Soil science
F. Rakhsh; A. Golchin; A. Beheshti Ale Agha
Abstract
Introduction
Soil texture is one of the most influential characteristics that affects the decomposition and retention of soil organic matter, as it directly or indirectly impacts the soil's physical, chemical, and biological properties. Soil clays play an important role in soil organic matter stability. ...
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Introduction
Soil texture is one of the most influential characteristics that affects the decomposition and retention of soil organic matter, as it directly or indirectly impacts the soil's physical, chemical, and biological properties. Soil clays play an important role in soil organic matter stability. Organic matter adsorbed on phyllosilicate clays is more resistant to microbial decomposition than organic matter that has not interacted with any mineral. Exchangeable cations through the influence of physical and chemical characteristics of the soil probably cause changes in the absorption and retention of organic matter. In previous studies, the effect of soil texture on organic matter retention has been investigated, but the impact of clay type and exchange cation has not been investigated. This study aimed to examine the effect of different contents of vermiculite and zeolite clays and exchange cations on the mineralization of organic nitrogen.
Materials and Methods
A factorial experiment was conducted in a completely randomized design with three replications to study the effect of the type and content of clay and the type of exchange cations on organic nitrogen dynamics. Experimental treatments include two types of clay (vermiculite and zeolite), four different levels of clay (0, 15, 30, and 45%), and three types of exchangeable cations (Na+, Ca2+, and Al3+). The experiment included 24 treatments and three replications. There were total of 72 experimental units. Artificial soil of 50 grams was prepared separately according to the amount and type of clay and the type of exchange cation. "Next, alfalfa plant residues were added to all samples at a rate of 5% w/w. After inoculating and air-drying the samples, the moisture content was adjusted to 60% of the field capacity (FC) using distilled water. To prevent excess water from affecting the final moisture readings, the samples were first air-dried, and then sufficient distilled water was added to each sample to achieve 60% of FC. The samples were then kept in the dark for 60 days at a temperature of 23 °C. Distilled water was added and sealed to the bottom of the incubation jars to keep the moisture content of the soil samples constant during incubation. The percentage of mineralized nitrogen, microbial biomass nitrogen, and the activity of acid and alkaline phosphatase and cellulase enzymes were determined in the prepared samples. The data were analyzed using ANOVA, and the means were compared using Duncan's Multiple Range Test (DMRT). Before applying ANOVA, the data's normality and variance homogeneity were checked using Kolmogorov- Smirnov and Levene tests, respectively. The SPSS software (Windows version 25.0, SPSS Inc., Chicago, USA) and SAS software (version 9.4, SAS Institute Inc., Cary, NC) were employed for data analysis.
Results and Discussion
The results of variance analysis of the data showed that the effect of the type and content of clay and the type of exchangeable cation on the percentage of mineralized nitrogen, microbial biomass nitrogen, and the activity of acid and alkaline phosphatase and cellulase enzymes were significant (p< 0.01). The results revealed that, regardless of the duration of the samples, with the increase in the amount of clay, the percentage of inorganic nitrogen and the activity of enzymes decreased, but the nitrogen of microbial biomass increased. The highest percentage of inorganic nitrogen was obtained 60 days after incubation of the samples and in clays saturated with calcium, and the lowest amount of these attributes was obtained 15 days after incubation of the samples and in clays saturated with aluminum. The results showed that nitrogen mineralization increased with the samples' incubation time. Also, the highest percentage of mineralized nitrogen, microbial biomass nitrogen, and enzyme activity were observed in soils with vermiculite.
Conclusion
The increase in the incubation duration enhanced the percentage of inorganic nitrogen. The percentage of mineralized nitrogen and microbial biomass nitrogen was higher in soils with vermiculite than in soils with zeolite. Moreover, regardless of the incubation duration of samples, with increasing clay content, the percentage of mineralized nitrogen and enzyme activity decreased, but with increasing clay nitrogen content, microbial biomass increased. The highest and lowest amounts of mineralized nitrogen and nitrogen of microbial biomass were measured in soils with calcium and aluminum, respectively. The results showed the effect of the clay type and content and the exchangeable cation type on organic nitrogen dynamics.
Masoud Noshadi; Hosein Valizadeh
Abstract
Introduction: Soil salinity is one of the major limitations of agriculture in the warm and dry regions. Soil sodification also damages soil structure and reduce soil permeability. Therefore, control of soil salinity and sodium is very important. Vetiver grass has unique characteristics that can be useful ...
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Introduction: Soil salinity is one of the major limitations of agriculture in the warm and dry regions. Soil sodification also damages soil structure and reduce soil permeability. Therefore, control of soil salinity and sodium is very important. Vetiver grass has unique characteristics that can be useful in phytoremediation.
Materials and Methods: This research was conducted to investigate the effects of irrigation with different salinities on vetiver grass and the effects of this plant on the control of soil salinity and soil reclamation.The experimental design was randomized complete block design. Irrigation water salinities were 0.68(blank), 2, 4, 6, 8 and 10 dS/m, respectively, which artificially were constructed using sodium chloride and calcium chloride. At first, vetiver was transplanted and then moved to the farm. The amount of soil moisture was measured by the neutron probe. Irrigation depth was applied to refill soil water deficit up to field capacity. To evaluate the soil salinity in above salinity treatments, soil was sampled in each plot from 0-30, 30-60 and 60-90 cm depths and for each layer, electrical conductivity of saturated extract (ECe), sodium, potassium and chloride concentrations was measured .To measure the sodium, potassium and chloride concentrations in the leaves and roots of vetiver plant, samples were dried in oven. The dried samples were powdered and passed through the sieve (No. 200) and they were reduced to ash in 250 ◦C. 5 ml HCl was added to one gram of the ash, and after passing through filter paper, the volume of sample was brought to 50 ml by boiled distilled water. After preparing plant samples, the sodium, potassium and chloride concentrations were measured by Flame Photometer.
Reults and discussion: The results showed that the vetiver grass was able to decrease soil salinity at different salinity levels except highest water salinity (10 dS/m) and prevented salt accumulation in the soil. However, in the salinity 10 dS/m, soil salinity was not well controlled, but soil salinity was lower than the irrigation salinity. In these water salinities, the mean ECes in 0-90 cm soil depth were increased 25.0, 60.4, 79.2, 87.5 and 215.5 percent, respectively, relative to a control treatment, which was much less than the increasing of irrigation water salinities. These increases in ECe were significant at 5% level of probability. The accumulated values of sodium in vetiver leaves showed significant difference between S0 treatment and the other treatments (S3, S4 and S5) at the 5% level of probability. The sodium contents in vetiver leaves were 22.2, 33.3, 70.4, 103.7 and 122.2% and in vetiver roots were 32.7, 66.5, 129.3, 218.2 and 281.8% higher than the control treatments (S0), respectively. Sodium contents in vetiver roots were 103.7, 121.2, 154.4, 174.1, 218.2 and 250% more than sodium contents in vetiver leaves in S0, S1, S2, S3, S4 and S5 treatments, respectively. Sodium contents were increased 14.3, 28.6, 64.3, 100.0 and 114.3 percent in vetiver leavesand 28.6, 64.3, 125.0, 214.3 and 275.0 percent in the vetiver roots , relative to the control treatment, respectively, at above salinity levels, which indicated an improvement of sodium accumulation in leaves and roots with increasing salinity levels. Chloride concentrations at irrigation water salinities S1, S2, S3, S4 and S5 treatments (2-10 dS/m) were 22.9, 35.6, 74.5, 107.2 and 121.9% in vetiver leaves and 27.02, 59.7, 118.9, 195.06 and 255.7% in vetiver roots more than control treatment, respectively. The mean values of sodium and chloride in all salinity levels in the roots were 170.3 and 164.1 percent more than the leaves, respectively.There were no significant differences in accumulated potassium in vetiver leaves and roots between different treatments, but vetiver leaves and roots absorbed and accumulated high value of potassium. The potassium contents were 4.38, 4.64, 4.18, 3.89, 3.82 and 3.68 mg/g in vetiver leaves and 3.12, 3, 3.62, 3.69, 3.84 and 3.68 mg/g in vetiver roots, in S0, S1, S2, S3, S4 and S5 treatments, respectively.
Conclusion: In general, the results showed that up to irrigation water salinity 8 dS/m, Vetiver grass had very good ability to control soil salinity and prevented the accumulation of salt in the soil, but at the salinity of 10 dS /m, soil salinity was not well controlled. However, in 10 dS /m, soil salinity was much less than water irrigation salinity.
The mean values of soil salinity in layer 3 (60-90 cm) were 0.48, 0.6, 0.77, 0.86, 0.9 and 1.5 dS/m in S0, S1, S2, S3, S4 and S5 treatments, respectively. ECes were 29.4, 70.0, 80.8, 85.7, 88.8 and 85.0 percent lower than irrigation water salinities 0.68, 2, 4, 6, 8 and 10 dS/m, , respectively. Sodium and chloride accumulated in the leaves and roots of vetiver that showed that Vetiver it is well able to absorb these elements. The accumulations of sodium and chloride in roots were170.3 and 164.1 percent more than leaves, respectively.
N. Najafi; S. Mardomi; Sh. Oustan
Abstract
In a greenhouse experiment, the effects of waterlogging, sewage sludge and manure on the uptake and concentrations of P, K, Ca, Mg and Na in root and shoot of sunflower (Helianthus annuus L.) were investigated. A factorial experiment based on completely randomized design with three replications including ...
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In a greenhouse experiment, the effects of waterlogging, sewage sludge and manure on the uptake and concentrations of P, K, Ca, Mg and Na in root and shoot of sunflower (Helianthus annuus L.) were investigated. A factorial experiment based on completely randomized design with three replications including duration of waterlogging at five levels (0, 2, 4, 8, 22 days), source of organic fertilizer at two levels (manure and sewage sludge) and each at three levels (0, 15, 30 grams per kg of soil) was conducted. The results showed that by increasing the duration of soil waterlogging, the P and K uptake and concentration in shoot and root, the concentration of Ca and Na in root, the Mg concentration in shoot, the uptake of Ca and Mg in root and the uptake and concentration of Na in shoot increased but P uptake and concentration in root and K uptake in root and shoot decreased again. By increasing the duration of soil waterlogging, the uptake and concentration of Ca in shoot decreased but the Ca concentration in shoot increased again. The effect of soil waterlogging on the Mg uptake in shoot was not significant. By application of sewage sludge and manure and increasing their amounts, the uptake and concentration of P in shoot and root, the uptake of Ca in shoot and root and the uptake and concentration of Na in shoot increased. The K uptake and concentration in shoot increased by application of manure and increasing its level while decreased by application of sewage sludge. The effect of soil waterlogging on the macronutrients and sodium uptake and concentrations in root and shoot was dependent on the source and amount of organic fertilizer and vice versa. The results demonstrated that even short periods of soil waterlogging (2 days) had considerable long-term effect on the concentrations of elements in plant. Generally, sunflower plant accumulated P, Mg and Na in root and Ca in shoot while the K concentration in root did not differ with shoot significantly.
