نشریه مدیریت خاک و تولید پایدار
سال سیزدهم شماره 2 (پیاپی 44، تابستان 1402)

With the progressive increase in industrial and agricultural activities leading to increase in pollutants, soil has received attention as an environmental component and recipient of many of these contaminants.Due to the direct relationship among soil, plants, and humans, pollution in one area may strongly have a negative impact on another.Heavy metals are considered as one type of soil pollutants that can enter the food chain in several ways.Cadmium (Cd) is a heavy metal that has particular importance among the others because it is easily absorbed by plants and causes toxicity.Its detrimental effects on the plant are higher than the other heavy metals.It is crucial to study the uptake and transfer of Cd in the cultivars of wheat which accumulate less amount of Cd.This study aimed to compare the susceptibility of different bread (Triticum aestivum) and durum (Triticum turgidum L.var.durum) wheat cultivars to absorb Cd in Cd-spiked soil.This study was conducted to investigate the effect of different levels of soil Cd (0 and 10 mg kg-1) on its concentration in the roots and shoots of four cultivars (Sirvan, Rakhshan, Talaei, and Parsi) of spring bread wheat and five cultivars (Behrang, Hana, Aran, Shabrang, and Sana) of spring durum wheat.The experiment was set up in a completely randomized factorial design with three replications as a pot experiment in the research greenhouse of the Faculty of Agriculture, Ferdowsi University of Mashhad.After harvesting, to determine the soil total concentration of Cd was used Aqua Regia method.The amount of cadmium in plant organs was also measured by the wet digestion method (nitric acid and hydrogen peroxide).The translocation and biological accumulation factor were calculated for cultivars of both species.Based on the results, the application of different levels of soil Cd had statistically significant increasing effect on the concentration of this element in roots and shoots of the study wheat cultivars (P<0.01).The Cd concentration in root was estimated more than shoot Cd levels in both wheat species.Among bread wheat cultivars, the most and lowest shoot Cd content was observed in Sirvan and Rakhshan, respectively.On the other hand, in Rakhshan and Talaei were calculated the most and lowest root Cd content, respectively.According to the Cd levels in aerial organs, translocation, and biological accumulation factor, Sirvan had high ability to accumulate cadmium and Rakhshan was more efficient in absorbing cadmium than other cultivars and stored and transported the least amount of this element.Furthermore, according to the information obtained, among durum wheat cultivars, Sana tended to have the lowest Cd concentration of shoot and Behrang tended to have the highest content.In contrast, the highest and lowest amount of Cd in root was related to Sana and Hana, respectively.According to translocation and biological accumulation factor, Sana had less ability to accumulate Cd rather than durum cultivars and Behrang had the highest amount of translocation factors and absorption of this element. Parsi from bread species and Shabrang from durum species had the highest dry weight of shoot in both Cd0 (Control sample) and Cd10 (10 mg kg-1) treatments.In general, bread wheat accumulated a higher amount of Cd in root and shoot than durum wheat.In general, the concentration of Cd in the shoots and roots of both bread and durum wheat species, as well as different their cultivars, was influenced by Cd-spiked soil.Transfer of cadmium from soil and root to aerial organs was an effective factor in the accumulation of this element in plants.According to the results, each wheat cultivar had different abilities to absorb and translocate Cd.Moreover, for the identification of permissible exposure limits of Cd in soil and wheat, some standards should be considered.

Ever-increasing need of human for agricultural productions has caused an ever-enhancing trend in use of different chemical fertilizers to achieve more yield production. On the other hand, augmenting the use of chemical fertilizers results in pollution and quality decline in soil and water resources, leading to production of unhealthy food products. Application of plant biostimulants like humic acid, fulvic acid, amino acids, mycorhizal fungi and seaweeds could be a useful approach to reduce using chemical fertilizers. It leads to reduce the use of chemical fertilizers without decline in quantitative and qualitative yield production. Therefore, the present research was accomplished in order to investigate the effects of some biostimulants on fertilzer use efficiency, as well as yield and quality of orange.

This experiment was carried out in a factorial manner based on completely randomized block design (CRBD) with three replications on 63 orange trees var. Washington novel, during two consecutive years in Hormozgan Haji-Abad agricultural research station. There were two factors consisting of 1-Application of chemical fertilzers in three levels (without any chemical fertilizers, %75 of the recommended chemical fertilizers, %100 of the recommended chemical fertilizers), and 2- Application of plant biostimulants in seven levels (control, amino acid foliar spray, seaweed extract foliar spray, soil applied humic acid, fulvic acid foliar spray, soil applied mycorhizal fungi, amino acid and seaweed extract foliar spray accompanied with soil applied humic acid and mycorhizal fungi). The harvesting was done in december, every year. Some plant responses such as yield production, the concentrations of iron, manganese and zinc in leaves, total soluble solids, vitamin C in fruit extract, and fertilizers use efficiency were determined. Finally, the results were interpreted based on the analysis of variances for the data set and comparison of means.

The results showed that application of biostimulants caused an increase in production yield and fertilizer use efficiency, as well as the concentration of iron, manganese and zinc in leaves. Some qualitative properties consisting of total soluble solids and vitamin C content in fruit extract were also improved. Furthermore, use of chemical and organic fertilzers corroborated the positive effects of biostimulants. In other words, interactive effects of biostimulants and fertilzers on quantitative and qualitative properties of orange were significant. The most positive effects were observed in the treatment containing soil applied humic acid and mycorhizal fungi accompanied with amino acids and seaweed extract foliar spray, and %100 of the recommended chemical fertilzers. However, fertilizer use efficiency in trees treated with %75 of the recommended chemical fertilizers was higher, as compared to those supplied with %100 of the recommended fertilizers.

It is recommended that instead of excessive use of chemical fertilizers, a combination of biostimulants including humic acid, amino acids, seaweed extract and mycorhizal fungi be applied along with %75 of the recommended chemical fertilizers in the integrated nutrition management, in order to achieve increased yield, improved fruit quality and reduced environment pollution.

Investigations showed that the pollution of heavy metals, especially lead, in fields has caused tension and decreased yield. This issue has caused concern about the risk of consuming contaminated food for human health. The role of plant regulators in heavy metal stress conditions has been of interest in recent years. Lead and zinc (in high concentration) are toxic metals for plants, which are easily absorbed by the plant's root system. As a result, they cause damage to plant growth and development and prevent enzyme activity. Maize is economically important for harvesting seeds and fodder. However, in areas contaminated with metal stress, due to the absorption of metals by the plant, the yield of the cultivated plant in these areas decreases, for this purpose, an experiment aimed at the effect of concentration and different methods of salicylic acid hormone on growth, photosynthesis and anatomical characteristics. and physiological in corn under the stress of zinc and lead metals and also the possibility of reducing the risk of toxicity of these elements is investigated.

In order to investigate the mitigating effects of two methods of applying salicylic acid hormone on corn plants under heavy metal stress, the experiment was carried out as follows. The concentration of metals included: different concentrations of lead (0 and 250 mM) and zinc (0 and 2500 mM) and the treatments were with two methods of foliar spraying and priming in zero concentrations (distilled water), 750 and 1500 μmol salicylic acid and a group of seeds without stress and no treatment were considered as controls. By implementing a factorial design on morphological traits (height, plant temperature, temperature difference between the environment and leaves, and leafing ratio) and physiological traits (membrane stability index, chlorophyll fluorescence, proline, soluble sugars, carotenoid, protein and some enzymes) as well as the absorption of lead and zinc metals in the root tissue and the aerial part of the plant under hydroponic cultivation conditions. The obtained results were subjected to statistical analysis using SPSS statistical software. The mean comparison of experimental data was also done with Duncan's test. Excel 2003 software was used to draw the figures.

Morphological traits such as: plant temperature, difference between Environment and leaf temperature and physiological traits such as: proline, soluble sugars, carotenoid, protein and some enzymes increased and some other traits such as: height, and leafing ratio, index Membrane stability, chlorophyll fluorescence decreased compared to the control. These traits showed better results in seed priming treatment without stress. However, the use of foliar spray under lead-zinc and lead stress improved the stress effects by reducing the absorption of heavy elements by the root system.

SA activates the defense system of plants by synthesizing a number of proteins and increasing proline osmolytes and soluble sugars and enzymatic and non-enzymatic antioxidants such as carotenoids. As a result of reducing the oxidative stress and protecting the chloroplast membrane and the photosynthetic apparatus, the photosynthetic production is improved, resultly, the height and the proportion of the leaves increased. SA also prevents the absorption of heavy metals by the root system of the plant and its transfer to the aerial part of the plant, which reduces the signs of stress in the aerial part of the plant. By applying salicylic acid, some properties were improved by reducing the effects of stress. The use of foliar spraying improved the physiological and morphological traits during plant growth and worked better than the seed priming method. resultly, in farms with two metals lead and zinc, it is possible to tolerate the stress of these two metals by foliar spraying treatment.

Actinomycetes are among the highly populated microbial groups in the soil, and they have significant positive effects on ecosystem preservation. Providing nutrients, especially phosphorus, in the plant rhizosphere, where its absorption is challenging for plants due to various reasons, is one of the positive effects of using growth-promoting actinomycetes. Humic acid is among the organic compounds that act as growth stimulants. Due to its significant role in soil fertility and the enhancement of soil microbial communities, it promotes the growth and activation of beneficial soil microorganisms residing in the rhizosphere of plants. It also improves the efficiency of phosphorus fertilizers. Therefore, the objectives of this study was as follows: 1) Screening the phosphate solubilization capacity of actinomycete isolates in various culture media, 2) investigating the effect of adding humic acid on soluble phosphorus concentration in different media culture, 3) evaluating the effect of inoculation with selected isolate on growth, physiological parameters, and phosphorus content of the maize variety 'Single Cross 704' in the presence of humic acid and different levels of phosphorus fertilizer.

In this research, a total of 20 actinomycete strains were isolated and purified from various agricultural and horticultural ecosystems in Golestan province, based on their morphological characteristics. These strains were utilized for screening purposes. The phosphate solubilization ability of bacterial strains was assessed in GA, NBRIP, and SMM media culture in the presence of commercial humic acid at a concentration of 0.5%. This experiment was conducted in a factorial design within a completely randomized design, with the following factors: bacterial strain (20 purified strains), culture media (three common phosphorus solubilization media), and humic acid (application, non-application) with three replications under laboratory conditions. To evaluate the effects of a selected actinomycete isolate and its combined effects with different levels of phosphorus and the application of humic acid, a pot experiment was conducted under light and ambient temperature conditions in a completely randomized design with factorial treatments of actinomycete inoculation (control, inoculation), phosphorus fertilizer (control, 20 and 40 kg pure phosphorus per hectare), and humic acid with three replicates on Single Cross 704 maize plants.

The screening results revealed that the NBRIP culture medium was more efficient for phosphorus release, and strains 47, 46, 79, 74, and 24 showed significant increases in phosphorus release. The application of humic acid resulted in an increase in the dissolution of tricalcium phosphate and the release of phosphorus by 11.12-, 118.06-, 4.76-, and 9.69-fold, respectively, in the NBRIP culture medium of the isolates mentioned. Isolate 47 exhibited the highest phosphorus solubility of 247.05 mg/litre with the addition of humic acid, and was selected as the superior isolate for the pot test. The sequencing results revealed that the superior isolate had the highest homology with the Streptomyces chartreusis isolate registered in the NCBI database with accession number KJ152149. The results of the pot experiment indicated that the optimal treatment was the combined application of high phosphorus content (40 mg/kg) together with humic acid and Streptomyces inoculation (P2B1H1), which resulted in the highest amount of shoot biomass (13.97 g per pot), root biomass (8.2 g per pot), plant height (32.26 cm), chlorophyll (32.87 SPAD numbers), and phosphorus content (0.23 percent).

Conclusion:

 Based on the results of this study, inoculation with the screened streptomyces isolate and its combined application with humic acid improved the efficiency of phosphorus fertilizer utilization and provided it effectively for the plant.

The loss of phosphorus (P) from agricultural lands and its entry into water resources has caused the algal bloom and eutrophication phenomena, and has marked the control of P entrance to aquatic ecosystems as an important challenge for the management of these resources. Algal assay is considered as the most reliable method for quantifying the potential of P bioavailability. The aim of this study was to investigate the bioavailability of P in three paddy soils and its relationship with the growth of Chlorella sp. microalgae.

Soil samples were taken from a depth of 0-10 cm of paddy fields located in five regions of Pasikhan, Pirbazar, Siahdarvishan, Fakhab and Lakan, which had annually received phosphorus fertilizer for a long time. At first, different P fractions were determined by Hedley sequential extraction method in 5 soils, and 3 soils (Psikhan, Pirbazar and Lakan) based on the total P content, P in different fractions and clay content were selected and added to the Chlorella sp. culture medium as the only P supply source. The experiment was performed as repeated measures in a completely randomized design with three replications. Chlorophyll a content, microalga cell number, total dissolved P (TDP) and particulate P (PP) concentrations were measured at days 0, 7, 14, 21, and 28 of incubation.

Phosphorus fractions of Pirbazar and Fakhab soils were similar as followed in oxide >residual >carbonate> solution-exchangeable. While in the other three soils, the phosphorus fractions followed the trend of residual >oxide >carbonate> solution- exchangeable. The chlorophyll a content showed an increasing trend in all samples and reached its maximum on the 14th day and was then almost constant. The number of microalgae cells in Pirbazar treatment showed an increasing trend until the 14th day of incubation, while it remained increasing in Lakan and Pesikhan treatments until the end of the incubation period. TDP concentration increased during the incubation period in all treatments until the 7th day and then decreased. Particulate phosphorus decreased sharply on the 7th day of incubation and then increased. The chlorophyll a content and the number of microalgae cells showed a significant positive correlation with TDP at the first two weeks of incubation, while the microalga growth was affected by particulate P in the next two weeks of incubation.

Since soil as the only source of P can accelerate the microalgae growth in aquatic ecosystems, considering P originated from agricultural lands along rivers to manage the eutrophication phenomenon is necessary especially in wetlands catchment.

Today, the cultivation of medicinal plants is more attractive among farmers. marigold is an annual herbaceous plant that belongs to the chicory family and is known as a medicinal plant along with its ornamental nature. The use of marigold extract in the treatment of some diseases has made its crop management important in order to increase the growth and percentage of the extract. Thus, the optimal supply of nitrogen, phosphorus, and potassium should be considered as a part of crop management in this research.

Since the ratio of nutrients absorbed by the plant is important in predicting the amount of nutrients supplied from the soil, two sample groups from two different climates (Fars and Kohgiluyeh and Boyer-Ahmad provinces) were prepared and the concentration and ratio of nitrogen, phosphorus, and potassium were measured. Due to the high concentration of potassium after nitrogen and subsequent phosphorus, the treatments used were based on the evaluation of the potential supply of these elements from the soil in a completely randomized experimental design with three replications including nitrogen (18.4, 20.7 and 23 mg/kg) phosphorous (23 and 34.5 mg (P2O5) /kg) and potassium sulfate (0 and 12.5 mg (K2O) /kg) from Urea, superphosphate and potassium sulfate respectively were applied in greenhouse conditions. After completing the plant growth (opening of 90% of flower buds(, some morphological characteristics, the concentration of nitrogen, phosphorus, and potassium as well as the percentage of plant extract were measured.

The samples from Fars, Kohgiluyeh and Boyer-Ahmad provinces showed that after nitrogen, potassium has the highest concentration. Soil test results showed that except for potassium, the soil suffers from nitrogen and phosphorus deficiency. The highest growth characteristics of the plant were obtained in the application of 20.7 and 23 mg/ kg of nitrogen and phosphorus, respectively, and the application of potassium had no significant effect on these characteristics. The highest percentage of the extract was in the same treatment, but on the other hand, the use of the same treatment with potassium increased the number of flowers.

In this study, it was observed that the highest percentage of the extract was obtained in the treatment of 20.7 and 23 mg/ kg of nitrogen and phosphorus respectively. The addition of potassium could not significantly change this characteristic and, according to the results of the soil test which showed the amount of potassium in the optimal range, was unexpected. On the other hand, compared to the application of 23mg (P2O5) /kg, consumption of 34.5mg(P2O5)/kg caused a sharp decrease in the plant extract. Despite the lack of phosphorus in soil, it indicates sensitivity in consuming this element. It is possible that the increase in phosphorus has caused a decrease in the uptake of micronutrients, especially iron and zinc, and as a result, a decrease in the percentage of the extract in the plant, which requires further study.