81 Annales Universitatis Paedagogicae Cracoviensis Studia Naturae, 2: 81–96, 2017, ISSN 2543-8832 DOI: 10.24917/25438832.2.6 Hamid Dorosti,1 Katarzyna Możdżeń,2 Peiman Zandi3*, Morteza Siavoshi4 1Rice Research Institute of Iran (RRII), P.O. Box 1658, Rasht, Iran 2Department of Plant Physiology, Pedagogical University of Kraków, Podchorążych 2, 30-084 Kraków, Poland 3Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, P.O. Box 10081 Beijing, P. R. China; *z_rice_b@yahoo.com 4Assistant Professor, Department of Agricultural Sciences, Payame Noor University, I.R. of Iran The influence of foliar “feeding” of urea on yield and its components of Iranian hybrid rice Oryza sativa L. ‘Bahar 1’ Introduction Rice (Oryza sativa L.) has become a highly strategic and priority crop in approxi- mately half of the global population with regard to procuring energy, proteins, and vitamins (IRRI, 2008). It is mainly cultivated in Asian countries under a hot humid climate in both tropical and temperate regions. Rice is regarded as the major source of food in Iran (population 77 million; 46 kg per capita/year), with an average annual domestic production of 2.35 million tons of paddy rice grown on 539.000 hectares and an annual consumption of 3.5 million tons (Ahmadi et al., 2014). It is projected that Iran needs to produce 5 million tons of rice by 2035 to achieve self-su�ciency (Akhgari, 2010). �e recent rice crisis proves again that a sustainable increase in rice production is crucial for food security in the rice-growing countries of Asia (IRRI, 2008). Hybrid rice technology is a key strategy for increasing rice production and maintaining self-su�ciency and food security (Dorosti, 2009). �ese rice varieties give about 15–25% more yield than improved inbred rice in farmers’ �elds (Xie, Har- dy, 2009). Its potential for enhancing rice production and productivity has motivated many countries, like Iran, to exploit this technology. �e hybrid rice program in Iran was launched at the Rice Research Institute of Rasht at the beginning of 1987 through establishing a collaborative project together with the International Rice Research In- stitute (IRRI, 2008), Philippines, as the major factor contributing to the remarkable success of hybrid rice technology in Iran (Dorosti, 2009). Providing e�cient quantities of nutrients needed by plants, in particular the es- sential elements, is one of the most important factors of crop management (Youse- H am id D or os ti, K at ar zy na M oż dż eń , P ei m an Z an di , M or te za S ia vo sh i 82 �, Zandi, 2012). Crop production can be increased through application of fertilisers containing these elements (Shen et al., 2013). Increasing the concentration of essential elements in plants assigns an important role in improving the quality of food products and improves the health of society (Tavakoli et al., 2014). Dwindling water resources, intermittent droughts, low fertility of agricultural lands, the lack of available nutrients, and their low accessibility to the organic resources are among barriers to accessing proper operation in the �eld of agriculture (Shirani Rad, Zandi, 2014). Fageria (2013) reported that nitrogen is one of the essential elements required for plant growth. Crop plants assimilate nutrients not only through their leaves but as well as the other shoot- ing parts, like young panicles, stems, and �owers. Fresh and swi�ly expanding leaves are more streamlined in absorption of foliar-sprayed nutrients from their upper/ low- er surfaces than those of fully matured ones (Mondal, Al-Mamun, 2011). Nitrogen contributes to grain �lling through elevating this element content in leaves and to sink size through increasing the hull size and mitigating the number of degenerated spikelets (Singh et al., 2014). Liu et al. (2014) declared that consuming nitrogen fertiliser in a proper time sequence helps to eliminate excessive use of it. Due to the high solubility of nitrogen fertilisers, proper timing of nitrogen application is assumed to be very pivotal in better e�ciency of nitrogen use and less loss of this element to the environment (Fageria, 2013). In their study on Aman rice, Bhuyan et al. (2012) demonstrated that foliar application of N fertiliser in a bed planting method increased yield attributes, such as grain yield, the number of panicles per square me- ter, the number of grains per panicle, 1000-grain weight, and water use e�ciency for biomass and grain production much more than the conventional methods. Singh et al. (2014) suggested that foliar feeding of rice by inputting higher doses of nitrogen fertil- iser enhanced the growth dynamic, biomass partitioning, and cha�y grain. However, in their study, nitrogen use e�ciency remained una�ected. Furthermore, the yield of rice and components were found to have less attribution to foliar application of urea fertilisation (Hasanuzzaman et al., 2009). �e highest crop in canola was recorded by foliar spraying of nitrogen at the stem elongation or right before the �owering stage (Tousikehal et al., 2011). Azarpour et al. (2011), in their study on rice crops, reported a consecutive enhancement in yield as a result of adding nitrogen to the soil. Although foliar spraying during mead-season had a positive e�ect on the grain yield of rice crop (Brown, Petrie, 2006; Asadi et al., 2014), the same result in grain protein was noticed exclusively when spraying was done at active tillering and booting stages (Asadi et al., 2015). In recent decades, agricultural products have mostly relied on the utilisation of chemical inputs, which in itself has detrimental e�ects on the environment (Zandi, Basu, 2016). Comparatively, the soil application of nitrogenous fertiliser does not appear to be a better method, because it causes the plants to absorb the nutrients 83 much slower, and large quantities will be required for normal growth in contrast to the smaller ones of the same generally required for foliar application (Mondal, Al-Ma- mun, 2011). In particular, the e�ectiveness of foliar feeding is augmented when the canopy microclimate is occupied by high levels of leaf sources (Akhgari, 2010). Due to the limited or inconclusive information on the e�ciency of the foliar application of urea fertiliser on yield attributes and the yield of hybrid rice grown under moderate conditions, it was decided to conduct this research. �e aim of the study was to examine the in�uence of foliar application of urea fer- tiliser at active tillering and booting stages on the yield of hybrid rice O. sativa ‘Bahar 1’ and �nding out the optimum concentration of urea fertilisation for the maximum yield of rice under moderate climatic conditions. It was hypothesised that di�erent concentrations of foliar application of urea fertiliser would receive more palatable ni- trogen fertiliser use e�ciency than conventional fertilising method. Materials and methods �e �eld experiment was conducted in Talesh County, Guilan-Iran in 2014, at latitude 48°37ʹN and longitude 54°48ʹE, with 45 m of altitude. �e climate, according to Köep- pen classi�cation, is Mediterranean with mild winters and warm-humid summers. Most precipitation occurs in late summer and early spring. Soil pH was determined using glass electrode in a 1: 2.5 soil/water suspension. Available phosphorus (P) in the soil samples was computed by leaching the soil with 0.002 N sulfuric acid (1 soil: 200 H2SO4 suspension, w/v) and agitating it for at least half an hour and �ltering it through Whatman �lter paper No. 42. Available P in the extract was determined spectropho- tometrically at the wavelength 690 nm (Ravikumar, Somashekar, 2013). Leaching the soil sample with 1N ammonium acetate at pH 7.0 (w/v), keeping it for overnight, �ltering it through Whatman �lter paper No. 42, and brining the volume up to 100 ml with distilled water, the exchangeable K+ in soil could be extracted a�er the method followed by Britzke et al. (2012). �e �ltrate (sample) containing K was then used for the �ame photometric determination of potassium. �e soil analysis showed that the texture of the experimental site (0–25 cm) was silty clay with 0.71 dS m-1 EC; 6.6 pH (H2O); 2.21% organic matter; 20.1 mg kg -1 available phosphorus; 127 mg kg-1 ex- changeable potassium, and 0.238% total nitrogen. �e experiment was laid out in a two-factor randomised complete block design (RCBD) with three nitrogen treatments (N0, N10, N20 kg N ha -1) and two application times (at tillering and booting stages), and it was replicated three times. Each plot was 3×4 m in size. Urea fertiliser (CO(NH2)2), as the best source of actual nitrogen (46% N) for aerial application (Norton, 2011), was considered for foliar spraying (Control or no N fertilisation, 10 kg N ha-1 ≈ 22 kg urea ha-1, 20 kg N ha-1 ≈ 44 kg urea ha-1) The influence of foliar “feeding” of urea on yield and its com ponents of Iranian hybrid rice O ryza sativa L. ‘B ahar 1’ H am id D or os ti, K at ar zy na M oż dż eń , P ei m an Z an di , M or te za S ia vo sh i 84 using a single-nozzle hand sprayer. �e urea spray volumes were prepared by mixing 5 kg of urea in 100 L of water (i.e. 5% urea solution) as per treatment (Asadi et al., 2014). �e plots were sprayed during late a�ernoon hours when the wind speed was less than 12 km hr−1. �e hybrid rice variety of ‘Bahar 1’ was used that was bred through combining a cytoplasmic male sterile line and a restorer line (IR58025A / IR42686R) (Dorosti, 2009). Fertiliser recommendations for experimental plots were based on soil surveys. Basal fertilisers of nitrogen (50 kg N ha-1), triple superphosphate (160 kg TSP ha-1), and potassium chloride (50 kg KCl ha-1) were applied right before transplanting. An additional amount of potassium chloride (50 kg KCl ha-1) was applied at the max- imum tillering stage. Crop cultivation was carried out on April 14th, and when the seedlings height was about 25 cm in early May (on May 5th), they were transferred (three seedlings per hill and 25×25 cm spacing) to the main �eld of transplantation. Weeds (Butachlor 4 L ha-1) and pests (Diazinon 5% granule) were controlled by adopting conventional methods of the region. All records were taken during the plant growth. At maturity, a�er eliminating the marginal lines on both sides of each plot, all plants in the harvest area (6 m2) were selected and cut at above ground level. �e crop was harvested at a grain moisture content of about 20–25% wet basis. Grain yield was calculated as kg ha-1 at 14% moisture content. �e rice panicles in the �nal-harvest- ing area were counted, and their average was reported as the number of panicles per square meter. �e number of grains per panicle was computed from the randomly selected plants in each plot. For the same samples, twenty panicles from each plot were randomly chosen. �e main panicle fertility percentage was measured based on the grain number in the main panicle and the number of sterile (non-fertile) �owers. �e �lled/fertile grains were then randomly selected from the grain samples correspond- ing to each plot and the mean weight of 10 replications of 100 grains multiplied by 10 reported as 1000-grain weight (g). �e experimental data were subjected to statistical veri�cation with Fishers anal- ysis of variance (ANOVA) using the SAS 9.1 statistical so�ware package. Means were separated based on multiple range test of Duncan (MSRT) at a 0.05 probability level. Bar graphs were depicted using Excel (Microso�, Redmond, WA, United States). Correlation coe�cients of Pearson were calculated on the traits studied for the correlation analysis. �e R package ‘Corrgram’ was employed to display the cor- relations between the selected traits by using a ‘correlogram’ (Asters et al., 2014). A correlogram was a direct visual display of the matrix of Pearson coe�cients that were estimated from the experimental data. By this method, correlations between traits were displayed by grouping traits that have similar characteristics, and the values and signs of the correlations were visualised schematically in numbers and 85 Tab. 1. Plant parameters of Iranian hybrid rice Oryza sativa L. ‘Bahar 1’ as a�ected by foliar spraying of nitrogen fertiliser and timing of application Mean Square df Source of variation Grain yield (kg ha-1) Panicle number per unit area Grain number per panicle Panicle fertility rate [%] 1000 grain weight [g] 202632.62 ns31.26 ns222.94 ns7.03 ns0.03 ns2R 5126514.14**9151.98**1999.83**364.38**0.26 ns2A 10076519.95**16642.17**3957.53**671.36**0.15 ns1linear A 176562.32 ns1661.78**42.13 ns57.39*0.36 ns1quadratic A 1256327.58*421.16 ns23.36 ns45.6*0.04 ns2B 2266943.83*650.4 ns11.20 ns47.46*0.07 ns1linear B 245711.34 ns191.91 ns35.52 ns11.74 ns0.001 ns1quadratic B 84789.78 ns24.80 ns24.77 ns7.32 ns0.16 ns4A×B 320634.79128.83136.2111.930.1716error 9.594.596.885.191.94-CV [%] Experimental MeansTreatments c 5101.10c 211.30c 154.01a 73.70a 21.26A1Foliar application at till- ering (A) kg ha-1 b 6020.90b 258.35b 171.49b 64.50a 21.10A2 a 6597.60a 272.11a 183.67b 41.67a 21.44A3 b 5484.20b 293.36a 169.74b 63.99a 21.34B1Foliar application at booting (B) kg ha-1 ab 6041.00a 251.02a 168.01a 67.47a 21.26B2 a 6194.00a 251.38a 171.32a 68.19a 21.21B3 Notes: * – p < 0.05, ** – p < 0.01, ns – p > 0.05; df – degrees of freedom, R – replication, A – tillering e�ect, B – booting e�ect; A×B – represent interaction terms between the treatment factors; CV [%] – coe�cient of variation, means in each column, down-parts of table 1, followed by the di�erent letters are signi�cant- ly di�erent (p < 0.05) according to Duncan test; A1, B1: Control or no N fertilisation, A2, B2: 10 kg N ha-1 ≈ 22 kg urea ha-1, A3, B3: 20 kg N ha-1 ≈ 44 kg urea ha-1 The influence of foliar “feeding” of urea on yield and its com ponents of Iranian hybrid rice O ryza sativa L. ‘B ahar 1’ colour-coded pie graphs. �e pie graphs were �lled in proportion to the Pearson coe�cient values, counter clockwise for negative correlations (in red) and clockwise or positive correlations (in blue). Results and Discussion Panicle number per unit area In this study, the number of panicles per unit area, being the most important com- ponents of grain yield, was strongly in�uenced by the time of fertilising, in a way that the foliar spraying of urea fertiliser at the tillering stage showed a highly signif- icant e�ect (p < 0.01), while it le� no e�ect at the booting stage (Tab. 1). �e result would likely re�ect the superior impact of urea fertiliser at the time of tillering in improving the number of reproductive units per unit area. Generally, the number of H am id D or os ti, K at ar zy na M oż dż eń , P ei m an Z an di , M or te za S ia vo sh i 86 productive panicles per plant is determined during the reproductive phase (Singh et al., 2014). �is indicates the hypothesis that most of the nitrogen foliar-sprayed at booting was utilised for improving the fertility rate of panicles rather than their quantity (Dorosti, 2009). �e interaction e�ect of foliar feeding of urea at di�erent stages of tillering and booting was found to be non-signi�cant on the number of panicles. A comparison of means associated with the tillering stage showed that, by gradual increasing of urea fertiliser application, the number of panicles per unit area increased as well. �e high- est (272.1) and the lowest (211.3) number of panicles belonged to those of plots en- riched with 20 and 0 kg of N per hectare (Fig. 1, Tab. 1). It is suggesting that the plant behaviour is completely proportional to the amount of urea being applied at tillering, and that the relationship between the number of panicles per unit area and the rate of urea fertiliser is slightly of a quadratic equation. In other words, nitrogen application up to level of 10 kg ha-1 drastically enhanced the number of panicles by 22%, and any further application contributed to only a 5% increase in panicle number, indicating that an extra N input was utilised for other processes (Liu et al., 2016). In support to our �ndings, Kazemeini and Ghadiri (2005), Peng et al. (2010) and more recently Cao et al., (2013) documented a noticeable decrease in photosynthetic N use e�ciency under an elevated use of N fertiliser. Fig. 1. In�uence of foliar applied N fertiliser (0 kg N ha-1, 10 kg N ha-1 ≈ 22 kg urea ha -1, 20 kg N ha-1 ≈ 44 kg urea ha-1) on panicle number per square meter; urea was applied in solution with 5% dry matter basis; Signi�cant di�erences between the treatments in tillering and booting stages are indicated with asterisks (* – p < 0.05, ** – p < 0.01, ns – p > 0.05, Duncan multiple range test); �e error bars denote the standard deviation (± SD) of the mean value; n = 6 87 Grain number per panicle Foliar spraying of urea in the tillering stage signi�cantly (p < 0.01) and linearly a�ected the number of grains generated in each panicle, while it had no e�ect on this trait dur- ing the booting stage. In other words, the number of grains in panicles of those plants receiving foliar spray of N, by the booting stage, did not di�er signi�cantly from that of untreated check plants, suggesting that the N fertiliser was exploited for other pro- cesses, such as improving panicles quality. �e number of grains per panicle is mainly associated with the factors in�uencing the growth parameters right before the initi- ation of pollination process. Accordingly, any defect in these requisite factors could likely reduce the grain number per panicle (Dorosti, 2009). �us, the availability of nitrogen through foliar spraying of urea prior to the formation of panicle could be the main reason for its e�ectiveness in increasing the grain number per panicle. A com- parison of mean values shows that the highest number of grains per panicle (183.6) was achieved by the application of 20 kg N ha-1 at the tillering stage, followed by 10 kg N ha-1, and the lowest value (154) was recorded in the untreated (non-sprayed) check plants (Fig. 2, Tab. 1). Liu et al. (2016), in their study on yield of lowland rice receiving N fertilisation treatment, concluded that the increase in the number of grains per pan- icle was in extremely close association with nitrogen application rate under constant submerged condition. The influence of foliar “feeding” of urea on yield and its com ponents of Iranian hybrid rice O ryza sativa L. ‘B ahar 1’ Fig. 2. In�uence of foliar applied N fertiliser (0 kg N ha-1, 10 kg N ha-1 ≈ 22 kg urea ha-1, 20 kg N ha-1 ≈ 44 kg urea ha-1) on grain number per panicle; urea was applied in solution with 5% dry matter basis; Signi�cant di�erences between the treatments in tillering and booting stages are indicated with asterisks (* – p < 0.05, ** – p < 0.01, ns – p > 0.05, Duncan multiple range test); �e error bars denote the standard deviation (± SD) of the mean value ; n = 6 H am id D or os ti, K at ar zy na M oż dż eń , P ei m an Z an di , M or te za S ia vo sh i 88 Panicle fertility rate �e data shows that the panicle fertility percentage (seed setting) was signi�cantly di�erent according to the timing of urea spraying (Fig. 3). A comparison of means regarding the levels of nitrogen fertiliser at the active tillering stage shows that the number of �lled grains in the panicles decreased by increasing the amount of urea fertiliser. �e maximum value of fertile panicles were recorded in untreated check plants (73.7), followed by 10 kg N ha-1 (64.5), which was on par with 20 kg N ha-1 (61.47) (Tab. 1). A notable reduction in the fertility percent of panicles was observed in return for enhanced N application in the tillering stage, which might be due to an increased number of infertile (or non-productive) tillers and panicles per unit area (Akhgari, 2010). Srividya et al. (2010) pointed out that an excess application of N input could increase the number of cha�y (un�lled) grains or sterile spikelets in a rela- tively high responsive manner to N fertilisation in comparison with optimum N dose. Urea spraying at the booting stage also had a signi�cant e�ect on the percentage of fer- tile panicles (p < 0.05). �e number of �lled grains in the panicles was increased in line with the increased level of urea fertiliser. Urea application that augment plant nitrogen before heading (at booting stage) can be highly e�ective in giving rise to the number of �lled grains and/ or spikelets (Kamiji et al., 2011). Fertiliser levels of 10 and 20 kg N ha-1, being on par with each other, was better than no spraying and revealed the ap- propriate timing for N application at this stage. Interaction between foliar feeding of N and developmental stages of tillering and booting was found to be non-signi�cant. Mingotte et al. (2013) believed that, if the N fertiliser supplementation is applied in the period that the spikelets initiated di�erentiation in the panicle, the plant itself does not encounter any problem regarding N de�ciency, especially when initiating �ower pri- mordia, and hence it will produce more �lled grains. Singh et al. (2014) demonstrated that the number of un�lled (sterile spikelets) rice panicles could be multiplied with the excess application of nitrogen as compared with the optimum N level. Indeed, a further increase in N levels decreases the physiological nitrogen-use e�ciency by reducing the nitrogen content in leaves to be remobilized during grain feeling (Cao et al., 2013; Kant et al., 2011). �ousand grain weight �ousand grain weight (TGW) is a complex quantitative genetic trait for rice and is one of the three key factors that in�uence the grain yield (Wei et al., 2014). �e grain weight is a highly stable varietal character (Fageria et al., 2011) that is determined during the ripening phase. �ere was no in�uence of urea fertilisation on TGW (p > 0.05) at both the growth stages (tillering and booting). Under urea fertiliser treatment, TGW varied from 21.1 to 21.44 g (tillering stage; average value of 21.3 g) and from 20.26 to 21.34 g (booting stage; average value of 21 g) (Tab. 1). Fageria et al. (2011) re- 89 ported TGW of lowland rice genotype ‘BRSGO Guar’ varied from 21.1 to 24.6 g, with an average value of 23.0 g. Similar results were also documented in those of previous studies that reported the lack of in�uence of soil (Azarpour et al., 2011) and foliar (Asadi et al., 2011, 2014) application of nitrogen on TGW between the genotypes test- ed. Sarwa et al. (2011) also stated that thousand-grain weight depends on the genetic constitution and is less a�ected by growing conditions. �e natural conditions and environment are believed to have more interference in determining grain quantity (seed size) rather than inherent factors (Wei et al., 2014). Grain yield In the present study, the grain yield was signi�cantly and linearly a�ected by various foliar N fertiliser levels at both the tillering (p < 0.01) and booting (p < 0.05) stages, while no interactive e�ect was noticed among the di�erent combination treatments (Fig. 4, Tab. 1). �e di�erences in the grain yield were largely because of variations in the yield components, including the number of grains per panicle, the number of panicles per unit area, panicle fertility percent, and thousand-grain weight (Hasanuz- zaman et al., 2009). �e comparison of means at the tillering stage revealed that the grain yield was increased by applying the amount of N fertiliser from 0 to 20 kg ha-1. �e treatment 20 kg N ha-1 resulted in the highest rice grain yield (6597 kg ha-1), which was followed by 10 kg N ha-1 (6020 kg ha-1). �is dose was found to be superior to 10 kg N ha-1 treatment and control. �e lowest grain yield was observed in untreat- The influence of foliar “feeding” of urea on yield and its com ponents of Iranian hybrid rice O ryza sativa L. ‘B ahar 1’ Fig. 3. In�uence of foliar applied N fertiliser (0 kg N ha-1, 10 kg N ha-1 ≈ 22 kg urea ha-1, 20 kg N ha-1 ≈ 44 kg urea ha-1) on panicle fertility percentage; urea was applied in solution with 5% dry matter basis; Significant di�erences between the treatments in tillering and booting stages are indicated with asterisks (* – p < 0.05, ** – p < 0.01, ns – p > 0.05, Duncan multiple range test); �e error bars denote the standard deviation (± SD) of the mean value ; n = 6 H am id D or os ti, K at ar zy na M oż dż eń , P ei m an Z an di , M or te za S ia vo sh i 90 ed/ unsprayed check plants. �e linear increase in grain yield with increasing foliar N fertiliser rates may be associated with more grain, panicle, and/or tiller number produced per plant (Tab. 1). Furthermore, the positive and signi�cant relationship between the grain yield and the number of panicles per unit land area at harvest time (Xu et al., 2015) might be an indicative of this result. �ere was a signi�cant and linear increase in grain yield with increasing N rates with urea in the booting stage. In other words, grain yield was signi�cantly improved in a linear fashion when N rates increased from 0 to 20 kg ha-1 by urea fertilisation. Maximum grain yield was achieved at 20 kg N ha-1 (6194 kg ha-1), which was on par with 10 kg N ha-1 treatment (6041 kg ha-1). �e increase in grain yield may be attributed to the high fertility percentage of panicles in return for increasing N rates during the booting stage. Mingotte et al. (2013), working with nitrogen topdressing, obtained the highest rice yield when foliar N application was made before the crop was headed (panicle di�erentiation). Our results are consistent with recently released investigations in terms of the existence of a noticeable increase in grain yield a�er foliar spraying of N fertiliser in maximum tillering (Asadi et al., 2011, 2014) and booting stages (Asadi et al., 2014, 2015). Correlations between the examined traits To determine if there were associations between all the tested traits, correlation analysis was performed on mean values derived out of ANOVA analysis, and the Fig. 4. Influence of foliar applied N fertiliser (0 kg N ha-1, 10 kg N ha-1 ≈ 22 kg urea ha-1, 20 kg N ha-1 ≈ 44 kg urea ha-1) on grain yield as kg ha-1; urea was applied in solution with 5% dry matter basis; Significant differences between the treatments in tillering and booting stages are indicated with asterisks (* – p < 0.05, ** – p < 0.01, ns – p > 0.05, Duncan multiple range test); The error bars denote (± SD); n = 6 91 correlation matrices were visualised schematically by using R package ‘Corrgram’ (Fig. 5). Correlations displayed in a correlogram were organised in the order that traits having similar characteristics were grouped together. �e colour-coded pie graphs were re�ected in the upper triangle, and the values and signs of the Pear- son coe�cients were represented schematically with the correlation coe�cients and the 95% con�dence intervals displayed in the lower triangle. Yield related traits, i.e. grain yield (GY), and grain number per panicle (GN.P) were found positively correlat- ed to each other with a coe�cient being at least 0.9 (p < 0.05). GN.P were also noticed to be correlated to panicle number per square meter (PN.SM; r: 0.72; p > 0.05) and thousand grain weight (TGW; r: 0.39; p > 0.05), and negatively correlated with panicle fertility rate (PFR; r: -0.88; p < 0.05). No signi�cant association was recorded for TGW. As per correlation coe�cients results associated with PFR, our study showed a close/ direct association between the number of cha�y grains and GN.P, which suggested that the mitigation of grain number per panicle is likely involved in enhancement of fertility rate. Conclusions Nitrogen is believed to be the most constraining factor on crop production in many of the world’s agricultural regions, and its e�cacious adoption is indispensable for the frugal sustainability of cropping systems. Moreover, the dynamic nature of this el- ement and its inherent tendency for loss from soil-plant systems creates a challenging and peerless space for its optimal management. Foliar fertilisation technique may also be a good alternative to the convectional soil application to avoid the risk of �xation or leaching of nutrients. �ese results clearly showed that foliar-applied urea at active tillering could have a better performance once applied at higher concentrations (≈ 44 kg urea ha-1). As an instance, the grain number per panicle and panicle number per unit area increased to about 19.26 and 28.78%, respectively, compared with those of untreated check plots. Plants fertilised with a lower dose of urea (10 kg N ha-1≈ 22 kg urea ha-1) in the boot- ing stage gave the more appropriate performance for both the panicle fertility rate and grain yield. In other words, high N fertiliser application exceeding 10 kg ha-1 in the boot stage has likely resulted in a considerable decline in N use e�ciency and could lead to an increased N loss risk. �ousand-grain weight was not appreciably a�ected by urea fertilisation timing, since it is mostly governed by genetic constitution. Although, the di�erent concentrations of urea fertiliser at two stages of growth were used, further investigations relying on timing and other concentrations are need- ed to be undertaken in di�erent agro-ecological regions. The influence of foliar “feeding” of urea on yield and its com ponents of Iranian hybrid rice O ryza sativa L. ‘B ahar 1’ H am id D or os ti, K at ar zy na M oż dż eń , P ei m an Z an di , M or te za S ia vo sh i 92 Fig. 5. Correlogram display of correlation matrices for experimental data (Grain yield: GY, �ou- sand grain weight: TGW, Panicle fertility rate: PFR, Panicle number per square meter: PN.SM; Gran number per panicle: GN.P); �e pie graphs are �lled in proportion to the Pearson’s coe�cient values, clockwise for positive correlations (in blue) and anti-clockwise for negative correlations (in red); �e numbers are Pearson coe�cients with 95% con�dence intervals References Ahmadi, K., Gholizadeh, H., Ebadzadeh, H.R., Hosseinpour, R., Hatami, F., Fazli, B., Kazemian, A. Ra�ei. M. (2014). Agricultural statistics of Iran: Crop plants. Tehran, Iran: Ministry of Agriculture Jihad Press. [In Persian] Akhgari, H. (2010). Rice (Agronomy, Fertilization, and Nutrition). 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Relationship between grain yield and quality in rice germplasms grown across di�erent growing areas. Breeding Science, 65(3), 226–232. DOI: 10.1270/jsbbs.65.226 Youse�, M., Zandi, P. (2012). E�ect of foliar application of zinc and manganese on yield of pumpkin (Cu- curbita pepo L.) under two irrigation patterns. Electronic Journal of Polish Agricultural Universities, 15(4), #02. Zandi, P., Basu, S.K. (2016). Role of plant growth-promoting rhizobacteria (PGPR) as biofertilizers in sta- bilizing agricultural ecosystems, Chapter 3. In: D. Nandwani (ed.), Organic Farming for Sustainable Agriculture. Germany: Springer International Publishing, 71–87. DOI: 10.1007/978-3-319-26803-3_3 Abstract Because of waterlogged conditions in rice cultivation, much of the surface-broadcasted urea dissolves in paddy water and is unreachable to the rice crop for this reason. A �eld experiment was conducted to esti- mate the in�uence of urea fertilisation on yield and yield components of hybrid rice ‘Bahar 1’. �ree doses (N0, N10, N20 kg N ha -1) of nitrogen from urea sources were foliar-sprayed once at active tillering and booting stages. Grain yield, the number of panicles per unit area, and the number of grains per panicle in the tillering 95 The influence of foliar “feeding” of urea on yield and its com ponents of Iranian hybrid rice O ryza sativa L. ‘B ahar 1’ stage of rice were signi�cantly (p < 0.01) increased in a linear fashion when N rates increased from 0 to 20 kg ha-1. �e rate of panicle fertility was negatively/positively in�uenced with increasing N rates in the tillering and booting stages, respectively, indicating the creation of more number of non/partial productive tillers per hill in the vegetative stage than in the reproductive stage. In line with panicle fertility (%), the grain yield was also signi�cantly a�ected by N treatments with urea fertilisation in the booting stage. Maximum grain yield was obtained with the application of 20 kg N ha-1 at both the tillering and booting stages. Foliar spray- ing of urea at tillering (20 kg N ha-1) and booting (10 kg N ha-1) stages had a pronounced e�ect on achieving higher yields as compared to other combinations. �e study suggests that foliar application of urea for hy- brid rice cultivation might have a potential role in improving nitrogen use e�ciency. Key words: Oryza sativa L. ‘Bahar 1’, foliar spraying, urea fertilisation, grain yield Received: [2017.07.11] Accepted: [2017.10.31] Wpływ „dożywiania” dolistnego mocznikiem na plon i jego składniki irańskiego mieszańca ryżu Oryza sativa L. ‘Bahar 1’ Streszczenie Ze względu na podmokłe warunki upraw ryżu, większość powierzchniowej transmisji mocznika rozpuszcza się w wodzie gruntowej i z tego powodu nie jest osiągalna dla uprawy ryżu. Przeprowadzono doświadczenie polowe w  celu oszacowania wpływu nawożenia mocznikiem na wydajność i  składniki plonu mieszańca ryżu Oryza sativa L. ‘Bahar 1’. Trzy dawki azotu (N0, N10, N20 kg N ha -1), pochodzące z zasobów mocznika, były rozpryskiwane na liście ryżu jednorazowo, przed stadiami krzewienia i tworzenia liścia �agowego. Plon ziarna, liczba wiech na jednostkę powierzchni i liczba ziaren przypadających na wiechę w fazie krzewienia ryżu wzrastały istotnie (p < 0,01) w sposób liniowy, gdy dawki azotu (N) wzrastały od 0 do 20 kg ha-1. Poziom płodności wiechy był odpowiednio uzależniony od wzrostu dawek azotu (N) w stadiach krzewienia i two- rzenia liścia �agowego; wskazując na utworzenie większej liczby częściowo nieproduktywnych na wierz- chołku źdźbeł w stadium wegetatywnym niż w stadium generatywnym. Z kolei, z płodnością wiech (%), plon ziarna był także istotnie uzależniony od azotu (N) poprzez traktowanie mocznikiem w stadium two- rzenia liścia �agowego. Maksymalna wydajność plonu ziarna uzyskano przy aplikacji 20 kg N ha-1 w obydwu stadiach: krzewienia i tworzenia liścia �agowego. Opryskiwanie liści mocznikiem w fazach krzewienia (20 kg N ha-1) i tworzenia liścia �agowego (10 kg N ha-1) miało wyraźny wpływ na uzyskiwanie wyższych plo- nów, w porównaniu z innymi kombinacjami. Badania wskazują, że dolistne zastosowanie mocznika w upra- wie mieszańców ryżu może odgrywać potencjalną rolę w  poprawie efektywności wykorzystania azotu. Słowa kluczowe: Oryza sativa L. ‘Bahar 1’, spryskiwanie dolistne, nawożenie mocznikiem, plon ziarna Information on the authors Hamid Dorosti He obtained his PhD from Gorgan University of Agricultural Sciences and Natural Resources in 2015. Before then, having Master degree in Plant Breeding, he joined RRRI (Rasht rice research institute, Gui- lan Prov., Iran). He had been involved in several projects performed at RRRI, Rasht, Iran as scientist fellow for over 30 years. Katarzyna Możdżeń Her scienti�c interests concentrate on the e�ects of di�erent environmental factors (light, ozone, heavy metals, allelopathic extracts) on the morphology and physiology of cultivated, protected, and invasive species of plants. Peiman Zandi He was deeply trained in agronomy (crop science) and specialising in stress physiology, biotic/abiotic stresses, and agroecology. He is also interested in working in di�erent areas of plant developmental biolo- H am id D or os ti, K at ar zy na M oż dż eń , P ei m an Z an di , M or te za S ia vo sh i 96 gy, agroecology, plant nutrition, botany, plant breeding, and genetics. His previous research project, whi- ch was funded by Payame Noor University (Ganaveh, Iran), was ‘Foliar application of ascorbate on the physiological and biochemical attributes of Iranian fenugreek (Trigonella foenum-graecum L.) landraces under drought stress’. Currently, he joined a research group at Chinese Academy of Agricultural Sciences (Beijing, China) attempting to discern the possible function of iron plaque on chromium acquisition, accumulation and translocation in selected rice (Oryza sativa L.) cultivars grown in di�erent planting media. �eir main aim is to verify IP role in wetland plants subjected to Si fertilisation as an e�ective strategy to decrease Cr accumulation in O. sativa grown in Cr-contaminated environments. Morteza Siavoshi He is an assistant professor and faculty member of agricultural science department in Payame Noor Uni- versity, Iran. He was awarded his PhD degree in Agronomy in Pune University, Pune, India. Now he is a college principal in Ganaveh Payame Noor College, Iran.