مجله تحقیقات آب و خاک ایران
سال چهل و چهارم شماره 3 (پیاپی 14، مهر و آبان 1392)

Today, in drainage projects under construction in Iran and especially in Khuzestan province, the huge part of costs allocated to preparing mineral envelope (gravelly) for subsurface drain pipes. In other hands, by soil characteristics of some areas and in base of technical recommendations, drainage performance without using envelope may also be an option. So, in this research and as one of the first experiments in real scales in Iran, through an experimental field with 20ha area and by wheat planting, subsurface drainage without using envelope (in considering the local soil characteristics), excess than conventional drainage by mineral envelopes, was performed in Shadegan region of Khuzestan province. Each experimental unit contains 5 laterals (subsurface drain pipes) by distance of 50m and drain depth and length of 1.7m and 220m, respectively. For study of water table condition, some piezometers with a depth of 2m were installed perpendicularly to laterals of each unit, around the middle one at distances of 0.5, 2.5, 5, 10 and 25m from drain pipe and manholes prepared for these laterals. Also, in a distance of 30m from the beginning and the end of the middle drain, 2 more piezometers with distance of 0.5 and 2.5m from it were installed. Drainage with mineral envelope performed in 2 units, but drainage without envelope only done in one unit, via to prevention of farmers (but data were collected from 3 middle drains in this unit). Investigation of water table depths indicated that the operation of drains without envelope were acceptable and for mineral ones were proper during an agricultural season. Calculation of Relative Ground Water Depth index (RGWD) showed that subsurface drains without envelope had acceptable operation during this research in Shadegan drainage plan area and with low sedimentation in manhole. Therefore, if proper operation happens in middle time and long time periods, it could be propounded as a practical option in areas same as Shadegan region.

In this study to segregate Iran''s climate precipitation، 130 climate variables were used from 81 synoptic meteorological stations and then 98 combined variables were calculated. Eventually 39 important combined variables were selected for analysis، using backward algorithm. After that by using factor analysis، the selected variables were summarized in six main factors: summer precipitation، spring precipitation and cold month’s rainfall intensity، number of snowy days، longitude، variability index and number of stormy days. These factors explained 82% of total variation in the data. Finally in order to determination of different patterns of precipitation in Iran، Factor scores were grouped by Ward hierarchical clustering algorithm. Using this algorithm six different precipitation climate regions were introduced which are grouped in four small area and two broad ones. Also to increase the homogeneity of broad area، each of the broad regions were divided into two smaller areas، regarding to dendrogram of selected meteorological stations.

Runoff production along with rainfall characteristics and soil properties is affected by the soil type. This study was carried out to investigate runoff variations as affected by the same rainfall events in different soil textures in Zanjan province. After initial tests، ten soil textures were recognized in the area and accordingly soil samples were taken from 0-30 depth. The experiment was done in the randomized complete block design with ten treatments at three replications. The soils were filled within the plots with a dimension of 60 × 80cm and 20 cm-depth on a sloped land (8%). Experimental plots were exposed to 10 simulated rainfalls with 55-mm h-1 intensity and 30-min duration. Soil moisture content was measured at the plots before each event using the weighted method. The initiation time and volume of the generated runoff were measured at the plots in each rainfall event. The results showed that there was significant differences among the soils in the initial soil moisture (P<0. 001)، runoff initiation time (P<0. 001) and runoff depth (P<0. 001). Rainfall events also significantly affected the moisture content (R2=0. 98، P<0. 001)، initiation time (R2=0. 95، P<0. 001) and runoff depth (R2=0. 96، P<0. 001) in the soils. From the first rainfall event to the forth event، the soil moisture content and runoff depth significantly increased and the runoff initiation time considerably declined. After the fifth event، the runoff parameters did not significantly vary probably due to the stop of the aggregates breakdown. Based on the results، both the runoff production and the runoff initiation time were remarkably related to the soil moisture content (R2=0. 96، P<0. 001 and R2=0. 94، P<0. 001، respectively).

Using low quality water on agricultural lands in South of Tehran has increased the risk of soil salinity and created problems for some agricultural crops. This study was carried out to determine of soil salinity distribution and to produce salinity map. The mapping of salinity can also identify the saline and non-saline regions that are very effective for land management and choosing kind of crops that are suitable. The study area is located in 20000 ha of lands in South of Tehran between expressways of Azadegan، Tehran- Qom and Tehran- Saveh. In order the soil salinity mapping، 196 surface soil samples (0-30cm) were taken from a regular grid of 1000×1000m. The electrical conductivity of saturated soil extract (ECe) was measured. Data analysis and soil salinity mapping has been done by GIS and kriging interpolation method. The results showed that ECe varies between 0. 2-14dS/m. Based on the soil salinity map، ECe of 0-2، 2-4، 4-8 and 8-16dS/m have covered 30. 41، 42. 44، 22. 63، and 4. 52 percent of the total area، respectively. The best model was fitted the exponential which has been achieved with a range of 1130 meter. Considering the threshold of salinity for many vegetable crops is less than 4 dS/m، thus increasing salinity to more than 4dS/m is worrying. The results showed that the soils of study area، due to differences in the depth of groundwater، relief، using low quality water in shallow wells، river، sewage water for irrigation، were affected on soil salinity.

Piping sometimes is occurred due to seepage of water in hydraulic structures. The continuty of this phenomenon decreases the safety or caused the failure of a structure. In this work، experimental tests were carried out on statically compacted natural and randomly reinforced silt sandy soil samples. The randomly reinforced samples were prepared with different lengths and percentages of an artificial fiber. The tests were done in special designed and made apparatus. During the tests، seepage velocity، hydraulic gradient، permeability and seepage force were measured and calculated in different samples and compared with natural soil. The results showed that in the case of randomly reinforced soil، the resistance of soil against piping was increased. in addition، the increasing of the length and percentage of fiber also have important role in improvement of soil.

Information about forms of phosphorus (P) is important for the evaluation of P status in soil and also understanding of the soil fertility and plant nutrition. To obtain such information and to determine the relationship between the P forms from soil characteristics، amount of different organic and inorganic P forms of 20 soil composite samples of Eastern Azerbaijan Province، Iran were determined by sequential fractionation method. According to the results، the amount of total P in soils ranged from 534 to 1061 mg kg-1 with an average of 771. 3 mg kg-1. Inorganic P concentrations was as follows: Apatite (Ca10-P) > octacalcium phosphate (Ca8-P) > aluminum phosphate (Al-P) > iron phosphate (Fe-P) > dicalcium phosphate (Ca2-P). Organic phosphorus concentrations was as follows: Moderately labile organic P (MLOP) > labile organic P (LOP) > Non labile organic P (NLOP). Results showed that calcium carbonate equivalent (CCE) with octacalcium phosphate and iron phosphate، pH with octacalcium P، iron phosphate، available phosphorus and organic carbon with moderately labile and non- labile organic P had significant correlations. Total calcium and total organic P had significant relationships with organic carbon. Total calcium phosphate and total inorganic P also showed significant correlations with the calcium carbonate equivalent. Ca2-P، Ca8-P، Fe-P، Al-P، LOP and MLOP had positive and significant relationship with the available-p، and between different forms of phosphorus Ca2-p had highly significant correlation with available phosphorus. Also، significant correlations were obtained between various types of phosphorus، which is presumably a reflection dynamic relationship between them in the soil. Regression analysis showed that calcium carbonate equivalent presumably is an important effective soil characteristic on distribution of P forms in studied soils.

Salicylic acid is an important organic acid in plants rhizosphere soil exuded in the phosphorus (P) deficiency condition. To study the sorption behavior of P in the presence of salicylic acid، a batch experiment was conducted with different concentrations of salicylic acid (0، 2، 5 and 10mM) and P (0- 45 mg P/L) in a calcareous soil. The results showed that application salicylic acid decreased the sorption of phosphate due to competition with organic acid for the sorption sites. The maximum phosphorus sorption (qmax) decreased by increasing salicylic acid concentration from 326 to 246 mg/kg. The application salicylic acid decreased all sorption parameters such as Langmuir binding strength (KL) (from 0. 20 to 0. 14 ml/g)، sorption capacity of Freundlich (Kf) (from 59 to 46 mg/kg)، the slope of Temkin equation (KT) (from 62 to 46) and the intercept of Temkin equation (A) (from 59 to 52 mg/kg). The standard phosphorus requirement (SPR) in equilibrium concentration 0. 3 mg P/L calculated by Langmuir (SPRL)، Freundlich (SPRF) and Temkin (SPRT) equations significantly decreased، for example SPRF decreased from 31. 5 to 24. 7 mg P/kg. Eventually it can be said، application salicylic acid and /or plants genetic improvement for more exudation this acid cause to increase P availability and reduce fertilizer requirement.

Soil reduces the hazardous effects of compounds on the components of ecosystem because of self –purification property and the ability for their fixation. Playing such a role in soils under redox conditions is performed by pedogenic Fe-Mn concentrations. In order to investigate cobalt، copper and lead accumulation in iron and manganese concentrations، at first the concentrations were precisely separated from the adjacent soil and nitric acid extractable iron (Fe­­t)، manganese (Mnt)، Copper (Cut) and lead (Pbt); free iron oxides (Fed) and amorphous iron (Feo) were measured. Mineralogy of Fe-Mn concentrations were determined by x-ray diffraction (XRD) technique، and microscopic investigation and elemental analysis were performed using scanning electron microscopy. Mean of the enrichment coefficients for Fet، Mnt، Cot، Pbt، Cut، Feo and Fed were obtained 1. 2، 12. 41، 7، 4. 47، 2. 13، 2. 16، 1. 33 respectively. Existence of lepidocrosite and goethite were taken as evidence for a combination of alternative oxidation and reduction conditions in concentrations. Mn enrichment coefficient was rather high compared to Fe due to its higher mobility in soil. Distinct difference between Feo amount of soil and concentrations shows the specific conditions dominated in concentrations. High adsorption surface of Fe and Mn oxides with، more amorphous structures، alternative redox condition causing heavy metals trapping، chemical properties of heavy metal such as different valence for cobalt and low pk1 for Pb and Cu were the effective factors in accumulation of these heavy metals in concentrations.

In this research، catalase activity and leaf Chlorophyll stability of Satsuma mandarin on some citrus rootstocks under waterlogging condition were studied. Experiment was conducted as factorial with randomized complete blocks and 6 replications. The first factor، include 7 soils from East Mazandaran and the second factor included 7 different citrus rootstocks: 1. Sour orange، 2. Swingle citromelo، 3. Carizo citrange، 4. Troyer citrange، 5. C35، 6. Smooth flat seville and 7. Gou tou. Seedlings were kept under continuous waterlogging stress condition in the second year of growth. The results showed that catalase activity and stability index of chlorophyll were significantly affected by waterlogging stress. Catalase activity increased under waterlogging stress and its amount in C35 was more than other rootstocks. Interaction of soil and rootstock also had significant effect on catalase activity. Also، rootstocks and different soils had significant differences in changes trend of the stability index of chlorophyll. Average of chlorophyll stability index in total waterlogging period showed that Gou tou، C35 and Swingle citromello had the highest chlorophyll stability; Sour orange had the least amount. Chlorophyll stability index of scion on different rootstocks in different soils indicated the different tolerance of rootstocks in various soils to waterlogging stress.

In this research، catalase activity and leaf Chlorophyll stability of Satsuma mandarin on some citrus rootstocks under waterlogging condition were studied. Experiment was conducted as factorial with randomized complete blocks and 6 replications. The first factor، include 7 soils from East Mazandaran and the second factor included 7 different citrus rootstocks: 1. Sour orange، 2. Swingle citromelo، 3. Carizo citrange، 4. Troyer citrange، 5. C35، 6. Smooth flat seville and 7. Gou tou. Seedlings were kept under continuous waterlogging stress condition in the second year of growth. The results showed that catalase activity and stability index of chlorophyll were significantly affected by waterlogging stress. Catalase activity increased under waterlogging stress and its amount in C35 was more than other rootstocks. Interaction of soil and rootstock also had significant effect on catalase activity. Also، rootstocks and different soils had significant differences in changes trend of the stability index of chlorophyll. Average of chlorophyll stability index in total waterlogging period showed that Gou tou، C35 and Swingle citromello had the highest chlorophyll stability; Sour orange had the least amount. Chlorophyll stability index of scion on different rootstocks in different soils indicated the different tolerance of rootstocks in various soils to waterlogging stress.

Sedimentation in reservoirs reduces dams storage and makes many problems in their operation. Therefore accurate computation of sediment volume is essential for appropriate design and optimum reservoir management during its operation. In this research long term field data of Sefid-rood dam were used to check the sediment volume computed for Ghezelozan basin. The Computed volume of sediment by rating curve and modified FAO method was compared with real volume as the result of hydrographic surveying to evaluate and calibrate computed methods. The results showed that the rating curve method was underestimated (approximately half of real volume)، while modified FAO method estimated sediment volume 10 times more than real volume. The investigations show that the modified coefficient equal to 2 presents logical results. Therefore، it is recommended to use the modified coefficient for field usage in Ghezelozan basin. In other words، the computed sediment volume by rating curve method should be doubled to obtain real volume.