نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال چهاردهم شماره 1 (پیاپی 51، بهار 1389)

Environment pollution is an important problem in the world. In agriculture; irrigation, drainage and fertilization activities cause water resource and environmental pollution by effecting on solute, nutrient and sediment transport. Combined methods of water and nutrient management could consider in pollution transport controlling that reducing runoff and deep percolation, providing opportunity for solute infiltration, reducing sediment transport even economic and easy usage. In this research, affect of two different management in irrigation (cutback and continues) and fertilization (solid and fertigation) on nutrient loss was evaluated. Comparing nitrate, phosphor and potassium loss in different management explicate cutback flow with no uniform solid distribution of fertilizer is more useful to prevent nutrient loss. Because of similar results, increasing in fertilizer distribution in furrow length and easy usage between nitrate losses in six managements, show cutback flow with three proceeding solid, fertigation and fertigation (with 1/4, 1/2 and 1/4 ratio) fertilization was recommended replacement of cutback flow with three proceeding solid fertilization.

Side weirs as flow diversion devices are usually used as emergency weirs in large hydraulic structures like dams and irrigation and drainage networks, because of their importance they require delicate design. As a result application of numerical and simulation models play an important role in design of these hydraulic structures. In this research, the flow pattern and shear stress distribution on broad crested side weirs with different widths and entrances; along with different discharges were studied by numerical solution under two and three dimensional conditions and then the results were compared with laboratory findings. These experiments were conducted in a rectangular channel with one side weir and a length of 70 cm. Experiments were done considering rounded and sharp entrances with different rounded radii and one constant discharge with intake proportions of 40 and 60 in main and branch channels, respectively. Comparison of numerical solution and experimental results show that side weirs with rounded entrance had a noticeable shear stress reduction (arrived in the bed and sides) and non-effective spinal flow, resulting in increased intake efficiency.

Estimating spatial distribution of precipitation is vital to execute water resources plans, drought, land-use plans; environment, watershed management, and agricultural master plans. High variation in amount of precipitation in various parts, lack of measurement stations, and the complexity of relationship between precipitation and parameters affecting it have doubled the importance of developing efficient methods in estimating spatial distribution of precipitation. Artificial neural network has been proved to be efficient as a new way for modeling and predicting the processes for which no solution and explicit relationship has been available in accurately identifying and describing them. The purpose of this study is to investigate the efficiency of artificial neural network in estimating spatial monthly precipitation. To achieve this objective, neural network with multilayer perceptorn topology was employed for preparing model for spatial monthly precipitation in five synoptic and rain-gauge stations located in Kurdistan province. In order to design the topology of the model in each station, as the adjustable parameters (including transfer function, learning rule, amount of momentum, number of hidden layers, number of neurons of the hidden layers, and the number of epochs) changed, different neural networks were made and carried out. In each case, the topology with the minimum amount of root mean square error (RMSE) was selected as the optimal model. Owing to the fact that the selection of each of the variable parameters of neural network necessitated recurring trails and errors, and consequently teaching a large number of networks with various topologies, genetic algorithm method was utilized for finding the optimization of these parameters; the efficiency of this method, too, was examined in terms of the optimization of neural network. The findings indicated that neural network enjoys a high degree of accuracy in modeling and estimating spatial distribution of monthly precipitation. In addition, combining it with genetic algorithm method was positively evaluated in optimizing the requirements for executing neural network. In most cases, mixed method proved its superiority over executing neural network without optimization. The most precise model in all of the stations under study was achieved by the use of transfer function, sigmoid, learning rule of Levenberg Marquardt; in the selected models, the determination coefficient (R2) observed between the model output amounts and the data observed in station were found to be 0.86; 0.89; 0.94; 0.77; and 0.94.

The application of N fertilizers with surface irrigation stream (surface N fertigation(is a key approach for fertilizer management. The main objective of this study was to investigate furrow fertigation management effects on distribution uniformity and runoff losses of nitrate in field scale. A field corn experiment was carried out with a complete randomized block design having 12 experiments. The field experiments were carried out in free draining furrows having 165 m length and 0.006 m/m slope in Karaj. Required urea fertilizer was applied in four stages: before planting, in seven leaves stage, shooting stage and earring stage. The first stage was accomplished by traditional method and other stages were applied with irrigation water (fertigation). Fertigation timing was respectively 60, 35, and 20 min in the three fertigation stages. Results showed that distribution uniformity of water and fertilizer of low half (DULH) provided high values for all experiments. DULH ranged between 88.0 to 99.0% and 89.7 to 96.0%, respectively for water and fertilizer. Also, distribution uniformity of low quarter (DULQ) ranged between 86.0 to 98.2% and 85.7 to 91.5%, respectively for water and fertilizer. Nitrate losses through surface runoff ranged between 5.7 to 42.0%. Duncan test results for comparison between different experiments showed that there was significant difference (p=0.95) between fertilizer losses at the level of fertilizer injection time of 60 and 35 minutes, but there was no significant difference between levels of 35 and 20 minutes.

The contamination of soils with lead is a major environmental problem throughout the world. Phytoextraction of heavy metals from contaminated soils has the prospect of being a more economic in situ alternative. Chemically enhanced phytoextraction has been proposed as an effective approach to remove heavy metals from contaminated soil through the use of high biomass plants. Using a pot experiment, the effects of the application of three rates of EDTA at 0, 1.5 and 3 mmol/kg soil and sulfuric acid at 0, 0.5 and 1 mmol/kg soil with two rates of Pb at 0 and 200 mmol.kg-1 on the uptake of Pb by corn (Zea mays L. single cross 704 var.), sunflower (Helianthus annuus L. ajili var.), and cotton (Gossypium hirsutum L. varamin var.) plants were studied. The results showed that EDTA was more effective than sulfuric acid in increasing the concentration of Pb in shoots and roots for all plants studied. The maximum amount with application of EDTA to soil for shoots of corn, sunflower, and cotton were 4.07, 6.49 and 31.33 times higher than the control, respectively. EDTA also enhanced Pb content of roots of corn, sunflower, and cotton 3.38, 1.63 and 1.09 times higher than the control, respectively. DTPA-Pb was higher in soil treated with EDTA than sulfuric acid. The application of EDTA also significantly increased shoot-to-root ratio of Pb in plants examined. The results of this study showed that corn was able to phytoextract more Pb than sunflower and cotton.

Geologic and pedologic controls are the main factors determining the behavior of elements in natural soil environments. In order to assess the role of these factors on content and distribution of selected major and trace elements in soil, six parent materials including: phyllite, tonalite, periditite, dolerite, shale and limestone were selected in Fuman-Masule region. Soil genesis and development of representive residual pedons were studied for each parent material and the total content of Si, Al, Ca, Mg, Fe, Ti, Mn, Ni, Co, Cr, Cu, Pb, V and Zn were compared among them. Enrichment/depletion patters of trace elements were assessed using Ti as reference element. Generally, Cr, Ni, Co and V are highest in soils derived from peridotite (984, 285, 53 and 204 mg/kg, respectively) and dolerite (1023, 176, 39 and 185 mg/kg, respectively). In the same way, Si and Al exhibit the features of parent materials in the sense that the lowest content was observed in soils developed on peridotite, dolerite and limestone. Zinc and Pb are highest in soils derived from shale (106 and 27 mg/kg, respectively). In a given pedon, different elements exhibited different enrichment/depletion patterns; moreover, a given element may behave differently not only in soils with different parent materials but also, in some cases, in soils developed on similar lithology. Lead, Zn, Cu and Mn have been generally enriched in most pedons, except in some acidic and strongly leached soils, whereas Co, Cr, Fe, Ni and V have been leached, especially from Dystrudepts and Eutrudepts. The latter elements, however, showed enrichment trend in Hapludalfs and Argiudolls parallel to the development of illuvial B horizons.

Similar to plants, soil salinity may reduce microbial growth and activities in different ways. The aim of this study was to determine the effects of different levels of salinity on some microbial indices in the presence and absence of plant's living roots. In this study, five levels of salinity using NaCl, CaCl2, MgCl2 and KCl; and three soil media (soil with no plant, soil cultivated with wheat and clover) replicated three times consisted our factorial experiment arranged in a completely randomized design. Results show that salinity caused a significant reduction in accumulated microbial respiration, microbial biomass carbon, substrate-induced respiration, and carbon availability index in uncultivated soil and in the soils planted with clover and wheat. Results also show that salinity caused a significant increase in metabolic quotient (qCO2) in uncultivated soil, and soils planted with clover and wheat. Microbial activity of cultivated soils at high salinity levels was almost similar to that of the uncultivated soils. We observed a small difference in soil microbial activity among the three media at high salinity levels, indicating the role of indirect effects of salinity might be less important with increasing salinity levels. We also found out that at low salinity levels, the available carbon was not a limiting factor for soil microflora, while at high salinity levels the activity of soil microbes might be carbon-limited. The lower values of qCO2 in cultivated soils compared with the uncultivated soil support the positive influence of root and its exudates on soil microbial activity in saline soils. The existence of plants in saline environments may help in alleviating the detrimental influence of low to medium salinity on most soil microbial activities, likely via the added root exudates and root turnover.

Gray mold, caused by Botrytis cinerea, is a serious disease of cut rose flowers (Rosa hybrida L.) in Iran. In order to elucidate the effects of different potassium and calcium levels in nutrient solution on susceptibility of cut rose flowers to gray mold, this experiment was carried out as factorial design in a randomized complete block with four replications at Safi Abad Agricultural Research center in 2008 for one year. In this experiment, rose plants were grown and subjected to three levels of potassium (1.0, 5.0 and 10.0 mM) in combination with two levels of calcium (1.6 and 4.8 mM) under hydroponic condition. Rose flowers from two consecutive harvesting periods were sprayed with the conidial suspension (104 spore/ml) of B. cinerea isolate. At the end of experiment the disease severity was recorded and analyzed. The results indicated that application of 10.0 mM K in the nutrient solution led to increasing rose disease severity to gray mold (30.4 % day-1) compared to 1.0 mM (24.8 % day-1) and 5.0 mM (26.2 % day-1) of K levels (P< 0.01). The increased susceptibility was associated with a decreased concentration of Ca in the rose petals. Correlation analysis revealed that susceptibility of rose flowers to gray mold significantly increased with K to sum cations ratio in the nutrient solution (r = 0.94*). The increase of Ca supply from 1.6 to 4.8 mM resulted in decline of disease severity from 29.6 to 24.6 % day-1 (P< 0.01). Therefore, balanced application of potassium and calcium (5.0 and 4.8 mM, respectively) is recommendable for preventing antagonistic effects between them and reducing of rose gray mold intensity under hydroponic conditions.

Determination of carbohydrates in soil requires prior extraction and numerous extraction methods were suggested for this purpose. Three methods and five extractants were applied in order to extract carbohydrate fraction in three soil types; forest, clayey and saline soils. The extraction methods were: 1) shaken in a plane rotary shaking machine for 16 h 2) heated in steam-bath for 2.5 h and 3) heated in oven for 24 h and extractants included 1) 0.5 M HCL, (2) 0.25 M H2SO4, 3) 0.5 M H2SO4, 4) 0.5 M K2SO4 and 5) distilled water. Carbohydrate content in soil was measured by phenol-sulphuric acid method. The addition of phenol to the extracted solution of HCl caused to milky precipitation. Therefore, this extractant can not be used for carbohydrate extraction in the phenol-sulphuric acid spectroscopic method. The results showed that in all soils and in the shaker extraction method, carbohydrate content was lower than in the oven and steam-bath extraction methods. In the forest and saline soils, the extracted carbohydrate content was not significantly different among the oven and steam-bath methods. For the clayey soil, the carbohydrate content was higher in the oven method than that of the steam-bath method. In all soils, the extracted carbohydrate by 0.5 M H2SO4 extractant was greater than those of other extractants. In the forest and saline soils, the extracted carbohydrate by distilled water was lower than those of other extractants. Using steam-bath method (for the forest and saline soils) and oven method (for the clayey soil) with 0.5 M H2SO4 extracted the highest amount of carbohydrates.

Tillage systems and organic manures could affect soil physical and mechanical properties. This study was conducted to investigate the impacts of two tillage systems including conventional tillage by moldboard plowing (plowing depth, 30 cm) and reduced tillage by disk plow (plowing depth, 15 cm) and three rates (0, 30 and 60 ton ha-1) of farmyard manure (FYM) on the soil penetration resistance under corn cropping in a split block design with 3 replications. The cone index (CI) decreased with increase of the tillage depth. It is attributable to soil disturbing and loosening of the deeper layers under conventional tillage compared to reduced tillage. This trend, however, was observed only in the first (after treatments’ application and before cropping) and second (the highest rate of vegetative growth) samplings. In the third sampling (after harvest), there were not significant differences between the CI values under two tillage systems in different soil depths. It might be due to soil re-compaction (approaching the pre-tillage state) as well as disappearance of the tillage effects seven month after commencement of the experiment. In fact, the soil mechanical resistance increased with the time indicating soil re-compaction over the growing season. Adding FYM to the surface layer (i.e. 0-10 cm) of ridge soil resulted in significant decrease of soil mechanical resistance compared to control treatment. The CI decreased significantly in the 30 ton ha-1 treatment up to the stage of highest rate of vegetative grow, but the effect on CI was diminished after harvest. However, the decreasing effects of the 60 ton ha-1 treatment on the CI continued to the harvesting time. There were no significant effects of FYM in the soil deeper than 10 cm from the ridge surface and in all of the layers in furrow. The CI did not decrease significantly in the furrow due to negligible effect of manure application for the inter-row position.

Drought is a natural feature of the climate condition, and its recurrence is inevitable. The main purpose of this research is to evaluate the effects of climatic factors on prediction of drought in different areas of Yazd based on artificial neural networks technique. In most of the meteorological stations located in Yazd area, precipitation is the only measured factor while generally in synoptic meteorological stations in addition to precipitation some other variables including maximum and mean temperature, relative humidity, wind speed, dominant wind direction and the amount of evaporation are also available. In this research it was tried to evaluate the role of the type and number of meteorological factor (as inputs of ANN model) on accuracy of ANN based drought prediction. Research area is a part of Yazd province containing only one synoptic and 13 non-synoptic meteorological stations. Three-year moving average of monthly precipitation was the main input of the models in all stations. The type of ANN used in this study was time lag recurrent network (TLRN), a dynamic architecture which was selected by evaluation of different types of ANN in this research. What was predicted is the three-year moving average of monthly precipitation of the next year, which is the main factor to evaluate drought condition one year before it occurs. For the Yazd synoptic meteorological station, several combinations of input variables was evaluated and tested to find the most relevant type of input variables for prediction of drought. However, for other 13 stations precipitation data was the only variable to use in ANN models for this purpose. Results in all stations were satisfactory, even where only one input (precipitation) was used to the models, although the level prediction accuracy was different from station to station. Result taken from this research, indicates high flexibility of ANN to cope with poor data condition where it is difficult to get acceptable results by most of the methods.

Gray mold, caused by Botrytis cinerea, is a serious disease of cut rose flowers (Rosa hybrida L.) in Iran. In order to elucidate the effects of different potassium and calcium levels in nutrient solution on susceptibility of cut rose flowers to gray mold, this experiment was carried out as factorial design in a randomized complete block with four replications at Safi Abad Agricultural Research center in 2008 for one year. In this experiment, rose plants were grown and subjected to three levels of potassium (1.0, 5.0 and 10.0 mM) in combination with two levels of calcium (1.6 and 4.8 mM) under hydroponic condition. Rose flowers from two consecutive harvesting periods were sprayed with the conidial suspension (104 spore/ml) of B. cinerea isolate. At the end of experiment the disease severity was recorded and analyzed. The results indicated that application of 10.0 mM K in the nutrient solution led to increasing rose disease severity to gray mold (30.4 % day-1) compared to 1.0 mM (24.8 % day-1) and 5.0 mM (26.2 % day-1) of K levels (P< 0.01). The increased susceptibility was associated with a decreased concentration of Ca in the rose petals. Correlation analysis revealed that susceptibility of rose flowers to gray mold significantly increased with K to sum cations ratio in the nutrient solution (r = 0.94*). The increase of Ca supply from 1.6 to 4.8 mM resulted in decline of disease severity from 29.6 to 24.6 % day-1 (P< 0.01). Therefore, balanced application of potassium and calcium (5.0 and 4.8 mM, respectively) is recommendable for preventing antagonistic effects between them and reducing of rose gray mold intensity under hydroponic conditions.