Aggregation, carbohydrate, total and particulate organic carbon changes by cultivation of an arid soil in Central Iran

The objectives of this paper were to determine the response of soil quality indicators and organic carbon (OC) distributions within different aggregate classes to changes in land use from desert soils to cropland occurring in the Abarkooh plain, Central Iran. Composite soil samples of the desert soil, wheat and alfalfa fields were taken from three different depths and soil quality indicators, including aggregate stability (MWD), OC, carbohydrate, particulate organic carbon existent in macro (POCmac) and microaggregates (POCmic) in these soils were determined. Conversion of desert soils to croplands resulted in a significant decrease in electrical conductivity (EC), but an increase in MWD, OC, carbohydrate, POCmac and POCmic contents. OC content increased with increased aggregate size and the aggregate; OC ratio in cultivated and desert soils was highest in the 1-2 and <0.05 mm aggregates, respectively. The improvement soil quality in cropland is due to the long-term use of irrigation water and soil fertilization and also the poor SOM in desert soils. The results of this study further indicate the POCmac, POCmic and POCmac/POCmic ratio are sensitive parameters that reflect differences of soil aggregation, SOM quality and tillage intensity in soils of this region. These parameters are more reliable indicators of soil quality than OC in reclaimed desert soils.