Document Type : Research Article
Authors
1
Gorgan University of Agricultural Sciences and Natural Resources
2
3. Associate Professor, Department of Chemical Engineering, Faculty of Engineering, University of Kurdistan, Sanandaj, Iran
3
Soil and Water Research Department, Kurdistan Agricultural and Natural Resources Research and Education Center
10.22067/jsw.2024.85725.1362
Abstract
Introduction:
Phosphorus is an essential element for all living organisms, and it cannot be replaced by any other element. Phosphorus is however a limited resource, and it is estimated that the extracted phosphorus resources (Apatite) will last for another 50 to 100 years. One of the most widely used technologies for recycling phosphorus is the precipitation of phosphorus from sewage sludge and leachate. Phosphorus Recovery as struvite (NH4MgPO4.6H2O) from sewage sludge has attracted special attention due to its potential for use as an ecological and slow release fertilizer. Struvite is a white, grain-like solid, odor-free and sludge –free ingredient, composed of magnesium, ammonium and phosphorus at equal moly concentrations. Therefore, this study is designed to examine the effect of struvite replacement with triple superphosphate fertilizer on some physiological parameters and phosphorus availability in wheat plants in calcareous soils deficient in phosphorus.
Methods and Materials:
Soil with phosphorus deficiency was collected from 0-30 cm depth under arable lands of Hajjiabad-e Seyyedeh located in Ghorveh township, Kurdistan Province, Iran. The soil was air-dried and ground to pass through a 2-mm sieve, followed by laboratory analysis to determine its physico-chemical properties. Struvite used in the research was obtained by optimizing the three main factors of sulfuric acid concentration, solid-to-liquid ratio, and time for the leaching process, and the three key factors of Mg/P ratio, N/P ratio and pH for the precipitation process by Response Surface Methodology. To achieve the aim of this study The factorial experiment was carried out in the form of a completely randomized design in 4 replications. The factors include the application of different proportions of struvite replaced with triple superphosphate (S0:P100, S25:P75, S50:P50, S75:P25 and S100:P0) and 4 levels of phosphorus (0, 50, 100 and 150 kg/ha) and a total of 54 pots. The application rate for struvite was calculated based on total phosphorus (P2O5). Then 10 wheat seeds were planted in each pot at 2-cm depth which after plant emerging and greening declined to 4 plants in each pot. The pots were randomly moved twice a week during the growth period to eliminate environmental effects. Irrigation and weeding operations were done by hand. Plants were harvested 60 days after planting (beginning of flowering), washed with distilled water and dry with tissue paper. The samples were air-dried and then oven dried at 70˚C to a constant weight in a forced air-driven oven. Phosphorus concentrations in plant extracts by the molybdenum vanadate or yellow method and chlorophyll content (a, b and ab) and carotenoids were measured using the Arnon method. The statistical results of the data were analyzed using SAS software and LSD test (at 5% level) was used for comparing the mean values.
Results and Discussion:
Based on the obtained results, all the investigated treatments and their interactions were significant at p<0.01. However, the interaction effect of fresh weight shoots and height was significant at p<0.05. The comparison of the average data showed that the highest amount of fresh weight shoots (7.79 gr/pot), dry weight shoots (1.130 gr/pot) and height (29.66 cm) was obtained from the application of S75:P25 150 kg/h P. By replacing struvite instead of triple superphosphate fertilizer, the phosphorus concentration and uptake of wheat increased at all three fertilizer levels, so that the highest phosphorus concentration (0.174%) is obtained from S75:P25 150 kg/ha P. Although there was no statistically significant difference with S100:P0 (0.169%). The highest amount of phosphorus uptake in wheat with an average of 0.197 gr/pot was obtained from the S75:P25 treatment of 150 kg/ha P, compared to the treatment of 100% struvite (S100:P0) and 100% triple superphosphate fertilizer (S0:P100) with the averages of 0.158 and 0.109 gr/pot, respectively, there was an increase equivalent to 19.79 and 44.67 percent. Also, the results showed that the treatment of 150 kg/ha 100% struvite (S100:P0) compared to 100% triple superphosphate fertilizer (S0:P100) can increase the amounts of chlorophyll a, b, ab and carotenoids by 7.78, 3.82, 6.44 and 6.84 percent, respectively.
Conclusions:
Despite struvite's low solubility, it is as effective for plants as highly soluble phosphorus fertilizers. However, the reasons for this apparent dichotomy and the specific mechanisms of struvite dissolution are still unclear. Hence, more accurate measurements for substrates with different pH and EC, investigation of physical and chemical properties of soil and phosphorus fractionation in soil will help to better understand the use of struvite. Therefore, it is recommended to optimize the timing and application rate of struvite in relation to the demand for different agricultural and garden crops.
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