Effect of Vegetation Type and Soil Chemical Properties on the Organic Carbon Content in the Soil of Flood Spreading Fields of Kowsar Station

Enhancing the soil organic carbon (SOC), not only sequesters the atmospheric CO2, but also often improves the processes and soil physical, chemical and biological properties. This investigation with the aim of evaluating vegetation cover and soil chemical properties on SOC was carried out in 2019 in the flood spreading fields of Kowsar station located in Gareh-Bygone Plain (Fasa, Fars Province). Flood spreading for feeding aquifers has been carried out since 1982 in an area of 2034 ha in this plain.

Land uses included Acaci (Acacia salicina Lindl), Eucalyptus (Eucalyptus camaldulensis Dehnh), Atriplex ([Atriplex lentiformis (Torr.) (Wats.)]) Plantation and natural rangeland, all of which are irrigated by flood spreading. By sampling of soils (depth 0-30 cm) in three replications in mentioned land uses, 13 characteristics: pH, ECe, CaCO3, SOC, TN, C/N, P, K, Na, Ca, Mg, Ca+Mg, SAR were measured and determined. After confirming the normality of the data by Kolmogorov-Smirnov test, the obtained data were analyzed in a randomized complete block design (RCBD) and the means were compared with Tukey test at p<0.05.

The analysis of variance showed that the effect of treatment (vegetation cover) on the all studied variables, except SAR was significant at p<0.01 and p<0.05.  Stepwise regression method was used to present the model. The results showed that C/N, TN, and ECe affect the amount of SOC and explain 99.7% of the changes in SOC. According to the standardized coefficients in the regression equation, for each unit increase of C/N ratio, the value of 0.939 units and for each unit of TN, the value of 0.338 units and with the increase of each EC unit, the value of 0.109 units is added to the SOC.

In general, recognizing the factors affecting the organic carbon storage in the soil, can provide appropriate management strategies to increase the organic carbon content and develop carbon storage capacity in the soil, improve soil fertility and mitigate the negative effects of climate change to a great extent.