Partial root zone drying irrigation, planting methods and nitrogen fertilization influence on physiologic and agronomic parameters of winter wheat

Agricultural Water Management 223 (2019) 105688

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Partial root zone drying irrigation, planting methods and nitrogen fertilization influence on physiologic and agronomic parameters of winter wheat

T

Fatemeh Mehrabia, Ali Reza Sepaskhaha,b,

⁎

a b

Irrigation Department, Shiraz University, Shiraz, Islamic Republic of Iran Drought Research Center, Shiraz University, Shiraz, Islamic Republic of Iran

ARTICLE INFO

ABSTRACT

Keywords: Variable alternate furrow irrigation Planting method Leaf water potential Leaf photosynthesis rate Stomatal conductance Leaf transpiration efficiency

The effectiveness of water-saving irrigation strategies such as partial root zone drying (PRD) should be explored to ensure food security as the availability of water for irrigation declines and population increases. PRD is easily performed by localized irrigation method; however very small percentage of irrigated area is under this irrigation method and main irrigation method is furrow irrigation that should be adapted to PRD. In this respect, present study was conducted to explore the effects of PRD in furrow irrigation strategies on physiological and agronomic behavior of winter wheat. The field experiment included two irrigation strategies (variable alternate furrow irrigation (VAFI) as PRD and ordinary furrow irrigation (OFI), two different planting method (in-furrow planting and on-ridge planting) and three nitrogen rates (0, 150, and 300 kg N ha−1) over 2015–2016 and 2016–2017. Results showed that decreasing leaf water potential (LWP) during the stem elongation stage resulted in increasing the sensitivity of winter wheat to water stress and yield reduction. The leaf photosynthesis rate (An) was not significantly lowered in VAFI (PRD) in comparison with that obtained in OFI. The VAFI strategy reduced the stomatal conductance (gs) about 12% and 7% in comparison with that obtained in OFI in the first and second year, respectively that were statistically significant. The lower slope of linear relationship between leaf transpiration efficiency (An/Tr) and vapor pressure deficit (VPD) in VAFI strategy indicated that with increasing VPD, leaf transpiration efficiency was higher than that obtained in OFI. As a consequence, VAFI strategy as PRD was effective in increasing An/Tr and can be an alternative irrigation management in winter wheat farms with limited water supplies. Although, in-furrow planting showed higher efficiency in increasing yield in comparison with that obtained in on-ridge planting, on-ridge planting showed higher effects on leaf transpiration efficiency. Furthermore, there was no significant difference between two application rates of nitrogen (150 kg N ha−1 and 300 kg N ha−1) for different parameters; therefore, application of 150 kg N ha−1 can be suggested as an effective rate to increase winter wheat yield. Consequently, in areas with scarce water and furrow irrigation, combination of VAFI, in-furrow planting and 150 kg N ha−1 is recommended to achieve optimum yield with possibility of saving water during the winter wheat growing season.

1. Introduction Although water scarcity generally associated with arid and semiarid climates, field and water resources management is essential to enhance the water productivity in all over the world in order to supply food for next generations. Deficit irrigation (DI) is one of the strategies that scientists have been used to reduce water application with negligible effects on yield. Results showed that in comparison with DI, the variable alternate furrow irrigation (VAFI) as an approach to partial rootzone drying irrigation (PRD) can decrease irrigation water without

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significant yield loss, while it may improve the yield quality (Abdelraouf and Ragab, 2018; Casa and Rouphael, 2014; Sepaskhah and Ahmadi, 2012; Ahmadi et al., 2010; Saeed et al., 2008; Kang et al., 2000). The advantage of this strategy is that water uptake from the wet side of the root system maintain a favorable plant water status, while part of the root system in drying soil can respond to the drying by sending a root-sourced signal (abscisic acid (ABA)) to the shoots where stomata opening may be inhibited by decreasing the stomata conductance (gs) so that water loss is reduced (Haworth et al., 2018; Hashem et al., 2018; Puértolas et al., 2014; Khalil and Grace, 1993) and

Corresponding author at: Irrigation Department, Shiraz University, Shiraz, Islamic Republic of Iran. E-mail address: [email protected] (A.R. Sepaskhah).

https://doi.org/10.1016/j.agwat.2019.105688 Received 21 January 2019; Received in revised form 23 April 2019; Accepted 23 June 2019 0378-3774/ © 2019 Elsevier B.V. All rights reserved.

Agricultural Water Management 223 (2019) 105688

F. Mehrabi and A.R. Sepaskhah

increase water use efficiency (Shahrokhnia and Sepaskhah, 2017; Ahmadi et al., 2010; Kang and Zhang, 2004; Davies et al., 2002). There are different findings on the effects of ABA concentration in root and shoot on stomata sensitivity. Some studies reported that xylem sap ABA is a function of root ABA as well as the flow rate of water from roots to shoots, and ABA can be a sensitive indicator in the shoot to show the effect of soil drying (Khalil and Grace, 1993 for sycamore); whereas, Puértolas et al. (2014) suggested that differences in root ABA accumulation did not influence xylem ABA concentration. ABA increases the stomatal sensitivity of C3 monocots as wheat in addition to lowering gs (Haworth et al., 2018). PRD works for crops with stomata that are sensitive to ABA. For example, certain varieties of olive are insensitive to the ABA signal derived from drying of one half of the root (Dbara et al., 2016). However, Collins et al. (2010) suggested that PRD reduced vine water use by up to 50% at moderate VPD (˜3 kPa) compared with control vines irrigated at the same level. It also increased stomatal sensitivity to VPD and decreased sap flow. Although, application of PRD using drip irrigation and subsurface irrigation is more convenient and practical as studies conducted on maize by Abdelraouf and Ragab (2018) and tomato by Hashem et al. (2018) and Casa and Rouphael (2014); however, globally, around 86% of the irrigated area equipped with surface irrigation, 11% is sprinkler irrigation and 3% is localized irrigation (FAO, 2016). Therefore, it is essential to implement and explore the PRD irrigation strategy in the surface irrigation method. Transpiration rate and leaf expansion are very sensitive to reduction in soil water deficit, and water stress inhibits transpiration rate (Tr), while photosynthesis rate (An) remains unchanged at mild stress (Sepaskhah and Ahmadi, 2012). Consequently, water productivity can be improved without significant effect on photosynthesis and yield. Investigations on winter wheat (Jia et al., 2014; Li et al., 2011; Sepaskhah and Hosseini, 2008), potato (Ahmadi et al., 2010) and safflower (Shahrokhnia and Sepaskhah, 2016) showed that VAFI improved water productivity. Additional effective way to improve more water saving along with PRD is use of appropriate planting patterns. In-furrow planting has reported as an effective strategy in water saving and increasing yield due to higher soil water and winter soil temperature (Yarami and Sepaskhah, 2015b; Shabani et al., 2013b). In addition, in-furrow planting has recognized as an appropriate strategy by many investigations in order to increase leaf area index (LAI), crop height, yield, dry matter, photosynthesis rate and stomatal conductance for different crops (Mehrabi and Sepaskhah, 2018; Shahrokhnia and Sepaskhah, 2017; Yarami and Sepaskhah, 2015a; Jia et al., 2014; Wang et al., 2014). In addition, nitrogen is another important factor that affected on physiologic and agronomic parameters of crops. Shangguan et al. (2000) suggested that under well-watered conditions, An and gs of winter wheat were increased in the high N rate (15 mM NO− 3 in irrigation water) in comparison with that obtained in the low N rate (1.5 mM NO− 3 in irrigation water), although its effect on An and gs was not identical under different water status. An and gs both decreased in water stress conditions, while the reaction to water stress was different between high and low nitrogen application rates. Alternatively, Tranavičiené et al. (2008) mentioned that nitrogen was not the only affecting factor and changeable environmental condition in different years can suspend or accelerate the decline in photosynthesis and reduce the grain yield. Water and N supply often showed interaction with each other (Wu et al., 2008a; Pandey et al., 2001; Frederick and Camberato, 1995). N supply under non-water limiting conditions can result in full yield potential, but under water limiting conditions, N may increase the severity of drought stress (Frederick and Camberato, 1995) that results in reducing yield and economic return. Besides, the interaction effects occurred between N application and soil water deficit on photosynthesis and transpiration (Wu et al., 2008b; Otoo et al., 1989). Regarding to various responses of nitrogen and other restrictive factors on physiologic and agronomic parameters, this study was

Table 1 Physico-chemical properties of the soil and water at the experimental site (Mehrabi and Sepaskhah, 2018). Characteristic

Sand Silt Clay Bulk density (BD) Field capacity (FC) Permanent wilting point (PWP) EC pH Cl− Na+ K+ Ca2+ Mg2+ HCO3− NO3,− (before first planting) NO3,− (after second harvesting)

Unit

Soil depth (cm)

Irrigation water

0–30

30–60

60–90

% % % g cm−1 cm3 cm−3 cm3 cm−3

35 35 30 1.39 0.32 0.11

23 38 39 1.44 0.34 0.14

21 39 40 1.47 0.36 0.16

– – – – – –

dS m−1 – (meq l−1) (meq l−1) (meq l−1) (meq l−1) (meq l−1) (meq l−1) (mg/kg soil)

0.90 8.26 9 1.6 0.53 2.6 1.2 4.1 14.56

0.73 8.46 10 2.1 0.14 3 1 4 9.46

0.795 8.18 11.6 2.4 0.15 3.8 1.4 3.8 18

0.58 7.45 0.50 0.48 0.013 1.80 2.0 3.6

(mg/kg soil)

9.33

6.33

6.36

conducted to evaluate the effects of different irrigation strategies including ordinary furrow irrigation (OFI) and variable alternate furrow irrigation (VAFI) as PRD, planting methods [on-ridge planting (ORP) and in-furrow planting (IFP)] and N application rates on some agronomic, physiologic and gas exchange parameters of winter wheat (Triticum aestivam) that was grown in a semi-arid region. 2. Materials and methods 2.1. Experimental site A set of 36 water balance lysimiters was used in this study for two years (2015–2016) in a semi-arid region. These lysimeters were installed in the Experimental Research Station of the Agricultural College, Shiraz University, Shiraz, Iran. Location of the station is 29°56΄N (latitude), 52°02΄E (longitude) and 1810 m (m.s.l.). The lysimeters dimension were 1.5 m × 1.5 m × 1.1 m. There was a 0.9 m soil layer (clay loam) in the lysimeters with field capacity of 0.34 m3 m−3 and wilting point of 0.14 m3 m−3. The properties of soil and irrigation water are shown in Table 1. Physical properties of the soil were taken from the study of Barzegari et al. (2017). The variation in climatic data that were measured in a station near the site in two years are figured (Fig. 1). Annual rainfall of 282 mm and 378 mm occurred in late fall and winter in the first year, and winter in the second year, respectively. Wheat (local Pishtaz cultivar) was seeded on October 29th and November 6th (2015 and 2016, respectively) in lysimeters. The well water with electrical conductivity (EC) of 0.72 dS m−1 was used for irrigation water. The drainage water was conducted to the individual sump and collected in containers. Four ridges (0.5 m spacing) and three furrows manually constructed in each lysimeter. Phosphorous fertilizer was applied as triple superphosphate at rate of 150 kg ha−1 (46% P2O5) and mixed with the soil surface layer at the time of soil preparation. Nitrogen fertilizer was applied as urea (46% N) at two times along with irrigation water at planting and beginning the stem elongation. Wheat seeding rate was 250 kg ha-1 in 6 rows in the furrows and on the ridges. The distance between two rows in each furrow or on ridge was 0.15 m. The spacing between two rows in consecutive furrow or ridge was 0.35 m. The experiment was conducted in a split-split-plot design with randomized complete blocks with three replications. Interaction effects of three factors were investigated in this study. These factors were irrigation strategies as main plot, planting method and nitrogen fertilizer 2

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Fig. 1. Monthly mean maximum and minimum temperature, relative humidity and rainfall during the growing season in 2015–2016 and 2016–2017 (Mehrabi and Sepaskhah, 2018).

rates as sub-plot and sub-sub-plots, respectively. Two different irrigation treatments were full irrigation by ordinary furrow (OFI) and partial root drying irrigation (PRD) as variable alternate furrow irrigation (VAFI). On-ridge planting (ORP) and in-furrow planting (IFP) were used as different planting methods. Nitrogen fertilizer treatments were N0 = 0, N1 = 150 and N2 = 300 kg N ha−1.

L × W was determined as follows: n

A= c

Soil water content before irrigation event was used to determine the crop irrigation requirement. An access tube of neutron meter was installed in the middle furrow. Soil water content was measured at three depths of 0.3 m, 0.6 m, and 0.9 m with neutron scattering method in the access tubes. In addition, soil water content at the depth of 0-0.1 m of surface soil was measured by the gravimetric method. The irrigation water was considered by raising the soil water in the lysimeter to the field capacity and it was calculated by the following equation:

A = 0.6915

(

fci

i)

zi

Li Wi

(R2 = 0.999, n = 130, SE = 7.75, p < 0.0001)

(3)

The measured leaf length and width were used in Eq. (3) to determine the plant leaf area. Then, the plant leaf area was divided by the devoted area of each plant to calculate the LAI. LAI was measured monthly until the breaking dormancy and every two weeks to the end of growing season. Within each lysimeter, one fully expanded leaf from the top of the plant was chosen for measuring the gas exchange parameters. These parameters were net photosynthesis rate (An), stomatal conductance (gs) and leaf transpiration rate (Tr) that were measured using LCi analyzer (ADC Bioscientific Ltd.) on different days. The measurements were made under periods of fair-weather condition. In order to measure leaf water potential (LWP), one fresh leaf from the top of the plant was selected in each lysimeter during different growth stages (early stem elongation, stem elongation, booting, heading in the first year and during the early stem elongation, stem elongation, early heading, early flowering and end of flowering in the second year) in the midday around 11 a.m. −1 pm and LWP was measured using pressure bomb (PMS Instrument Company- Model 1000 Pressure Chamber Instrument). Furthermore, growing degree days (GDD) was calculated by following equation (McMaster and Wilhelm, 1997):

n i=1

(2)

Where A is the total area of crop leaves, Li leaf length, Wi leaf width and c equation coefficient. In order to obtain leaf area index (LAI), one plant was specified in each lysimeter and its leaf length (L) and width (W) was measured during the growing season. At first, a linear relation was obtained between total leaf area of a plant and multiplication of L × W by regression analysis [Eq. (3)], then plant leaf area was determined using this equation during the growing season.

2.2. Irrigation requirement

d=

Li Wi k=1

(1)

Where d is the irrigation water depth (m), i is the soil layer number, n is the total number of soil layers, fci and i are the volumetric soil water content at field capacity and before the irrigation event (m3 m−3), respectively and z i is the soil layer thickness (m). The irrigation application efficiency of 70% was used to convert the irrigation water to gross irrigation water. For the first irrigation, all lysimeters were irrigated with OFI method to provide uniform seed germination and plant stands. The amount of applied water in the first irrigation was about 27 mm in the first year (about 77 mm of rainfall occurred during the week after sowing) and 111 mm in the second year. Crop water requirement was generally provided by precipitation till March in the first year. Afterward, the irrigation treatments were started. However, in the second year due to lack of adequate rainfall after sowing, second irrigation event (80 mm) was applied in OFI. The gross irrigation water was applied with 10-days irrigation interval in all irrigation furrows in OFI. The amount of applied irrigation water in each irrigation event for VAFI was 2/3 of that applied in OFI and it was applied in the furrows which were dry in the preceding irrigation cycle.

n

GDD = 0

Tmax + Tmin 2

Tb if Tave < Tb, Tave = Tb, if Tave > TUT , Tave = TUT

(4)

Where Tmax and Tmin are the maximum and minimum air temperature in °C, respectively, Tb is the crop base temperature and it was considered as zero for winter wheat and TUT is the upper temperature threshold that was considered as 25 °C for wheat (McMaster and Smika, 1988).

2.3. Crop parameters measurement Since the leaf area varies among cultivation, sowing density and nitrogen rate in winter wheat (Bavec et al., 2007), it was measured during the growing season to investigate the effects of different treatments on wheat growth. In different growth stages, one plant was detached from the field and the leaf length (L) and width (W) were measured by ruler and the leaves area were measured by an area meter. A relationship between the measured leaf area and multiplication of

2.4. Statistical analysis The interaction effects between irrigation method, planting method and nitrogen application rate were evaluated by using analysis of variance (ANOVA) and means were compared by Duncan’s multiple range 3

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Table 2 Seasonal applied irrigation water and maximum LAI (LAImax) for wheat in different treatments. Characteristics

Applied irrigation water, mm 2015-2016 2016-2017 LAImax 2015-2016 2016-2017

Irrigation

On-ridge planting

In-furrow planting

regime

N0

N1

N2

N0

N1

N2

OFI VAFI OFI VAFI

743 504 683 493

941 636 920 651

1138 768 1154 809

727 494 684 493

865 586 833 592

1003 678 975 689

OFI VAFI OFI VAFI

2.95* def 2.20 ef 3.79 bc 3.02 bc

4.72 3.29 7.36 6.26

9.93 a 6.15 bc 10.13 a 6.60 abc

1.74 3.96 2.80 3.85

cde def ab abc

f cdef c bc

4.67 5.19 5.88 6.88

cde bcd abc abc

7.57 7.20 9.55 8.58

b b a a

LAImax: Maximum leaf area index; N0= control N fertilizer; N1 = 150 kg N ha−1; N2 = 300 kg N ha−1; OFI = ordinary furrow irrigation; VAFI = variable alternate furrow irrigation. * Means followed by the same letters in each trait are not significantly different at 5% level of probability.

Fig. 2. Soil water content in furrows for different treatments during the winter wheat growing period in two years. a: N0P1 in 2016–2017; b: N0P1 in 2015–2016; c: N0P2 in 2016–2017; d: N0P2 in 2016-2016; e: N2P1 in 2016–2017; f: N2P1 in 2015–2016; g: N2P2 in 2016–2017; h: N2P2 in 2015–2016.

4

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Fig. 3. The leaf area index (LAI) of winter wheat as function of growing degree days (GDD) for different treatments. a: On-ridge planting in 2016–2017; b: In-furrow planting in 2016–2017; c: On-ridge planting in 2015–2016; d: In-furrow planting in 2015–2016. I1: Ordinary furrow irrigation (OFI). I2: Variable alternate furrow irrigation (VAFI). N0: 0 kg N ha−1. N1: 150 kg N ha−1. N2: 300 kg N ha−1. P1: on-ridge planting method. P2: in-furrow planting method.

Table 3 Wheat agronomic yields for different treatments (Mehrabi and Sepaskhah, 2018). Characteristics

Grain yield, Mg ha−1 2015-2016 2016-2017 Top dry matter, Mg ha−1 2015-2016 2016-2017

Irrigation

On-ridge planting

regime

N0

OFI VAFI OFI VAFI

3.27 2.87 6.14 4.78

OFI VAFI OFI VAFI

12.45 10.98 13.90 13.22

In-furrow planting N1

( ± 0.44) ( ± 0.26) ( ± 1.15) ( ± 1.81)

cd* d c c

( ± 1.58) ( ± 1.43) ( ± 1.42) ( ± 2.34)

e e e e

5.28 4.32 9.38 9.07

( ± 1.53) ( ± 0.28) ( ± 2.25) ( ± 0.73)

20.35 19.14 25.05 24.10

ab bc b b

( ± 2.78) ( ± 2.62) ( ± 2.19) ( ± 2.20)

cd d cd d

N2

N0

5.68 ( ± 1.04) a 4.85 ( ± 0.92) ab 10.16 ( ± 0.52) b 10.16 ( ± 1.55) b

3.32 3.09 5.37 5.38

23.05 21.29 29.04 28.49

13.32 12.29 15.00 14.56

( ± 1.72) ( ± 2.79) ( ± 1.76) ( ± 2.37)

bc bcd b bc

( ± 0.41) ( ± 0.32) ( ± 0.84) ( ± 1.11)

( ± 0.82) ( ± 0.69) ( ± 2.53) ( ± 1.66)

OFI: Ordinary furrow irrigation. VAFI: Variable alternate furrow irrigation. N0: 0 kg N ha−1. N1: 150 kg N ha−1. N2: 300 kg N ha−1. * Means followed by the same letters in each trait are not significantly different at 5% level of probability.

5

cd cd c c e e e e

N1

N2

4.90 ( ± 0.73) ab 4.27 ( ± 0.64) bc 10.84 ( ± 0.64) ab 8.75 ( ± 1.43) b

5.96 ( ± 0.49) a* 5.38 ( ± 0.82) ab 12.46 ( ± 1.02) a 9.90 ( ± 0.42) b

23.58 19.46 27.83 25.55

26.69 22.29 32.79 28.27

( ± 0.81) ( ± 1.66) ( ± 1.11) ( ± 2.38)

b d bc bcd

( ± 1.72) ( ± 2.19) ( ± 1.09) ( ± 2.02)

a bc a bc

Agricultural Water Management 223 (2019) 105688

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Fig. 4. The leaf water potential for different treatments. a: Variable alternate furrow irrigation (VAFI) in 2015–2016; b: Ordinary furrow irrigation (OFI) in 2015–2016; c: Variable alternate furrow irrigation (VAFI) in 2016–2017; d: Ordinary furrow irrigation (OFI) in 2016–2017. P1: On-ridge planting. P2: In-furrow planting. N0: 0 kg N ha−1. N1: 150 kg N ha−1. N2: 300 kg N ha−1. P1: on-ridge planting method. P2: in-furrow planting method.

tests at 5% level of probability. The statistical analyses were carried out by MSTATC software.

3.2. Leaf area index The leaf area index was figured to days after planting and GDD for different treatments during the growing season in 2015–2016 and 2016–2017; although, it has been presented as a function of GDD (Fig. 3). The LAI reached its maximum, 176 and 167 days after planting in the first and second year, respectively. The corresponding GDD was about 1261 °C and 1441 °C at maximum LAI (LAImax) for the first and second year, respectively; although, the growing season in the first year was longer than that in the second year. This reduction of GDD resulted from inappropriate weather condition and spring cold in the first year that also resulted in less LAI and yield (Tables 2 and 3). Besides, a relationship between LAImax and irrigation water depth was determined by following equation:

3. Results and discussion 3.1. Water application With regard to Table 2, in-furrow planting reduced the applied water in comparison with that obtained in on-ridge planting about 10–15% in 300 kg N ha−1 application rate in the first and second year, respectively. Therefore, in-furrow planting reduced the surface evaporation and preserved soil water in the root zone especially in higher N fertilizer rates. Consequently, less water applied to in-furrow planting compared with that applied in on-ridge planting. Application of higher nitrogen rate also increased the applied water in different irrigation regimes. In general, application of 150 kg N ha−1 increased the applied water about 26–33% in on-ridge planting and 18–20% in in-furrow planting compared with that obtained in 0 N application. These increases were about 52–66% in on-ridge planting and 37–40% in infurrow planting in 300 kg N ha−1 compared with that obtained in 0 N application. Soil water content was measured in the middle furrow (OFI and VAFI) and side furrow in VAFI strategy during two growing seasons and results are presented in Fig. 2. Soil water content was almost the same in two irrigation methods at the early season due to rainfall occurrence, then it showed differences after irrigation treatment initiation and applying VAFI strategy. Soil water content differed in two different furrows in VAFI strategy due to applying irrigation in different furrows in every irrigation cycle. Generally, soil water content in VAFI strategy was lower than that obtained in OFI strategy due to applying lower amount of irrigation water.

LAImax = 0.009 IRR 0.96 (R2 = 0.47, n = 24, SE = 1.85, p = 0.0002)

(5)

Where LAImax and IRR are the maximum LAI and irrigation water depth (mm), respectively. Eq. (5) showed that by 107 mm of irrigation water depth (threshold) the LAImax started to increase from zero and reached 10 at irrigation water application of 1004 mm. The threshold indicated that some portion of the irrigation water lost by deep percolation and surface evaporation. Regarding Table 2, the LAImax reached its highest value as 9.93 and 10.13 and the lowest values as 1.74 and 2.8 in the first and second year, respectively. As for LAImax, Bavec et al. (2007) reported 1.0–7.5 for an especial variety among control and 120 kg N ha−1 treatments with 600 seeds m-2 (same seed density in this study). The maximum values of LAI belonged to on-ridge planting in OFI and 300 kg N ha−1 and minimum values were observed in in-furrow planting with OFI and no N 6

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Fig. 5. The relationship between yield and leaf water potential (-LWP) for different treatments. a: Stem elongation in on-ridge planting; b: Stem elongation in infurrow planting; c: Booting in on-ridge planting; d: Booting in in-furrow planting; e: Heading in on-ridge planting; f: Heading in in-furrow planting.

obtained in on-ridge planting for all nitrogen application rates in two consecutive years. In contrast, LAI value in in-furrow planting with VAFI increased compared with that obtained in on-ridge planting. These results are in contradiction to those obtained by Shahrokhnia and sepaskhah (2017) for safflower. Increasing in LAImax value in on-ridge planting with OFI can be related to higher tilering in this treatment compared with that obtained in in-furrow planting. However, better conditions for plant growth may be provided by in-furrow planting due to higher soil water and temperature (Shabani et al., 2013b; Yarami and Sepaskhah, 2015b) in VAFI treatments and resulted in higher LAImax (Table 2). Moreover, application of nitrogen increased LAImax in comparison with that obtained in no N application (Table 2). Compared with no N application rate, application of 150 kg N ha−1 increased LAImax as 55% and 100% in the first and second year, respectively. Similarly, application of 300 kg N ha−1 increased LAImax about 200% and 143% in the first and second year, respectively that was similar to the results reported by Shahrokhnia and Sepaskhah (2017) for safflower. Higher values of LAI are rooted in larger leaf area and more tillering compared with that obtained in non-fertilized plants. There is no significant interaction between irrigation strategies and planting methods or nitrogen rates (Table 2) on LAImax. The only factor affecting on LAImax was nitrogen rate (p < 0.05). Results indicated

Fig. 6. The relationship between net photosynthesis rate and leaf water potential (-LWP) for different treatments.

application rate (N0) in both years. Decrease in irrigation water reduced LAI (Azizian and Sepaskhah, 2014a; Zhang et al., 2009). As it is observed in Table 2, OFI enhanced LAImax compared with that obtained in VAFI strategy; although, this increase is not statistically significant with an exception in the first year (N2P1). On the other hand, LAImax was lower in the in-furrow planting with OFI in comparison with that 7

Agricultural Water Management 223 (2019) 105688

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Fig. 7. Variations of gas exchange parameters. a: Net photosynthesis rates (An); b: Stomatal conductance (gs) during the growing season in two years. *Means followed by the same letters in each trait are not significantly different at 5% level of probability.

Fig. 8. Variations of gas exchange parameters. a: Leaf transpiration rates (Tr); b: Leaf transpiration efficiency (An/Tr) during the growing season in two years. *Means followed by the same letters in each trait are not significantly different at 5% level of probability.

that application of 300 kg N ha−1 caused a significant increase in LAImax compared with that obtained in no N application and 150 kg N ha−1. However, there is no significant difference in application of 150 kg N ha−1 on LAImax compared with that obtained in 300 kg N ha−1. In general, application of 150 kg N ha−1 had the optimum LAImax with no significant difference in crop yield in comparison with that obtained in application of 300 kg N ha−1.

LWP. Besides, a simple linear relationship was obtained between the net photosynthesis rate (An) and LWP (Fig. 6) as follows:

An = 5.09 ( LWR) + 23.58 (R2 = 0.35, n = 72, SE = 3.02, p < 0.01)

(6)

Results indicated that with decreasing the leaf water potential, photosynthetic rate decreased linearly. Therefore, soil water condition and leaf water condition has a direct role on net photosynthetic rate during the growing season.

3.3. Leaf water potential Fig. 4 illustrates the leaf water potential (LWP) during the growing season for different treatments in two years. It is shown that LWP in the 2015–2016 was lower than that in 2016–2017. The higher value of LWP in the second year was accounted due to about 183 mm rainfall during 17 days before the first measurement of LWP. This difference in LWP between two years affected yield and showed the sensitivity of winter wheat to water stress during the stem elongation stage. Overall, leaf water potential decreased during growing season due to increase in air temperature (Fig. 1). The relationship between grain yield and LWP in different growth stages was figured (Fig. 5) for two different planting methods. Since the relationship between grain yield and LWP in flowering stage was not significant it was not shown. The relationship between yield and LWP showed that with decreasing in LWP, yield reduced with a non-linear relationship in both planting methods. However, reduction in grain yield in in-furrow planting was more severe than that obtained in on-ridge planting, since PRD may have no function in this case due to the fact that both sides of the crop root irrigated in each irrigation event but with longer irrigation interval. Therefore, VAFI with on-ridge planting is considered as PRD strategy that is effective in decreasing the reduction of grain yield by decreasing

3.4. Net photosynthesis rate (An) According to Fig. 7a, net photosynthesis rate was measured for different growth stages in two years; although, An was not measured because of cloudy weather during the flowering stage and stem elongation in the first and second year, respectively. Furthermore, it should be noticed that about two weeks after the first measurement, the second part of nitrogen (50%) was applied to the field. Besides, it should be mentioned that VAFI strategy was not applied during the stem elongation because of enough rainfall occurrence at this time in the second year. Results indicated that none of the irrigation strategies, planting methods and N application rates showed significant difference in net photosynthesis rate of winter wheat (p > 0.05). Hashem et al. (2018) reported that PRD irrigation did not affect net photosynthesis rate of tomato compared with that obtained in full irrigation, although PRD decreased the stomatal conductance. The An values varied between 5.48–23.1 μmol m−2 s−1 and 6.91–19.7 μmol m−2 s−1 for different treatments and growth stages in the first and second year, respectively. 8

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Highest value of An was obtained during the stem elongation after applying the second part of nitrogen fertilizer in the first year that was in accordance with the results reported by Shahrokhnia and Sepaskhah (2017) and Kazemeini et al. (2015) for safflower and Shabani et al. (2013a) for rapeseed. However, net photosynthesis rate started to decrease after stem elongation stage and gradually continued until end of growing season; although, during the booting, An decreased sharply in the first year because of spring cold and it increased again as the weather condition improved. It is observed (Fig. 7a) that An decreased much more in OFI compared with that obtained in VAFI strategy and indicated that VAFI strategy increased plant tolerance against the spring cold. The photosynthesis rate was reduced gradually after heading during the winter wheat growing season due to increase in air temperature higher that for optimum photosynthesis rate. As other studies suggested for safflower and rapeseed (Shahrokhnia and Sepaskhah, 2017; Kazemeini et al., 2015; Shabani et al., 2013a), the An had the highest values in stem elongation stage. 3.5. Stomatal conductance (gs) The stomatal conductance (gs) of winter wheat varied between 0.08 to 0.57 mol m−2 s−1 in the first year and 0.09 to 0.51 mol m−2 s−1 in the second year (Fig. 7b). The VAFI strategy (PRD) reduced gs values about 12% and 7% in comparison with that obtained in OFI in the first and second year, respectively that were not significant showing that this strategy can be used effectively in saving water instead of OFI. Likewise, Shahrokhnia and Sepaskhah (2017) and Azizian and Sepaskhah (2014b) reported a reduction of about 24% and 43% in gs for safflower with VAFI strategy and maize with deficit irrigation (DI); respectively, that shows winter wheat is more tolerant to water stress than safflower and maize. As previously stated, stomatal conductance decreased sharply during booting stage because of spring cold in the first year and VAFI strategy (PRD) showed higher gs in this stage (Fig. 7b). In response to water stress, stomata closure generally occurs due to atmospheric vapor pressure along with root-generated chemical signals like producing stress hormone (abscisic acid) (Ashraf and Harris, 2013; Sepaskhah and Ahmadi, 2012). As an illustration, Hashem et al. (2018) reported that the values of the abscisic acid (ABA) contents were higher under PRD and regular deficit irrigation than that obtained in full irrigation. Since stomata closure have more inhibitory effect on

Fig. 9. Relationship between photosynthesis rate and stomatal conductance. a: Data individually in different stages in year 2015–2016; b: Data individually in different stages in year 2016–2017; c: All the data during the growing season in two years.

Table 4 Linear relationship between photosynthesis rate and stomatal conductance for different treatments in years 2015–2016 and 2016–2017. First year Linear relationship

R2

pv

An = 22.6gs+7.12 An = 16.0gs+12.7 An = 50.8gs+3.60 An = 22.7gs+9.15

0.80 0.70 0.82 0.77

Irrigation strategy OFI VAFI

An = 33.5gs+6.26 An = 29.4gs+6.19

Planting method ORP IFP Nitrogen rate N0 N1 N2

Treatment Growth stage Early stem elongation Stem elongation Booting Heading Early flowering End of flowering

Second year Linear relationship

R2

pv*

< 0.0001 < 0.0009 < 0.0001 0.0001

An = 22.7gs+8.32

0.15

0.20

An = 22.7gs+8.36 An = 15.4gs+10.07 An = 27.9gs+5.55

0.67 0.38 0.56

0.001 < 0.033 < 0.005

0.86 0.91

< 0.0001 < 0.0001

An = 29.4gs+6.26 An = 23.8gs+7.78

0.74 0.69

< 0.0001 < 0.0001

An = 30.0gs+6.68 An = 30.3gs+6.35

0.84 0.88

< 0.0001 < 0.0001

An = 26.9gs+7.19 An = 24.7gs+7.22

0.75 0.64

< 0.0001 < 0.0001

An = 39.8gs+4.54 An = 29.3gs+6.50 An = 25.0gs+8.05

0.90 0.93 0.74

< 0.0001 < 0.0001 < 0.0001

An = 26.0gs+7.18 An = 24.7gs+7.34 An = 27.30gs+6.96

0.47 0.67 0.88

0.003 0.0001 < 0.0001

* Pv: probability level of R2.

9

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Fig. 10. Relationship between gas exchange parameters and VPD, a: photosynthesis rate (An) in on-ridge planting; b: photosynthesis rate (An) in in-furrow planting; c: stomatal conductance (gs) in on-ridge planting; d: stomatal conductance (gs) in in-furrow planting; e: leaf transpiration rate (Tr) in on-ridge planting; f: leaf transpiration rate (Tr) in in-furrow planting for all treatments in two years.

transpiration than that on CO2 diffusion into the leaf tissues (Ashraf and Harris, 2013), it was not seen any significant difference in An in this study. Consequently, PRD can be used as a proper strategy with mild stress in field irrigation management. Application of 150 kg N ha−1 increased stomatal conductance of winter wheat about 2.8% and 28.4% compared with that obtained in no N application rate in the first and second year, respectively. Higher application rate of nitrogen (300 kg N ha−1) enhanced the gs values around 18.8% and 8.6% in comparison with that obtained in 150 kg N ha−1 in the first and second year, respectively. High N supply lead to a less carbon loss compared with that under a low N supply. Besides, N deficiency can decrease the stomatal aperture by increasing their sensitivity to endogenous abscisic acid (Sun et al., 2016).

affection on transpiration rate. Shahrokhnia and Sepaskhah (2017) suggested that VAFI decreased transpiration rate about 27% for safflower in comparison with that obtained in OFI; although, it was not significant as well. Application of 150 kg N ha−1 increased leaf transpiration rate of winter wheat about 5% and 14% compared with that obtained in no N application rate in the first and second year, respectively. Application of 300 kg N ha−1 enhanced the Tr values about 10% and 3% in comparison with that obtained in 150 kg N ha−1 in the first and second year, respectively. Overall, N application rates and planting methods did not show any specific influences on leaf transpiration rate in various growth stages. Leaf transpiration rate variation was similar to net photosynthesis rate during the growing season for different crop growth stages.

3.6. Leaf transpiration rate (Tr)

3.7. Leaf transpiration efficiency (An/Tr)

The transpiration rate of winter wheat leaf varied between 2.84 to 10.05 mmol m−2 s−1 in the first year and 2.89 to 7.92 mmol m−2 s−1 in the second (Fig. 8a). The VAFI strategy (PRD) reduced Tr values in most of treatments about 6% and 14% in the first and second year, respectively. This reduction can be linked to decreasing the gs as stated before and its

Fig. 8b shows the variation of leaf transpiration efficiency in different irrigation strategies in both years. The VAFI strategy (PRD) showed higher An/Tr in comparison with that obtained in OFI without any significant decrease in photosynthesis rate for different N application rates. However, there was a significant difference in An/Tr between 10

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Fig. 11. Relationship between An/gs and An/Tr and VPD. a: An/gs in on-ridge planting; b: An/gs in in-furrow planting; c: An/Tr in on-ridge planting; d: An/Tr in infurrow planting for all treatments in two years.

Table 5 Linear relationship between gas exchange parameters and VPD for different treatments. On-ridge planting

In-furrow planting

Parameters

Irrigation strategy

Linear relationship

n

SE

R2

pv

Linear relationship

n

SE

R2

pv

Photosynthesis rate

OFI VAFI OFI VAFI OFI VAFI OFI VAFI OFI VAFI

An = 6.65VPD+4.13 An = 3.20VPD+8.78 gs = 0.22VPD-0.07 gs = 0.10VPD+0.08 Tr = 4.23VPD-0.13 Tn = 2.40VPD+1.72 An/gs=-27.06VPD+99.05 An/gs =-14.94VPD+88.55 An/Tr =-0.78VPD+3.51 An/Tr =-0.70VPD+3.66

8 8 8 8 8 8 8 8 8 8

2.37 2.77 0.06 0.05 0.64 1.03 6.34 10.87 0.40 0.24

0.58 0.19 0.73 0.24 0.89 0.49 0.76 0.25 0.40 0.60

0.03 0.27 < 0.01 < 0.01 < 0.01 0.05 < 0.01 0.21 0.09 0.02

An = 4.80VPD+5.63 An = 5.19VPD+5.24 gs = 0.18VPD-0.04 gs = 0.16VPD-0.03 Tr = 3.70VPD+.35 Tn = 2.92VPD+0.75 An/gs=-30.38VPD+109.51 An/gs =-24.67VPD+107.04 An/Tr =-0.86VPD+3.53 An/Tr =-0.50VPD+3.36

8 8 8 8 8 8 8 8 8 8

2.99 2.97 0.09 0.07 1.36 0.96 15.70 9.65 0.33 0.33

0.32 0.35 0.38 0.48 0.57 0.62 0.40 0.54 0.55 0.29

0.15 0.12 0.10 0.06 0.03 0.02 0.09 0.04 0.04 0.17

Stomatal conductance Leaf transpiration rate An/gs An/Tr

no N application rate (N0) with VAFI strategy and other N application rates. Although, the difference between OFI and VAFI strategies was not significant for most of the treatments during growth stages, the leaf transpiration efficiency showed efficient water use in VAFI strategy. Similar findings are also reported for potato by Ahmadi et al. (2010) and Liu et al. (2005).

slope of fitted line in booting stage was high that showed spring cold made net photosynthesis rate very sensitive and with a slight decline in gs, photosynthesis rate decreased remarkably. However, higher slope (S = 27.89, p = 0.005) belonged to the relationship between An and gs during the end of flowering in the second year (Fig. 9b), and it showed that net photosynthesis rate was more sensitive to closing the stomatal in this growth stage. Fig. 9c illustrated the relationship between net photosynthesis rate and gs for all growth stages together in two years. A power relationship was fitted to the relationship between An and gs during the growing season (Fig. 9c). Besides, in order to find out the effects of irrigation strategies, planting methods and nitrogen rate on the relationship between An and gs in winter wheat, it was determined for each treatment separately (Table 4). The slope of fitted lines in VAFI strategy (PRD) is lower than that obtained in OFI, and indicated when gs decreases under PRD conditions, the An values are reduced with lower rates; therefore, this strategy was efficient in water use reduction and winter wheat showed adaptation with this strategy against water stress. This finding agrees with study of Shahrokhnia and Sepaskhah (2017) for safflower in PRD

3.8. Relationship between An and gs Since the relationship between An and gs was recognized as a drought-adaptation index (Chaves, 1991), linear relationship between the An and gs was determined for different growth stages in two years (Fig. 9) like that was found for safflower by Shahrokhnia and Sepaskhah (2017), maize by Azizian and Sepaskhah (2014b), and saffron by Yarami and Sepaskhah (2015a). Fig. 7a and b, showed the linear relationship between An and gs in different growth stages in the first and second year, respectively. With regard to fair weather requirement for measuring the photosynthesis rate, it could not be measured in some growth stages for both years (flowering in the first year and stem elongation and booting in the second year). Regarding with Fig. 9a, the 11

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condition. However, the slopes of linear relationship in various planting methods were close to each other; therefore, drought adaptation was not varied by different planting methods that is consistent with the finding of Shahrokhnia and Sepaskhah (2017) for safflower and Yarami and Sepaskhah (2015a) for saffron. The slopes of linear relationship for different N fertilization rates in the first year indicated that non-fertilized plants were more sensitive to water deficits in contrast to that found in the second year. Finding of Shahrokhnia and Sepaskhah (2017) showed that fertilized plant was more sensitive to water stress. This difference can be due to occurrence of spring cold along with the water stress in the first year and it increased the sensitivity of the photosynthesis rate in plants with lower N rate to water shortage. On the other hand, application of 300 kg N ha−1 was more vulnerable to water shortage in the second year that maybe due to having larger canopy and higher water requirement in this treatment (Shahrokhnia and Sepaskhah, 2017).

Although, in-furrow planting showed higher efficiency in increasing yield in comparison with on-ridge planting; however, on-ridge planting showed higher leaf water use efficiency. Since, it was not observed a significant difference between two application rates of nitrogen (150 kg N ha−1 and 300 kg N ha−1) on different parameters, application of 150 kg N ha−1 in proper weather condition (proper temperature during booting and flowering, enough rainfall occurrence during the effective growth stages and preparing proper soil water content) can be suggested as an effective rate to increase winter wheat yield. Therefore, in areas with scarce water, combination of VAFI (PRD) strategy and 150 kg N ha−1 application rate could be recommended to achieve optimum yield with possibility of saving water and adaptation to water stress during the growing season. Acknowledgements This research supported in part by a research project funded by Grant no. 97-GR-AGR 42 of Shiraz University Research Council, Drought Research Center, the Center of Excellent for On-Farm Water Management, and Iran National Science Foundation (INSF).

3.9. Relationship between air vapor pressure deficit (VPD) and gas exchange parameters In order to discover the effect of irrigation strategy on water stress adaptation, the relationship between gas exchange parameters and VPD was illustrated (Figs. 10 and 11) for two different planting methods and irrigation strategies. The slope of the linear relationship between An and VPD in two irrigation strategies (Table 5) showed that VAFI (PRD) with on-ridge planting slightly decreased An vs. VPD indicating that VAFI (PRD) is an efficient strategy to water stress adaptation. However, VAFI strategy with in-furrow planting did not show any difference in comparison with OFI strategy. Regarding Fig. 10c–f, increasing VPD affected much more the gs and Tr than An. With increasing VPD during the growing season, gs and Tr increased; although, the slope of the line revealed that transpiration rate and gs had a slight rise in VAFI (PRD) with on-ridge planting compared with that obtained in OFI and VAFI with in-furrow planting. The slope of the line in Fig. 11a–d revealed that the rate of intrinsic water use efficiency (An/gs) and leaf transpiration efficiency (An/Tr) decreased with increase in VPD due to increasing the gs and Tr during the growing season. Intrinsic water use efficiency and leaf transpiration efficiency in VAFI (PRD) was higher than that obtained in OFI, and the slope of linear relationship was lower (−14.9 and −0.5 in An/gs and An/Tr, respectively) in VAFI (PRD) with on-ridge planting and in-furrow planting, respectively in comparison with those obtained in OFI (−27.06 and −0.85 in An/gs and An/Tr, respectively) with on-ridge planting and in-furrow planting. These results indicated the possibility of plant water stress adaptation in PRD strategy without much effect on the leaf transpiration efficiency reduction (Ahmadi et al., 2010).

References Abdelraouf, R.E., Ragab, R., 2018. Applying partial root drying drip irrigation in the presence of organic mulching. Is that the best irrigation practice for arid regions? Field and modelling study using the saltmed model. Irrig. Drain. 67 (4), 491–507. Ahmadi, S.H., Andersen, M.N., Plauborg, F., Poulsen, R.T., Jensen, C.R., Sepaskhah, A.R., Hansen, S., 2010. Effects of irrigation strategies and soils on field-grown potatoes: gas exchange and xylem [ABA]. Agric. Water Manage. 97, 1486–1494. Ashraf, M.H.P.J.C., Harris, P.J.C., 2013. Photosynthesis under stressful environments: an overview. Photosynthetica 51, 163–190. Azizian, A., Sepaskhah, A.R., 2014a. Maize response to different water, salinity and nitrogen levels: agronomic behavior. Int. J. Plant Prod. 8, 107–130. Azizian, A., Sepaskhah, A., 2014b. Maize response to water, salinity and nitrogen levels: physiological growth parameters and gas exchange. Int. J. Plant Prod. 8, 131–162. Barzegari, M., Sepaskhah, A.R., Ahmadi, S.H., 2017. Irrigation and nitrogen managements affect nitrogen leaching and root yield of sugar beet. Nutrient Cycling in Agroecosystems 108, 211–230. Bavec, M., Vuković, K., Grobelnik, S., Rozman, Č., Bavec, F., 2007. Leaf area index in winter wheat: response on seed rate and nitrogen application by different varieties. J. Cent. Eur. Agric. 8, 337–342. Casa, R., Rouphael, Y., 2014. Effects of partial root-zone drying irrigation on yield, fruit quality, and water-use efficiency in processing tomato. J. Hortic. Sci. Biotechnol. 89, 389–396. Chaves, M.M., 1991. Effects of water deficits on carbon assimilation. J. Exp. Bot. 42, 1–16. Collins, M.J., Fuentes, S., Barlow, E.W., 2010. Partial rootzone drying and deficit irrigation increase stomatal sensitivity to vapour pressure deficit in anisohydric grapevines. Funct. Plant Biol. 37, 128–138. Davies, W.J., Wilkinson, S., Loveys, B., 2002. Stomatal control by chemical signalling and the exploitation of this mechanism to increase water use efficiency in agriculture. New Phytol. 153, 449–460. Dbara, S., Haworth, M., Emiliani, G., Mimoun, M.B., Gómez-Cadenas, A., Centritto, M., 2016. Partial root-zone drying of olive (Olea europaea var.’Chetoui’) induces reduced yield under field conditions. PLoS One 11, e0157089. Food and Agriculture Organization of the United Nations, 2016. Irrigation Area Visualizations. (Accessed 15 December 2018). http://www.fao.org/nr/water/ aquastat/irrigationdrainage/treemap/index.stm/. Frederick, J.R., Camberato, J.J., 1995. Water and nitrogen effects on winter wheat in the southeastern Coastal Plain: II. Physiological responses. Agron. J. 87, 527–533. Hashem, M.S., El-Abedin, T.Z., Al-Ghobari, H.M., 2018. Assessing effects of deficit irrigation techniques on water productivity of tomato for subsurface drip irrigation system. Int. J. Agric. Biol. Eng. 11, 156–167. Haworth, M., Marino, G., Cosentino, S.L., Brunetti, C., De Carlo, A., Avola, G., Centritto, M., 2018. Increased free abscisic acid during drought enhances stomatal sensitivity and modifies stomatal behaviour in fast growing giant reed (Arundo donax L.). Environ. Exp. Bot. 147, 116–124. Jia, D.Y., Dai, X.L., Men, H.W., He, M.R., 2014. Assessment of winter wheat (Triticum aestivum L.) grown under alternate furrow irrigation in northern China: grain yield and water use efficiency. Can. J. Plant Sci. 94, 349–359. Kang, S.Z., Shi, P., Pan, Y.H., Liang, Z.S., Hu, X.T., Zhang, J., 2000. Soil water distribution, uniformity and water-use efficiency under alternate furrow irrigation in arid areas. Irrig. Sci. 19, 181–190. Kang, S., Zhang, J., 2004. Controlled alternate partial root-zone irrigation: its physiological consequences and impact on water use efficiency. Environ. Exp. Bot. 55, 2437–2446. Kazemeini, S.A., Mohamadi, S., Pirasteh-Anosheh, H., 2015. Growth and photosynthesis responses of safflower cultivars to water stress at two developmental stages. Biol. Forum 7 (2), 923–929.

4. Conclusions It was concluded that decreasing LWP during the stem elongation stage resulted in yield reduction due to extreme sensitivity of winter wheat to water stress during this growth stage. The values of An and gs were not significantly reduced in VAFI (PRD) in comparison with that obtained in OFI; although, the reduction in gs was higher than An which saved 30% irrigation water with a slight reduction in grain yield. The slope of fitted lines in VAFI (PRD) strategy in comparison with that obtained in OFI indicated that when gs decreases under water shortage conditions, the An values are reduced with lower rates; therefore, VAFI (PRD) strategy is efficient and winter wheat can show adaptation with this strategy against water stress. The lower slope of linear relationship between An/Tr and VPD, in VAFI (PRD) strategy indicated that with increasing VPD leaf transpiration efficiency decreased in VAFI (PRD) with lower rate than that obtained in OFI. As a consequence, VAFI (PRD) strategy can be an alternative irrigation management in winter wheat farms with limited water supplies. 12

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F. Mehrabi and A.R. Sepaskhah Khalil, A.A., Grace, J., 1993. Does xylem sap ABA control the stomatal behaviour of water-stressed sycamore (Acer pseudoplatanus L.) seedlings? Environ. Exp. Bot. 44, 1127–1134. Li, Q., Chen, Y., Zhou, X., Songlie, Y., 2011. Effects of deficit irrigation and planting modes on leaves’ water physiological characteristics and grain yield of winter wheat. New. Tech. Agric Eng. In: International Conference. pp. 305–308. Liu, F., Jensen, C.R., Shahanzari, A., Andersen, M.N., Jacobsen, S.E., 2005. ABA regulated stomatal control and photosynthetic water use efficiency of potato (Solanum tuberosum L.) during progressive soil drying. Plant Sci. 168, 831–836. McMaster, G.S., Wilhelm, W.W., 1997. Growing degree-days: one equation, two interpretations. Agric. For. Meteorol. 87, 291–300. McMaster, G.S., Smika, D.E., 1988. Estimation and evaluation of winter wheat phenology in the central Great Plains. Agric. For. Meteorol. 43, 1–18. Mehrabi, F., Sepaskhah, A.R., 2018. Interaction effects of planting method, irrigation regimes, and nitrogen application rates on yield, water and nitrogen use efficiencies of winter wheat (Triticum aestivum). Int. J. Plant Prod. 12, 265–283. Otoo, E., Ishii, R., Kumura, A., 1989. Interaction of nitrogen supply and soil water stress on photosynthesis and transpiration in rice [Oryza sativa]. J. 58, 424–429. Pandey, R.K., Maranville, J.W., Admou, A., 2001. Tropical wheat response to irrigation and nitrogen in a Sahelian environment. I. Grain yield, yield components and water use efficiency. Eur. J. Agron. 15, 93–105. Puértolas, J., Conesa, M.R., Ballester, C., Dodd, I.C., 2014. Local root abscisic acid (ABA) accumulation depends on the spatial distribution of soil moisture in potato: implications for ABA signalling under heterogeneous soil drying. Environ. Exp. Bot. 66, 2325–2334. Saeed, H., Grove, I.G., Kettlewell, P.S., Hall, N.W., 2008. Potential of partial rootzone drying as an alternative irrigation technique for potatoes (Solanum tuberosum). Ann. Appl. Biol. 152, 71–80. Sepaskhah, A.R., Ahmadi, S.H., 2012. A review on partial root-zone drying irrigation. Int. J. Plant Prod. 4, 241–258. Sepaskhah, A.R., Hosseini, S.N., 2008. Effects of alternate furrow irrigation and nitrogen application rates on yield and water-and nitrogen-use efficiency of winter wheat (Triticum aestivum L.). Plant Prod. Sci. 11, 250–259. Shabani, A., Sepaskhah, A.R., Kamgar-Haghighi, A.A., 2013a. Growth and physiologic response of rapeseed (Brassica napus L.) to deficit irrigation, water salinity and

planting method. Int. J. Plant Prod. 7, 569–596. Shabani, A., Sepaskhah, A.R., Kamgar, H.A., 2013b. Responses of agronomic components of rapeseed (Brassica napus L.) as influenced by deficit irrigation, water salinity and planting method. Int. J. Plant Prod. 7, 313–340. Shangguan, Z.P., Shao, M.A., Dyckmans, J., 2000. Nitrogen nutrition and water stress effects on leaf photosynthetic gas exchange and water use efficiency in winter wheat. Environ. Exp. Bot. 44, 141–149. Shahrokhnia, M.H., Sepaskhah, A.R., 2016. Effects of irrigation strategies, planting methods and nitrogen fertilization on yield, water and nitrogen efficiencies of safflower. Agric. Water Manage. 172, 18–30. Shahrokhnia, M.H., Sepaskhah, A.R., 2017. Physiologic and agronomic traits in safflower under various irrigation strategies, planting methods and nitrogen fertilization. Ind. Crops Prod. 95, 126–139. Sun, J., Ye, M., Peng, S., Li, Y., 2016. Nitrogen can improve the rapid response of photosynthesis to changing irradiance in rice (Oryza sativa L.) plants. Sci. Rep. 6, 31305. Tranavičiené, U., Urbonavičiuté, A., Samuoliené, G., Duchovskis, P., Vagusevičiene, I., Sliesaravičius, A., 2008. The effect of differential nitrogen fertilization on photosynthetic pigment and carbohydrate contents in the two winter wheat varieties. Agron. Res. 6, 555–561. Yarami, N., Sepaskhah, A.R., 2015a. Physiological growth and gas exchange response of saffron (Crocus sativus L.) to irrigation water salinity, manure application and planting method. Agric. Water Manage. 154, 43–51. Yarami, N., Sepaskhah, A.R., 2015b. Saffron response to irrigation water salinity, cow manure and planting method. Agric. Water Manage. 150, 57–66. Wang, G.Y., Han, Y.Y., Zhou, X.B., Chen, Y.H., Ouyang, Z., 2014. Planting pattern and irrigation effects on water-use efficiency of winter wheat. Crop Sci. 54, 1166–1174. Wu, F., Bao, W., Li, F., Wu, N., 2008a. Effects of drought stress and N supply on the growth, biomass partitioning and water-use efficiency of Sophora davidii seedlings. Environ. Exp. Bot. 63, 248–255. Wu, F.Z., Bao, W.K., Li, F.L., Wu, N., 2008b. Effects of water stress and nitrogen supply on leaf gas exchange and fluorescence parameters of Sophora davidii seedlings. Photosynthetica 46, 40–48. Zhang, S., Fang, B., Zhang, Y., Zhou, S., Wang, Z., 2009. Utilization of water and nitrogen and yield formation under three limited irrigation schedules in winter wheat. Acta Agron. Sin. 35, 2045–2054.

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