Further studies on the effect of soil treatments on shoot and root growth

The effect of several soil treatments on shoot and root parameters was compared in paired glasshouse and field experiments. Nitrogen was applied at four doses to field plots; these soils were sampled and used in a glasshouse experiment. The effect of soil fumigation was also compared in both the glasshouse and field. Nitrogen increased shoot and root growth, root length, primary root number and primary root diameter in the glasshouse experiment. Over the 12-month cropping period in the field, nitrogen increased shoot weight but not root length density, nor the proportion of root length down the profile. Soil fumigation (methyl bromide) increased root length density but not the proportion of the root system down the profile.