چكيده لاتين :
Introduction:Soil quality as an important part from soil resource sustainability, consistently isinfluenced by
human activities.Today, the presence of accurate information about variability of soil quality properties is
considered more than ever to apply this information in economic modeling, environmental predictions, accurate
farming and natural resources management. Soil quality is defined as: “capacity of the soil to function, within the
ecosystem and land-use boundaries, to sustain biological productivity, maintain environmental quality, and
promote plant and animal health”; therefore, it is one of the most important factors in developing sustainable
land management and sustaining the global biosphere. The definition of soil quality encompasses physical,
chemical and biological characteristics, and it is related to fertility and soil health. Many indicators can be used
to describe soil quality, but it is important to take into account sensitivity, required time, and related properties,
than can be explained. Properties related to organic matter content, such as microbial respiration, microbial
biomass carbon (MBC) and enzymatic activity (urease and phosphatases) can be used as soil quality indicators.
They provide early information about mineralization processes, nutrient availability and fertility, as well as
effects resulting from changes in land use or agricultural practices (e.g. tillage or application of different types of
organic matter). In this context, biological properties have been used as soil quality indicators, because of their
relationship with organic matter content, terrestrial arthropofauna, lichen, microbial community (biomass or
functional groups), metabolic products as ergosterol or glomalin and soil activities as microbial respiration and
enzyme production. This study was carried out for evaluation the spatial variability of biological soil quality
indicators in wheat farms of Pasargad plain.
Materials and Methods: After reviewing the initial map of Pasargad, a total of 60 samples were provided
using a systematic grid square sampling pattern with 500×500 m over the 1200 ha area of Pasargad at surface
soil depth (0-30 cm). The characteristics of soil including organic carbon, pH, EC, microbial respiration,
microbial biomass carbon , soil alkaline phosphatase and urease enzymes activity, ratio of microbial biomass
carbon to organic carbon (MBC/OC) andmicrobial metabolic quotient(qCO2) were measured and calculated.
Results were analysed with SPSS, Excel, GS+, and ArcGIS sotwares. Summary statistics were calculated for the
60 samples including mean, maximum and minimum, coefficient of variation (CV), kurtosis and skewness. In
addition, Pearson correlation coefficients were calculated for untransformed data. For evaluation of different
interpolation methods of soil characteristics in Pasargad plain root mean square error (RMSE), mean bias error
(MBE) and mean absolute error (MAE) were used. We also constructed maps of the spatial distributions for each
individual variable using best interpolators including kriging, inverse distance weighting (IDW) and cokriging
methods.
Results and Discussion; The results showed that in the most cases the studied properties had too much
variation. Based on the coefficient of variation, pHand qCO2had the lowest and highest variations, respectively.
There was significant linear correlation between most of soil properties. From lognormal transformation was
used for normalization of EC and qCO2. Best model for single semivariogram of organic carbon, microbial
respiration, urease enzyme activity, microbial biomass carbon, qCO2 and MBC/OC in the soil was spherical
model, for pH in the soilwas exponential model and for EC and phosphatase enzyme activity was gaussian
model. Also, the best interpolator for pH, EC, organic carbon, microbial biomass carbon, urease activity,
qCO2and MBC/OC was kriging, for alkaline phosphatase activity was inverse distance weight, and for microbial
respiration was cokriging method. Amount of pH increased from north to south of Pasargad plain, but amounts
of EC and organic carbon were inverse of pH.The higher amounts of microbial respiration and urease activity
were observed at the south and east, respectively. The amount of phosphatase activity in the soil of Pasargad
plain was scattered, and wide area in the plain had the activity between 215-275 μg PNP/g.hr. The higher
amount of MBC and MBC/OCand lower amount of qCO2were observed at the west.
Conclusions: The biological soil properties were sensitive and rapid indicators of effects of soil
management. Generally, according to the spatial variabilitymap, the areas in the region are critical situations in
terms of biological indicators of soil. So the management techniques that are applied by farmers in these areas
have to be changed. The results of this study used in the improvement of regional planning for sustainable
management of soil.
