نشریه تحقیقات کاربردی خاک
سال دوم شماره 1 (تابستان 1393)

Micronutrients concentrations in soil solution affect nutrient uptake by plant. In this research, the effects of rice (Oryza sativa cv. Ali-Kazemi) cultivation and application of sewage sludge and chemical fertilizers on the changes in iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) concentrations in the soil solution after submergence were studied at greenhouse conditions. A factorial experiment based on randomized complete blocks design with two replications including duration of submergence at 10 levels (2, 11, 30, 37, 42, 49, 56, 63, 78, 92 days) and source and amount of organic and chemical fertilizers in six levels (control, 100% chemical fertilizers, 20g sewage sludge per kg of soil with and without 50% chemical fertilizers, 40g sewage sludge per kg of soil with and without 50% chemical fertilizers), with and without rice cultivation was carried out. The results showed that after submergence, Zn concentration of the soil solution decreased significantly in both of the cultivated and uncultivated treatments while Fe concentrations of the soil solution in all uncultivated treatments (except 100% chemical fertilizers) initially increased and then decreased significantly. After submergence, Mn concentrations of soil solution in all uncultivated treatments initially increased and then decreased. Application of sewage sludge and chemical fertilizers increased Fe, Mn and Zn concentrations of the soil solution in the cultivated and uncultivated treatments. In all treatments, Cu concentration in the soil solution was negligible. At the end of growth period, Fe and Mn concentrations of the soil solution in the cultivated treatments (rhizosphere) were significantly greater than the uncultivated treatments (non-rhizosphere), while Zn concentration of the soil solution showed no significant differences between cultivated and uncultivated treatments. In general, the rice plant cultivation (rhizosphere processes) and application of sewage sludge and chemical fertilizers can alter the micronutrients concentrations in the soil solution.

Soil surface conditions such as roughness, structure, vegetation and rock fragment cover have very important effects on infiltration, run-off and soil erosion. Rock fragments at the soil surface directly affects soil erosion processes, particularly in arid and semiarid environments where vegetation cover is poor. The objective of the present research was to study the influence of rock fragment cover on the rate of soil loss and the hydraulic properties of flow such as roughness coefficient and shear stress in a loess soil sample from Golestan province. The investigation was conducted using a flume with 6 m length, 0.5 m width, and 3% gradient. The treatments included rock fragment covers (0, 10, 20 and 30%), and flow discharges of 0.5, 1.0 and 1.5 (10-4 m3 s-1). With increasing of rock fragment cover from 0 to 30% in flow discharges of 0.5, 1.0 and 1.5 (10-4 m3 s-1), relative velocity of water flow decreased 68.9, 67.7 and 70.9%, respectively. The value of relative roughness coefficient and shear stress increased linearly (R2=0.99) with increasing of rock fragment covers. In addition, with increasing of rock fragment cover from 0 to 30%, the rate of relative soil loss in flow discharges of 0.5, 1.0 and 1.5 (10-4 m3 s-1) decreased 85.0, 83.7 and 73.6%, respectively. Decreasing soil loss rate was related to Rock fragment cover by an exponential function (R2=0.98).

Soil water retention curve (SWRC) is one of the main soil characteristics with many applications. Its direct measurement is costly and time-consuming. Therefore, it is often predicted through indirect methods such as pedotransfer functions (PTFs). Many models have been developed for quantitative description of SWRC and also a lot of PTFs has been developed for their estimation. However, predictability of soil water content through different SWRC models by using different input variables and artificial neural networks have not been investigated, so far. In this study, 75 soil samples were taken from Guilan province and basic soil properties have been measured. Water contents were measured at 12 matric potentials (0, 1, 2, 5, 10, 25, 50, 100, 200, 500, 1000 and 1500 kPa). Ten well known and frequently applied SWRC models were fitted to the measured data. The Perrier model was fitted on the particles and aggregates size distributions and fractal parameters were obtained. The fractal parameters of particles and aggregates size distributions along with clay, sand and bulk density were used to estimate water content in two input levels by different SWRC models. Results showed that the models of Seki, Fermi and Gardner were predicted more accurately, in comparison with other models. In spite of the expectation, the models of Dexter and Durner were not predicted accurately and according to the cluster analysis were classified in different groups. It was observed that the prediction capabilities of different models were changed and their arrangements were altered in the tables by changing input variables. Overall, Fermi and Dexter models had the highest and the least predictability with the first input levels, respectively. Gardner and Tani models had the highest and the least predictability with the second input levels, respectively.

There are concerns regarding arsenic (As) contamination of soil and water resources and its potential risk to human health and environment safety. Wheat and marigold as one of the most important agricultural crops and ornamental plant, respectively, are used in phytoremediation of contaminated soils. For evaluating the effects of As and phosphorus (P) on concentration and uptake of calcium (Ca), magnesium (Mg) and potassium (K) in wheat and Marigold, a two factorial experiment was conducted consisting of two factors including three levels of As (0, 50 and 100 mg kg-1) and P (0, 20 and 40 mg kg-1). The experiments were carried out in a randomized complete block design with three replications in greenhouse conditions. Results indicated that content of Ca, Mg, and K in shoot and root of wheat and marigold decreased with increasing As levels. With increasing P levels, content of Ca in root of marigold, the content of Mg and K in shoot and root of wheat and marigold was increased. Also, interaction between As×P on most measured attributes of the plants was significant and P application partly offset the negative effect of As.

Microbial inoculation improves plants growth and increases their tolerance to environmental stresses and induces phytoremediation of heavy metals contaminated soils. In order to evaluate the role of some strains of AMF (a mixture of Glomus speciesincluding G. intraradices, G. mosseae and G. fasciculatum) and PGPR (a mixture of Pseudomonas speciesincludeing P. putida, P. fluorescens, and P. aeruginosa) in reclamation of cadmium (Cd) contaminated soils by Onopordon (Onopordon acanthium L) a factorial experiment based on a randomized complete block design and in three replications was carried out in greenhouse condition. The first factor was Cd concentration in four levels including 0, 10, 30 and 100 mg kg-1 and the second factor was microbial treatment in three levels including non-inoculation, and AMF or PGPR inoculation. A soil sample was spiked uniformly with Cd nitrate salt to create different Cd concentrations. The contaminated soils were then sterilized and subsequently inoculated with AMF and PGPR. Results showed that with increasing soil Cd concentration, colonization percent, and abundance of rhizobacteria, shoot biomass and shoot relative biomass significantlydecreased, while proline content and the shoot Cd concentration significantly increased (P ≤ 0.05). Mean Cd extracted in AMF and PGPR treatments were respectively 3.1 and 2.6 order of magnitude higher compared to the corresponding blank treatments. Therefore, it could be concluded that inoculation with species of AMF and PGPR can be a promising technique for enhancing the potential of onopordon plant in extraction of Cd from contaminated soils.

Colonization of roots with arbuscular mycorrhizal fungi (AMF) often improves micronutrients uptake by most of the plants. Measurement of pH in mycorrhizae leachates is an evidence for acidification or alkalinization of rhizosphere and hyphosphere. Leachate pH is very important factor for assessment of micronutrient uptake by AMF. This experiment was laid out in factorial complete randomized block design with three replications. The first factor consists of arbuscular mycorrhizal fungi with Glomus etunicatum and Glomus intraradices species and control, the second factor was Rorison’s nutrient solution with zero, half and full strength of micronutrients, and the third factor was time of measurement of leachates pH that was include 45, 65 and 85 days after sowing. Tomato (Lycopersicon esculentum Miller) and sorghum (Sorghum bicolor L.) plants were grown in sterile perlite and were inoculated with either Glomus etunicatum or G. intraradices, while the control set was left un-inoculated. Rorison's nutrient solution with three levels of 0, half and full strength of micronutrients was applied to the pots during vegetative growth period. The pH of leachates Measured at 45, 65 and 85 days after sowing (DAS). Results show that, colonization of sorghum roots by G. etunicatum and G. intraradices fungi were 43 and 37%, respectively. On the contrary of sorghum plants, the mycorrhizal symbiosis was not observed in tomato plants. The pH of leachates was lower in mycorrhizal than non-mycorrhizal plants. G. intraradices were efficient than G. etunicatum in this respect. The reduction in leachate pH was induced at 0 levels of the micronutrients. 65 DAS, leachates had minimum amount of pH. In all of treatments, pH of leachates were higher than 7.6. It seems that, the main agent of this phenomenon is nitrate nutrition of plants, because nitrate is the most source of N in Rorison’s nutrient solution.

This study was carried out to obtain soil organic matter (SOM) influence on phosphorous (P) sorption in the 12 calcareous soil samples. SOM was removed with sodium hypochlorite (NaOCl) solution (pH=8).Soils were brought into equilibrium with varying solution concentrations of P, and the amounts removed from solution were used to check the fit to three adsorption isotherms, namely, Freundlich, two- surface Langmuir and Dubinin- Radushkevich. Results showed that the amount of P sorption after SOM removal was increased and fits of adsorption equations showed that single-surface Langmuir equation did not describe P sorption in the soils, but a two-surface Langmuir, Freundlich and Dubinin-Radushkevich equations showed statistically significant (P

Due to the indiscriminate use of nitrogen fertilizers, pollution caused by the use of fertilizers and high production costs, the present study examined the effects of plant growth promoting biofertilizers and nitrogen fertilizer on increasing the quality and quantity of wheat. The experiment was conducted in two-factor factorial design in three replications; (T0: as control treatment without biofertilizer T1: biofertilizer containing Azotobacter chroococcum and Azospirillum brasilense with population density of 106 cfu ml-1 of inoculum, T2: bio-fertilizer containing Azotobacter chroococcum and Azospirillum brasilense with population density of 108 cfu ml-1 of inoculum, T3: the bio-fertilizer containing Azotobacter chroococcum, Azospirillum brasilense, Pseudomonas putida and Baillus subtilis with population density of 108 cfu ml-1 of inoculum) and nitrogen fertilizer (N0: Control, N1:25, N2:50, N3:75, N4:100 kg N ha-1) in a completely randomized design. The results showed that the main effect of bio-fertilizer was related to treatment T3 which resulted respectively in 13, 20.4, 8, 19.7 and 8%increase in the 1000-grain weight, plant height, grain nitrogen content, grain yield and grain protein content in comparison to the control. In the case of main effect of chemical fertilizer levels on the mentioned parameters, the treatments 75 and 100 kg N ha-1 were the best treatments and they didnt show a significant difference (P>0.05). Regarding interactions of the treatment T3 with N3 had the highest amount and resulted respectively in 50, 51, 57.3, 81.3 and 50.5% increase in the 1000-grain weight, plant height, grain nitrogen content, grain yield and grain protein content.

Unmanaged use of natural resources such as soil would lead to deterioration of its quality and fertility. Consequently, spatial monitoring of these properties is necessary to find the optimal management options to protect soil fertility. Thus, in this study, the long-term effects of treated wastewater irrigation on qualitative properties of surface soil layer were spatially monitored using geostatistical methods and were compared with worldwide standards. Consequently, the soil qualitative properties including sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), electrical conductivity (EC) and acidity (pH) was analyzed in pixels with 150×105 meter dimension and the possibility of extracting raster maps using weighting moving average (WAM), kriging and co-kriging methods was investigated. Results showed that kriging and WMA had the least estimation error for ESP and the other parameters, respectively, based on the evaluating indices. Also using covariates does not have positive effect on increasing range of influence and interpolation accuracy. Comparing the prepared raster maps by the selected method with the standard values of Soil Survey Manual of USA showed that unmanaged use of unconventional water caused more than 97% of the study area to have saline soils. Also, hazard of sodium in the soils dominated to salinity problem in more than 94% of the study area. These could have irreparable damages under water crisis through degrading soil structure. In conclusion, for sustainable agriculture and food security in the study area it is necessary to offer management options for soil improvement such as leaching in uncultivated seasons or combined irrigation with fresh water to protect economic and environmental issues