Soil science
Mansour Mirzaei Varouei; Sh. Oustan; A. Reyhanitabar; N. Najafi
Abstract
Introduction
Savory is considered one of the most important medicinal plants, which is used in various food and medical industries. Nitrogen (N) plays a major role on the growth and yield of medicinal plants. Therefore, an adequate supply of N is required for successful production of savory. However, ...
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Introduction
Savory is considered one of the most important medicinal plants, which is used in various food and medical industries. Nitrogen (N) plays a major role on the growth and yield of medicinal plants. Therefore, an adequate supply of N is required for successful production of savory. However, the application of chemical N fertilizers is associated with many obstacles such as groundwater pollution, N enrichment of surface waters, and drop in the quality of plants. Accordingly, nowadays, great attention has been paid to organic fertilizers. In this regard, humic acid-based fertilizers have shown promising results. Humic acids (HAs) could be converted into nitrohumic acids (NHAs) through the nitration process, in which nitro groups (NO2) are located on the aromatic rings. This process increases the N content of the HA. Thus, NHAs can be used as organic N fertilizers in the cultivation of medicinal plants whose organic production is a priority. However, the effects of these types of fertilizers on plant growth and physiological characteristics have not been well understood. Accordingly, the present study for the first time investigates the effectiveness of NHA on the morphological and physiological characteristics of savory, as well as N loss through leaching.
Materials and Methods
In the current study, HA was initially extracted from leonardite (purchased from Yazd Golsang Kavir Company) as a rich source of HA. Then, NHA was prepared through the nitration process using nitric acid (50% by volume). After that, using FT-IR (Fourier transform infrared spectroscopy) and CHNS analysis the extracted HA and NHA were characterized, and their N content was determined. Afterward a greenhouse experiment in a completely randomized design (CRD) with three replications was conducted to determine the effects of 16 treatments, including control (without urea, HA and NHA), urea (U1, U2 and U3), humic acid (HA1, HA2 and HA3), nitrohumic acid (NHA1, NHA2 and NHA3), urea-humic acid (U1HA1, U2HA2 and U3HA3), and urea-nitrohumic acid (U1NHA1, U2NHA2 and U3NHA3) on the morphological and physiological characteristics of savory plant. The treatment levels were determined as 40, 80, and 120 mg N kg-1 for the first, second and third level of the treatments, respectively. In the combined treatments of urea and HA or NHA, an equal fraction of the total nitrogen (N) was applied. At the end of the experiment, standard methods were used to assess various characteristics, including root length, leaf area, plant height, root volume, wet and dry weights of shoot and root, leaf chlorophyll index, concentrations of phosphorus, potassium, nitrogen, nitrate, and nitrate reductase in both the shoot and root. Additionally, leaching was conducted on specific days during the experiment, and the leachate was collected for nitrate measurement.
Results and Discussion
The results showed that using the nitration process, some characteristics of the NHA such as total acidity, the content of carboxylic and phenolic groups as well as N content improved as compared to the initial HA. Moreover, the results indicated that most of the morphological and physiological traits of savory plants, including leaf area, plant height, root length, fresh and dry weights of root and shoot as well as chlorophyll index, and the concentration of nitrogen, phosphorous, potassium, nitrate and nitrate reductase enzyme were significantly higher in the NHA treatments than those of HA. In addition, the highest shoot dry weight was obtained in the combined treatments of U3NHA3 and U3HA3 as well as in the U3 treatment alone. The average rate of nitrate concentration increase in the U treatments was 1.77 times higher than the UNHA treatments. According to the results, U3 treatment indicated the highest nitrate loss which by using the U3NHA3 treatment, the mean concentration of nitrate in the leachate decreased by about 40.5% as compared to the U3 treatment.
Conclusion
The findings of this research revealed that most of the morphological and physiological traits of savory plant showed better responses to the combined treatments of U3NHA3 and U3HA3 as well as to the U3 treatment alone. However, with regard to the lower accumulation of nitrate in the shoot of savory as well as to the lower nitrate leaching, the combined treatments were preferred. Accordingly, NHA can be a alternative nitrogen source in increasing the yield and growth indicators of savory. However, the reasons behind the fact of the better performance of combined nitrogen treatments than the individual ones require more research in the future.
M. Mahdizadeh; A. Reyhanitabar; Sh. Oustan
Abstract
Introduction: Sorption and desorption are important processes that influence phosphorus (P) chemistry in soil. Desorption is a process more complex than sorption and usually not all that is adsorbed is desorbed. This indicates that adsorption and desorption mechanisms are not similar and it seems that ...
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Introduction: Sorption and desorption are important processes that influence phosphorus (P) chemistry in soil. Desorption is a process more complex than sorption and usually not all that is adsorbed is desorbed. This indicates that adsorption and desorption mechanisms are not similar and it seems that such reactions are irreversible. Such irreversibility is usually called hysteresis. Major factors such as chemical changes in the structure of minerals, non-equivalent processes, inflation of adsorbent material, changes in the strength of crystals, irreversible fixation of adsorbed molecules in fine pores and equilibrium time less than its true value lead to hysteresis phenomenon. The concentration of phosphate in soil solution and thus its availability for plant are closely related to sorption processes by soil components. This relationship can be explicated by sorption isotherms. Soil organic matter (SOM) especially in arid and semiarid regions is one of the important indices of soil quality and plays important role in phosphate chemistry and fertility. Organic matter could decrease P sorption, maximum buffering capacity, and bonding energy and could increase P concentration in calcareous soils solution. Organic matter and organic acids resulted from its decomposition may coat calcium carbonate surfaces and prevent the formation of apatite precipitation. There are several methods to remove soil organic matter including using hydrogen peroxide and sodium hypochlorite solutions. It has been reported that H2O2 is penetrated into the interlayer spaces of phlogopite and vermiculite through exchange with water and cations and decomposes into H2O and O2. Therefore, this study was conducted to quantify the hysteresis indices, to investigate the effect of organic matter removal on phosphorus (P) hysteresis indices and to evaluate the relationship between hysteresis indices and soil characteristics and selection of index with the close correlation.
Materials and Methods: This study was carried out to obtain soil organic matter (SOM) removal with sodium hypochlorite solution (NaOCl, pH=8) effects on P hysteresis indices in 12 calcareous soils of Iran with different characteristics. For experiment of P sorption, 2 gr of soil subsamples was placed in separate 50 mL centrifuge tubes, to which were added 20 ml of monocalcium phosphate containing 5, 10, 15, 20, 30, 40, 60, 80 and 100 mg P L-1, which had been prepared in 0.01 M CaCl2 solution as background. Centrifuge tubes were shaken in a shaker incubator for 48-hour period to reach an equilibrium. Then, they were centrifuged at 4000 rpm for 5 minutes. The supernatant was filtered through a filter paper and the P concentration of filtrates determined using a spectrophotometer. The difference between initial and final P concentrations was assumed to be the amount of P adsorbed by the soil. Desorption experiments were assumed at the end of sorption experiments at the highest initial concentration of P with 0.01 M CaCl2 solution. The tubes were shaken to reach phosphate desorption equilibrium time (24 hours) at 25 °C in incubator shaker. Then, it was centrifuged for 5 minutes at 4000 rpm and 15 ml of the supernatant solution was pipetted and then 15 ml of solution of 0.01 M CaCl2 was added to tubes and the above steps continued to 9 steps. Freundlich model was used to describe the sorption – desorption isotherms data. DataFit 9.0.59 software (1995-2008) was used for nonlinear fitting of Freundlich to sorption data.
Results and Discussion: According to the results, P sorption and desorption data showed hysteresis which indicates adsorption and desorption mechanisms are not the same. As expected, nonlinear Freundlich equation showed a best fit (R2=0.96) to the data. The mean value of desorbed P in studied soils after SOM removal was decreased by 40%, so it was concluded that P sorption was more irreversible. In NaOCl treated soils, the mean values of seven studied hysteresis indices (HI) increased. Regression analysis indicated that the fourth hysteresis index, obtained from the distribution coefficient (Kd), had close relation with clay (r = 0.69, p < 0.05) and active calcium carbonate (r = 0.7, p < 0.05) concentration. Moreover, this hysteresis index showed significant (p<0.01) positive correlation with Kfsorb and Kfdesorb, which suggests that increasing bonding energy in sorption and desorption isotherms decreased desorption amount due to the strong interaction between adsorbed P and absorbent surface, increasing this hysteresis index.
Conclusion: It was concluded that among seven used hysteresis indices, HI4 can be introduced as the best index for the studied calcareous soils. It is predicted that using organic matter or preventing its reduction in arid and semi-arid calcareous soils may increase the efficiency of P fertilizer, given an increase in hysteresis index after the removal of the organic matter.
Solmaz Kazemalilou; Nosratollah Najafi; adel reyhanitabar
Abstract
Introduction: Sunflower as one of the most important oil crops in the world is affected by water deficit stress. Water deficit stress is one of the most important limiting factors of crops growth and production in Iran and many regions of the world. Because of the low water productivity in Iran, the ...
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Introduction: Sunflower as one of the most important oil crops in the world is affected by water deficit stress. Water deficit stress is one of the most important limiting factors of crops growth and production in Iran and many regions of the world. Because of the low water productivity in Iran, the water conservation and increasing of water use efficiency through good management including integrated application of organic and chemical fertilizers and balanced nutrition of plants are necessary. One of the negative effects of water deficit stress is impaired uptake of nutrients such as phosphorus (P) by plants and a decrease in plant yield. It has been found that use of P can reduce the negative effects of drought stress on plants that means the tolerance of plants to drought stress increases with optimal nutrition of P. In Iran, due to the lack of organic matter and the high cost of chemical fertilizers, farmers tend to use organic wastes such as sewage sludge that can have an important contribution in the improvement of soil fertility and plant nutrition and lead to an increase in water use efficiency. Also, integrated and suitable nutrition of plants is a method of sustainable management of soil fertility under environmental stresses. Therefore, this study aimed to evaluate the effects of sewage sludge (SS) and triple superphosphate (TSP) on sunflower (Helianthus annuus L. cv. Farrokh) seed yield and its components and determining the optimal levels of their consumption under optimum and limited irrigation conditions.
Materials and Methods: This experiment was conducted as a split-plot factorial arrangement in a randomized complete block design in Agricultural Research Station of Khoy under field conditions for two years. Experimental factors were irrigation time at two levels (irrigation after 60 and 150 mm evaporation from class A evaporation pan), triple superphosphate at three levels (0, 100 and 200 kg/ha), sewage sludge at four levels (0, 14.2, 28.4 and 56.7 t/ha) and year at two levels (2014 and 2015) with three replications. The 1000 seed weight of sunflower, weight and number of seeds per plant, the percentage of empty achenes, head diameter and seed yield were measured at the end of plant growth period. Statistical analysis of the data was performed using MSTATC software and means comparison was done by Duncan’s multiple range test at 5% probability level.
Results and Discussion: The combined analysis of variances showed that the effect of year was significant for weight of seeds per plant, head diameter and seed yield but it is not significant for 1000 seed weight, number of seeds per plant and percentage of empty achenes. Although water deficit stress significantly increased the percentage of empty achenes but 1000 seed weight, weight and number of seeds per plant, head diameter and seed yield significantly decreased compared to optimum irrigation conditions. The application of integrated application of 200 kg TSP and 56.7 tons SS per ha increased yield and yield components significantly compared to the control treatment. The interaction effects of TSP×SS×irrigation were significant for all studied characteristics. Under optimum irrigation condition, the highest 1000 seed weight (64 g), weight of seeds per plant (85 g), number of seeds per plant (1513), head diameter (22 cm) and seed yield (5576 kg/ha) were observed in intergrated treatment of 200 kg TSP+56.7 tons SS/ha. Under limited irrigation condition, the highest 1000 seed weight (57 g), seeds weight per plant (81 g), seeds number per plant (1494), head diameter (19.6 cm) and seed yield (5322 kg/ha) were obtained from 56.7 tons SS/ha treatment which showed no significant difference with 100 kg TSP+56.7 tons SS/ha treatment. Under optimum and limited irrigation conditions, the percentage of empty achenes were significantly decreased by integrated treatments of 200 kg TSP+56.7 tons SS/ha and 100 kg TSP+56.7 tons SS/ha (70 and 81 percent, respectively) compared to the control.
Conclusion: The results of this study indicated that integrated application of triple superphosphate and sewage sludge can mitigate negative effects of drought stress; therefore in order to reduce the use of chemical fertilizers, increasing sunflower seed yield and development of sustainable agriculture, integrated treatments of 200 kg TSP+56.7 tons SS/ha under optimum irrigation and 100 kg TSP+56.7 tons SS/ha under limited irrigation can be recommended at similar conditions (from the aspect of soil, plant, sewage sludge and climate).
Adel Reyhanitabar
Abstract
Knowledge about the P critical level and plant response to application of P can effectively help with the proper use of this element. In this study, P critical level for corn (Zea mays L.) was determined in 25 combined soils samples from corn fields of East Azerbaijan province during 2011-2012. Corn ...
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Knowledge about the P critical level and plant response to application of P can effectively help with the proper use of this element. In this study, P critical level for corn (Zea mays L.) was determined in 25 combined soils samples from corn fields of East Azerbaijan province during 2011-2012. Corn have been cultivated in two level of P (zero and 40 mg P kg-1) as a factorial experiment in a randomized complete blokes design with three replications .After 60 days, the plant growth parameters in shoot and root were measured. According to the results, in studied soils, clay content ranged from 12.4 to 57.3 with a mean 31.1 %. Calcium carbonate equivalent ranged from 7 to 35 with a mean 21.5 % and active calcium carbonate ranged from 1.47 to 10.78 with a mean 5.1 %. Application of P significantly increased shoot and root dry weight and their P content. According to the results, applied phosphorus levels, soil type and their interaction had a significant effect on corn growth parameters. Critical level of soil P for corn with Olsen-P, based on 90% relative yield, was determined 12, 14.44 and 10.46 (mg P kg-1 soil) by using graphical Cate–Nelson, Cate–Nelson analysis of variance and Mitscherlich-Bray methods, respectively. Mitscherlich-Bray equation coefficient C1 and C2, for Olsen-P, were 0.0956 and 0.0073 (kg soil mg-1P) respectively. Dry weight of shoot was positively and significant correlated with Olsen –P.