نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال چهاردهم شماره 2 (پیاپی 52، تابستان 1389)

Deficit irrigation is one of the irrigation management methods that is used to increase Water Use Efficiency. Considering the internal plant adaptability characteristic to water shortage, Partial Root Drying method has been introduced in recent years. In this field research improvement of Water Use Efficiency for Soybean was determined. This experiment which was conducted at four furrow irrigation treatments at the Research Field of Tehran University in Karaj in 2008, consists of full irrigation (100% soil moisture deficit compensation), conventional deficit irrigation at 50 and 75 percent soil moisture deficit compensation and Partial Root Drying at 50 percent soil moisture deficit compensation with three replications. The amounts of irrigation used were exactly compensation level (negligible loss). Results indicated that Water Use Efficiency according to Duncan's Multiple Range Test at the five percent level of probability there was a significant difference between partial root drying treatment (PRD50%) and conventional deficit irrigation treatment at fifty percent soil moisture deficit compensation (DI50%),. Water Use Efficiency in PRD50% compared with DI50%, DI75% and full irrigation increased by 48.3%, 61.9% and 70.1% respectively.

Using treated wastewater led to increasing crop yield, but it may causes heavy metals accumulations and also their toxicity in soil and plant. In order to investigate the effects of wastewater on yield, forage yield components, and heavy metals concentrations in stem and leaf of sorghum, an experiment was conducted in the agricultural Research Institute of Zabol University in 2006-2007, using a randomized complete block design with four replication. The irrigation treatments were: 1) well water for whole growing season as control (T1), 2) well water for all growing season along with NPK application (T2), 3) wastewater during the first half of growing season (T3), 4) wastewater during the second half of growing season (T4), 5) wastewater and tapwater alternately (T5) and 6) wastewater for whole growing season (T6). The results showed that irrigations with wastewater and well water alternately and wastewater for whole growing season produced the maximum forage yield and the maximum heavy metal accumulation in plant organs observed by irrigation with wastewater for hole growing season, and wastewater and well water alternately. There was significant increase between T5 and T6 relative to control and other treatments. The elements concentration such as Cu, Pb and Fe in leaf was more than stem, but Zn and Ni concentration in stem were more than leaves. There were no significant differences for Mo and Cr concentration between stem and leaf. Forage yield in T6 and T5 relative to T2 were increased 38.96 and 51.95 percent respectively. In all irrigation treatments the amount of elements and heavy metals in sorghum were lower than standard limits. Based on the results, alternative irrigation method (T5) is recommended for forage sorghum production.

An extensive data collection on precipitation and runoff is required for development and implementation of soil and water projects. The unit hydrograph (UH) is an appropriate base for deriving flood hydrographs and therefore provides comprehensive information for planners and managers. However, UH derivation is not easy job for whole watersheds. The development of UH by using easily accessible rainfall data is then necessary. Besides that, the validity evaluation of different statistical modeling methods in hydrology and UH development has been rarely taken into account. Towards the attempt, the present study was planned to compare the efficiency of different modeling procedures in hydrograph and 2-h representative UH relationship in Kasilian watershed with concentration time of some 10h. The study took place by using 23 storm events occurred during four seasons within 33 years and applying two and multivariable regression models and 36 variables. According to the results, the median of estimated errors in estimation of 2-h UH dependent variables for verification stage varied from 37 to 88%. The results verified the better performance of cubic and linear bivariate models and logarithm-transformed data in multivariable model as well. The efficiency of multivariable models decreased when they were subjected to principle component analysis. The performance of backward method was frequently proved for estimation of dependent variables based on evaluation criteria, whereas the forward was found to be more efficient for time-dependent factors estimation.

Erosion plots are basically used for studying erosion processes and many related problems. However, the possibility to extend the results of experimental plots to surrounding watersheds is rarely taken into account. In the present study, an attempt was made to study on the accuracy of soil erosion plots in estimation of runoff and sediment yield from small watersheds. Towards this attempt, 12 experimental plots with length of 2, 5, 10, 15, 20 and 25 meter were installed on two north and south facing slopes in Sanganeh watershed, northeastern Razavi Khorasan Province with an area of ca. 1 ha. The performance of the plots in estimation of runoff and sediment was controlled by data collected at the main outlet associated with 12 storm events occurred during November 2006 to June 2007. The results showed that the accuracy of plot estimates on sediment and runoff improved while the plot length increased. The optimal length for estimation of sediment and runoff parameters was found to be equal to average slope length and more than 20m.

Drought is among the most costly weather-related events and Iran is highly vulnerable to the economic, social and environmental impacts of drought In this study expected profit maximization model and utility efficient programming were applied to determine optimal crop pattern, expected gross margin and water use with and without, drought condition at representative farms of homogenous groups. This study was based on two databases. A sample of 180 farmers was selected for interview and collected necessary farm level data in 2007. The sample farms were drawn using two-stage stratified random sampling method. Results indicated that the largest reduction in expected profit is directed toward farmers who use surface water from river or canal. These groups of farms ultimately suffered a severe reduction in expected income (53%-64%) as a consequence of the drought, largely because their access to water was cut substantially. The least quantity of damage is directed toward homogenous groups of farms that use groundwater or conjunctive use of groundwater and surface water. Reduction in expected income of these groups is equal to 7 and 32 percent of expected income in the normal year, respectively. Finally, the results showed that the pattern of release water from gate of Drodzan have not been optimal in the planting years 2001-2002 and 2006-2007 based on the calculated shadow price of each cubic meter water in different deciles of year.

Potassium (K) fixation by phyllosilicates clay minerals is a very important process influencing the availability of K for plants. Information about K fixation is limited in Hamadan soils. The objectives of this research were to determine potassium fixation capacity (PFC) and potassium fixation index (PFI) of 10 surface soils of Hamadan province and the correlation of these parameters with soil charge characteristics. Potassium fixation capacity was obtained using six different levels of added K as KCl and three wetting and drying cycles. Also charge characteristics of soils were determined. Tetrahedral CEC of soils was determined after saturation of samples with LiCl and heating at 300 oC to reduce octahedral charge near zero. The results showed that tetrahedral and octahedral CEC ranged from 4.6 to 16.0 and 0.8 to 4.9 cmolckg-1 respectively. Mineral and organic portion CEC ranged from 6.1 to 20.9 and 0.97 to 9.7 cmolckg-1 respectively. The amount of PFC increased with increasing added K. Mean amount of PFC ranged from 58.2 to 175.03 mgkg-1. Potassium fixation index ranged from 0.23 to 0.67. The results of correlation studies indicated that PFI were significantly correlated with octahedral CEC, mineral and organic portion CEC, total CEC, exchangeable and nonexchangeable K. The results of this research showed that PFI very different in soils. So that this parameter should be consider in K soil testing.

Phytoremediation is a new, in-situ and emerging remediation technology for contaminated soils. This technology, compared to other methods, is a sustainable, natural, relatively cheap and applicable to large scale area. Modeling phytoremediation provides quantitative insight for the governing process as well as for managers to assess the remediated sites. The objective of this study was to introduce a macroscopic phytoremediation model for Ni and Cd- polluted soils. The proposed model assumes that relative transpiration reduction function can resemble total soilNi and Cd concentrations. Combining the related functions of soil and plant responses to soil Ni and Cd concentrations, the phytoremediation rate of Ni and Cd was predicted. In order to test the proposed model, large quantities of soil were thoroughly polluted with Ni and Cd. Upland Cress (Lepidum sativum) and Ornamental Kale (Brassica olerace var. Viridis) seeds were then germinated in the contaminated soils. The experimental pots were irrigated with fresh water to reach field capacity. Upland Cress and Ornamental Kale were harvested three and four times, respectively. At each harvest, relative transpiration, Ni and Cd contents of soil samples and plants were measured. Comparison of the maximum error, root mean square error, coefficient of determination, modeling efficiency and coefficient of residual mass indicated that the non-threshold non-linear model provide high efficiency to predict relative transpiration for Upland Cress and Ornamental Kale, respectively. The results also indicated that the proposed macroscopic model can well predict the phytoemediation rate of the Ni and Cd by Upland Cress (R2>0.83) and Ni by Ornamental Kale (R2=0.78).

Most part of the applied phosphorus is fixed in the calcareous soil. Some part of residual phosphorus can be recovered by the plants of the following years. It is reported that organic matter is one of most important factors in phsphorus recovering. This expriment was designed in permanent plot to evaluate the effect of organic matter on residual phosphorus recovering in a calcareous soil. The expriment was conducted on randomized complete block design in a factorial manner with three replications in four years. Treatments were consisted of farm yard manure(FYM) in three levels (0, 15, and 30 ton ha-1) and three levels of phosphrus (0, 90 and 180 kg ha-1 as P2O5 from triple super phosphate (TSP). Phosphorus fertilizer was applied only in the first year of expriment, but FYM was used in all of the years. Onion, canola, bean and spinage were planted in the four years of experiment, respectively. Results showed that maximum yield, P concentratin in plant and soil phosphorus availability were followed by application of FYM and P(residual) together in all of the years. This increase was mainly by direct effect of P in the first year of expriment, but recovered phosphrus by FYM had maximum role in the later years. More than 53% of increase in phosphrus availability in soil and 21% of increase in yield resulted from recovered phosphprus by FYM in the treatment of 30 ton.ha-1 FYM and 180 kg.ha-1 P2O5 together in the last year.

Among the biodiversity of soil microorganisms, bacteria have the basic role in soil functions. In order to determine the diversity and abundance of soil bacteria in arid regions, and also to study the effect of agricultural practices on them, a study was conducted in winter wheat fields on Shirvan, Mashhad and Gonabad. In each region, high and low input fields of winter wheat and a natural system for comparison were selected. Use of agricultural inputs was criteria for selection of low and high input fields in each region. Soil sampling was done on fields and natural systems and organic matter content, abundance and diversity of soil bacteria were measured in soil samples. Species richness and abundance of soil bacteria was affected by region and so that natural system of Gonabad has the minimum of species richness among the studied systems and the differences of other systems was not significant. Abundance of soil bacteria in 1 g dry soil was maximum in Gonabad and minimum in Shirvan. Abundance of soil bacteria was affected by organic matter and in low and high input systems of Gonabad and low input system of Mashhad was greater than other systems. Overall, 19 species of bacteria that belonged to 4 genus were detected. Results showed that species richness and abundance of soil bacteria in studied systems were relatively low and agricultural practices have not significant impact on these organisms, so that species richness and abundance of soil bacteria were improved in agricultural systems of Mashhad and Gonabad. Pattern of bacterial diversity showed that regional and agricultural stresses were affected on bacterial function so that in high level of stresses, species richness decreased and function of soil bacteria was restricted to decomposition of organic matter. Therefore, organic matter of soil must be increased and agricultural stresses must be decreased to improve of soil bacterial functions.

Sewage sludge application on farmland as fertilizer is commonly practiced in many countries. However, high concentration of heavy metals like mercury (Hg) in sludge can cause pollution of soil, plant and the human food chain. In order to examine the risk of Hg transfer into plants a five year field experiment was conducted in which we investigated uptake of Hg from a sludge-amended soil by corn. Sludge application rates were 0, 25, 50 and 100 Mg ha-1. To study cumulative and residual effects of the sewage sludge, applications were repeated on 4/5 of each plot in second year, on 3/5 of plots in third year, on 2/5 of plots in fourth year and in 1/5 of plots in fifth year. After the fifth year, soil samples from the 0-20 and 20-40 cm depths were taken and analyzed for total Hg. Corn plants were harvested and roots, stems and grains were separately analyzed for Hg concentrations. Sludge application significantly increased total Hg concentration in soil. Total Hg concentration in soil ranged from 20 µg kg-1 (in control plots) to 1200 µg kg-1 (in plots with 500 Mg ha-1 sludge application). Sludge application significantly increased uptake of Hg in different plant parts. At the end of the fifth year the average Hg concentrations in root, stem, and grain were 91, 9, and 8 µg kg-1, respectively. Corn yield increased significantly with sludge application and this fertilizer effect was visible five years after a single sludge application.

Soil temperature is one of the important variables in hydrology, agriculture, meteorology and climatology studies. Owing to the fact that soil temperature is only measured at synoptic stations, reconstruction of this variable in other places is of great importance for many relevant agricultural surveys. Using 10-year (1996-2005) daily meteorological observations, including: air temperature, global solar radiation, precipitation, relative humidity, vapor pressure, wind speed and air pressure data, different empirical relationships are suggested. At statistically significant level (P<0.05), the suggested regressions are reliable for estimating soil temperature in various depths (5, 10, 20, 30, 50 and 100 cm) and different climate types. Using soil temperature as the dependent variable and the other meteorological parameters as the independent variables, the multivariable relationships are classified accordingly. The results indicate that the impact of meteorological parameters on soil temperature is not the same. At statistically significant level (P<0.05), the mean daily air temperature presented the highest correlation coefficients with soil temperature for all climate types (on average, from R2>0.91 for warm semi-arid, to R2>0.85 for humid climates). Other results highlighted that the correlation coefficients decreased as the soil depth increased. The behavior of statistical validation criteria of the suggested relations are also discussed for all the mentioned climates.

An increase in the emission of greenhouse gases such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from the soil surface to the atmosphere has been of worldwide concern over the last several decades. Carbon dioxide is recognized as a significant contributor to global warming and climatic change, accounting for 60% of total greenhouse effect. The aim of this research was to determinate the emission of greenhouse gases from different land under agricultural uses. Four types of agricultural land farm, including wheat field, canola field, citrus garden and fallow land were selected to investigate the fate of CO2 in these fields. Gas chromatography technique and close chamber method were used to analyze soil gas samples. Total carbon losses from soil in form of greenhouse gases was 4.47, 3.72, 3.38 and 1.89 Mg C ha-1 yr-1 for wheat field, canola field, citrus garden and fallow land, respectively. Total additional carbon to soil from biomass for wheat field and canola field was 4.1 and 4.6 Mg C ha-1 yr-1, respectively. ECB (ecosystem carbon budget) = ∑ C input - ∑ C output. For wheat field and canola field ECB was -0.37 and +0.88, respectively. This indicated that in wheat field carbon was lost and in canola field carbon was sequestrated. Under citrus garden due to changes in soil organic carbon form previous year has showed that carbon was sequestrated.

This study was carried out to evaluate the application of zinc and copper sulfate by different methods such as foliar application and deep-placement and time of application on the some quantitative and qualitative properties of pistachio trees. For this purpose, a complete randomized block design experiment with 12 fertilizer treatments and 3 replications at 2 consecutive years was conducted in the experimental garden of Rafsanjan. Treatments included deep-placement of medium amounts (54.2 and 11.1 kg/ha of elemental Zn and of Cu respectively) and high amounts (81.3 and 16.7 kg/ha of Zn and of Cu respectively), foliar application of 0.15 kg/ha elemental Cu in the form of Cu sulfate and 1.8 kg/ha of the elemental Zn in the form of Zn sulfate (34%) at the rate of 1000 liter water on Esfand (late dormant), Farvardin (after flowering) and Mehr (post harvest). Results indicated that in first year, the maximum yield was obtained with foliar application of Cu on Esfand. Also, qualitative properties such as Split/non split ratio significantly increased by above treatment. The protein content increased with foliar application of Cu on Esfand and Zn on Farvardin by 22 and 16.5%, respectively compared to the control. The analysis of leaf samples, demonstrated that the foliar spray of Cu+Zn on Esfand increased Zn leaf by 119% as compared with control. In second year, yield increased by the foliar application of Zn on Esfand. Also, qualitative properties such as the number of seeds per ounce significantly increased by foliar application of Cu on Mehr. The highest and the lowest rate of split/non-split ratios were observed in treatments of high and low localized placement. The protein content decreased in the treatment of high deep placement as compared to the control. Foliar spray of Zn on Esfand caused the highest increase of leaf Zn concentration and foliar spray of Cu and Zn+Cu in Mehr increased significantly Cu leaf. The results indicated that the effects of treatments on oil content and stem nutrients concentration were not significant on two years. Due to saline and lime effects in the soil in pistachio orchards, soil application of micronutrients had no significant on the the yield.