جستجوی مقالات مرتبط با کلیدواژه « phosphorous » در نشریات گروه « آب و خاک »

The best management practices are solutions to reduce non-point pollution in catchments. In many cases, the use of these solutions requires knowing the features of the watershed and investing in this sector. Accordingly, the use of computer models to simulate real catchment conditions can be an effective way to reduce time and cost. This research aimed to investigate the effect of different management scenarios on non-point source pollution losses in Dashte Bezorg catchment in Iran using the ArcSWAT model. To collect observational data, river water was sampled from September 2020 to June 2021. Calibration data were selected from September to March and validation data from April to June. After identifying critical areas, three non-structural scenarios and five structural scenarios were simulated using the model. The results revealed that the ArcSWAT model provides a good prediction in estimating non-point source pollution loads (nitrate, total nitrogen, and total phosphorus). The "wheat-potato-tomato" and "wheat, rice-wheat, mung bean-wheat" rotation scenarios showed the highest total nitrate and nitrogen loss, while the lowest total phosphorus loss was observed in the "wheat-potato-tomato" rotation. The terracing and buffer strip methods were recognized as the best methods of reducing the load of non-point pollution. The findings showed that the application of management practices in dominant land use and reduc the degree of slope can significantly reduce the non-point source pollution loads.

In order to investigate P acquisition efficiency (PACE) and P utilization efficiency (PUTE) of the corn in the presence of phosphate-solubilizing microorganisms (PSMs), a factorial experiment was carried out in a completely randomized design in the greenhouse. The factors were including P sources (tricalcium phosphate (TCP) and rock phosphate (RP)) and microbial inoculation (control, soluble P as KH2PO4 (Ps), inoculation with bacteria (PSB), inoculation with fungi (PSF), co-inoculation of PSB + PSF). At the end of growth period, plant dry weight and P content in plant and soil available-P were measured and then PACE, PUTE and phosphorus efficiency (PE) indices were calculated. The results showed that, the interaction of phosphate source and microbial inoculation was significant with respect to shoot P content, soil P, PUTE and PE. PSF-TCP treatment increased 7 times shoot phosphorus content compared to cont-RP treatment.  PUTE in Cont-TCP treatment was 2.35 times higher than the TCP-PS. The inoculation of PSF increased the PACE 1.61 times compared to co-inoculation of PSB + PSF tretment. Also, the highest PE index (99%) was obtained from SF-TCP treatment. In general, in calcareous soils with low P availability, inoculation of PSM with insoluble phosphorus sources can meet the phosphate needs of the plant.

In order to evaluate the effects of phosphorus (P) fertilizer and contaminations of lead (Pb) and zinc (Zn) on root Pb, Zn, and P concentrations, pyromorphite (Pb5(PO4)3Cl,F,OH)) formation in a calcareous soil, an experiment was conducted as factorial on the basis of completely randomized design with three replications under greenhouse and laboratory conditions with three factors of Pb at four levels (0, 200, 400, and 800 mg kg−1 soil as Pb(NO3)2), Zn at three levels (0, 25, and 250 mg kg−1 soil as ZnSO4.7H2O) and P at three levels (0, 50, and 500 mg kg−1 soil as Ca(H2PO4).2H2O). At the end of the rice growth period, root Pb, Zn, and P concentrations were measured. The treatment of Pb800P500Zn250 was subjected to X-ray diffraction (XRD) analysis for pyromorphite formation. The results showed that application of P fertilizer resulted in reducing the average root Pb and Zn concentrations by 15 and 2%, respectively. The application of Zn fertilizer resulted in reducing the average root Pb and P concentrations by 13 and 6%, respectively. The XRD results showed the formation of poorly crystalline chloropyromorphite. Also, in Pb and Zn polluted soils, application of P fertilizer could decrease mobility and bioavailability of these metals and restrict their uptake by plant.

Using of microorganisms in stress affected soils can alleviate the condition in plants. In order to assess the effects of phosphate-solubilizing microorganisms (PSB: Pseudomonas fluorescens, PSF: Aspergillus niger) and mycorrhizal fungies (M: Funneliformis mosseae (G. mosseae),Rhizophagus irregularis (G. intraradices), Rhizophagus fasciculatus (G. fasciculatum)) and their interactions on improving nutrient uptake under salinity stress condition, an experiment carried out in a randomized complete block design under greenhouse conditions. Some plant growth indicators and nutrient concentrations in plant shoot were measured at the end of growing period (70 days). The results showed the significant influence of salinity levels on phosphorous uptake, potassium, sodium, and chlorine concentrations, and shoot length. Proline accumulation in leaves (0.96 µmol g-1) was resulted with increasing of salinity levels. Among all microbial treatments, the maximum values of the parameters were resulted with mycorrhiza treatment, including shoot length (78.89 cm), shoot dry weight (15.77 g pot-1) and root dry weight (8.47 g pot-1). Unlike shoot sodium and chlorine concentrations, leaves nitrogen and potassium contents increased in microbial inoculation condition. Leaf proline was increased by 14.46% and 15.85% with fungi and mycorrhizal treatments compared to control, respectively. It is inferred that inoculation of AMF drastically decreased salinity effects in compared to other phosphate-solubilizing microorganisms in corn.

In order to evaluate the effects of phosphorus (P), contamination of lead (Pb) and zinc (Zn) and soil waterlogging on extraction kinetics of the available P, Zn and Pb in a calcareous soil, an experiment was conducted as factorial on the basis of completely randomized design with two replications under laboratory conditions with four factors consisting waterlogging duration at six levels  (0.1, 2, 6, 12, 36 and 72 days), Zn at two levels (0 and 250 mg kg−1 soil), P at two levels (0 and 500 mg kg−1 soil) and Pb at two levels (0 and 800 mg kg−1 soil). The extractable-P, Zn and Pb contents were measured at the end of each time by Soltanpour and Schwab method. The results showed that application of P, Zn and Pb increased the extractable-P, Zn and Pb, respectively. The extractable-P was significantly increased with increasing duration of waterlogging under no P fertilizer application whereas P application (500 mg kg−1 soil) resulted in reducing the average extractable-P by 23%. The extractable-Zn and Pb significantly decreased with increasing duration of waterlogging and application of P fertilizer, regardless of Zn and Pb applications. The results showed that in Pb and Zn contaminated soils, application of P fertilizer and soil waterlogging could decrease mobility and bioavailability of these heavy metals, leading to restrict their entrance in waters and plants.

Controlled drainage is one of the practices which aim to improve the conditions of the growing environment, increase the plant's yield and reduce the losses of chemical fertilizers and consequently reduces environmental pollution. The present study was conducted to investigate the effect of controlled drainage with constant and variable depth on discharge and salinity changes, as well as transfer of drainage nitrate and phosphorus during the growing season in the dominant products of Moghan plain, barley and corn. For this purpose, three treatment included, Free Drainage (FD) or conventional drainage is used to area, Controlled Drainage with a control level of 70 cm below the soil surface (CD70) and Controlled Drainage with variable control during the growing season (CDch) and each treatment in Three repetitions were considered. The results of the study showed that discharge rate of drainage in barley field in CD70 and CDch treatments was 55.0 and 44.9 percent lower than free drainage respectively, and in corn, decreased by 51.2 and 43.8 percent, respectively. The amount of nitrate losses in barley filed in the CD70 and CDch treatments was 48.4 and 42.4 percent, compared to free drainage and 50.8 and 46.0 percent, respectively. Changes in phosphorus concentration in treatments were low, but phosphorous losses between controlled drainage treatments and free drainage showed a significant difference at level of one percent. drainage salinity in controlled drainage treatments was lower than free drainage treatment. Controlled drainage treatments, in addition to reducing the amount of drainage volume, have improved the quality of drainage in terms of nitrate, phosphorus and salinity.