Measurement of the critical level of phosphorus due to several economical and biological reasons is of great importance in paddy fields. The present research was done for determining the critical level of phosphorus in the paddy fields cultivated by rice cv. Hashemi using 6 extraction methods including Olsen, Morgan, Soltanpoor, Colwell, Bray and Mehlich 3. In this project, among 100 paddy fields evaluated for their soils, 27 fields were chosen based on the maximum range of variation in their pH, organic matters and extractable phosphorus. In the selected fields we did two fertilizer treatments of 0 and 120 kg of triple super phosphate per hectare, and then the critical level of phosphorus in the extraction having the best correlation with the rice yield was measured via the visual method of Cate-Nelson. By this approach the critical level of phosphorus for Colwell, Olsen, Soltanpoor and Morgan extraction methods were 35, 16, 3 and 4.5 mg/kg, respectively. With respect to the presence of a good relationship between Olsen extraction method and relative rice yield, also owing to the cost- effectiveness and time- saving feature of this technique we strongly recommend this approach as a suitable way to extract the absorbable phosphorus, and the use of the phosphate fertilizers is suggested  in the paddy fields of Guilan province.

In order to study the effect of amounts, methods of application and sources of phosphorus fertilizer on grain yield of wheat as well as Total phosphorus uptake, an experiment was conducted in two cropping years (2007-2009) in Safi-Abad Agr. Res. Cen of Dezful, Iran. The experiment design was a completely randomized block with factorial arrangement with three relplications and 16 treatments. The first factor was at four levels of phosphorus fertilizer consisting of 0, 0.5, 1 and 1.5 times to phosphorus fertilizer recommended on the basis of soil testing, equivalent with 50, 100 and 150 kg phosphorus fertilizer per ha, the second factor consisting of methods of applying phosphorus fertilizer including band and broadcast and mixed with surface soil and third factors consisting of source of phosphorus fertilizer type tripel superphosphate and phosphate diamonium. The results showed that phosphorus different levels and the applying fertilizer type on grain yield, straw yield and 1000-grain weight were significant. The method of fertilizer application on straw yield was significant, only. The highest grain yield (5316 kg ha-1) was due to application of 50 kg phosphorus fertilizer as phosphate diamonium. Method of P application on harvest index was significant, only. The effect of levels of phosphorus fertilizer and method of its application on Total uptake of phosphorus was significant. The effect of experiment treatments on phosphorus utilization efficiency and harvest index of phosphorus was not significant.

Some contaminants associate with soil particles and, thus, their transport and fate in the environment is determined by the soil erosion processes. Eutrophication, low oxygen levels and high nutrient (nitrogen and phosphorus) concentrations in reservoirs, canals and other water courses, is a common water pollution feature. phosphorus (P) is one of the major plant nutrients and also the major nutrients controlling eutrophication of surface water. P load pulsed by heavy rainfall may damage the ecological quality of downstream. The present study was conducted in Kojour Watershed located in Mazandaran province. The results showed that P loss varied from 0.26 gr lit-1 to 1860.64 gr lit-1. It also proved that P concentration could not estimated by flow discharge, while sediment concentration can estimate loss of P with determination coefficient and estimation error of 94% and 23%, respectively. The results could facilitate the application of given methods obtained in the present study to other ungauged watersheds with similar conditions and leading to the suitable soil and water management and planning.

Objective Root structure modification is associated with the efficient water uptake and the nutrient utilization. It also provides structural support for the anchoring in soil. Genetic engineering for the improvement of plant root structure may help to maintain higher yields under drought conditions. The aim of this study was to modify the root structure of rice in order to improve drought tolerance and the efficiency of nutrient uptake. For this purpose, simultaneous transformation of Deeper Rooting1 or OsDRO1 gene, which is involved in the regulation of growth angle of the root in order to adapt to drought conditions, and phosphorus-Starvation Tolerance1 or OsPSTOL1 gene, which is effective in increasing phosphorus uptake and improving root structure, were considered for rice root structure modification. Materials and methods The OsDRO1 and OsPSTOL1 genes derived from the wild rice cultivars were cloned together in a single construct under the control of the root specific and the ubiquitin promoters, respectively. The resulting construct, pUhrDroPstol is transformed into the Agrobacterium tumefactions strain EHA105 and used for the gene transformation into Hashemi cultivar. Putative transgenic plants, survived on 50 mg/L Hygromycin during tissue culture steps, are transplanted into the Yoshida solution and then into the pots until they set seeds. Construct specific and gene specific PCR analysis are used to confirm the transgenic plants. Results In this study, 12 putative transgenic rice events were obtained, of which 10 showed the presence of both OsDRO1 and OsPSTOL1 genes in the PCR analysis. Transgenic plants show stronger root structure compared to the non-transgenic ones. Molecular analysis in the T1 and T2 generations determined the homozygous events. Conclusions In this study, two candidate genes affecting root structure, nutrient uptake and drought tolerance were transferred to the Hashemi rice using genetic engineering. So far, simultaneous transfer of these two candidate genes have not been reported. Transgenic plants present better root system compared to the control plants. The mentioned construct can be used for the transformation of other crops to improve their root structure, nutrient uptake and their drought tolerance. It is hoped that the production of the transgenic rice with modified root structure and efficient phosphorus uptake increases its drought tolerance and reduce water consumption in rice cultivation.

To investigate the effects of water deficit stress and bio and non-bio fertilizers on Thymus Vulgaris, a split plot experiment was conducted based on randomized complete block design with three replications in 2017 in Asgarya agricultural field in Yazd. The treatments included water tension: W1=7 (Control), W2=12 and W3=17 days irrigation intervals as the main factor and bio and non - bio fertilizers at five levels including B1= control (without fertilizer), B2= endo mycorrhiza (Glomus), B3= Azospirillum bacteria, B4= Pseudomonas bacteria and B5= chemical fertilizer (NPK) a sub – factors. Results showed that the highest flowering branches yield, a, b, and Total chlorophylls and nitrogen and phosphorus elements were observed in 17 days of irrigation (W3). 12 days of irrigation treatment (W2) showed the highest potassium element rate. The highest a, b and chlorophylls and nitrogen were observed in Azospirillum treatment (B3). The highest Total chlorophyll, phosphorus element, carotenoids and flavonoids were observed in Pseudomonas treatment (B4); the highest potassium element rate were obtained in mycorrhiza treatment (B2); the highest flowering branches yield were observed in NPK treatment (B5) and control (B1) treatment resulted in the highest anthocyanin

There is critical need for a practical indicator to assess the potential of phosphorus (P) movement from a given site to surface waters, either via surface runoff or subsurface drainage. The Degree of P Saturation (DPS), which relates a measure of P already adsorbed by a soil to its P adsorption capacity, could be a good indicator of that soils P release capacity. For our country soils, there is not any report for DPS calculating. This study aimed to develop techniques of calculating the DPS for calcareous soils of western Azerbayjan, Uremieh Lake sub-watershed, obtaining DPS levels for calcareous soils, and evaluating DPS by use of soluble P as indicator of P runoff potential. For this purpose, 30 surface soil samples with widely P contents were selected and after determining some of general physico-chemical properties, useing of four measures of soil available P and four indices of P sorption capacity, sixteen different forms of DPS were obtained. Significant correlation was obtained between soluble P and different forms of DPS in this study. Threshold P concentration between four extractants, were obtained for Olsen, Mehlich-3, and Soltanpour ones, except in calculations with Mg as P adsorbed contributor in range of 0.4-33 percent, with 8.14 mean, and for FeO extractant, only in calculations with Ca + Mg as adsorbing one was obtained that was equal to 1.3 percent. Degree of P saturation in soils with higher than threshold P concentration values are sustainable to P runoff via surface runoff or leaching, and as a result eutrophication intensification, and for control this phenomenon should apply management practices with regard to different situations of watershed.

Study has shown that the soil available-P content in 71. 8% of the agricultural lands in Iran falls below 15 mg. kg-1. Moreover, excessive use of P-fertilizers in calcareous soils not only increases costs but also leads to P-accumulation and reduced uptake of micronutrients, especially Zinc, to pose serious threats to public health. Generally, only a small percentage (15‒ 20%) of P-fertilizers used each year may be absorbed by plants while the remaining portion precipitates to increase soil Total-P in lands with high pH levels. This process can cause environmental problems in areas close to lakes or those near surface waters used to supply drinking water. These observations warrant the quest for indicators that address both plant requirements and adverse environmental effect. It is worth noting that P is far more easily released in calcareous soils than in acidic ones because the bond between phosphate ions and calcium is by five times weaker than that between phosphate ions and iron or aluminum. It may, therefore, be concluded that application of P fertilizers should be based on local soil analysis and that P fertilizers should be recommended in soils whose available phosphorus concentration is below a critical level. Thus, such appropriate practices as applying P-fertilizers with due consideration of soil analysis results, increasing soil organic matter, and using P solubilizing bio-fertilizers may be recommended in order not only to enhance uptake of soil non-available P but to meet plant requirements, optimize fertilizer consumption, and prevent environmental hazards as well.

Natural pyrite was modified by calcination under nitrogen (N2) atmosphere to produce a novel sorbent for removing phosphorus (P) with low concentration from aqueous solutions. The crystallinity, porous texture, magnetic susceptibility and performance in P removal of pyrite calcinates depended on calcination temperatures. The sorbent obtained at calcination temperature of 500-600 oC possessed the most efficient P removal. Solution pH in the range of 3.0-9.0 and anions of chloridion (Cl-), nitrate (NO3)- and sulfate (SO4 2-) had ignorable effect on P removal. The batch adsorption experiment shows that the maximum sorption capacities for P of this novel sorbent (q m) were up to 1.61-5.36 mg P/g at adsorption temperatures of 15-35 oC. Dynamic sorption and regeneration experiments were conducted in an adsorption column filled with pyrite calcined at 600 °C. The study found that oxygen was an important control factor responsible for P adsorption because the oxidization of Fe2+ to Fe3+ on the surface of the sorbent followed by P being bound to a ferric hydroxide surface film was the crucial processes. The mechanism was confirmed with surface characterization techniques including field emission scanning electron microscope and X-ray photoelectron spectroscopy. This research potentially provides a cheap, abundant sorbent for P removal from the secondary effluent of municipal wastewater treatment plant.