Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals

Journal of Agricultural Science and Technology B 5 (2015) 365-375 doi: 10.17265/2161-6264/2015.06.001 D DAVID PUBLISHING Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals Syed Shah, Sarah Hookway, Andrew Richards, Carl Flint, Sarah Wilkinson and John Mark Fletcher Agrii Technology Centre (AgriiFocus), North Farm, Swindon, SN8 2JZ, UK Abstract: Crop nutrition has a significant effect on disease incidence, resistance or tolerance of various crops. There is currently a lack of reliable recent UK-based research about the effect of copper, zinc and boron on disease incidence, green leaf area (GLA), green leaf retention (GLR) and grain yield of winter wheat, spring wheat and spring barley. Data analysis showed that these trace elements had positive effects on GLR. These positive effects may have been due to the role of copper, zinc and boron in the production of defence related compounds (phenolics and lignin), which may have reduced the disease incidence resulting in prolonged GLR. Grain yield was significantly enhanced by the application of these trace elements on the crop grown on high ph calcareous soil, which can be partly attributed to enhanced GLR. Also trace elements have a positive role in reproductive growth, flowering and male fertility. On average, zinc was found to be the most consistent trace element in terms of enhancing GLR and grain yield. Across all trials, it was noted that for every 10% increase in GLA from trace elements, grain yields increased by 4.2% in 2012-2013, by 4.4% in 2013-2014 in winter wheat and by 3.9% in spring wheat in 2014. These are remarkably consistent and indicate that increasing GLA by 10% by early dough stage was associated with a yield improvement of about 4%. These trace elements also had a positive effect on grain protein content (GPC). This research concluded that the trace elements had positive effects in enhancing GLA and yield. It can be speculated that with the use of these trace elements, there may be more scope for using less robust or reduced rates of fungicides to control foliar diseases, which may help to maximize farm profits. Key words: Trace elements, copper, zinc, boron, cereals, GLR, grain yield. 1. Introduction Crop resistance, tolerance and susceptibility to disease are generally variety specific [1], but environment and nutrition have a significant role in disease incidence and grain yield [2]. Crop nutrition affects the development of a disease by affecting plant physiology [3]. Nutrients affect the growth rate of the plant, and sufficient supply of nutrients can result in higher growth rate enabling seedlings or plants to escape or avoid infection [4]. Nitrogen (N) is the most important nutrient for achieving higher yield [5]. It has been reported that N affects the occurrence of pests and diseases in several crops [6, 7]. At higher N rate, disease can be a limiting factor [8] and the severity of disease increases with N [9]. This is because at higher N rate, the metabolism of the plant Corresponding author: Syed Shah, Ph.D., research fields: plant and soil science. changes, which leads to lower content of defence related compounds (phenolics and lignin) [10]. At low N rate, an increased synthesis of these defence related compounds has been reported [3]. However, it is worth mentioning that the effect of N on disease incidence is dependent on the type of pathogen and genotype. For example, the severity of obligate pathogens, such as Puccinia graminis and Erysiphe graminis tends to increase [10], while the severity of facultative pathogens, such as Alternaria and Fusarium tends to decrease with N rate [3]. Phosphorous (P) is the second important nutrient for achieving higher yield. Its role in controlling seedling and fungal diseases has been reported, but P was found to be more beneficial when its application resulted in a rapid root development, allowing plants to escape diseases [11]. Foliar application of P has shown to have benefits against downy mildew in oilseed rape. Similar to P, potassium (K) is also very

366 Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals important for achieving higher yields and has a very important role to play in plant susceptibility or resistance to different diseases. K may promote the development of thicker outer walls in epidermal cells and may improve resistance against diseases [12]. Obtaining the optimum balance between N, P and K can improve disease resistance of plants [3]. Calcium (Ca), magnesium (Mg) and sulphur (S) have also shown positive effects on plant disease resistance [7, 13, 14]. In recent years, trace elements, such as manganese (Mn), copper (Cu), zinc (Zn), boron (B) and silicon (Si) have become of specific interest to various researchers. There are several reasons for this, but the primary reason is the role of these trace elements in improving resistance against biotic and abiotic stresses. These trace elements also have a vital role in reproductive growth as well as the uptake and utilization efficiency of N, P and K [15], which can have a positive effect on grain quality, such as grain protein content (GPC), 1000-grain weight and specific weight [16]. Amongst trace elements, Mn has a very important role in the development of disease resistance in plants [17]. Mn application has been reported to have positive effects in controlling many foliar diseases, such as powdery mildew, downy mildew, tan spot and take-all [11, 17, 18]. This is because Mn controls the biosynthesis of lignin and suberin through the activation of several enzymes [17]. Lignin and suberin have a crucial role in resistance against most foliar diseases in wheat [2, 11]. It has been reported that Cu has a very important role in disease resistance [15, 19] and reproductive growth [20]. Cu deficiency may play a role in increased infection, because Cu is necessary for cell wall lignification. When lignification is disrupted, cell walls are more susceptible to penetration by fungi [21]. In addition to its effects on leaf disease susceptibility, evidence exists that pollen sterility and male sterility are enhanced when Cu is deficient in cereal crops [22]. Cu deficient plants produced smaller anthers, and the pollen had a high incidence of male sterility, which had negative effects on grain yield [23]. Zn is a structural component of several enzymes and is required for enzyme activation. Its application may reduce disease severity, which could be due to the direct effects of Zn on the pathogen but not through the plant s metabolism [4]. The role of Zn in protein and starch synthesis is well documented, and their positive effects on GPC and the baking quality of winter wheat flour have been observed [16]. Zn deficiency has negative effects on carbohydrate metabolism and pollen structure which results in lower yield [24]. B plays important roles in cell wall synthesis and structure, and possibly membrane stability [25]. It has a significant role in disease resistance, which is attributed to its role in cell wall structure, cell membrane permeability, stability and its role in the production of phenolics and lignin [26, 27]. It has been observed that B deficiency causes abnormal development of reproductive organs [28, 29] which reduces crop yield [30]. This paper reports the results obtained from a range of Agrii trials which were carried out at the Agrii Technology Centre (AgriiFocus), Swindon, UK, during three growing seasons (2011-2014). The main objective of these trials was to investigate the effects of foliar application of the trace elements (Cu, Zn and B) on disease incidence and green leaf area (GLA). It was hypothesised that the trace elements have the potential to improve disease resistance, which may enhance green leaf area retention (GLR) and maximize grain yield in situations when the supply of N, P, K, S, Mg and Mn is sufficient. 2. Materials and Methods Five trials were carried out at the Agrii Technology Centre, Swindon, UK, located at 51 30 N and 1 39 W. These trials investigated the effect of a range of trace elements, in particular Cu, Zn and B on GLR, grain yield and yield related components of winter

Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals 367 wheat, spring wheat and spring barley during the 2011-2014 growing seasons on high ph calcareous soil. The calcareous and high ph soil for the trials was chosen, because these soils are likely to be deficient in micronutrients or the availability is limited due to high ph. The range of products used in these trials is listed in Table 1. Prior to planting, 24 individual cores (0-10 cm depth) were collected at different points from the fields which were used for these trials. All the cores were mixed in a clean plastic container and a sub-sample was sent to Lancrop Laboratories, Wellington Road, Pocklington, York, UK, for broad spectrum soil analysis. Selected chemical properties of the field are listed in Table 2. Plots were drilled using a 16 row Wintersteiger plot drill. Winter wheat plots received 270:150:150:75:37.5 kg/ha of N:P 2 O 5 :K 2 O:SO 3 :MgO, respectively, as a standard maintenance fertilizer treatment. Spring wheat and spring barley received 180 kg/ha of N, while P 2 O 5 :K 2 O:SO 3 :MgO were the same as for winter wheat. A robust herbicide, insecticide, fungicide programme was employed to control all weeds, pests and diseases during the growing seasons. Trace element treatments were applied at T0 (tillering stage), T1 (1st node detected), T2 (flag leaf just visible) and T3 (ear fully emerged) using a standard plot sprayer with 110 flat fan nozzles. Plots were monitored to assess the effects of treatments on disease incidence and grain yield. Plots were assessed two to three times to record the level of disease (Septoria and Rhynchosporium where applicable), but data in this paper were selected from the last assessment at Zadoks growth stage (ZGS-73), the early milk stage, at which the effects of treatments were more noticeable. On each assessment date, 10 tillers were randomly selected, and the percentage area of the top three leaves with visible infection was recorded. Since it was difficult to separate symptoms of disease and natural senescence, results are expressed as GLA [31]. Grain yield of the plots was determined by combine harvesting one strip 1.85 m wide and 10 m long using a Sampo 2010 plot combine. Table 1 List of the products and their active ingredient (L/ha) used in the trials at the Agrii Technology Centre (Swindon, UK). Product name Active ingredient (g/l) Maximum individual rate (L/ha) Manufacturer Hu-man extra S (93):Mn (150):Mg (12) 2.0 Verdicrop, UK Magnor N (50):Mg (100) 2.0 Verdicrop, UK Zinic S (20):Zn (140) 2.0 Verdicrop, UK Copper 435 Cu (250) 0.5 Headland, UK Opte B B (150) 2.0 Agrii, UK Nutri-phite PGA 26% phosphite 5.0 Verdesian, UK 4-yield extra Mn (105):S (75):Mg (8.6):Cu (21) 2.0 Verdicrop, UK Table 2 Selected chemical properties of the fields used for the trials during 2011-2014. Properties Crop and growing season 2011-2012 2012-2013 2013-2014 Winter wheat Winter wheat Winter and spring wheat Spring barley ph 6.9 7.7 8.0 7.5 P (ppm) 20.0* 13.0^ 17.0* 12.0^ K (ppm) 256.0* 203.0* 261.0* 153.0* Mg (ppm) 75.0* 64.0* 69.0* 66.0* Mn (ppm) 126.4* 62.0^ 63.5 ^ 128.0* Cu (ppm) 3.8^ 3.8^ 3.8^ 4.1* B (ppm) 3.4* 2.5* 4.7* 2.8* Zn (ppm) 7.5* 4.1* 9.1* 4.3* * means normal and ^ means slightly low.

368 Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals Table 3 List of treatments, product rate (L/ha) and date of application for winter wheat trial carried out the Agrii Technology Centre during 2011-2012. Product, rate (L/ha), application stage and date Untreated - (1) Nutri-phite PGA (0.5) + 4-yield extra (1.5) + Zinic (0.5) at T0 applied on April 2, 2012; (2) Nutri-phite PGA (0.5) + 4-yield extra (1.5) + Zinic (0.5) at T1 applied on April 24, 2012; (3) Nutri-phite PGA (0.5) + Magnor (1.5) + Copper 435 (0.25) + Zinic (0.5) + Boron 150 (0.3) at Best trace elements programme T2 applied on May 17, 2012; (4) Nutri-phite PGA (0.5) + Magnor (1.5) + Copper 435 (0.25) + Zinic (0.5) + Boron 150 (0.3) at T3 applied on June 18, 2012. Table 4 List of treatments, product rate (L/ha) and date of application for winter wheat trial carried out the Agrii Technology Centre during 2012-2013. Product, rate (L/ha), application stage and date Control - Zn Cu B Zn + Cu + B Zinic (0.75) at T0 and T1 applied on April 24, 2013 and May 21, 2013, respectively; Copper 435 (0.35) at T1 and T2 applied on May 21 and June 3, 2013, respectively; Opte B (0.3) at T2 and T3 applied on June 3 and June 26, 2013, respectively; Zinic (0.75) at T0 applied on April 24, 2013, followed by Zinic (0.75) + Copper 435 (0.35) at T1 applied on May 21, 2013 followed by Copper 435 (0.35) + Opte B (0.3) at T2 applied on June 3, followed by Opte B (0.3) at T3 applied on June 26, 2013. The grain yield was adjusted at 15% moisture content. The 1,000-grain weight and grains/m 2 were recorded to aid the interpretation of the effects of treatments in the discussion section of this paper. GPC was recorded using the Infratec TM 1241 grain analyzer (FOSS, Denmark). This instrument has an extended wavelength range of 570-1,100 nm of near infra-red (NIR), which scans and analyses 10 sub-samples of the input sample and gives a recorded reading of GPC. Data were analyzed by analysis of variance (ANOVA), using Genstat (14th ed., 2011, VSN International). Means were separated by least significant difference (LSD) when F values were significant at P < 0.05. 2.1 Effect of Trace Elements on GLR and Grain Yield of Winter Wheat Variety (KWS Santiago) during 2011-2012 This trial was drilled on September 14, 2011 in a randomized complete block design with four replicates to investigate the effect of wide a range of trace elements (Table 3) on disease incidence and grain yield of winter wheat (KWS Santiago). The whole plot area received an over spray of Hu-man extra (1.0/ha) at T0 and T1, and Magnor (1.5/ha) at T2 and T3, respectively to supply Mn and Mg. Plots were combined on September 7, 2012 to determine grain yield. 2.2 Effect of Cu, Zn and B on GLR and Grain Yield of Winter Wheat (KWS Santiago) during 2012-2013 and 2013-2014 Two trials were carried out during the 2012-2013 and 2013-2014 growing seasons. These trials were drilled on October 29, 2012 and October 30, 2013, respectively, in a randomized complete block design with four replicates to investigate the effect of the treatments (Tables 4 and 5) on GLA and grain yield. The whole plot area received an over-spray of Hu-man extra (1.0/ha) at T0 and T1, and Magnor (1.5/ha) at T2 and T3, respectively to supply Mn and Mg. Grain yield was determined by harvesting plots on September 1, 2013 and August 23, 2014. 2.3 Effect of Cu, Zn and B on GLR and Grain Yield of Spring Wheat (KWS Alderon) in 2014 This trial was drilled on March 27, 2014 in a randomized complete block design with three replicates. The trial was combined on August 24, 2014 to determine the effect of Zn, Cu and B (Table 6) on grain yield. The whole plot area received an over spray of

Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals 369 Table 5 List of treatments, product rate (L/ha) and date of application for winter wheat (KWS Santiago) at the Agrii Technology Centre during 2013-2014. Product, rate (L/ha), application stage and date Control - Zn Cu B Zn + Cu + B Zinic (0.75) at T0 and T1 applied on April 9, 2014 and April 26, 2014, respectively; Copper 435 (0.35) at T1 and T2 applied on April 26, and May 14, 2014, respectively; Opte B (0.3) at T2 and T3 applied on May 14, and May 30, 2014, respectively; Zinic (0.75) at T0 applied on April 9, 2014, followed by Zinic (0.75) + Copper 435 (0.35) at T1 applied on April 26, 2014, followed by Copper 435 (0.35) + Opte B (0.3) at T2 applied on May 14, 2014, followed by Opte B (0.3) at T3 applied on May 30, 2014. Table 6 List of treatments, product rate (L/ha) and date of application for spring wheat (KWS Alderon) at the Agrii Technology Centre in 2014. Product, rate (L/ha), application stage and date Control - Zn Cu B Zn + Cu + B Zinic (0.75) at T0 and T1 applied on May 17, 2014 and May 30, 2014, respectively; Copper 435 (0.35) at T1 and T2 applied on May 30, and June 11, 2014, respectively; Opte B (0.3) at T2 and T3 applied on June 11 and June 30, 2014, respectively; Zinic (0.75) at T0 applied on May 17, 2014, followed by Zinic (0.75) + Copper 435 (0.35) applied on May 30, 2014, followed by Copper 435 (0.35) + Opte B (0.3) applied on June 11, followed by Opte B (0.3) applied on June 30, 2014. Table 7 List of treatments, product rate (L/ha) and date of application for spring barley (Rhyncostar) at the Agrii Technology Centre in 2014. Product, rate (L/ha), application stage and date Control - Zn Cu B Zn + Cu + B Zinic (0.5) at T0, T1 and T2 applied on April 21, May 5 and May 28, 2014, respectively; Copper 435 (0.25) at T0, T1 and T2 applied on April 21, May 5 and May 28, 2014, respectively; Opte B (1.0) at T0, T1 and T2 applied on April 21, May 5 and May 28, 2014, respectively; Zinic (0.5) + Copper 435 (0.25) + Opte B (1.0) at T0, T1 and T2 applied on April 21, May 5 and May 28, 2014, respectively. Hu-man extra (1.0/ha) at T0 and T1, and Magnor (1.5/ha) at T2 and T3, respectively to supply Mn and Mg. 2.4 Effect of Cu, Zn and B on GLR and Grain Yield of Spring Barley (Rhyncostar) in 2014 This trial investigated the effect of Cu, Zn and B applied at different growth stages (Table 7) on GLR and yield of spring barley Rhyncostar. The trial was drilled on March 18, 2014 in a randomized complete block design with four replicates and combined on August 20, 2014 to determine grain yield. 3. Results 3.1 Effect of Trace Elements on GLR and Grain Yield of Winter Wheat (KWS Santiago) during 2011-2012 Trace elements had a significant effect on GLA. The untreated plots had lost most of the green area of the top two leaves, while the treated plots remained green for a longer period and had 40% green leaves on the assessment date (July 22, 2012) (Fig. 1). The untreated plots produced 1 ton/ha lower yield than the treated plots (Fig. 2). 3.2 Effect of Cu, Zn and B on GLR and Grain Yield of Winter Wheat (KWS Santiago) during 2012-2013 and 2013-2014 Combined analysis of the two year data showed that the trace elements had a significant effect on GLA compared with the control plots (averaged over two years) (Table 8). However, there was a significant interaction of year and trace element. Plots which received Zn, Cu and B in a sequence at different growth stages produced 0.5 ton/ha higher yield than the

370 Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals Untreated Best trace elements programme Fig. 1 Effect of trace elements on GLA of KWS Santiago on July 22, 2012. Grain yield (ton/ha) Fig. 2 Effect of trace elements on grain yield (ton/ha) of KWS Santiago during 2011-2012. control plots in the trial carried out during the growing season of 2012-2013. Similar results were obtained in 2013-2014, but the plots treated with Zn alone produced higher yields than the individual application of Cu or B (Table 8). Zn treated plot had the highest GPC (Fig. 3). 3.3 Effect of Cu, Zn and B on GLR and Grain Yield of Spring Wheat (KWS Alderon) during 2014 GLA was significantly affected by trace elements (P < 0.001), and the Zn treated plot had the highest GLA followed by Cu, while the lowest was recorded in the B treated plots (Table 9). Grain yield was also significantly (P < 0.028) affected by the trace elements, and the highest yield was recorded from the Cu + Zn + B treated plots, while the lowest yield was recorded from the B treated plots, which was not significantly different than the control plots (Table 9).

Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals 371 Table 8 Effect of Cu, Zn and B on GLA (%) and grain yield (ton/ha) of KWS Santiago at the Agrii Technology Centre, Swindon during 2012-2013 and 2013-2014. GLA (%) Grain yield (ton/ha) 2012-2013 2013-2014 Mean 2012-2013 2013-2014 Mean Control 76.7 60.8 68.7 9.73 11.25 10.49 Zn 77.1 71.2 74.2 9.70 11.82 10.76 Cu 78.3 63.5 70.9 9.73 11.56 10.65 B 78.8 63.0 70.9 9.64 11.68 10.66 Zn + Cu + B 88.7 66.5 77.6 10.17 11.69 10.93 Mean 79.9 65.0 9.8 11.6 P-value Year (< 0.001), treatment (< 0.001), interaction (< 0.001) Year (< 0.001), treatment (< 0.001), interaction (< 0.001) LSD (P < 0.05) Year (1.79), treatment (2.83), interaction (4.0) Year (0.099), treatment (0.157), interaction (0.222) CV (%) 3.8 1.4 Grain protein content (%) Fig. 3 Effect of Cu, Zn and B on GPC of KWS Santiago during 2013-2014. Table 9 Effect of Cu, Zn and B on GLA (%) and grain yield (ton/ha) of spring wheat (KWS Alderon) at the Agrii Technology Centre, Swindon during 2014. GLA (%) Grain yield (ton/ha) Control 72.9 8.94 Zn 80.5 9.21 Cu 76.2 9.07 B 68.0 8.65 Zn + Cu + B 77.0 9.24 P-value < 0.001 0.028 LSD (P < 0.05) 3.76 0.371 CV (%) 3.3 2.7 Table 10 Effect of Cu, Zn and B on grain yield of spring barley (Rhyncostar) in 2014. Grain yield (ton/ha) Untreated 8.23 Cu 8.72 Zn 8.72 B 8.29 P-value 0.092 LSD (P < 0.05) 0.49 CV (%) 3.6

372 Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals 3.4 Effect of Cu, Zn and B on GLR and Grain Yield of Spring Barley (Rhyncostar) during 2014 Trace elements had a positive effect on GLA and GLR, but these effects were not significant (P > 0.05) (data not reported). Grain yield was also affected by the trace elements but the effect was not significant (P = 0.092) (Table 10). 4. Discussion Foliar diseases reduce the GLA of crops, which consequently has negative effects on photosynthetic activity and yield [32]. The extent of yield losses is dependent on the crop growth stage at the time of infection, rate of disease development and genotypes [33]. Fungicides are one of the most commonly used methods for controlling Septoria (Mycosphaerella graminicola) and leaf blotch (Rhynchosporium secalis) in susceptible varieties of wheat and barley, respectively [34, 35]. Amongst fungicides, triazole based chemicals when applied with succinate dehydrogenase based products can give a better control of Septoria in wheat [36] and leaf blotch in barley [35]. It has been reported that trace elements have a crucial role in enhancing disease resistance of various crops, including cereals [3]. In one of the trials reported in this paper, the effects of the best trace elements programme (Mn, Cu, Zn, B along with Mg and phosphite) were investigated on winter wheat variety KWS Santiago. This variety was chosen due to its susceptibility to Septoria and yellow rust, which could help us to investigate the benefits of using these trace elements in enhancing disease resistance and yield. Although the whole trial area had received a robust fungicide programme to control all diseases, it was noticed the plots which had not received any trace elements had lost their entire GLA by July 22, 2012. The trace element treated plots remained green for a longer period (16 d) and looked brighter and healthier. This outcome can be attributed to the combined positive effects of Mn, Mg, Cu, Zn and B. This result is in agreement with Dordas [3], Graham and Webb [4], and Brown et al. [26], who have reported the benefits of trace elements in controlling diseases and maintaining GLA. This is because trace elements, such as Mn control the biosynthesis of lignin and suberin. These two defence-related compounds have a crucial role in the resistance against foliar diseases [4]. Similarly, Cu, Zn and B play an important role in lignification and the production of suberin [2, 11], which may have been one of the reasons for enhanced GLR in our study. The effect of Mn in controlling foliar and root diseases is well documented [3], but the effects of Cu, Zn, B in controlling diseases, e.g., Septoria, and enhancing GLR in the UK climatic conditions are limited. Two years trials data reported in this paper indicated that Cu, Zn and B had enhanced GLA and GLR, but there was a significant interaction of year and trace element. This significant interaction was partly attributable to the differences in weather conditions and disease incidence. In the growing season of 2012-2013, disease pressure was low, and although the individual application of Cu, Zn and B had positive effects on GLR, it was not significant when compared with the control plots. However, applying these trace elements in a sequence at different growth stages resulted in a significantly higher GLA than the control plots. The trial carried out in 2013-2014 during which disease pressure was high, tended to confirm the benefits of these trace elements, but Zn alone proved to be best treatment in enhancing GLA and GLR by 5 d compared with the control and other trace elements. The benefits of using Cu, Zn and B in maintain GLA were also noticed in spring wheat and spring barley. The individual applications of Zn, Cu and B in a sequence at different growth stages resulted in higher GLA and GLR when compared with control plots of spring wheat variety KWS Alderon. Also, in the spring barley (Rhyncostar), the greening effects of these trace elements were noticed, but these effects

Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals 373 were statistically not significant (data not reported). This outcome may have been due to the fact that this barley variety has a good level of disease resistance against Rhynchosporium and probably did not need the application of these trace elements to enhance disease resistance. Further trials are needed to confirm this suggestion. It has been reported that foliar diseases reduce GLA, which consequently has a negative effect on photosynthesis and grain yield [32]. Any strategy which protects green leaf, in particular the flag and the penultimate leaves, can have positive effects on grain yield [37]. In this paper, the enhanced trace element programme prolonged the GLR, which resulted in 11% higher yield than the plots which did not receive any trace elements. Data analysis of other trials showed the benefits of using Cu, Zn and B and the application of these three trace elements in a sequence at the key growth stages produced 0.44 ton/ha and 0.3 ton/ha higher yield for winter and spring wheat, respectively. These yield enhancements were attributed to increased grains/m 2 and average grain weight. This outcome is in agreement with the results of Refs. [16, 19, 20], which reported the positive effects of Cu, Zn and B on yield due to the crucial role of these trace elements in flowering, reproductive growth and disease resistance. However, such effects were not significant for spring barley. This outcome can be attributed to differences in the susceptibility of the varieties to different diseases. The varieties KWS Santiago and KWS Alderon are susceptible to Septoria. The application of trace elements improved the diseases resistance, indicated by better GLR, which had positive effects on yield. The spring barley variety used in this trial was moderately resistant to the main barley disease (Rhynchosporium), and as a result, the benefits of trace elements in terms of grain yield enhancement were not observed. Across all trials, it was noted that for every 10% increase in GLA, grain yields increased by 4.2% in 2012-13, by 4.4% in 2013-14 and by 3.9% in spring wheat in 2014. These are remarkably consistent and indicate that increasing GLA by 10% by early dough stage will be associated with a yield improvement of about 4%. Further trials are needed to confirm the benefits of these trace elements on susceptible and moderately resistant varieties of wheat and barley in controlling diseases and enhancing yield. It has been reported that Cu, Zn and B can improve uptake and utilization efficiency of N, P and K [15], which can have positive effects on grain quality, such as the GPC [16, 38]. In this study, Zn had a positive effect on GPC of KWS Santiago, which is in agreement with the results of Peck et al. [16] on bread wheat. It is worth noting that Zn can alter grain protein composition, such as gluten, which is a major component of flour protein that determines the processing quality [39]. In this study, grain protein composition was not assessed, but further trials are recommended to investigate the effect of Zn on GPC and composition of milling wheat. This may help to improve GPC and baking quality of milling wheat currently grown in the UK. 5. Conclusions The set of trials reported in this paper confirmed the importance of trace element nutrition (Cu, Zn and B) in enhancing disease resistance. These benefits, in most cases, were translated into higher yields, which could be partly attributed to higher grains/m 2 and average grain weight. The higher average grains/m 2 and grain weight were due to the positive effects of these trace elements on GLA and GLR. Prolonged GLR may have allowed the crop to produce carbohydrates for a longer period, which were translocated to the ear during the grain filling period. Also these trace elements have a positive role in reproductive growth, flowering and male fertility, which may have resulted in higher grains/m 2 and consequently high yield. The results indicated that, although the availability of trace elements in the soil was optimum, their foliar application had positive effects on enhancing disease resistance and grain yield.

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