a. r. hosseinpur

In addition to the distribution of elements in the soil solid phase, element species in the solution are also very important due to their importance of providing elements for root uptake. For a deeper study of the chemical cycle of elements in saline soils treated with biochar, the study of speciation is very useful and provides a method to reduce or transform the toxicity caused by toxic elements in saline soils. Therefore, to investigate the effect of biochar on Cd speciation in two saline calcareous soils, 15 mg kg-1 Cd as cadmium chloride was added to the soil sample (200 g), and the soils were incubated for three weeks at 25±2 °C at 80% field capacity. After the incubation period, salinity levels of 20 and 40 mmol kg-1 as sodium chloride (equal to 3.65 and 7.30 dS m-1) were added to the soils. Then, the 1% (w/w) of the sugarcane bagasse and biochars produced at 400 and 600 °C were added to the soils, and then incubated for three months at 25±2 °C at 80% field capacity. At the end of the incubation period, for the speciation of Cd in the soil solution (in a 1 to 2 ratio), the concentration of dissolved cations and anions in the soil samples was measured. The results showed that the interaction between salinity, biochar, and soil on Cd2+, CdCl+, CdCl20, and Cd(SO4)22- was significant. The application of biochar in sandy soil reduced (p <0.05) the concentration of CdCl+, CdCl20, CdSO40, and CdOH+ species compared to the control soil, while it did not affect clay soil. Also, salinity caused by sodium chloride in sandy soil increased the concentration of CdCl+ and CdCl20 species and decreased CdSO40 and CdOH+ species compared to the control soil (p <0.05). The results showed that biochar in saline sandy soil was more effective than clay soil in reducing Cd toxicity.

Sequestrene 138 Fe (Fe-EDDHA), one of the most common fertilizers, is used as a source of iron (Fe) in soilless cultures, but its high price leads to increased production costs. This experiment was conducted to investigate the effect of nano iron chelate (consisting of Fe, Zn and Mn) in comparison with Fe-EDDHA on the micronutrients concentration, leaf photosynthetic pigments and yield of two lettuce (Lactuca sativa L.) cultivars in soilless culture. A factorial experiment using completely randomized design was carried out with two factors of iron fertilizers and lettuce cultivars (Teresa and California) and three replications at Shahrekord University. Lettuce plants were nourished with 20 and 40 μmol L-1 of Fe in nutrient solution from sources of Fe-EDDHA and nano iron chelate (provided that this fertilizer can supply or is not able to supply Zn and Mn required for the plant). The results indicated no significant difference between the application of 40 μmol L-1 of Fe from either nano iron chelate (provided that this fertilizer can supply Zn and Mn required for the plant) or Fe-EDDHA fertilizers in respect to leaf chlorophyll and carotenoid contents, root and shoot fresh weights, and shoot Fe concentrations of the studied lettuce cultivars. Although the highest shoot fresh weight (436 g plant-1) was obtained in 40 μmol L-1 of Fe as Fe-EDDHA, it was not significantly different with shoot fresh weight (387 g plant-1) gained by application of 40 μmol L-1 of Fe as nano iron chelate. Based on the results, nano iron chelate might be an ideal substitution for the Fe-EDDHA in soilless culture of lettuce, however further research is still required to completely evaluate its potential risks to the environment and food safety.

Ammonium (NH4+) and nitrate (NO3-) ions are the two main forms of nitrogen (N) for plants. But, they influence differently on growth and chemical composition of plants. The effect of N form on plant growth depends on plant species, development stage of plant, pH, and temperature, ratio of NH4+ /NO3- and nitrogen level of nutrient solution. Lettuce is one of the leafy vegetables that has been cultivated in soilless culture in many greenhouses in the world. This plant can respond well to NH4+ nutrition, but the information about optimum NH4+/NO3- ratio in the nutrient solution and respond of lettuce cultivars to partial replacement of NO3- by NH4+ is scarce. Application of nitrification inhibitors such as 3, 4-dimethylpyrazole phosphate (DMPP) with ammonium fertilizers lead to high N-use efficiency as well as reducing denitrification and leaching losses. Nitrification inhibitors are compounds that delay the biological oxidation of ammonium to nitrite by depressing the activity of Nitrosomonas bacteria. This study was conducted to elucidate the effect of nitrogen form (N-NO3− and N-NH4+) and the use of a nitrification inhibitor (DMPP) on chemical composition and yield of lettuce (Lactuca sativa L.) cultivars in research greenhouse of Shahrekord University.

A factorial experiment using completely randomized design was carried out with two factors of NH4+/NO3- ratio (0:100, 15:85 with and without DMPP, 30:70 with and without DMPP) and lettuce cultivars (Teresa and California) with three replications under hydroponic conditions. Lettuce plants were grown in 1.7 L plastic pots (one plant per pot) and the substrate used was mixture of cocopeat + perlite with ratio of 2:1 (v/v). Different nutrient solutions were applied by hand two or three times per week to obtain a leaching fraction of 5 to 20%. After seven weeks plants were harvested, fresh weight of shoots and roots were determined and plants were dried in an oven at 60 °C. Then, dry weight of shoots and roots were measured and plants were ground for nutrient analysis including of P, K, Ca, Mg, Fe, Mn, Zn and Cu.   

The results showed that application of nutrient solution with NH4+/NO3- ratio of 30:70 in California cultivar and 15:85 in Teresa cultivar led to significant increase shoot P concentration compared with the 0:100 of NH4+/NO3- ratio (40 and 13%, respectively). This was due to synergistic effect of NH4+ on the uptake of P by roots. In both Teresa and California cultivars, replacing 30% NO3- in the nutrient solution with NH4+ resulted to significant decrease shoot K concentration (27.3 and 14.8% in Teresa and California cultivars, respectively) as well as shoot Ca concentration (42.0 and 31.1% in Teresa and California cultivars, respectively) compared with the 0:100 of NH4+/NO3- ratio. This decrease is related to antagonistic effects of NH4+ on the uptake of K and Mg by roots. In Teresa cultivar, increasing the NH4+/NO3- ratio to 15:85 led to the meaningful increase of shoot Fe (97%), Mn (68%) and Zn (54%) concentration in comparison with 0:100 of NH4+/NO3- ratio. But, in California cultivar shoot Mn concentration increased (65%) with 30% replacement of NO3- by NH4+. This means that changing NH4+/NO3- ratio in the nutrient solution is an excellent approach to control the relative uptake of cations and anions by the plant. The greatest quantity of shoot fresh weight in Teresa (334 g pot-1) and California (435 g pot-1) cultivars were obtained from 0:100 and 15:85 of NH4+/NO3- ratios, respectively. The current study indicates that the lettuce cultivars respond differently to the form of N supply. There is a genotypic variability in the ability of plants to supply carbon skeletons for NH4+ assimilation in the roots. Thus, California cultivar is a genotype sensitive to enhanced ammonium nutrition and Teresa cultivar is a genotype insensitive to enhanced ammonium nutrition. Increasing the NH4+/NO3- ratio to 30:70 led to the meaningful decrease (42%) of root fresh weight in comparison with nutrient solution without NH4+. Application of nitrification inhibitor DMPP with the NH4+/NO3- ratios of 15:85 and 30:70 had not significant effect on the shoot fresh and dry weight as well as the concentration of P, K and Cu in the shoot of both lettuce cultivars in comparison to these ratios without DMPP.

The results suggest that the NH4+/NO3- ratios of 0:100 and 15:85 can be recommended for production of Teresa and California lettuce cultivars under the conditions of the present study, respectively.

In order to increase the available Phosphorous (P), chemical fertilizers are applied; however, P chemical fertilizers are transformed into low available forms over time. Organic amendments could be effective in improving the efficiency of P fertilizers. The aim of this study was to investigate the effect of P fertilizers and vermicopost on the availability and fractions of P and maize (Zea Mays L.) indices in a calcareous soil. This study was performed in a factorial completely randomized design with three replicates. The experimental factors included chemical fertilizer (0 and 50 mg/kg P) and vermicopost (0 and 1 %W). After 2 months of planting in greenhouse, the shoots of maize were removed and the maize indices (P concentration, dry matter and P uptake) were determined. Then, the soil samples taken from each pot, P available, and P fractions were evaluated by a modified method developed by Hedley et al (1982). The results showed that the effect of the interaction beyween P fertilizer and vermicopost on the available P was significant. Also, the interaction of P fertilizer and vermicopost on the soluble and exchangeable P (P<0.05) and organic P (P<0.01) was significant. By applying the P fertilizer or % 1 vermicompost, all P fractions (except Ca bound P) were increased. The results, therefore, showed that the effect of the interaction between P fertilizer and vermicopost on P concentration, dry matter and P uptake was not significant (P>0.05). Vermicopost application increased the dry matter from 6.9 to 10.5 g pot-1, while application of 50 mg kg-1 P as fertilizer increased the dry matter from 7.7 to 9.7 g pot-1. Also, by adding vermicopost (11.1%), the i P uptake was increased, as compared to 50 mg kg-1. The results, therefore, indicated that the beneficial effect of vermicompost on the dry matter and P uptake in maize was more than that of the chemical fertilizer. Moreover, P fertilizer and manure could influence P fractions and P availability.

Soil salinity in huge parts of the world, especially in arid and semi-arid regions, is a factor limiting growth of plant and other organisms. Earthworm can be considered as an indicator of soil quality in agroecosystems, because of a positive correlation between earthworm abundance and the productivity of cropped plants. The main objective of this study was to realize the interaction between soil salinity and organic amendments on the growth and populations of anecic earthworm (Lumbricus terrestris L.) under controlled greenhouse conditions. The experiment was a 4×4 factorial consisting of three levels of salinity (2, 4 and 8 dSm-1) obtained using NaCl (plus a control) and three organic amendments (alfalfa and corn residues, cow manure and control) arranged in a completely randomized design replicated three times. The experiment lasted 15 weeks. Results showed that increasing soil salinity caused a significant reduction (P ≤ 0.001) in all the earthworm's growth indices. The increase in salinity from 0.49 dS m-1 (control) to 8 dS m-1 reduced the number of earthworms (32%), fresh weight of worms (54%), dry weight of worms (54%), worms length (25%) and the number of cocoon (35%), suggesting the harmful effect of salinity on earthworms growth. The application of organic amendments has, to some extent, alleviated salinity effects on earthworms, and resulted in increases in earthworm growth rates at all salinity levels. Soils amended with alfalfa residues showed the highest alleviating outcomes. In summary, salinity reduced the growth and activity of earthworms L. terrestris and the added organic materials, however, lowered the detrimental effects of salinity on earthworms in the studied soil.

Soil properties play a significant role in phosphorus (P) sorption. Information about P sorption is limited in Hamadan soils. The objectives of this research were to study the P sorption in twelve soils of Hamadan, assess the capability of different kinetics equations describing P sorption and correlate the P sorption characteristics with the soil properties. The soils were fertilized with 200 mg P kg-1 as KH2PO4. Fertilized soil was incubated at 25±1 ˚C for 2520 h. The incubated samples at 1, 2, 4, 8, 24, 48, 72, 96, 120, 144, 168, 240, 336, 504, 672, 840, 1008, 1176, 1344, 1512, 1680, 1848, 2016, 2186, 2352, 2520 hours after P addition were extracted by two extractants. The soil phosphorous was extracted by 0.5 M sodium bicarbonate (Olsen solution) or by AB-DTPA. Zero order, first order, simplified Elovich equation, parabolic diffusion law and power function equations were fitted on the experimental data. The results showed that P sorption was initially rapid followed by a slow phase. The amounts of P sorption after 2520 h, ranged from 162.7 to 253.84 and 193.37 to 235.11 mg kg-1 for the Olsen and AB-DTPA methods, respectively. Regarding to higher determination coefficient and lower standard error, Elovich and power function equations were suitable to describe P sorption kinetics. Rate constants of the Elovich and power function equations ranged from 0.036 to 0.49 and 0.157 to 0.304 mg kg-1h-1 for Olsen and from 0.074 to 0.76 and 0.184 to 0.382 mg kg-1h-1 for AB-DTPA. The trend of the data implied a discontinuity in slope at 336 h, as two region models might better satisfy the trend of the data in to two range ( 0 to 336 and 336 to 2500 hr). At the first section, the P sorption could be describe by simplified Elovich, power function and parabolic diffusion law kinetics equations. Rate constants in these equations varied among the soils. At the second section, kinetics equations could not describe the P sorption. The results of this study indicated that P sorption rates varied among the soils and Fe , Al and CaCo3 affected on P sorption kinetics.

Phosphorus (P) after nitrogen limits agricultural production in most region of the world. Information about P release rate is limited in Hamadan soils. The objective of this research was to study P release in 10 soils from Hamadan province by successive extraction with 0.5 M NaHCO over a period of 1752 h and the correlation of P release characteristics with soil properties and corn plant (Zea mays) indices. The results showed that soil P release began with a fast initial reaction, followed by a slow secondary reaction until 1752 h. The amounts of soil P released after 1752 h ranged from 309 to 586 mg kg-1. The cumulative P release was evaluated by six kinetics equations. Statistical analysis showed that phosphorus release kinetics were described by parabolic diffusion law, first order and power function equations. The correlation study indicated that soil P release coefficients such as rate constant of first order, parabolic diffusion law, power function equations, P released after 168 and 1752 h were significantly correlated with some soil properties such as Olsen-P, calcium carbonate equivalent, sand and silt. The correlation studies between plant indices and constants of kinetics equation showed that rate constant of first order equation was not significantly correlated with plant indices. Equation constants of parabolic diffusion law, power function and P release after 1752 h were significantly correlated with plant indices. The results of this research indicated that release rate of P is different in soils and is an important factor in supplying available P to plants.

Information about nonexchangeable potassium (NEK) release rate in Hamadan soils is limited. The objective of this study included an investigation of the dynamics of NEK in some soils from Hamadan Province by successive extraction with dilute citric acid over a period of 2500 h and determination of the correlation between the rate constants in this kinetic equation with soil properties. The results of this experiment showed that the initial NEK release rate was rapid which slowed down later on. The amount of NEK released after 2500 h ranged from 0.87 to 2.89 cmol kg-1. The amount of NEK released after 2500 h was significantly correlated with CEC, NEK, and soil separates. First order, parabolic diffusion law and power function equations described well the NEK release kinetics based on their highest determination coefficient and their lowest value of the standard error of the estimate. Release rate constant in the first order, parabolic diffusion law and power function equations ranged from 1.0×10-4 to 3.0×10-4, 1.7×10-4 to 10.6×10-4 and 2.75×10-1 to 4.6×10-1, respectively. In the correlation study the rate constants in the kinetic equations were correlated with some chemical properties and particle size distribution. The results of this experiment also showed that dilute citric acid can be used in the study of NEK release.

Garlic (Allium Sativum) is a major crop in Hamadan Province. However, adequete information on K status in this region is not available and no suitable extracting solution can yet be introduced. This experiment was carried out to determine the available K level in 10 soils from Hamadan region. The treatments included two K levels (0 and 200 mg K /kg soil as K2SO4) and 10 Soils in a factorial experiment in a randomized block design with three replications. The results indicated that K application increased yield, K concentration and K uptake of garlic. On the basis of K extracted, the extractants were classified in 4 groups, and the correlation between extractants in each group was significantly high. The correlation studies showed that NH4OAC, AB-DTPA and boiling 1 M HNO3 can not be used as an available K extractant. The correlation of other extractants with relative yield, plant response and additional uptake were significant. Therefore, these extracting solutions can be used as available K extractant. Potassium critical levels by extractants were also determined using Cate-Nelson method. Potassium critical levels for 90 percent relative yield were 131, 50, 46, 184, 163,203, 202, 41, 50 and 31 mg kg-1 for Mehlich 1, 0.002 M SrCl2, 0.01 M CaCl2, 0.1 M BaCl2, SrCl2 + Citric acid, Sodium acetate, 0.1 M HCl, 0.05 M HCl, 0.025 M H2SO4 and distilled water, respectively.

Iron oxide-coated strips (Pi) can serve as a sink to continuously remove P from solution. In this way, probably, P extraction is analogous to P absorption by plant root. The objective of this study was to evaluate the iron oxide-coated paper strips to estimate the availability of soil P of corn (Zea mays) grown under greenhouse conditions in some soils of Hamadan Province. Sixteen soil samples with different physico-chemical properties were examined for available P by Olsen, Colwell, Mehlich1, 0.01 M CaCl2, AB-DTPA, 0.1 M HCl methods and two (Pi1, Pi2) Pi methods. Furthermore, the effects of two P levels ( 0 and 250 mg P Kg-1 soil) on the plant responses (P uptake, P concentration, and relative yield) were studied in the greenhouse experiment using 12 soil samples. The results showed that the amount of extractable P decreased in the order: 0.01 M Cacl2 < Pi2 < AB-DTPA < Pi1 < Olsen