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

PLANT INDICATORSProduction costs Assess whether production costs have increased because of increasedtillage <strong>and</strong> fertiliser requirements over the years (see opposite). Theassessment can be based on your broad perceptions (‘gut feeling’),but reference to annual balance sheets will probably give a moreprecise answer.TILLAGE AND FERTILISER INPUTS account for some of the highestcosts in any <strong>cropping</strong> operation, <strong>and</strong> can increase significantly withincreasing soil degradation. As degradation increases, the density <strong>and</strong>strength of the soil increases <strong>and</strong>, as a result, the soil becomes moreresistant to tillage forces. Plough resistance increases so that largertractors are required to avoid excessive wheel slip <strong>and</strong> the need tooperate at slow ground speeds in a lower gear. The size, density, <strong>and</strong>strength of soil clods also increase with increasing loss of soil structure,<strong>and</strong> careful timing <strong>and</strong> additional energy is needed to break them downto a seedbed. This energy is generally applied by using more intensivemethods of cultivation <strong>and</strong> by making a greater number of passes. As aresult, tillage costs can increase by over 300 percent.Continuous <strong>cropping</strong> using conventional cultivation techniques can giverise to a significant loss of organic matter <strong>and</strong>, as a result, cansubstantially reduce soil fertility <strong>and</strong> the ability of the soil to supplynutrients. Soil organic matter provides <strong>and</strong> stores significant amountsof several plant nutrients. High amounts of fertiliser are needed tocompensate for the loss of these nutrients.Reductions in crop yield are often not recognised as the result of thedegradation of soil structure. Growers often assume that plant nutritionis at fault <strong>and</strong> increase their production costs by applying extra fertiliser.48 VISUAL SOIL ASSESSMENT: Volume 1