Editing Soil structure (section)

==Hardsetting soil==
Hardsetting soils lose their structure when wet and then set hard as they dry out to form a structureless mass that is very difficult to cultivate. They can only be tilled when their moisture content is within a limited range. When they are tilled the result is often a very cloddy surface (poor [[tilth]]). As they dry out the high soil strength often restricts seedling and root growth. Infiltration rates are low and runoff of rain and irrigation limits the productivity of many hardsetting soils.<ref name="Daniells2012">{{cite journal|last1=Daniells |first1=Ian G. |title=Hardsetting soils: a review |journal=Soil Research |date=2012 |volume=50 |issue=5 |pages=349–359 |doi=10.1071/SR11102}}</ref>

===Definition===

Hardsetting has been defined this way: "A hardsetting soil is one that sets to an almost homogeneous mass on drying. It may have occasional cracks, typically at a spacing of >0.1 m. Air dry hardset soil is hard and brittle, and it is not possible to push a forefinger into the profile face. Typically, it has a tensile strength of 90 kN<sup>–2</sup>. Soils that crust are not necessarily hardsetting since a hardsetting horizon is thicker than a crust. (In cultivated soils the thickness of the hardsetting horizon is frequently equal to or greater than that of the cultivated layer.) Hardsetting soil is not permanently cemented and is soft when wet. The clods in a hardsetting horizon that has been cultivated will partially or totally disintegrate upon wetting. If the soil has been sufficiently wetted, it will revert to its hardset state on drying. This can happen after flood irrigation or a single intense rainfall event."<ref name="Mullins1997">{{cite book |last1=Mullins |first1=CE |editor1=R Lal |editor2=WH Blum |editor3=C Valentin |editor4=BA Stewart |title=Methods for assessment of soil degradation |date=1997 |publisher=CRC Press |location=Boca Raton, FL |isbn=978-0-8493-7443-2 |chapter=Hardsetting |page=121 |url=https://books.google.com/books?id=4gv5HEOrX8YC |access-date=18 August 2016}}</ref>