نشریه مدیریت خاک و تولید پایدار
پیاپی 1 (بهار و تابستان 1390)

Soil salinity and sodicity are serious challenges related to soil management and sustainable production in arid and semi-arid regions. This study investigates different methods of calcareous saline-sodic soil amelioration which emphasized on time variability of leachate quality. The experiment was factorial based on CRD using 6 soil treatments consist of control, cattle manure, pistachio residue, gypsum, and their combination; 2 leaching treatments (with and without sulfuric acid) and 3 replicates, which was conducted in laboratory conditions using soil column. Four intermittent leaching steps with one month interval and one pore volume were applied. The results showed that in the calcareous soil, application of gypsum led to -3 to -35 percent reductions in sodium leaching, while in presence of sulfuric acid, this gypsum efficiency raised to 10-34 percent. Because of higher decomposition rate of cattle manure than pistachio residue, more sodium removed out of soil column. Among four studied cations, potassium showed the lowest variations of change (CP) with time. In this regard, pistachio residue released higher potassium amounts into soil solution. Moreover, the efficiency of amendments in removing calcium out of soil profile was reduced for the subsequent leaching steps. This finding was attributed to some reduction in organic matter decomposition and resultant organic acids, which caused an increase of pH. Time variations of CP for potassium were similar to that of the calcium. Without application of sulfuric acid, the highest CP values of EC and SAR were observed for cattle manure+gypsum and cattle manure treatments with amounts of 305 and 163 percent, respectively. The findings of this research reveal that gypsum alone can not be applied for ameliorating calcareous saline-sodic soils.

This study was conducted to investigate the effects of slope gradient and land use changes on soil organic pools in particle-size fractions under natural forest in hilly regions in western Iran. Three common land uses in the selected site including natural forest (NF), disturbed forest (DF) and cultivated land (CL) and three slope gradients (0-10%, S1, 10-30%, S2, and 30-50%, S3) were selected as a basis for soil sampling. A total of 108 soil samples were taken from the 0-10 cm surface layer in the whole studied region. Some physical and chemical properties as well as particulate organic matter (POM), particulate total nitrogen (PTN) and organic carbon (OC) and total nitrogen (TN) associated with different primary particle size fractions were measured. The results showed that the POM in the forest land use was considerably higher than the deforested and cultivated lands in all slope gradients. POM was mainly concentrated in the sand-size fraction. The values of PTN were significantly higher in the forest land use and in the down lower slopes than in the deforested and cultivated counterparts and steep slopes except for the CL land use. The C:N ratios in POM fraction were around 17-18 in the forest land and around 23 in the cultivated land. In forest land, the silt-associated OC had highest values among the primary particles. The enrichment factor of SOC, EC, was the highest for POM. For the primary particles, EC of both silt and clay primary fractions for selected land uses and slope gradients tend to be in the following orders: CL>DF>NF and S3>S2>S1. Slope gradient significantly affected the OC and TN contents associated with the silt and clay particles, whereas higher OC and TN contents were observed in lower positions and the lowest value was measured in the steep slopes. Overall, the results showed that native forest land improves soil organic carbon storage and can reduce the carbon emission and soil erosion especially in the mountain regions with high rainfall in western Iran.

In order to investigate the influence of vermicompost (VC) on the concentration of nickel (Ni) and chromium (Cr) in soil and rice this research was conducted as a split plot based on randomized complete block design with three replications in 2008. Main factor (fertilizer) was added to soil in 6 levels, 20 and 40 ton ha-1 VC, 20 and 40 ton ha-1 VC enriched with 50% chemical fertilizer (CF), CF (based on soil testing comprise 100 kg. ha-1 urea, 150 kg. ha-1 triple super phosphate and 100 kg. ha-1 potassium sulphate) and control. Sub plot, were considered application periods that comprise 1, 2 and 3 years application. Results showed that the maximum available Ni (2.20 mg kg-1) belonged to 3 years application of 40 ton enriched VC. In 3 continuous years application of enriched 20 and 40 ton ha-1 measured the highest available Cr (0.109 mg kg-1). The highest concentration of Ni in root belong to 3 continuous years application of 40 ton VC +50% chemical fertilizer that was about 63% more than control treatment. With application of 40 ton VC per hectare during 2 and 3 years, measured the maximum Ni concentration in grain with about 2 times of control treatment. Also, the most content of Cr in root (8.43 mg kg-1) and grain (4.25 mg kg-1) belonged to 3 years application of enriched 40 and 20 ton ha-1, respectively.

In this study, the possibility of contamination of some aromatic compounds with high toxicity in surrounding area around antibiotic's factory of Iran was evaluated. pH, organic matter, organic carbon, soil texture and non-volatile organic compounds of 26 samples were tested and the type of pollution was determined. Groundwater sampling, including three consecutive steps includes Pumping of groundwater from nine wells around the factory and analyzing with gas chromatography, the second stage of pumping from 14 wells and analyzing by Gc-Mass, and the third stage of sampling was done by serving Niskin instrument by possibility of drawing of contamination's profile of wells. Suspended solids and volatiles due to water turbidity was measured in wells and the results indicated absence of non-volatile contaminants in the soil. Factory solvent's and soil sample's charts did not fit. Therefore, the possibility of main solvent's factory in soil samples tested was rejected. Some peaks in the graphs Gas Chromatography, showed good overlap with the heavier compounds such as pesticides, fertilizers and agricultural chemicals. Underground water pollution results in all three stage of sampling of water wells, did not show any pollutants except methane peaks. Increasing suspended solids and volatile suspended in all wells, indicated favorable conditions for decomposition of organic matter by microorganisms and biological degradation in this region. Thus, despite the emission of contamination, due to the high level of underground water, distribution and transport phenomena of convection with the water flow to the sea (the slope of the ground layer), evaporation and biological degradation, concentration of pollutants reached to negligible levels over five years (the time interval between the pipe fracture till test time).

In watershed management and conservation programs, hill slope form (slope length and gradient) is the most important indicator of erosion intensity. In the Universal Soil Loss Equation (USLE), combined effects of slope length and gradient has been introduced as the topography factor (LS). Computation of this factor is difficult and ambiguous one among other factor of the USLE. Considering the importance of the LS factor, in the present study some of the equations for LS computation including representative hill slope and raster based hill slope methods has first been explained. Then LS factor was computed using four equations, six conditions of these methods in the Kamal Saleh dam watershed in the Markazi Province. Then performance of values using precision index has been evaluated. The results showed that precision index value in representative hill slope method for USDA diagram is 0.883 and for Mishra equation is 0.860. These results were under-estimation for two equations. In raster hill slope method with resolutions of 30, 50 and 100 meters; precision index values were 1.031, 1.326 and 1.837 respectively. These results showed over-estimation for theses three conditions. According to the results, LS factor value of Moore and Wilson equation with resolutions of 30 m showed the highest precision. Therefore this model can be introduced as optimal model in Kamal Saleh watershed.

The aim of this study was to investigate the effect of different crop rotations on soil micromorphological properties in southern Gorgan River plain. Therefore three cultivated lands including cotton-wheat, canola-wheat and rice-wheat were selected adjacent to each other with same management and typical profiles were dug in each of rotations. Sampling were carried out in the first harvesting season and undisturbed samples from all of the horizons were collected for the preparation of thin sections. Each of the rotations had been practiced at least for 15 years. The soil micromorphological observations indicated that the cotton-wheat rotation was in first place with regard to the soil quality because of maintaining considerable organic matter, presence of higher terrestrial animals and excrement that has created voids of channel and large vugh type with favorite crumb microstructure. Moreover typic and large nodules of calcite and cytomorphic calcite were also observed. In the rice-wheat rotation, the channels were lower and voids were mainly of fine vughs and planar type. The microstructure was weakly separated subangular blocky and massive because of being flooded and also loosening of soil structure. While in the canola-wheat rotation, microstructure was of subangular blocky with moderately separated to well separated type and had an intermediate place between two other rotations with regard to soil quality.