spring, <strong>and</strong> whetherthe soil is being damaged by pugging. Grey subsoil colours in loamy,silty or clayey soils suggest the soil is poorly drained. Grey soil coloursin the topsoil suggest the soil is waterlogged <strong>and</strong> deficient of oxygenfor long periods. Poor aeration leads to a build-up of carbon dioxide<strong>and</strong> methane, <strong>and</strong> reduces the ability of plants to take up water <strong>and</strong>nutrients, particularly nitrogen, phosphorus <strong>and</strong> potassium. Pooraeration also slows the breakdown of organic residues, <strong>and</strong> can inducechemical reactions toxic to plant roots.60 VISUAL SOIL ASSESSMENT: Volume 1