Effects of irrigation and nitrogen fertilization on root growth and root characteristics of wheat on a clay terrace soil of Bangladesh

A field research was conducted at the university farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh, during November 1997 to March 1998 in order to study the effects of irrigation and nitrogen fertilization on the root growth and root characteristics of wheat. The experiment was executed in the split-plot design comprising the combination of the five levels of irrigation arranged as a main plot and the four rates of N application distributed to a sub-plot, The treatments for the study were the same as before. Both irrigation and N application have created a remarkable impact on root length density, root weight density and root-to-shoot ratio of wheat. Root length density and root diameter in the surface layer increased with the increasing level of irrigation or N application. Root growth in the subsurface layers increased when either irrigation or N application was limited while the other was in the optimum level. Root-to-shoot ratio was negatively correlated with the frequency and amount of irrigation and N application. Higher frequency of irrigation has remarkably reduced soil strength in the surface layer, but N application could not create any impact on it.