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

PLANT INDICATORSWeed infestation Assess the degree of weed infestation by visually estimating thenumber of weeds between rows at crop maturity according to thetable opposite. Consider how often a given level of weed infestationoccurs in the paddock from season to season, <strong>and</strong> at what level it isperceived to be a problem.THE QUALITY OF THE SEEDBED <strong>and</strong> the use <strong>and</strong> timing of herbicidesprays influence the level of weed infestation. Soil structural degradationreduces soil aeration <strong>and</strong> the rooting potential of the crop, allowingmore vigorous weeds to establish <strong>and</strong> compete with the crop. A highweed population uses a lot of the soil moisture <strong>and</strong> nutrients otherwiseavailable to the crop. In extreme cases, weeds can shade out the crop.44 VISUAL SOIL ASSESSMENT: Volume 1