PHOSPHORUS (P) is a macronutrient of high consumption required by plants. Most agricultural soils around the world are poor in PHOSPHORUS and P fertilizers are USEd as a remedy. Not only are the fertilizers low in USE EFFICIENCY but their application has also exacerbated the eutrophication of water bodies and the associated environmental pollution. This is while P fertilizers are extracted from the finite and non-renewable phosphate rock reserves, causing their rising prices over time as more P fertilizers will be needed to produce more food for the growing global population. P fertilizer management is, therefore, a key parameter in agricultural production. This is why a lot of attention has been recently paid to the application of sustained/controlled-release P fertilizers (SRF/CRF) in order to improve upon P USE EFFICIENCY and plant growth at reduced environmental costs. The designation SRF/CRF is due to the lower water solubility of such fertilizers compared to conventional ones so that nutrients are supplied to plant roots over longer periods of time. Unlike SRFs, CRFs are characterized by well-controlled nutrient release rate, pattern, and duration. The methods USEd to manufacture P SRF include: 1) Coating the fertilizer with such materials as: a) polymers (including biodegradable polymers like chitosan, water-superabsorbent polymers, PVDC copolymers, polyolefins, polyurethanes, urea-formaldehyde resins, polyesters, and alkyd resins), b) sulfur, c) sulfur-polymers, d) organic acids, e) paraffin, f) clays, and g) fly ash; 2) Preparing SRFs from materials with a low solubility or a low mineralization rate; 3) Conversion of phosphate rock into P SRF using such different methods as partial acidification and phosphate solubilizing microorganisms; 4) Manufacturing P SRFs via nanotechnology-based techniques; 5) Producing P SRFs using phosphateloaded layered double hydroxides, biochar, and hydrsochar; and 6) Using fly ash to manufacture SRF. The present article examines these methods and the effects of each on P USE EFFICIENCY and the growth of different plants. It is generally concluded that P SRFs or CRFs improve P USE EFFICIENCY and plant growth.

Saffron (Crocus sativus L.) is an annual plant from a biological aspect, but it has a perennial cycle in the field conditions. Cytological impairments such as triploid and self- incompatibility mechanisms are considered as the most important reasons for male- sterility in saffron. Therefore, saffron reproduction is made by meristems tissues and establishment of new daughter corms which are produced by the mother corms. During the growing season, mother corms deteriorate gradually with increasing daughter corms growth. Each daughter corm is considered as a mother corm for replanting in the next growing season. Duo to the life cycle of saffron as a perennial plant in the field conditions, the gradual deterioration of mother corms during the growing season and also the remobilization of nitrogen and PHOSPHORUS from aerial part to daughter corms at the end of each growing season, the study of acquisition and USE EFFICIENCY of nitrogen and PHOSPHORUS in saffron is more complicated than other annual or biannual plants. Firstly, the objective of this review article is to describe the nitrogen and PHOSPHORUS concentration in aerial parts and daughter corms in saffron. In addition, relevant literaturerelated to the most important strategies for improving nitrogen and PHOSPHORUS USE EFFICIENCY is reviewed. Secondly, the relationship between nitrogen and PHOSPHORUS USE EFFICIENCY in saffron isdiscussed.

In order to evaluate the effect of increasing soil soluble PHOSPHORUS (P) and its effect on nitrogen (N) and P uptake, P uptake EFFICIENCY and P harvest index of black seed (Nigella sativa L.) in a calcareous soil; a field experiment was conducted as factorial layout based on a randomized complete block design with three replications at Research Station, Faculty of Agriculture, Ferdowsi University of Mashhad, Iran, in year 2013. The experimental treatments were all combination of soil amendment in four levels (vermicimpost (V) + Tiobacilus (T), Sulfur (S) + T, V+S+T and control) and three levels of PHOSPHORUS (0, 30 and 60 kg.ha-1). Results showed that S+T and V+S+T had significant effects on reducing soil pH (by 0.94 and 0.61 units, respectively). The resources of soil amendment (V+T, S+T and S+V+T) significantly increased the P uptake by plant and P harvest index of black seed. A significant positive correlation was observed between P and N concentration of plant. However, there was a significant negative correlation between grain yield and P uptake EFFICIENCY of black seed.

A factorial completely randomized block design experiment with 3 replications was carried out in the greenhoUSE to evaluate cereals genotypic variation in PHOSPHORUS acquisition and utilization during 2006. Treatments consisted of 8 bread wheat (Triticum aestivum L.), 3 durum wheat (Triticum durum L.), 3 barley (Hordeum vulgare L.), 1 rye (Secale cereale L.), 1 oat (Avena sativa L.) and 1 Triticale (X Triticosecale L.), and two levels of P (0 and 84 mg P/kg soil). Genotypes showed significant differences in number of tillers, shoot P concentration and content, and dry weight. Also, P EFFICIENCY (taken as the relative above-ground yield) significantly differed among genotypes and ranged from 0.42 for a barley line (M-80-16) to 0.97 for bread wheat cultivar (Azadi) with the average of 0.71. Application of P significantly increased shoot P concentration and content from 0.19% and 13.24 mg P/pot to 0.47% and 46 mg mg P/pot, respectively. In treatment P0, durum wheat (Yavaroos) with 20.15 mg P/pot and a barley line (M-80-16) with 5.85 mg P/pot had the highest and lowest P uptake, respectively. Oat produced the highest dry weight per unit of P uptake and, hence, was considered to be very efficient in P utilization. Azadi and Yavaroos with 0.45 and 0.43 had the highest relative P uptake, respectively. Therefore, these varieties were efficient in P acquisition. There was no correlation between P EFFICIENCY and shoot P concentration of genotypes, but the relationship between P EFFICIENCY and shoot P content was highly significant (r=0.66**).

Sugarcane cultivation has been revived in Khuzestan province of Iran since the 1960s and due to good results, gradually began to grow from north to south of this region. Currently, sugarcane is cultivated in more than 100, 000 hectares of the province's land and almost 25% of the country’ s demand for sugar is produced in this region. Regarding the very low rainfall and water resources reduction of the country in recent years, the optimal USE of irrigation water is very important. Sugarcane fields in Iran due to irrigation problems such as distribution and consumption management, and the lack of continuous and uniform water supply, have high water USE per hectare. In other words, the irrigation water USE of farms is twice to three times of the real water need of sugarcane. Irrigation water USE EFFICIENCY or WUE, which can be calculated from the ratio of plant dry matter to water consumption per hectare (Anyia and Herzog, 2004), is a very important criterion that can be of USE in evaluating and improving irrigation operations and optimal water consumption. The water USE EFFICIENCY of sugarcane depends on various factors such as climate, soil characteristics, irrigation management, cane cultivar and plant growth stage. Irrigation water quality, climate change, weeds and soil characteristics (high pH and low organic matter, for example) are the main factors that affect production of sugarcane in Iran. Therefore, the yield of the sugarcane is also far from the potential yield. Sugarcane fields of Khuzestan province are mainly rich in lime percentage and poor in organic matter and PHOSPHORUS. Soil pH in this region of the country is also about 8-8. 5 and uptake of some elements such as PHOSPHORUS, by plants and PHOSPHORUS fertilizer EFFICIENCY in these soils (alkaline and calcareous soils) are expected to be low (Wang and Wang, 1995). The optimum USE of PHOSPHORUS fertilizer and water irrigation are essential for the quantitative and qualitative function of sugarcane plants. Due to the very low mobility of PHOSPHORUS in soil, its uptake by plants such as sugarcane is affected by the number of soil and plant factors (especially plant root characteristics). Changes in these factors can lead to reduction or increase of P uptake by the crop. BecaUSE of the role of organic compounds in improvement of mobility and PHOSPHORUS uptake, the USE of organic maters has been considered in several researches. Organic compounds can play a direct and indirect role in plant factors and in phosphorous uptake improvement, yield increase and finally water USE EFFICIENCY improvement

Soil and water salinity is one of the most important problems of agriculture in Iran. Application of chemical fertilizers, particularly PHOSPHORUS (P) fertilizers, may lead to improve the yield quality and quantity. The effects of salinity and P on growth, chemical composition and water USE EFFICIENCY (WUE) of canola (Brassica napus L.) were investigated. The experimental treatments were five saline water levels [non-saline water (EC= 0.3 dS/m), 3, 6, 9, and 12 dS/m] and four applied PHOSPHORUS rates (0, 20, 40, and 80 mg/kg soil as KH2PO4). This experiment was factorially arranged in a randomized complete block design with three replicates. The results indicated that the dry matter and grain yields of canola were decreased significantly by increasing salinity levels. Application of 20 and 40 mg P/kg soil increased grain end dry matter yield, respectively. The applied saline water increased Cl, Na, B, and P concentrations and decreased Ca, K and N in plant. On the other hand, application of P decreased Cl concentration of plant significantly. The water USE EFFICIENCY, at first, was increased and then decreased by increasing salinity levels. Application of PHOSPHORUS in high levels resulted in decreasing WUE.

Plant species differ in their ability to grow at low available P soils in other words, plant species differ in P USE EFFICIENCY at low P supply. This ability can be investigated by comparing P uptake EFFICIENCY of plants and relative effective factors. A pot experiment was carried out in the growth chamber and sugar beet, maize and groundnut were grown in a low available P soil in a completely randomized design with three P fertilizer levels of low, medium and high. Three harvests were performed at two different growth periods. The results showed that at low P supply, sugar beet was the most efficient plant among three species as it showed the highest relative yield. The higher P USE EFFICIENCY of sugar beet was due to a higher P uptake EFFICIENCY. PHOSPHORUS uptake for sugar beet was 29 mg P plant-1 while those for maize and groundnut were 19 and 0.8 mg P plant-1, respectively. The main reason for higher P uptake EFFICIENCY of sugar beet was its higher P influx as compared to maize and groundnut. Under low P supply during the first growing period, P influx of sugar beet was higher than that of maize and groundnut by factor 4 and 22, respectively. Finally, the higher P USE EFFICIENCY of sugar beet was due to a higher P uptake EFFICIENCY which in turn was due to a high P influx.

In order to determine the EFFICIENCY of different safflower (Carthamus tinctorius L. ) cultivars in terms of their uptake and response to PHOSPHORUS fertilizer application, a 2-year (2016-2018) experiment was conducted in a randomized complete block design as 2 x 5 factorial with three replications at the Arak Agricultural Research Center Station. Treatments included two cultivars of Sina and Padideh and five levels of PHOSPHORUS (0, 25, 50, 75 and 100 kg. ha-1 ) as triple superphosphate. The results of analysis of variance showed that grain yield, number of bolls, 1000-seed weight, PHOSPHORUS, nitrogen, and potassium uptake, and total PHOSPHORUS yield were affected by the effect of cultivar and PHOSPHORUS levels. Apart from the total dry matter weight and PHOSPHORUS concentration, other studied characteristics were affected by the year. Plant height and nitrogen concentration were affected only by cultivar, while total dry matter weight and PHOSPHORUS concentration were affected by PHOSPHORUS levels. Comparison of the mean effect of PHOSPHORUS levels on grain yield showed that the maximum grain yield in both cultivars was obtained in treatment of 25 kg P/ha. In terms of total PHOSPHORUS EFFICIENCY, the level of 50 and in terms of PHOSPHORUS grain uptake EFFICIENCY and PHOSPHORUS-stress factor the level of 25 kg P/ha were optimal. PHOSPHORUS EFFICIENCY indices did not differ significantly between the two cultivars, but Sina cultivar showed higher PHOSPHORUS uptake than Padideh.

In order to determine the EFFICIENCY of different safflower (Carthamus tinctorius L. ) cultivars in terms of their uptake and response to PHOSPHORUS fertilizer application, a 2-year (2016-2018) experiment was conducted in a randomized complete block design as 2 x 5 factorial with three replications at the Arak Agricultural Research Center Station. Treatments included two cultivars of Sina and Padideh and five levels of PHOSPHORUS (0, 25, 50, 75 and 100 kg. ha-1) as triple superphosphate. The results of analysis of variance showed that grain yield, number of bolls, 1000-seed weight, PHOSPHORUS, nitrogen, and potassium uptake, and total PHOSPHORUS yield were affected by the effect of cultivar and PHOSPHORUS levels. Apart from the total dry matter weight and PHOSPHORUS concentration, other studied characteristics were affected by the year. Plant height and nitrogen concentration were affected only by cultivar, while total dry matter weight and PHOSPHORUS concentration were affected by PHOSPHORUS levels. Comparison of the mean effect of PHOSPHORUS levels on grain yield showed that the maximum grain yield in both cultivars was obtained in treatment of 25 kg P/ha. In terms of total PHOSPHORUS EFFICIENCY, the level of 50 and in terms of PHOSPHORUS grain uptake EFFICIENCY and PHOSPHORUS-stress factor the level of 25 kg P/ha were optimal. PHOSPHORUS EFFICIENCY indices did not differ significantly between the two cultivars, but Sina cultivar showed higher PHOSPHORUS uptake than Padideh.