Effect of organic amendments on soil quality and profitability in cotton farming systems

Abstract

Soil quality is the capacity of a soil to maintain both environmental and economic sustainability. Soil organic matter is considered to be of central importance as it plays a vital role in influencing soil's different physical, chemical and biological properties. One management technique whereby soil organic matter content in agricultural soils can be increased is the addition of organic waste materials with a view to partially, or fully, replacing inorganic fertilizers and to enhance soil structure. Information on the effects of addition of organic waste products on the quality of heavy clay soils, such as the cracking clays (Vertosols) used for irrigated cotton production systems in Australia is sparse. The primary objectives of this study were to identify the ability of easily available organic amendments to improve the quality of these soils, to examine the economic viability of such amendments and to determine their optimal rates of application. A secondary objective was to examine the effects of some potential organic amendments on Vertosols with varying sodicity levels. The experimental approach taken in this project used a combination of both field and pot experimental studies. Chemical, physical and biological aspects of soil quality were monitored following additions of different organic amendments to cotton production systems in two locations in eastern Australia. To extend the findings of field trials, several pot experiments examined the effects of a wider range of application rates and types of organic amendments on soil quality and sodicity but under the controlled conditions of a constant temperature growth chamber. Results obtained from these field and pot experiments provided information for an examination of the economic feasibility of using organic amendments that had proved to be environmentally effective in improving soil quality and sodicity.