Soil Chemistry and Pollution
Khosro Betyar; Neda Moradi; Abdolamir Moezzi; Shila Khajavi-Shojaei
Abstract
Introduction Phosphorus deficiency is one of the major problems of calcareous soils and a limiting factor for crop production in these soils and excessive use of phosphate fertilizers can cause pollution in soil and water. The use of organic amendments such as compost, biochar or a combination of them ...
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Introduction Phosphorus deficiency is one of the major problems of calcareous soils and a limiting factor for crop production in these soils and excessive use of phosphate fertilizers can cause pollution in soil and water. The use of organic amendments such as compost, biochar or a combination of them can be effective in improving the amount of available phosphorus of the soil. For this purpose, the effect of combined application of compost and biochar of sugarcane bagasse on phosphorus sorption and desorption were investigated.Materials and Methods Sugarcane bagasse and compost were provided from Debal Khozaei agro-industry Company. The oven-dried sugarcane bagasse 105 ºC were pass through 2 mm sieve and slow pyrolysed at 500 ºC using a laboratory muffle furnace with a heating rate of 5 ºC min-1 and presence of N2 flow to provide an anoxic condition. Some physico-chemical properties of samples were determined. The soil sample was collected from 0-30 cm of the campus of Shahid Chamran University of Ahvaz, Ahvaz, Khuzestan province, SW Iran (48° 65′91.12′′E31°30′53.82′′N). The studied soil classified as a Typic Haplocalcids. The air-dried soil samples were sieved (˂ 2 mm) and used for physico-chemical analysis. The incubation experiment was conducted with 7 treatments. The treatments including (1) control (without any amendments), (2) 100% sugarcane bagasse, (3) 100% sugarcane bagasse compost, (4) 100% sugarcane bagasse biochar, (5) 50% compost +50% biochar, (6) 75% compost + 25% biochar, (7) 25% compost + 75% biochar were added as 2% w/w to soil. The 200 g air-dried soil and treatments were mixed and kept in poly-ethylene containers for 120 days. Samples were incubated in 25 2 ºC and soil moisture was adjusted to soil field capacity using distilled water during the incubation time. At the end of incubation time, soil phosphorus sorption isotherm was measured. A 2.5 g of each treatment was transferred to a 50 ml centrifuge tube. Then, a 25 mL of CaCl2 0.01 M containing 0, 10, 20, 40, 60, 80, and 100 mg P L-1 (prepared from KH2PO4) was added to each centrifuge tube. Two drops of chloroform were added to each centrifuge tube to inhibit microbial growth. Samples were equilibrated at 25 1 ºC for 24 h on shaker at 150 rpm, and then centrifuged for 5 min at 3000 rpm and pass through 0.45-μm filter paper. The phosphate desorption was conducted on soil remaining in the filter immediately after sorption experiment. For this purpose, each treatment was resuspended with 25 ml of CaCl2 0.01 M solution without phosphate and shaken for 24 h. after collecting the supernatant, desorbed phosphate was measured. For assessing the adsorbed phosphate, the difference between the initial phosphate concentration and the phosphate concentration at equilibrium was calculated. The Langmuir, Freundlich and temkin isotherm models were used to describe the sorption of phosphate. In addition, some phosphorus buffering indices including maximum buffering capacity (MBC), standard buffering capacity (SBC), equilibrium buffering capacity (EBC) and standard phosphorus requirement (SPR) were obtained from P sorption equations at 0.2 mg P L-1 concentration in soil solution. The experimental data were fitted by Microsoft Excel-SOLVER and graphs were plotted by Microsoft Excel.Results and Discussion The soil was had loam texture, with low SOC content and high pH and calcium carbonate content, also the results of the characteristics of sugarcane bagasse compost and biochar showed that the compost had high salinity and the biochar had high pH and C/N ratio. The amount of phosphorus absorption increased with increasing the initial concentration of phosphorus in the treated soils. The highest and lowest amount of phosphorus absorption were in the control in compost treatments, respectively. In general, different levels of biochar and compost treatments caused a decrease in phosphorus absorption compared to the control treatment. The results showed that P sorption and desorption are described well by the Freundlich and Langmuir equations with a high correlation coefficient; however, the Temkin equation described the P sorption and desorption in the soils poorly. Biochar and compost treatments significantly decreased the Freundlich n parameter. Results showed that the effects of compost and 75% compost + 25% biochar were significantly greater than the effects of other treatments on the n parameter exponential adsorption equation. Application of different treatments of sugarcane bagasse compost and biochar application caused a significant increase in MBC (25.4-70.7%) and EBC (33.1-69.4%). The standard P requirements (SPR) were lower in soils treated than in control soil.Conclusion The results showed that the combined application of biochar-compost of sugarcane bagasse reduced the sorption and increased desorption of phosphorus. The maximum buffering capacity (MBC) and equilibrium buffering capacity (EBC), standard buffering capacity (SBC) and standard phosphorus requirement (SPR) in compost and compost 75% + biochar 25% showed more decrease than the control. In general, the results of this study indicate that the combined application of biochar-compost of sugarcane bagasse reduces phosphorus sorption in soil in calcareous soils, which can increase the availability phosphorus for plants.
Naser Rashidi; Abdolamir Moezzi; Afrasyab Rahnama
Abstract
Introduction Salinity is one of the growth-limiting factors for pistachio (Pistacia vera L.) crop production in semiarid and arid soils of Iran. Salinity poses two major threats to plant growth: osmotic stress and ionic stress. In addition, it also manifested an oxidative stress. The deleterious effects ...
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Introduction Salinity is one of the growth-limiting factors for pistachio (Pistacia vera L.) crop production in semiarid and arid soils of Iran. Salinity poses two major threats to plant growth: osmotic stress and ionic stress. In addition, it also manifested an oxidative stress. The deleterious effects of salinity affect different physiological and metabolic processes of plants. The uptake of high amounts of salt by the plant leads to the increase of the osmotic pressure in the cytosol. Under this condition compatible osmoprotectant, such as proline and soluble sugars, is produced to protect the cells against the adverse effects from salt stress. High accumulation of proline is associated with tolerance to stress. Na+ and K+ homeostasis plays a vital role in the growth and development of higher plants under salt conditions owing to potassium–sodium (K+–Na+) interaction and is often associated with K+ deficiency. Application of potassium fertilizer affect plants growth and tolerance under salinity stress. The potassium is indispensable for several physiological processes, including the maintenance of membrane potential and turgor, enzyme activation, stomatal movement, regulation of osmotic pressure. Therefore the objective of this study was to evaluate the effect of potassium sulfate fertilizer application on growth, photosynthetic pigments, proline, soluble sugar and Na and K Uptake by Badami-riz Zarand P. vera L. (the main pistachio rootstock in Iran’s pistachio plantation area) seedlings under salinity stress. Materials and methods This study carried out in greenhouse condition as a factorial experiment based on a completely randomized design and in three replications. Experimental factors was salinity of irrigation water (in three levels including 0.65, 5 and 10 dS m-1) and potassium sulfate fertilizer application )in three levels including without application or control, 150 and 250 mg kg-1 soil). Pistachio (Pistacia vera L. cv. Badami-riz Zarand) seeds were surface sterilized with solution of sodium hypochlorite in distilled water. Seedlings were transplanted in plastic potscontaining 10 kg of soil. The pots were maintained in the greenhouse under 25 ± 4 ◦C temperature and under natural light. The mean relative humidity was 40 %. At the end of growth period (six mounth), the plants were harvested and leaf area, root dry weight, shoot dry weight, chlorophyll a and b, total chlorophyll, carotenoids, proline, spluble sugar, root and shoot K and Na concentration were measured. In addition, the K and Na uptake in shoot and root, as well as K/Na ratio were calculated. Analysis of variance (ANOVA) was performed using SAS program version 9.4 (SAS Institute, Cary, NC). Significant differences of the mean values (P <0 .05 for F-test) were determined by Duncans’s Multiple Range Test. Results and Discussion Results indicated that with increasing salinity stress, leaf area, root, and shoot dry weight, chlorophyll content and shoot and root K uptake decreased, while carotenoids and shoot and root Na concentration increased. The highest and lowest value of leaf area, root, and shoot dry weight, chlorophyll content and shoot and root K uptake were observed in control and high salinity levels (10 dS m-1) treatments respectively. Application of potassium sulfate fertilizer at both levels (150 and 250 mg kg-1) led to a significant increase in leaf area (8.1 and 8.7 % respectively), root dry weight (21.2 and 20.0 %), shoot dry weight (21.3 and 19.9 %), total chlorophyll (10 and 7.8 %), carotenoids (32.2 % and 35.7), proline (21.1 and 14.4 %), root K concentration (44.1 and 56.2 %), shoot K concentration (11.0 and 26.9 %) and K uptake in root and shoot. in high salinity treatment seedlings showed higher Na+/K+ ratio in the roots than that of the shoots. In addition, application of potassium sulfate fertilizer decreased Na uptake in shoot and root. Moreover, the addition of potassium fertilizer increased K/Na ratio in the shoot and root. The results also indicated there were no significant difference between potassium sulfate fertilizer levels (150 and 250 mg kg-1) effects on investigated traits. Conclusion It could be concluded that application of potassium sulfate fertilizer results in reduce the negative effects of salinity stress and subsequently enhance tolerance to salinity stress and improved P. vera L. seedlings growth. Therefore, nutrient management of potassium can be considered for decline of negative effects of salinity in P. vera L. v. Badami-riz Zarand seedlings.
