Changes in properties of sodic Australian vertisols with application of organic waste products

Abstract

In Australia, the surface and subsurface soils of the majority of cotton ('Gossypium hirsutum' L.)-growing regions are sodic. Application of organic amendments can be an option to stabilize the structure of sodic Vertisols due to their potential positive effect on soil physical properties. An incubation experiment was conducted for 4 wk in a temperature-controlled (30°C) growth chamber to study the effect of organic amendments on the properties of two Vertisols with different sodicity levels. The exchangeable Na percentages (ESPs) in these Vertisol soils collected from the Australian Cotton Research Institute (ACRI) near Narrabri, New South Wales, and a commercial cotton farm near Dalby, Queensland, were modified such that three different sodicity levels resulted, i.e., nonsodic (ESP<6), moderately sodic (ESP 6-15), and strongly sodic (ESP>15). The organic amendments used were cotton gin trash (60 Mg ha⁻¹), cattle manure (60 Mg ha⁻¹), and composted chicken manure (18 Mg ha⁻¹), as well as an unamended control. The organic amendments improved the physical properties of both Vertisols by decreasing clay dispersion. In the Dalby soil, cotton gin trash produced the largest decrease (29%) in the dispersion index over the control at the moderate sodicity level, whereas in the strongly sodic soil, the lowest dispersion index resulted from the application of chicken manure. Nutrient availability (N, P, and K) was also increased significantly at higher sodicity levels for both the ACRI and Dalby soils by using organic amendments. These results indicate that using organic amendments can be beneficial for the amelioration of sodic vertisols and also to sustain soil quality.