Soil science
H. Hatami; H. Parvizi; A. Parnian; Gholamhassan Ranjbar
Abstract
IntroductionThe availability of phosphorus (P) is a limiting factor for the production of crops due to its reactions with soil components. Furthermore, there are concerns about the depletion of non-renewable global rock phosphate (the main source of P) reserves because of the high demand for P fertilizers. ...
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IntroductionThe availability of phosphorus (P) is a limiting factor for the production of crops due to its reactions with soil components. Furthermore, there are concerns about the depletion of non-renewable global rock phosphate (the main source of P) reserves because of the high demand for P fertilizers. Therefore, it is essential to revisit existing agricultural practices to determine new resource management practices that utilize renewable resources. The application of sewage sludge could be an alternative P source; contrary to inorganic fertilizers, sewage sludge is cheap, contains nutrients, and improves soil quality due to contained organic matter. The total P content of sewage sludge may vary from less than 0.1% to over 14% on a dry solid basis, depending on the nature of the raw sewage being treated and the treatment process under consideration. However, the use of organic P resources can affect the soil chemistry, leading to changes to the P fractions and their quantities. Hence, the objective of this study was to compare the effect of the application of municipal sewage sludge and triple superphosphate on the distribution of soil-P fractions under saline and non-saline conditions.Materials and MethodsTo investigate the effect of municipal sewage sludge and triple superphosphate on changes in P fractions an incubation experiment was conducted in a completely randomized factorial design with three levels of triple superphosphate (0, 75, and 100 Kg ha-1 which were named T0, T1, and T3, respectively), three levels of municipal sewage sludge (0, 0.25 and 0.5% w/w which were named M0, M1 and M3, respectively), two levels of salinity of irrigation water (2 and 12 dS m−1, which were named saline and non-saline, respectively) and three replicates. The total number of samples was 54. The treated soils were incubated for three months and maintained at field capacity by adding the appropriate amount of saline and non-saline waters. P fractionated to KCl-P (soluble and exchangeable P), NaOH-P (Fe- and Al bound P), HCl-P (Ca-bound P), Res-P (residual P), and organic-P by sequential extraction method. Moreover, P percentage recovery for Olsen-P at each treatment was calculated. P concentration in samples was determined by the molybdate method. Data analysis was performed by MSTAT-C software, and the means were compared at α꞊5% by Duncan test. Results and DiscussionThe results showed that although the relative distribution of fractions followed the order of HCl-P < Organic-P < KCl-P < NaOH-P <Res-P, the changes in each fraction were dependent on the type of treatment and fraction. The amounts of KCl-P for application of municipal sewage sludge and fertilizer TSP combined, especially, T2M2 were 3.1 and 2.3 times higher than T0M0 in non-saline and saline conditions, respectively. The same result was obtained for NaOH-P. The combined and separate application of municipal sewage sludge diminished the relative distribution of HCl-P compared with triple superphosphate and control treatments in both salinities. However, the HCl-P in all treatments was more than 57% of the total P, suggesting that most of the soil P was in the carbonate phase. The treatments did not have a considerable impact on Res-P. The relative distribution of Organic-P increased by increasing levels of salinity and municipal sewage sludge. Therefore, it seems that municipal sewage sludge addition along with fertilizer P can reduce the negative effects of salinity and increase soil P availability compared with alone use of P fertilizer through growing the contents of KCl-P, NaOH-P, and organic-P fractions and, consequently, decreasing P entry into HCl-P fraction. Moreover, the application of municipal sewage sludge plus triple superphosphate increased P recovery as Olsen-P compared to a separate application of triple superphosphate which confirmed the advantage of the combined use of these sources.ConclusionThe findings of this study indicate that the simultaneous application of municipal sewage sludge and triple superphosphate can effectively improve phosphorus (P) availability in saline conditions. This enhancement is attributed to the alteration of the relative distribution of non-stable P fractions, such as KCl-P and NaOH-P, which increase, while stable P fractions like HCl-P decrease. Moreover, the addition of municipal sewage sludge into soils led to a significant increase in organic C as well as the relative distribution of organic-P. Therefore, application of municipal sewage sludge can improve the physico-chemical properties of saline soil along with increase of P availability. Hence, further research on the growth response of halophyte plants as affected by these treatments is recommended.
Soil science
Z. Sokhanvar Mahani; N. Boroomand; M. Sarcheshmeh Pour
Abstract
IntroductionPhosphorus (P) is one of the most important elements necessary for plant growth and production of agricultural products. In calcareous soils, phosphorus deficiency is a general issue due to high pH, high soil calcium carbonate content, lack of organic matter and moisture. Phosphorus absorption ...
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IntroductionPhosphorus (P) is one of the most important elements necessary for plant growth and production of agricultural products. In calcareous soils, phosphorus deficiency is a general issue due to high pH, high soil calcium carbonate content, lack of organic matter and moisture. Phosphorus absorption capacity depends on different soil reactions such as: adsorption, sedimentation, stabilization and release. The speed and amount of plant available P depends on the soil reactions. Studying the kinetics of P release from soil is a good indicator to check the status of P uptake by plant. The kinetics of P release in soils is a subject of importance in soil and environmental sciences. The aim of this research was to investigate the kinetics of P release and derive the most suitable equation to describe the release of P from a calcareous soil when subjected to the acidification of rock phosphate and the addition of vermicompost. Materials and MethodsIn order to investigate the ability of acidified rock phosphate and vermicompost in P release, an experiment was conducted with 2 replications on a light-textured soil with low OC and Olsen-P (1.2 mg/kg). One hundred grams air dried calcareous soil was transferred into special containers and 5 treatments including: 1- control (soil), 2- rock phosphate, 3- acidified rock phosphate (20 CC nitric acid 0.1 N and 5 g rock phosphate), 4- vermicompost, and 5- acidified vermicompost (20 CC nitric acid 0.1 N and 5 g vermicompost) were applied. The treatments incubated two weeks in 20±2℃ temperature. The Kinetics of P release was studied by adding 20 mL of 0.5N NaHCO3 to, one gram of air dried treatments. Extraction times were considered to be 0.25 h to 256 h (in 11 times) based on the time of adding the NaHCO3 extractant until filtering. After adding the extractant, the samples were shaken and centrifuged. After filtering, the concentration of released P in samples were determined by spectrophotometer (Model: CE 292 Series2, ultraviolet). For higher accuracy in the measurements, acid-washed containers were adjusted based on the amount of soil moisture which was dried in the oven (105℃). Finally, the P release data were fitted to different kinetic equations. The effect of different fertilizer treatments on P release in specified times and then kinetics parameters were investigated and compared with the control. Results and DiscussionAddition of acidified and non acidified rock phosphate and vermicompost increased the amount and speed of P release in the calcareous soil. Six kinetic equations were fitted to describe the release of P in the period of 0.25 h to 256 h from the soil to evaluate the effect of the treatments. The highest release of P was in vermicompost and acidified rock phosphate treatment, which were an organic fertilizer and a source for preparing phosphate fertilizers. To describe the release rate, kinetic equations were used. The best equations were chosen by highest coefficient of determination (R2) and the least of standard error (SE). The zero, first, second order equations could not describe the release of P in the studied calcareous soil. The R2 value decreased from the zero to second order equation. The simplified Elovich equation described well the release of P from the soil with the average R2 of 0.79 and with the average SE of 0.4. Comparison of the average effect of the studied treatments with the control showed that the acidifed vermicompost and rock phosphate treatments increased the capacity and speed of P release compared to the control. On the other hand, acid addition has increased the capacity and speed of P release in the calcareous soil. ConclusionThe findings indicated an initial rapid release of P, which then decreased over time. Notably, the application of vermicompost and the acidification of the soil with rock phosphate resulted in a pronounced and accelerated release of P. Generally, organic fertilizer treatments exhibited a higher release of P compared to chemical fertilizer treatments. This observation is in accordnce with the findings of the data presented by Ghorbanzadeh et al. (2009), who explored the P release potential of bone meal. Their data demonstrated that the acidification of bone meal accelerated and enhanced P release. To further enhance the practical relevance of these results, it is recommended to conduct this research in the presence of plants.
hamid reza motaghian; alireza hosseinpuor; Shahram Kiani
Abstract
Introduction: Use of organic fertilizers such as vermicompost in agricultural soils with low organic matter content is almost considered as a one way for adding nutrients in these soils. However, application of these fertilizers may affect micronutrient release characteristics. Micronutrient release ...
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Introduction: Use of organic fertilizers such as vermicompost in agricultural soils with low organic matter content is almost considered as a one way for adding nutrients in these soils. However, application of these fertilizers may affect micronutrient release characteristics. Micronutrient release Kinetics in soils especially in amended soils give information about potential of amended soils to release these elements into solution. Although it is important to study kinetics of micronutrient release from soils to identify soil micronutrients buffering capacity, little attention has been paid to micronutrients desorption rate studies especially in amended soils. The rate of release micronutrients from soil solid phase by considering micronutrients as adsorbed ions or in mineral forms is an important parameter in nutrition of plants by microelements and a dynamic factor that regulates its continuous supply to growing plants; nonetheless, little attention has been paid to micronutrients kinetics inrelease studies.
Material and Methods: In this study, kinetics of zinc (Zn) and copper (Cu) were compared in one calcareous soil amended with 0, 0.5, and 1% (w/w) of manure and vermicompost in a completely randomized design and then amended and un-amended soils were incubated at field capacity, for 30 days. After incubation period, amended and un-amended soils were air-dried and were prepared to kinetics study. Kinetics of Zn and Cu release were studied by successive extraction with DTPA-TEA solution. Two grams of the amended and un-amended soils, in triplicate, suspended in 20 ml DTPA-TEA solution were equilibrated at 25±10C for 1, 8, 24, 48, 72, 96, 120, 144, 168, 336 and 504 h by shaking for 15 min. before incubation and 15 min. before the suspensions were centrifuged. Seven drops of toluene were added to each 1000 ml of extractant to inhibit microbial activity. Zinc and copper desorption with time was fitted by using different equations (Zero-order, First-order, Parabolic diffusion, Simplified Elovich, and Power function).
Results and Discussion: Results showed that released Zn in soils amended with manure and vermicompost compared to control soil significantly increased (p0.05) and released Cu in soil amended with vermicompost decreased significantly (p
