agronomy Article
Resource Use Efficiencies of C3 and C4 Cereals under Split Nitrogen Regimes Zartash Fatima 1 , Qaiser Abbas 1 , Amna Khan 1 , Sajjad Hussain 1 , Muhammad Arif Ali 1 , Ghulam Abbas 1 , Haseeb Younis 1 , Shahrish Naz 1 , Muhammad Ismail 1 , Muhammad Imran Shahzad 1 , Muhammad Nadeem 1 , Umair Farooq 1 , Shahzad Usman Khan 1 , Kashif Javed 1 , Azhar Ali Khan 2 , Mukhtar Ahmed 3 ID , Muhammad Azam Khan 4 and Shakeel Ahmad 1, * 1
2 3 4
*
Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan 60800, Pakistan;
[email protected] (Z.F.);
[email protected] (Q.A.);
[email protected] (A.K.);
[email protected] (S.H.);
[email protected] (M.A.A.);
[email protected] (G.A.);
[email protected] (H.Y.);
[email protected] (S.N.);
[email protected] (M.I.);
[email protected] (M.I.S.);
[email protected] (M.N.);
[email protected] (U.F.);
[email protected] (S.U.K.);
[email protected] (K.J.) PARC, Research and Training Station, Bahauddin Zakariya University, Multan 60800, Pakistan;
[email protected] PMAS, Arid Agriculture University, Rawalpindi 46300, Pakistan;
[email protected] In-service Agriculture Training Institute, Sargodha 40100, Pakistan;
[email protected] Correspondence:
[email protected]; Tel.: +92-300-731-8911
Received: 8 April 2018; Accepted: 7 May 2018; Published: 9 May 2018
Abstract: Resources are limited, thus improving resource use efficiency is a key objective for cereal-based cropping systems. This field study was carried out to quantify resource use efficiencies in selected C3 and C4 cereals under split nitrogen (N) application regimes. The study included the following treatments: six cereals (three C3 : wheat, oat, and barley; and three C4 : maize, millet, and sorghum) and four split N application regimes (NS1 = full amount of N at sowing; NS2 = half N at sowing + half N at first irrigation; NS3 = 13 N at sowing + 13 N at first irrigation + 13 N at second irrigation; NS4 = 14 N at sowing + 14 N at first irrigation + 14 N at second irrigation + 14 N at third irrigation). Results revealed that C4 cereals out-yielded C3 cereals in terms of biomass production, grain yield, and resource use efficiencies (i.e., radiation use efficiency (RUE) and nitrogen use efficiency (NUE)), while splitting N into three applications proved to be a better strategy for all of the selected winter and summer cereals. The results suggest that C4 cereals should be added into existing cereal-based cropping systems and N application done in three installments to boost productivity and higher resource use efficiency to ensure food security for the burgeoning population. Keywords: barley; maize; millet; oat; radiation use efficiency; sorghum; wheat
1. Introduction Cereals constitute a large proportion of food supplements. These are used in diets as end-products and provide greater than 70% of the worldwide caloric intake. Wheat (Triticum aestivum L.), oat (Avena sativa L.), barley (Hordeum vulgare L.), maize (Zea mays L.), millet (Pennisetum americanum L.), and sorghum (Sorghum bicolor L.) are the main C3 winter and C4 summer cereals being grown in Asia [1–4]. The classification and physiological characteristics of cereals are presented in Table 1 [5]. The historical area and production of first-, second-, and third-order cereals in Pakistan is presented in Figure 1 [6]. Currently, productivity and resource use efficiency of C3 winter and C4 summer cereals Agronomy 2018, 8, 69; doi:10.3390/agronomy8050069
www.mdpi.com/journal/agronomy
Agronomy 2018, 8, 69
2 of 16
Agronomy 2018, 8, x FOR PEER REVIEW
2 of 16
are low in Pakistan compared to other countries in the region [7–17], indicating a substantial potential winter and C4 summer cereals are low in Pakistan compared to other countries in the region [7–17], to increase resource use efficiencies [6,18–26]. indicating a substantial potential to increase resource use efficiencies [6,18–26].
Nutrient uptake
Root system
Exhaustive
Fibrous
C3
C4
Seed
C3
Photosynthesis
Propagation
Pollination Self-pollinated
Photoperiod
Growth habit Determinate
Crosspollinated Self-pol linated
Rice (Oryza sativa L.)
Long-day
Winter
Millet (Pennisetum americanum L.) Sorghum (Sorghum bicolor L.)
Dayneutral
Maize (Zea mays L.)
Summer
Barley (Hordeum vulgare L.)
Short-day
Life cycle Annual
Wheat (Triticum aestivum L.) Oat (Avena sativa L.)
Season
Family
Crop/Botanical Name
Poaceae
Table 1. Classification of commonly grown C3 and C4 cereal crops in Asia. Table 1. Classification of commonly grown C3 and C4 cereal crops in Asia.
Source: al.[5]. [5]. Source: Nazir Nazir etetal.
The world nitrogen-use efficiency (NUE) for cereal production is around 33% [27,28]. Reported The world nitrogen-use efficiency (NUE) for cereal production is around 33% [27,28]. Reported N N losses (Figure 2) are presented in Table 2 [29–38]. Lower production is due to the meager use of all losses (Figure 2) are presented in Table 2 [29–38]. Lower production is due to the meager use of all available resources along with climate variability and change [3,39–42]. Paradoxically, growers available resources along with climate variability and change [3,39–42]. Paradoxically, growers growing growing C3 and C4 cereals adopt conventional practices instead of approved practices that make C3 and C4 cereals adopt conventional practices instead of approved practices that make more efficient more efficient use of resources [43–50]. Nitrogen is the key constituent of agricultural inputs to use of resources [43–50]. Nitrogen is the key constituent of agricultural inputs to maintain production of maintain production of these cereals throughout their lifecycle [51–54] (Figure 3). Surplus N and/or these cereals throughout their lifecycle [51–54] (Figure 3). Surplus N and/or N applied without splitting N applied without splitting can be lost through pathways such as nitrification and volatilization can be lost through pathways such as nitrification and volatilization [8,40,41] (Figure 1). Principally, it [8,40,41] (Figure 1). Principally, it is essential to boost NUE through better approaches to increase is essential to boost NUE through better approaches to increase RUE. So, split N application regimes RUE. So, split N application regimes result in considerable boost in NUE, production, and result in considerable boost in NUE, production, and resultantly RUE by reducing losses and improving resultantly RUE by reducing losses and improving uptake [41]. It is a rising concern that most of the uptake [41]. It is a rising concern that most of the available or applied N is lost, thereby reducing NUE, available or applied N is lost, thereby reducing NUE, which is just 29% for cereals in developing which is just 29% for cereals in developing agrarian economies [55,56]. This research study was carried agrarian economies [55,56]. This research study was carried out to validate the influence of split N out to validate the influence of split N application on biomass accumulation, grain yields, and resource application on biomass accumulation, grain yields, and resource use efficiencies such as NUE and use efficiencies such as NUE and RUE for C3 winter and C4 summer cereals. RUE for C3 winter and C4 summer cereals. Table 2. Losses of N fertilizer in cereal crops. Table 2. Losses of N fertilizer in cereal crops. N losses N losses
Loss (%) Loss (%) 52–73 52–73 NitrateNitrate >21 >21 9.59.5 1010 Denitrification Denitrification >10 >10 RunoffRunoff 1–13 1–13 Volatilization 4040 Volatilization Drainage 23 Drainage 23
Crop/Condition Crop/Condition Corn Corn Winter Winter wheat wheat Winter Winter wheat wheat Rice Rice Corn Corn Without incorporated incorporated Without Tile Tile
Source: Raun et al. [28].
Source: Raun et al. [28].
Reference Reference [30] [30] [31] [31] [32] [32] [33] [33] [34] [34] [35,36] [35,36] [37,38] [37,38] [39] [39]
Agronomy 2018, 2018, 8, 8, 69 x FOR PEER REVIEW Agronomy
33 of of 16 16
10000
30000 25000
8000
20000
7000
15000
6000
10000
5000
5000
4000
0
2800
(b) Rice
2600
Area (000 ha)
6000 2400 2200 4000
2000 1800 1600
2000 1400
Production (Million tons)
(a) Wheat 9000
1200 0
1000
(c) Maize 1200
4000
1000
3000
800
2000
600
1000
400
0 1960
1970
1980
1990
2000
2010
Years Wheat area Wheat production
Rice area Rice production
Maize area Maize production
Figure Wheat,rice, rice, maize areaproduction and production in Pakistan 1960 to 2016. Source: Figure 1.1.Wheat, andand maize area and in Pakistan from 1960from to 2016. Source: Government Government of Pakistan [7]. of Pakistan [7].
Agronomy Agronomy 2018, 2018, 8, 8, 69 FOR PEER PEER REVIEW REVIEW Agronomy 2018, 8, xx FOR
of 16 of 16 16 444 of
Figure 2. 2. Generalized Generalized N N cycle cycle representing representing different different inputs, inputs, losses, losses, and and plant plant uptakes uptakes for for C3 and and C C4 Figure Figure 2. Generalized N cycle representing different inputs, losses, and plant uptakes for CC33 and C44 cereal crops. cereal crops. cereal crops.
Figure 3. 3. A A simplistic simplistic schematic schematic chart chart of of N N in in C C33 and and C C44 cereal cereal crop crop plants plants representing representing different different Figure 3. N in C and C Figure A simplistic schematic chart of 3 4 cereal crop plants representing different transformations that that occur occur during during the the life life span span from from sowing sowing to to harvesting harvesting of of C C33 and and C C44 cereal cereal crops. crops. transformations sowing to harvesting of C transformations that occur during the life span from 3 and C4 cereal crops. The N uptake, absorption, remobilization, and redistribution are represented with different lines in The N uptake, absorption, remobilization, and redistribution are represented with different lines in The N uptake, absorption, remobilization, and redistribution are represented with different lines in relation to various growth stages. (Source: Modified and adapted from [54].) relation to various various growth growth stages. stages. (Source: (Source: Modified Modified and and adapted adapted from from [54].) [54].) relation to
2. Materials Materials and and Methods Methods 2. 2.1. 2.1. Site Site and and Experiment Experiment Description Description Research experiments were were carried out at at the at Bahauddin Bahauddin Zakariya Research experiments carried out the Agronomic Agronomic Research Research Area Area at Zakariya ◦ 0 ◦ 0 University, Pakistan (30°15′ N latitude, 71°30′ E longitude, and 126.6 m a.s.l.). The research was University, Pakistan (30 15 N latitude, 71 30 E longitude, and 126.6 m a.s.l.). The research site site was situated under irrigated conditions in an arid environment of a silt clay loam textural class. The situated under irrigated conditions in an arid environment of a silt clay loam textural class. The detailed detailed description of the physical and chemical of the haspublished been published previously description of the physical and chemical featuresfeatures of the soil hassoil been previously [1,10]. [1,10]. The meteorological conditions for C 3 winter and C 4 summer cereal seasons are presented 4 cereal seasons are presented in Figure in The meteorological conditions for C3 winter3 and C4 summer 4, Figure and the treatments and experimental details in are outlined in Table 3. There were three and the4,treatments and experimental details are outlined Table 3. There were three replications and replications net plot size has in been mentioned in Table 3. net plot size and has been mentioned Table 3.
Agronomy 2018, 8, 69
5 of 16
Table 3. Agronomic practices for C3 winter (wheat, oat, and barley) and C4 summer (maize, millet, and sorghum) cereals. Wheat
Crops/Cultural Practices Sowing date N (kg
ha−1 )
125
Oat
Barley
Maize
Millet
C3 Cereals
C4 Cereals
November 14
August 18
115
50
227
Sorghum
170
100
Irrigations
December 7, January 14, February 1, March 11
September 12, September 28, October 17, October 31
Fertilizer dates
November 14, December 10, January 17, February 3
August 18, September 12, September 28, October 31
NS1 = whole N at sowing; NS2 = 12 N at sowing + 12 N at first irrigation; NS3 = 13 N at sowing + 13 N at first irrigation + 13 N at second irrigation; NS4 = N at first irrigation + 14 N at second irrigation + 14 N at third irrigation
Split N treatments
2m×5m
Net plot size
2m×5m
2m×5m
Sand 28%, silt 52%, and clay 20%, pH 9.6, EC 3.42 ds m−1 , OM 0.74%, total N 0.033%, P 4.92 ppm, and K 255 ppm
Soil properties Harvest date
24 April
26 April
22 April
8 m × 10 m
1 4
6 m × 10 m
N at sowing +
1 4
3.5 m × 10 m
pH 8.02, EC 2.3 ds m−1 , Corg 0.76%, Ntot 0.039%, POlsen 5.1 mg kg−1 , and Kext 110 mg kg−1 11 December
6 December
14 December
EC = Electrical conductivity; OM = Organic matter; Ntot = Nitrogen total; POlsen = Phosphorus Olsen; Kext = Potassium extractable.
2.2. Data Collection Common techniques were employed to record growth data. The leaf-area index (LAI) of a sample (10 g) of fully expanded fresh leaves for C3 winter and C4 summer cereal crops were taken, and leaf-area was recorded by means of a leaf-area meter. LAI was recorded using the methodology of Watson [57]. LAI (C3, C4 Cereals) = Leaf area (C3, C4 Cereals) /Land area (C3, C4 Cereals)
(1)
The RUE was computed for C3 winter and C4 summer cereal crops as follows: RUE TDM (C3, C4 Cereals) = TDM (C3, C4 Cereals )/∑Sa (C3, C4 Cereals )
(2)
where ∑Sa is the cumulative photosynthetically active radiation PAR for C3 winter and C4 summer cereal crops that was anticipated to be half of the total daily instance radiation, and TDM is total aboveground biomass [58] and calculated using the following equation: Sa (C3, C4 Cereals ) = Fi (C3, C4 Cereals ) × Si (C3, C4 Cereals )
(3)
where Si is the incident PAR for C3 winter and C4 summer cereal crops, and Fi was appraised from corresponding cereal crop LAIs by means of the Monteith and Elston [59] equation. Fi (C3, C4 Cereals ) = 1 − exp (−k (C3, C4 Cereals) × LAI (C3, C4 Cereals) )
(4)
where Fi is the fraction of intercepted radiation, k is an extinction coefficient for the total solar radiation, and the LAI is for C3 winter and C4 summer cereal crops [60]. The standards of k for wheat, oat, barley, maize, sorghum, and millet were 0.70, 0.63, 0.74, 0.65, 0.63, and 0.52, respectively [61–64]. Multiplying the totals by proper estimates of Fi plus Si produced the quantity of intercepted radiation (Sa) for C3 winter plus C4 summer cereals. The NUE was calculated as the ratio of grain yield (GY) to quantity of N application [1,10,65]: NUE (C3, C4 Cereals) = Grain yield (NX (C3, C4 Cereals) )/N application rate (C3, C4 Cereals)
(5)
Agronomy 2018, 8, 69
6 of 16
2.3. Statistical Analysis Agronomy 2018, 8, xcollected FOR PEER after REVIEW Data thus field
of 16 experiments were analyzed by Statistix 8.1 (Tallahassee, FL, 6USA) for ANOVA. Treatment differences were addressed through the methodology of Steel et al. [66].
50
50
40
40
30
30
20
20
10
10
o
Minimum temperature ( C)
(a)
o
Maximum temperature ( C)
C3 cereals season
C4 cereals season 0
0
25
Rainfall (mm)
15
40
10
-2
20
Solar radiation (MJ m )
60
20 5 (b) 0
0 0
50
Maximum temperature
100
150 200 Day of year Minimum temperature
250
300 Rainfall
350 Solar radiation
Figure Figure 4. 4. (a) (a) Daily Daily maximum maximum (upward (upward triangles) triangles) and and minimum minimum (downward (downward triangles) triangles) temperatures, temperatures, precipitation (unfilled bars), and solar radiation (unfilled stars) (b) during C precipitation (unfilled bars), and solar radiation (unfilled stars) (b) during C33 and and C C44 cereal cereal seasons seasons (represented by lines) lines) at at Multan, Pakistan. (represented by Multan, Pakistan.
3. Results 3.1. Biomass Seasonal differential accumulation of biomass occurred throughout the life cycle (including vegetative and reproductive stages till maturity) in all C3 winter and C4 summer cereals (Figure 5). Almost half of the biomass was accumulated till anthesis by all the C3 and C4 cereal crops. Overall, C4
Agronomy 2018, 8, 69
7 of 16
3. Results 3.1. Biomass Seasonal differential accumulation of biomass occurred throughout the life cycle (including Agronomy 2018, 8, x FOR PEER REVIEW of 16 vegetative and reproductive stages till maturity) in all C3 winter and C4 summer cereals 7(Figure 5). Almostcereals half ofperformed the biomass was accumulated till anthesis by all the C and C cereal crops. Overall, C 4 better than C3 cereals. Across winter and summer3 cereals4 and split N regimes, cerealsaverage performed better than C winter and split N regimes, average 2 and and 3 cereals. biomass varied from 425 toAcross 703 g/m 1083summer to 1660 cereals g/m2 among C3 and C4 cereals, 2 and 1083 to 1660 g/m2 among C and C cereals, respectively biomass varied from 4255). toAmong 703 g/m respectively (Figure these cereals, wheat and maize produced 3higher biomass compared 4 to other C 3 and C 4 crops, respectively. The biomass productivity of these cereal crops was higher (Figure 5). Among these cereals, wheat and maize produced higher biomass compared to other C3 and when N was applied in three equal doses compared to other regimes. The lowest biomass was C4 crops, respectively. The biomass productivity of these cereal crops was higher when N was applied when compared N was applied in four splits. These C3 winterwas and C 4 summer cereals reached in threerecorded equal doses to other regimes. The selected lowest biomass recorded when N was applied peak LAI just before the anthesis stage, which varied substantially among crops and split N in four splits. These selected C3 winter and C4 summer cereals reached peak LAI just before the anthesis application regimes (statistics not given). stage, which varied substantially among crops and split N application regimes (statistics not given). 800 (A) Wheat
(D) Maize 1500
600
1000
400
a b c d
a b c d
200
0
0 (E) Sorghum
-2
-2
1400
C4 Cereals biomass (g m )
(B) Oat
C3 Cereals biomass (g m )
500
600
1200 1000
400
800
a b c d
200
a b c d
0
600 400 200 0
(F) Millet
(C) Barley
1200
600
1000 800
400 600
a b c d
a b c d
200
0
400 200 0
0
20
40
60
80
100 120 140 160 0
20
40
60
80
100
120
Days after sowing 3 N splits
2 N splits
1 N split
4 N splits
Figure 5. Total biomass production of winter C3 (A–C) and summer C4 (D–F) cereals under split N
Figure 5. Total biomass production of winter C3 (A–C) and summer C4 (D–F) cereals under split N application regimes. Bars and letters represent standard error and significance, respectively. application regimes. Bars and letters represent standard error and significance, respectively.
Agronomy Agronomy2018, 2018,8,8,69x FOR PEER REVIEW
88ofof1616
3.2. Grain Yield (GY) 3.2. Grain Yield (GY) The data for GY for these winter and summer cereals significantly differed among crops with data for GYregimes for these(Figure winter6). and summer significantly with split 2 in the crops splitThe N application Overall, GYcereals ranged from 198 todiffered 883 g/mamong case of cereals 2 in the case of cereals and Nand application regimes (Figure 6). Overall, GY ranged from 198 to 883 g/m split N application regimes. The C4 cereals also out-yielded C3 in terms of GY, and it varied from split N regimes. also terms ofcereals, GY, and it varied from 198 to 2 for the 4 cereals 198 toapplication 338 g/m2 and 205 to The 883 C g/m C3out-yielded winter andCC34in summer respectively. Among 2 and 205 to 883 g/m2 for the C winter and C summer cereals, respectively. Among winter 338 g/m 2 2 3 4 winter and summer cereal wheat (338 g/m ) and maize (883 g/m ), crops produced higher GY, 2 ) and maize (883 g/m2 ), crops produced higher GY, respectively, and summer cereal wheatto(338 g/m respectively, compared other cereal crops. However, in all C3 winter and C4 summer cereals, compared to other cereal crops. However, in all C4 summer cereals, higher was 3 winter higher GY was recorded when N was applied in C three splitsand compared to other regimes. TheGY lowest recorded when N was applied in three splits compared to other regimes. The lowest GY was observed 2 2 GY was observed for oat (198 to 253 g/m ) and millet (205 to 266 g/m ) crops. Among N application 2 and millet (205 to 266 g/m2 ) crops. Among N application regimes, the lowest for oat (198the to lowest 253 g/m regimes, GY) was recorded when N was applied in four splits. GY was recorded when N was applied in four splits. 400
1000 (A) Wheat
(D) Maize 800
300 600 200 400 100
a
a
b
b
c
c
d
d
200
0 (B) Oat
-2
C4 Cereals grain yield (g m )
(E) Sorghum
-2
C3 Cereals grain yield (g m )
0
800 300
a b
600
c 200
d 400 a
100
b
200
c d 0
0 (F) Millet
(C) Barley
800 300 600
a 200
b c
100
400
d
a b
200
c d 0
0 0
20
40
60
0
10
20
30
40
50
60
Days after anthesis 3 N splits
2 N splits
1 N split
4 N splits
Figure6.6.Grain Grainyield yield of of winter winter CC3 (A–C) (A–C) and and summer summer C C4 (D–F) cereals under split N application Figure 3 4 (D–F) cereals under split N application regimes. Bars and letters represent standard error and significance, respectively. regimes. Bars and letters represent standard error and significance, respectively.
Agronomy 2018, 8, x FOR PEER REVIEW
9 of 16
Agronomy 2018, 8, 69
9 of 16
3.3. Radiation Use Efficiency (RUE)
The RUEUse forEfficiency wheat, (RUE) oat, barley, maize, sorghum, and millet crops and split N application 3.3. Radiation regimes significantly differed (Figure 7). Overall, among all these cereal crops, C4 summer cereals The RUE forCwheat, oat, barley, maize, sorghum, and millet crops and split N application regimes also out-yielded 3 winter cereals in terms of capturing photosynthetically active radiation. The RUE significantly differed (Figure among these cerealofcrops, cereals also −1 in 4 4summer varied from 0.90 to 1.42 g MJ−17). andOverall, 1.95 to 2.31 g MJall the case C3 andCC cereals, respectively. out-yielded cereals in terms capturing RUE photosynthetically active radiation. The RUE 3 winter Among splitCN application regimes, theofmaximum (2.31 g MJ−1) was found in the treatment −1 and 1.95 to 2.31 g MJ−1 in the case of C and C cereals, respectively. varied from 0.90 to 1.42 g MJ −1 3 4 where N was applied in three splits, and the lowest (0.90 g MJ ) was recorded for the four splits Among split N application regimes, the maximum RUE (2.31 g MJ−1 ) was found in the treatment where condition. N was applied in three splits, and the lowest (0.90 g MJ−1 ) was recorded for the four splits condition. 2.5 (A) 2.0
1.5
a
a a b b
a
b b
b
b b
b
-2
Radiation use efficiency (MJ m )
1.0
0.5
0.0
a a b
b
b
b
a
b
b
(B) a b
b
2.0
1.5
1.0
0.5
0.0 1 N split
2 N splits
3 N splits
4 N splits
Split N application regimes Wheat
Oat
Barley
Maize
Millet
Sorghum
Figure 7.7.Radiation Radiationuse useefficiency efficiency of C 3 winter ((A) wheat, oat, and barley) and C4 summer ((B) Figure of C 3 winter ((A) wheat, oat, and barley) and C4 summer ((B) maize, maize, millet, and sorghum) cereals under N application regimes. Bars represent standard millet, and sorghum) cereals under split N split application regimes. Bars represent standard error. error.
Agronomy 2018, 8, 69
10 of 16
Agronomy 2018, 8, x FOR PEER REVIEW
10 of 16
3.4. Nitrogen Efficiency (NUE) 3.4. Nitrogen Use Use Efficiency (NUE) NUE for (wheat, C3 (wheat, barley) and 4 (maize, millet, sorghum) cereal crops and split N The The NUE for C oat,oat, barley) and C4C(maize, millet, sorghum) cereal crops and split N 3 application regimes differed significantly (Figure 8). Overall, among all these cereal crops, C4 application regimes differed significantly (Figure 8). Overall, among all these cereal crops, C4 summer summer cereals also out-yielded C3 winter cereals in terms of NUE, varying from 17.84 to 38.88 kg cereals−1also out-yielded C3 winter cereals in terms of NUE, varying from 17.84 to 38.88 kg kg−1 and −1 in the case of C3 plus C4 cereals. Among split N application regimes, kg and 17.18 to 51.86 kg kg 17.18 to 51.86 kg kg−1 in the case of C3 plus C4 cereals. Among split N application regimes, the highest the highest NUE (51.86 kg kg−1) was found in the treatment where N was applied in three splits, NUE (51.86 kg kg−1 ) was found −1in the treatment where N was applied in three splits, while the lowest while the−1lowest (17.84 kg kg ) was recorded for four splits. The 1:1 lines between the RUE and NUE (17.84 kg C)4 was recorded for four of kg C3 and cereals are presented insplits. FigureThe 9. 1:1 lines between the RUE and NUE of C3 and C4 cereals are presented in Figure 9. 60 (A) 50 a
40
a a a b b
30 b
c c
b
c
c -1
Nitrogen use efficiency (kg kg )
20
10
0
a
(B) 50
a
a a
40 b
b
30 b
c
c
b c
c
20
10
0 1 N split
2 N splits
3 N splits
4 N splits
Split N application regimes Wheat
Oat
Barley
Maize
Millet
Sorghum
Figure 8. Nitrogen use efficiency (NUE) of C3 winter ((A) wheat, oat, and barley) and C4 summer ((B) Figure 8. Nitrogen use efficiency (NUE) of C3 winter ((A) wheat, oat, and barley) and C4 summer maize, millet, and sorghum) cereals under split N application regimes. Bars represent standard error. ((B) maize, millet, and sorghum) cereals under split N application regimes. Bars represent standard error.
Agronomy 2018, 8, x FOR PEER REVIEW Agronomy 2018, 8, 69
1111 of of 1616
54
54
(a) Wheat
52 50
50
NUE (kg kg )
48
-1
-1
NUE (kg kg )
(d) Maize
52
46 44 42
48 46 44 42
40
y = -11.01 + 43.98x 2 R = 0.98
38
y = -55.72 + 46.86x 2 R = 0.96
40 38 2.00
1.10 1.15 1.20 1.25 1.30 1.35 1.40 1.45
2.05
2.10
RUE (g MJ )
2.20
2.25
2.30
RUE (g MJ )
23
28
(b) Oat
(e) Sorghum
22
26 -1
NUE (kg kg )
21
-1
NUE (kg kg )
2.15
-1
-1
24
20 19 18
22 y = -10.14 + 35.11x 2 R = 0.96
y = -17.71 + 17.80x 2 R = 0.94
17
20 0.85
0.90
0.95
1.00
1.9
1.05
RUE (g MJ-1)
2.1
2.2
RUE (g MJ-1)
28
23
(f) Millet
(c) Barley
22
2.0
26 -1
NUE (kg kg )
-1
NUE (kg kg )
21 20 19 18 17
y = -7.42 + 27.08x 2 R = 0.99
24
22
y = -26.03 + 24.25x 2 R = 0.93
20
16 0.85
0.90
0.95
1.00
1.05
1.85 1.90 1.95 2.00 2.05 2.10 2.15 2.20
1.10
RUE (g MJ-1)
-1
RUE (g MJ ) Wheat
Oat
Barley
Maize
Sorghum
Millet
1:1 Lines
Figure Relationshipbetween betweenRUE RUE and NUE 3 winter (a–c) and 4 summer (d–f) cereals Figure 9. 9.Relationship and NUE of of C3Cwinter (a–c) and C4Csummer (d–f) cereals at at Multan, Pakistan. Multan, Pakistan.
Discussion 4. 4. Discussion 4 summer cereals (maize, millet, and sorghum) having C4 carbon metabolism were found to be C4Csummer cereals (maize, millet, and sorghum) having C4 carbon metabolism were found to be superior accumulating biomass C3 winter cereals at different N application regimes. superior in in accumulating biomass to Cto3 winter cereals at different splitsplit N application regimes. The CThe 4 C4 cereals produce higher biomass grain yields as compared 3 cereal crops. This variation for cereals produce higher biomass and and grain yields as compared to Cto3 C cereal crops. This variation for biomass and grain yield was possibly due to the supremacy of C4 cereals as compared to C3 cereal crops towards harnessing higher resource use efficiencies for N [67,68].
Agronomy 2018, 8, 69
12 of 16
biomass and grain yield was possibly due to the supremacy of C4 cereals as compared to C3 cereal crops towards harnessing higher resource use efficiencies for N [67,68]. The N application in three splits proved to be an effective strategy for all six C4 and C3 cereal crops as compared to other split application regimes. N application at sowing without splitting likely increases the losses through volatilization, nitrification, denitrification, and leaching (Figure 1). However, N application in four splits creates hidden hunger and did not fulfil the optimum nutrient requirements of all C4 and C3 summer and winter cereals during the crop lifetime. This deficiency is reflected in the form of low biomass, grain yields, NUE, and RUE in this study as well as elsewhere [69,70]. Growth dilution effect with variations in N in C4 and C3 cereal crops necessitate the splitting of N. The N is directly linked with leaf photosynthesis as well as higher NUE [40,71]. Variation in N dynamics as well as NUE has substantial effects on photosynthetic efficiency and growth [72]. In this study, C4 summer cereals out-yielded C3 winter cereal in terms of RUE and NUE. The RUE and NUE varied from 0.90 to 2.31 g MJ−1 and 17.84 to 51.86 kg kg−1 for the C3 and C4 cereals. Among split N application regimes, the highest RUE and NUE were found in the treatment in which N was applied in three splits, possibly due to the continuous and optimum availability of resources. It is a well-established fact that at optimum availability of N, the RUE of C3 and C4 cereals is enhanced, producing more height, LAI, light interception, and canopy development [1,10,73–75]. Similar trends of RUE against applied N in C4 cereals indicated that RUE might be even somewhat better on a total biomass basis. The C4 cereals displayed additional LAI compared to C3 . Conversely, it seems inadequate for C3 cereals to accrue leaf N to obtain the level of C4 cereals. Splitting N approach for C3 and C4 crops will increase productivity in the form of grain yield, then likewise increase NUE as well as biological harvest. The strategies in which the N losses of C3 and C4 crops are reduced will boost the C3 and C4 crop productivity in future. 5. Conclusions Reduced resource use efficiencies, such as NUE and RUE, in selected C3 winter (wheat, oat, barley) and C4 summer (maize, millet, sorghum) cereal crops could be augmented through splitting N fertilizer in irrigated arid conditions. The poor resource use efficiencies are due to lesser NUE in cereal crops and its possible losses by nitrification and runoff as well as leaching. Therefore, N application in three splits (at sowing time and first irrigation as well as second irrigation) to C3 winter (wheat, oat, barley) and C4 summer (maize, millet, sorghum) cereals may be considered as a substitute strategy to enhance resource use efficiencies by decreasing N losses in irrigated arid conditions. Author Contributions: The authors contributed in the study in the following ways: S.H., M.A.A., A.A.K., M.A. and M.A.K. conceptualized the study; Q.A., M.I., M.I.S., M.N., U.F. and S.U.K. did field experimentation and related work; A.K., H.Y. and S.N. analyzed data using Software; K.J. did figure work; Z.F. and G.A. write first draft; S.A. did Supervision and overall Project Administration. All authors read the final draft before submission to journal. Acknowledgments: The authors acknowledge funding by the Higher Education Commission (HEC), Islamabad (HEC-NRPU-4511), and Bahauddin Zakariya University, Multan. Conflicts of Interest: The authors declare no conflict of interest.
References 1.
2.
3.
Ahmad, S.; Ali, H.; Ismail, M.; Shahzad, M.I.; Nadeem, M.; Anjum, M.A.; Zia-Ul-Haq, M.; Firdous, N.; Khan, M.A. Radiation and nitrogen use efficiencies of C3 winter cereals to nitrogen split application. Pak. J. Bot. 2012, 44, 139–149. Ahmad, S.; Hussain, S.; Fatima, Z.; Abbas, G.; Ur Rehman, A.; Khan, M.R.; Younis, H.; Naz, S.; Sohail, M.; Ajmal, M.; et al. Application of DSSAT model for sowing date management of C4 summer cereals for fodder and grain crops under irrigated arid environment. Pak. J. Life Soc. Sci. 2016, 14, 104–114. Hussain, M.; Ahmad, S.; Hussain, S.; Lal, R.; Ul-Allah, S.; Nawaz, A. Rice in saline soils: Physiology, biochemistry, genetics and management. Adv. Agron. 2018, 148, 231–287.
Agronomy 2018, 8, 69
4.
5. 6. 7. 8.
9.
10.
11.
12.
13.
14. 15.
16.
17.
18.
19. 20.
21.
13 of 16
Rehman, A.; Ashfaq, M.; Naqvi, S.A.A.; Adil, S.A.; Bashir, K.; Ahmad, A.; Ahmad, S.; Ali, A.; Imran, A. Is climate change worsening the poverty of maize growers? Evidence from Punjab province of Pakistan. Cienci. Tec. Vitivinic. 2015, 30, 105–116. Nazir, M.S.; Bashir, E.; Bantel, R. Crop Production; Bashir, E., Bantel, R., Eds.; National Book Foundation: Islamabad, Pakistan, 1994; pp. 234–274. Government of Pakistan. Economic Survey of Pakistan, 2016–2017; Economic Wing, Finance Division, Government of Pakistan: Islamabad, Pakistan, 2017; pp. 19–40. Ahmed, M.; Hassan, F.U.; Razzaq, A.; Akram, M.N.; Aslam, M.; Ahmad, S.; Zia-ul-Haq, M. Is photothermal quotient determinant factor for spring wheat yield. Pak. J. Bot. 2011, 43, 1621–1627. Ahmad, S.; Ahmad, A.; Soler, C.M.T.; Ali, H.; Zia-ul-Haq, M.; Anothai, J.; Hussain, A.; Hoogenboom, G.; Hasanuzzaman, M. Application of the CSM-CERES-Rice model for evaluation of plant density and nitrogen management of fine transplanted rice for an irrigated semiarid environment. Precis. Agric. 2012, 13, 200–218. [CrossRef] Ahmad, S.; Ahmad, A.; Ali, H.; Hussain, A.; Garcia y Garcia, A.; Khan, M.A.; Zia-ul-Haq, M.; Hasanuzzaman, M.; Hoogenboom, G. Application of the CSM-CERES-Rice model for evaluation of plant density and irrigation management of transplanted rice for an irrigated semiarid environment. Irrig. Sci. 2013, 31, 491–506. [CrossRef] Ahmad, S.; Ali, H.; Farooq, U.; Khan, S.U.; Rehman, A.U.; Sarwar, N.; Shahzad, A.N.; Dogan, H.; Hussain, S.; Sultan, M.T.; et al. Improving nitrogen and radiation-use-efficiencies of C4 summer cereals by split nitrogen applications under irrigated arid environment. Turk. J. Agric. For. 2016, 40, 280–289. [CrossRef] Ahmad, S.; Abbas, Q.; Abbas, G.; Fatima, Z.; Rehman, A.U.; Naz, S.; Younis, H.; Khan, R.J.; Nasim, W.; Habib ur Rehman, M.; et al. Quantification of climate warming and crop management impacts on cotton phenology. Plants 2017, 6, 7. [CrossRef] [PubMed] Ahmad, S.; Hasanuzzaman, M. Integrated effect of plant density, N rates and irrigation regimes on the biomass production, N content, PAR use efficiencies and water productivity of rice under irrigated semiarid environment. Not. Bot. Horti Agrobot. Cluj-Napoca 2012, 40, 201–211. [CrossRef] Ali, H.; Iqbal, N.; Shahzad, A.N.; Ahmad, S.; Khan, Z.M.; Sarwar, N. Agro-management practices for sustainable wheat production under scarce water condition of arid climate. Turk. J. Field Crops. 2014, 19, 70–78. [CrossRef] Ali, H.; Sarwar, N.; Hasnain, Z.; Ahmad, S.; Hussain, A. Zinc fertilization under optimum soil moisture condition improved the aromatic rice productivity. Philipp. J. Crop Sci. 2016, 41, 71–78. Shabbir, R.N.; Waraich, E.A.; Ali, H.; Nawaz, F.; Ashraf, M.Y.; Ahmad, R.; Awan, M.I.; Ahmad, S.; Irfan, M.; Hussain, S.; et al. Supplemental exogenous NPK application alters biochemical processes to improve yield and drought tolerance in wheat (Triticum aestivum L.). Environ. Sci. Pollut. Res. 2016, 23, 2651–2662. [CrossRef] [PubMed] Shahzad, A.N.; Fatima, A.; Sarwar, N.; Bashir, S.; Rizwan, M.; Qayyum, M.F.; Qureshi, M.K.; Javaid, M.H.; Ahmad, S. Foliar application of potassium sulphate partially alleviates drought-induced kernel abortion in maize. Int. J. Agric. Biol. 2017, 19, 495–501. [CrossRef] Noreen, S.; Fatima, K.; Athar, H.U.R.; Ahmad, S.; Hussain, K. Enhancement of physio-biochemical parameters of wheat through exogenous application of salicylic acid under drought stress. J. Anim. Plant Sci. 2017, 27, 153–163. Ahmad, S.; Zia-ul-Haq, M.; Ali, H.; Shad, S.A.; Ammad, A.; Maqsood, M.; Khan, M.B.; Mehmood, S.; Hussain, A. Water and radiation use efficiencies of transplanted rice (Oryza sativa L.) at different plant densities and irrigation regimes under semi-arid environment. Pak. J. Bot. 2008, 40, 199–209. Ahmad, S.; Zia-ul-Haq, M.; Imran, M.; Iqbal, S.; Ahmad, M. Determination of residual contents of pesticides in rice (Oryza sativa L.) crop from different regions of Pakistan. Pak. J. Bot. 2008, 40, 1253–1257. Ahmad, A.; Iqbal, S.; Ahmad, S.; Khaliq, T.; Nasim, W.; Husnain, Z.; Hussain, A.; Zia-ul-Haq, M.; Hoogenboom, G. Seasonal growth, radiation interception, its conversion efficiency and biomass production of Oryza sativa L. under diverse agro-environments in Pakistan. Pak. J. Bot. 2009, 41, 1241–1257. Ahmad, S.; Ahmad, A.; Zia-Ul-Haq, M.; Ali, H.; Khaliq, T.; Anjum, M.A.; Khan, M.A.; Hussain, A.; Hoogenboom, G. Resources use efficiency of field grown transplanted rice (Oryza sativa L.) under irrigated semiarid environment. J. Food Agric. Environ. 2009, 7, 487–492.
Agronomy 2018, 8, 69
22.
23. 24.
25.
26.
27. 28.
29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39.
40.
41. 42.
43.
14 of 16
Ahmad, S.; Zia-ul-Haq, M.; Ali, H.; Ahmad, A.; Khan, M.A.; Khaliq, T.; Husnain, Z.; Hussain, A.; Hoogenboom, G. Morphological and quality parameters of Oryza sativa L. as affected by population dynamics, nitrogen fertilization and irrigation regimes. Pak. J. Bot. 2009, 41, 1259–1269. Sarwar, N.; Ali, H.; Ahmad, A.; Ullah, E.; Ahmad, S.; Mubeen, K.; Hill, J.E. Water wise rice cultivation on calcareous soil with the addition of essential micronutrients. J. Anim. Plant Sci. 2013, 23, 244–250. Sarwar, N.; Ali, H.; Maqsood, M.; Ullah, E.; Shahzad, A.N.; Shahzad, M.; Mubeen, K.; Shahid, M.A.; Ahmad, S. Phenological response of rice plants to different micronutrients application under water saving paddy fields on calcareous soil. Turk. J. Field Crops. 2013, 18, 52–57. Sultana, S.R.; Ali, A.; Ahmad, A.; Mubeen, M.; Zia-Ul-Haq, M.; Ahmad, S.; Ercisli, S.; Jaafar, H.Z.E. Normalized difference vegetation index as a tool for wheat yield estimation: A case study from Faisalabad, Pakistan. Sci. World J. 2014, 2014, 725326. [CrossRef] [PubMed] Mubeen, M.; Ahmad, A.; Wajid, A.; Khaliq, T.; Hammad, H.M.; Sultana, S.R.; Ahmad, S.; Fahad, S.; Nasim, W. Application of CSM-CERES-Maize model in optimizing irrigated conditions. Outlook Agric. 2016, 45, 173–184. [CrossRef] Raun, W.R.; Johnson, G.V. Improving nitrogen use efficiency for cereal production. Agron. J. 1999, 91, 357–363. [CrossRef] Raun, W.R.; Solie, J.B.; Johnson, G.V.; Stone, M.L.; Mullen, R.W.; Freeman, K.W.; Thomason, W.E.; Lukina, E.V. Improving Nitrogen Use Efficiency in Cereal Grain Production with Optical Sensing and Variable Rate Application. Agron. J. 2002, 94, 815–820. [CrossRef] Francis, D.D.; Schepers, J.S.; Vigil, M.F. Post-anthesis nitrogen loss from corn. Agron. J. 1993, 85, 659–663. [CrossRef] Harper, L.A.; Sharpe, R.R.; Langdale, G.W.; Giddens, J.E. Nitrogen cycling in a wheat crop: Soil, plant, and aerial nitrogen transport. Agron. J. 1987, 79, 965–973. [CrossRef] Aulakh, M.S.; Rennie, D.A.; Paul, E.A. Gaseous nitrogen losses from cropped and summer fallowed soils. Can. J. Soil Sci. 1982, 62, 187–195. [CrossRef] DeDatta, S.K.; Buresh, R.J.; Samsom, M.I.; Obcemea, W.N.; Real, J.G. Direct measurement of ammonia and denitrification fluxes from urea applied to rice. Soil Sci. Soc. Am. J. 1991, 55, 543–548. [CrossRef] Hilton, B.R.; Fixen, P.E.; Woodward, H.J. Effects of tillage, nitrogen placement, and wheel compaction on denitrification rates in the corn cycle of a corn–oats rotation. J. Plant Nutr. 1994, 17, 1341–1357. [CrossRef] Blevins, D.W.; Wilkison, D.H.; Kelly, B.P.; Silva, S.R. Movement of nitrate fertilizer to glacial till and runoff from a claypan soil. J. Environ. Qual. 1996, 25, 584–593. [CrossRef] Chichester, F.W.; Richardson, C.W. Sediment and nutrient loss from clay soils as affected by tillage. J. Environ. Qual. 1992, 21, 587–590. [CrossRef] Fowler, D.B.; Brydon, J. No-till winter wheat production on the Canadian prairies: Placement of urea and ammoniumnitrate fertilizers. Agron. J. 1989, 81, 518–524. [CrossRef] Hargrove, W.L.; Kissel, D.E.; Fenn, L.B. Field measurements of ammonia volatilization from surface applications of ammonium salts to a calcareous soil. Agron. J. 1977, 69, 473–476. [CrossRef] Drury, C.F.; Tan, C.S.; Gaynor, J.D.; Oloya, T.O.; Welacky, T.W. Influence of controlled drainage-subirrigation on surface and tile drainage nitrate loss. J. Environ. Qual. 1996, 25, 317–324. [CrossRef] Mahmood, M.; Ullah, H.; Shahzad, A.N.; Ali, H.; Ahmad, S.; Zia-Ul-Haq, M.; Honermeier, B.; Hasanuzzaman, M. Dry matter yield and chemical composition of sorghum cultivars with varying planting density and sowing date. Sains Malays. 2013, 42, 1529–1538. Ahmad, S.; Ali, H.; Rehman, A.U.; Khan, R.J.; Ahmad, W.; Fatima, Z.; Abbas, G.; Irfan, M.; Ali, H.; Khan, M.A.; et al. Measuring leaf area of winter cereals by different techniques: A comparison. Pak. J. Life Soc. Sci. 2015, 13, 117–125. Ahmad, S.; Raza, I.; Muhammad, D.; Ali, H.; Hussain, S.; Dogan, H.; Zia-Ul-Haq, M. Radiation, water and nitrogen use efficiencies of Gossypium hirsutum L. Turk. J. Agric. For. 2015, 39, 825–837. [CrossRef] Abbas, G.; Ahmad, S.; Ahmad, A.; Nasim, W.; Fatima, Z.; Hussain, S.; Habib ur Rehman, M.; Khan, M.A.; Hasanuzzaman, M.; Fahad, S.; et al. Quantification the impacts of climate change and crop management on phenology of maize-based cropping system in Punjab, Pakistan. Agric. For. Meteorol. 2017, 247, 42–55. [CrossRef] Ali, E.A. Impact of nitrogen application time on grain and protein yields as well as nitrogen use efficiency of some two-row barley cultivars in sandy soil. Am. Eurasian J. Agric. Environ. Sci. 2011, 10, 425–433.
Agronomy 2018, 8, 69
44. 45.
46.
47.
48.
49.
50.
51. 52. 53.
54.
55.
56.
57.
58. 59. 60. 61. 62.
63. 64.
15 of 16
Ali, H.; Riaz, M.; Zahoor, A.; Ahmad, S. Response of sunflower hybrids to management practices under irrigated arid-environment. Afr. J. Biotechnol. 2011, 10, 2248–2257. Ali, H.; Sarwar, N.; Ahmad, S.; Tariq, A.W.; Shahzad, A.N. Response of wheat crop to phosphorus fertilizers and application methods grown under agro-climatic conditions of Southern Punjab. Pak. J. Agric. Sci. 2012, 49, 485–489. Ali, H.; Tariq, N.; Ahmad, S.; Chattha, T.H.; Hussain, A. Effect of irrigation at different growth stages and phosphorus application methods on agronomic traits of wheat (Triticum aestivum L.). J. Food Agric. Environ. 2012, 10, 1371–1375. Ali, H.; Tariq, N.; Ahmad, S.; Rasheed, M.; Chattha, T.H.; Hussain, A. Growth and radiation use efficiency of wheat as affected by different irrigations levels and phosphorus application methods. J. Anim. Plant Sci. 2012, 22, 1118–1125. Ali, H.; Tariq, N.; Zia-Ul-Haq, M.; Ali, A.; Ahmad, S. Effect of phosphorus application methods and zinc on agronomic traits and radiation use efficiency of wheat (Triticum aestivum L.). J. Food Agric. Environ. 2012, 10, 757–763. Rehim, A.; Hussain, M.; Abid, M.; Zia-Ul-Haq, M.; Ahmad, S. Phosphorus use efficiency of Triticum aestivum L. as affected by band placement of phosphorus and farmyard manure on calcareous soils. Pak. J. Bot. 2012, 44, 1391–1398. Rehim, A.; Hussain, M.; Hussain, S.; Noreen, S.; Dogan, H.; Zia-ul-Haq, M.; Ahmad, S. Band application of phosphorus with farm manure improves phosphorus use efficiency, productivity and net returns of wheat on sandy clay loam soil. Turk. J. Agric. For. 2016, 40, 319–326. [CrossRef] Ali, A.; Iqbal, Z.; Hassan, S.W.; Yasin, M.; Khaliq, T.; Ahmad, S. Effect of nitrogen and sulphur on phenology, growth and yield parameters of maize crop. Sci. Int. (Lahore) 2013, 25, 363–366. Ali, H.; Iqbal, N.; Ahmad, S.; Shahzad, A.N.; Sarwar, N. Performance of late sown wheat crop under different planting geometries and irrigation regimes in arid climate. Soil Tillage Res. 2013, 130, 109–119. [CrossRef] Ali, H.; Iqbal, N.; Shahzad, A.N.; Sarwar, N.; Ahmad, S.; Mehmood, A. Seed priming improves irrigation water use efficiency, yield and yield components of late-sown wheat under limited water conditions. Turk. J. Agric. For. 2013, 37, 534–544. [CrossRef] Hirel, B.; Le Gouis, J.; Ney, B.; Gallais, A. The challenge of improving nitrogen use efficiency in crop plants: Towards a more central role for genetic variability and quantitative genetics within integrated approaches. J. Exp. Bot. 2007, 58, 2369–2387. [CrossRef] [PubMed] Dawson, J.C.; Huggins, D.R.; Jones, S.S. Characterizing nitrogen use efficiency in natural and agricultural ecosystems to improve the performance of cereal crops in low-input and organic agricultural systems. Field Crops Res. 2008, 107, 89–101. [CrossRef] Beatty, P.H.; Anbessa, Y.; Juskiw, P.; Carroll, R.T.; Wang, J.; Good, A.G. Nitrogen use efficiencies of spring barley grown under varying nitrogen conditions in the field and growth chamber. Ann. Bot. 2010, 105, 1171–1182. [CrossRef] [PubMed] Watson, D.J. Comparative physiological studies ongrowth of field crops. 1. Variation in net assimilation rateand leaf area between species and varieties and within andbetween years. Ann. Bot. 1947, 11, 41–76. [CrossRef] Szcicz, G. Solar radiation for plant growth. J. Appl. Ecol. 1974, 11, 617–636. [CrossRef] Monteith, J.L.; Elston, L.F. Performance and productivity of foliage in the field. In The Growth and Functioning of Leaves; Dale, J.E., Milthorpe, F.L., Eds.; Cambridge University Press: London, UK, 1983; pp. 499–518. Monteith, J.L. Climate and the efficiency of crop production in Britain. Philos. Trans. R. Soc. Lond. B 1977, 281, 277–294. [CrossRef] Monteith, J.L. Light interception and radiative exchange in crop stands. In Physiological Aspects of Crop Yield; Eastin, J.D., Ed.; ASA: Madison, WI, USA, 1969; pp. 89–111. Anten, N.P.R.; Schieving, F.; Werger, M.J.A. Patterns of light and nitrogendistribution in relation to whole canopy carbon gain in C3 and C4 mono- anddicotyledonous species. Oecologia 1995, 101, 504–513. [CrossRef] [PubMed] Ong, C.K.; Monteith, J.L. Response of pearl millet to light and temperature. Field Crops Res. 1985, 11, 141–160. [CrossRef] Muurinen, S.; Peltonen-Sainio, P. Radiation-use efficiency of modern and old spring cereal cultivars and its response to nitrogen in northern growing conditions. Field Crops Res. 2006, 96, 363–373. [CrossRef]
Agronomy 2018, 8, 69
65.
66. 67.
68. 69. 70. 71.
72. 73.
74. 75.
16 of 16
Rahimizadeh, M.; Kashani, A.; Zare-Feizabadi, A.; Koocheki, A.R.; Nassiri-Mahallati, M. Nitrogen useefficiency of wheat as affected by preceding crop, application rate of nitrogen and crop residues. Aust. J. Crop Sci. 2010, 4, 363–368. Steel, R.G.D.; Torrie, J.H.; Dickey, D.A. Principles and Procedures of Statistics: A Biometrical Approach, 3rd ed.; McGraw-Hill: New York, NY, USA, 1997; pp. 400–428. Reich, P.B.; Walters, M.B.; Ellsworth, D.S.; Vose, J.M.; Volin, J.C.; Gresham, C.; Bowman, W.D. Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: A test across biomes and functional groups. Oecologia 1998, 114, 471–482. [CrossRef] [PubMed] Niu, S.L.; Jiang, G.M.; Li, Y.G.; Gao, L.M.; Liu, M.Z. Diurnal gas exchange and superior resources use efficiencyof typical C4 species in HunshandakSandland, China. Photosynthetica 2003, 41, 221–226. [CrossRef] Sogbedji, J.M.; van Es, H.M.; Yang, C.L.; Geohring, L.D.; Magdoff, F.R. Nitrate leaching and nitrogen budget as affected by maize nitrogen rate and soil type. J. Environ. Qual. 2000, 29, 1813–1820. [CrossRef] Greenwood, D.J.; Lemaire, G.; Gosse, G.; Cruz, P.; Draycott, A.; Neeteson, J.J. Decline in percentage N of C3 and C4 crops with increasing plant mass. Ann. Bot. 1990, 66, 425–436. [CrossRef] Foulkes, M.J.; Hawkesford, M.J.; Barraclough, P.B.; Holdsworth, M.J.; Kerr, S.; Kightley, S.; Shewry, P.R. Identifying traits to improve the nitrogen economy of wheat: Recent advances and future prospects. Field Crops Res. 2009, 114, 329–342. [CrossRef] Yuan, Z.; Liu, W.; Niu, S.; Wan, S. Plant nitrogen dynamics and nitrogen-use strategies under altered nitrogen seasonality and competition. Ann. Bot. 2007, 100, 821–830. [CrossRef] [PubMed] Muchow, R.C.; Davis, R. Effect of nitrogen supply on thecomparative productivity of maize and sorghum in a semi-aridtropical environment. II. Radiation interception and biomassaccumulation. Field Crops Res. 1988, 18, 17–30. [CrossRef] Lemcoff, J.H.; Loomis, R.S. Nitrogen influences on yield determination in maize. Crop Sci. 1986, 26, 1017–1022. [CrossRef] Zahoor, A.; Riaz, M.; Ahmad, S.; Ali, H.; Khan, M.B.; Javed, K.; Anjum, M.A.; Zia-Ul-Haq, M.; Khan, M.A. Ontogeny growth and radiation use efficiency of Helianthus annuus L. as affected by hybrids, nitrogenous regimes and planting geometry under irrigated arid conditions. Pak. J. Bot. 2010, 42, 3197–3207. © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
