Supplemental irrigation effect on canola yield components under semiarid climatic conditions

Agricultural Water Management 98 (2011) 1403–1408

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Supplemental irrigation effect on canola yield components under semiarid climatic conditions E. Dogan a,∗ , O. Copur b , A. Kahraman b , H. Kirnak a , M.E. Guldur c a b c

Department of Agricultural Structure and Irrigation, Faculty of Agricultural Engineering, Harran University, 63040 Sanliurfa, Turkey Department of Crop Science, Faculty of Agricultural Engineering, Harran University, 63040 Sanliurfa, Turkey Department of Plant Protection, Faculty of Agricultural Engineering, Harran University, 63040 Sanliurfa, Turkey

a r t i c l e

i n f o

Article history: Received 17 January 2011 Accepted 22 April 2011 Available online 31 May 2011 Keywords: Canola Sprinkler irrigation Water stress Semiarid climatic conditions

a b s t r a c t With the availability of irrigation water, supplemental irrigation in winter-grown crops, such as lentil, wheat, and barley, has been intensely practiced to prevent crop yield losses due to the incidence of intermittent drought stress. In the crop growing seasons of 2006–2007 and 2008–2009, a study was conducted to determine the effect of supplemental irrigations on Canola (Brassica napus L. cv. Elvis F1) under the semiarid climatic conditions of the Harran plain, Sanliurfa, Turkey. A sprinkler irrigation system was used to irrigate the study plots. The irrigation treatments included 0.0, 0.25, 0.50, 0.75, and 1.0 (full irrigation) of Class-A pan evaporation amounts. The full irrigation treatment during both years consisted of 250 and 225 mm, respectively. In turn, crop water use values during the same years and treatments were 462 and 449 mm. In general, plant height and 1000 seed weight ranged from 140 to 165 cm and from 2.5 to 3.3 g, respectively, and these variables significantly differed among irrigation treatments (p < 0.05). Crop yield and above ground biomass measurements were affected by irrigation treatments and varied from 1094 to 3943 kg ha−1 and from 6746 to 18,311 kg ha−1 , respectively (p < 0.05). Similarly, harvest index values were affected (p < 0.05) and ranged from 0.16 to 0.23 on average. The water use efficiency obtained in the different treatments indicated a strong positive relationship between crop yield and irrigation. Overall, our results indicate that supplemental irrigation substantially increased canola yield; however, for an optimum yield, full irrigation is suggested. © 2011 Elsevier B.V. All rights reserved.

1. Introduction The Harran plain is part of the Fertile Crescent area of the upper Mesopotamia in Turkey. This region was gradually opened to irrigation since 1995 as part of the Southeastern Anatolian Project (locally called GAP), which is a social and agricultural integrated project covering approximately 1.8 million hectares of agricultural land. Even though cotton is the dominant crop grown in the plain, there is a need to diversify crop patterns to ensure sustainable farming practices; hence, alternative crops such as canola could easily fit as a second crop rotation. Although there is enough fresh water for the whole plain, some farms, particularly at the lower areas, suffer from drought mainly due to inefficient irrigation practices in the upper part of the plain. In addition, because of the increased water table, currently covering 35,000 ha of agricultural land at the lower part of the plain (State Hydraulic Works, DSI˙ , 2004), salinity

∗ Corresponding author. Current address: Harran University, Faculty of Agricultural Engineering, Irrigation Department, 63040 Sanliurfa, Turkey. Tel.: +90 414 2470383; fax: +90 414 2474480. E-mail address: [email protected] (E. Dogan). 0378-3774/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2011.04.006

has gradually increased (Bahceci and Nacar, 2009) and is severely affecting agricultural production. Canola as an oil crop and, due to its tolerance to salty conditions (FAO, 2002), could easily be cultivated in the lower part of the plain as a winter crop. Due to a low annual oil crop production, Turkey exports 1.72 million ton of oil seeds to meet demand (BSYD, 2011) and, as a result, canola constitutes a critical oil crop for the country. In particular, canola seeds contain approximately 40–45% high quality oil that could not only be used for human consumption but also as biodiesel (Ariolu et al., 2010). Moreover, the remaining seed pulp can be used as animal food. Traditionally, canola is grown under dry conditions; however, with the incentives of governmental subsidies and high prices, it is currently cultivated in irrigated fields as well. In Turkey, canola production increased from 0.028 to 0.112 million kg from 2007 to 2009, respectively (BSYD, 2011), and its cultivated area is expected to expand to the whole country, including the southeast region, because of favorable climatic conditions and availability of water sources. Drought stress is a key limiting factor leading to lower crop yields, especially in the late growing season of winter crops because there is not enough precipitation during the spring months. Reddi and Reddi (1995) indicated that, in many parts of the world, water

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is the major factor limiting crop production because water shortage affects several plant physiological processes (Sinaki et al., 2007). Therefore, the availability of water improves most crops’ yield, including canola yield (Smis et al., 1993). Likewise, most field crops, including canola, are sensitive to water stress during flowering and seed filling stages (Richards and Thurling, 1978; El Hafid et al., 1998; Costa and Shanmugathasan, 2002; Karam et al., 2005; Dogan et al., 2007). Taylor et al. (1991) indicated that, in addition to precipitation, supplemental irrigation increased canola yield and yield components. Similarly, Kar et al. (2007) reported that there was a need for irrigation of safflower in addition to winter and spring precipitations. Most irrigation studies are conducted concomitantly with fertilizer trials (Cheema et al., 2001; Svecnjak and Rengel, 2006); therefore, irrigation studies alone are limited and needed (Abuelos et al., 2002). Abuelos et al. (2002) conducted an irrigation study to determine the effect of water stress on canola and applied irrigation water in varying amounts from 0.0 to 359 mm. As a result, there was a significant difference between yield and yield components of full and insufficiently or no irrigated canola. Jensen et al. (1996) stated that water deficit during vegetative growth and pod-filling stages decreased the number of seeds, harvest index and yield. Similarly, Sharma and Kumar (1989) and Singh et al. (1991) reported that water stress resulted in lower leaf area index, harvest index, number of leaf and branches and, thereby, in a significant yield loss. Likewise, similar to other field crops, canola response to water stress depends on the growth stage in which the stress occurs; specifically, any stress during and/or prior to flowering resulted in a lower number of pods, 1000-seed weight and reduced yield (Taylor et al., 1991; Mendham and Salsbury, 1995; Angadi et al., 1999; Johnston et al., 2002; Gan et al., 2004). Parallel results were reported by Richards and Thurling (1978); however, they claimed that, even though drought stress resulted in less number of seeds in pods, the 1000-seed weight tended to increase. Drought stress during vegetative, flowering and seed formation stages in canola resulted in considerably reduced yield (Muhammad et al., 2007). Ahmadi and Bahrani (2009) stated that canola yield was mainly limited by water stress and high temperatures in arid and semiarid regions, especially during crop reproductive stages where a slight water and temperature stress could result in lower yield. Similar to other studies, Ahmadi and Bahrani (2009) reported that water stress during flowering resulted in the highest reduction of canola yield (29.5%). Mandal et al. (2006) conducted a study to determine the effect of irrigation and nutrients on mustard growth and yield under central India conditions. They applied water at different stages (pre-sowing, post-sowing and flowering) at 60 mm rates. Finally, they reported evapotranspiration (ET) values that varied from 90 to 290 mm. Overall, water stress resulted in reduced root development, biomass, and yield, and irrigation almost doubled the yield. Many researchers agree that there is a need to determine a proper irrigation schedule, to apply the appropriate amount of water needed by the crop, thereby increasing the water use efficiency (Kipkorir et al., 2002; Kar et al., 2007). Information on the possible effects of irrigation on canola physiological characteristics is limited and needs to be further evaluated under different climatic conditions. Because of water shortage at the lower part of the Harran Plain, the probable effect of climate change, which might decrease the annual precipitation rate in approximately 20% in the region, and the high frequency of drought stress in the rapid crop growing season, the effect of supplemental irrigation on development and yield components needs to be determined. Therefore, the objectives of this study were (1) to monitor the effects of seasonal supplemental irrigation on canola growth and yield components and (2) to deter-

mine water use efficiency and irrigation water use efficiency under the semiarid climatic conditions of the study area. 2. Materials and methods The experiment was conducted at the Agricultural Engineering Research Field (37◦ 08 N, 38◦ 46 E, with an altitude of 465 m) of the Harran University, Sanliurfa, Turkey. The research station is located in the southeast of Turkey, at 45 km from the Syrian border, and it is characterized by semiarid climatic conditions. The clay loam soil type is classified within the Ikizce soil series (Vertic Calciorthid Aridisol) with a field capacity of 32%, permanent wilting point of 22%, 155 mm/120 cm of available water, and infiltration rate of 13 mm h−1 (Table 1). Long term average temperature, relative humidity, and wind speed values of the study area were 18.1 ◦ C, 52%, and 1.7 m s−1 , respectively. A commonly grown canola cultivar, ‘Elvis’, was used as the plant material for the experiment. The source of irrigation water was a deep well with pH and EC values of 7 and 0.31 dS m−1 , respectively. A sprinkler irrigation system with a 12 × 12 arrangement was used to deliver water to treatment plots, and the used sprinkler heads were of impact type with 0.35 l s−1 flow rates. Due to the sprinkler irrigation set up, the treatment plots were 144 m2 in size. There was a 12.0 m buffer zone among plots, to eliminate any effect of one plot on another. In both study years, there was no need for postsowing irrigation because there was precipitation after planting. In total, there were 3 supplemental irrigation events during the spring months of both study years. The irrigation events were scheduled to apply an amount of water equal to the evaporation obtained from a standard Class-A Pan located close to the study area. Irrigation events were initiated when the soil available water content reached 50%. Canola seeds were sown by a pneumatic precision planter on November 18th and 15th of 2006 and 2008, respectively. All treatments received 150 kg ha−1 of pure N in two equal amounts: one at sowing and the other in the spring of both growing seasons. In addition, 60 kg ha−1 of pure P was applied to treatment plots at sowing. Weed control was managed by two hand-hoeing events, and herbicide and pesticide were not applied in either year. In this study, irrigation amounts were determined with the following equation, I = Epan × Kp × CP × A

(1)

where I is the applied irrigation water (mm), Epan is the cumulative evaporation amount in the irrigation interval (mm), Kp is a pan coefficient, CP is the crop soil coverage (%), and A is the area (m2 ). Crop evapotranspiration (ETc) during the irrigation period of each treatment was calculated according to the water balance approach (Doorenbos and Pruitt, 1992), ET = I + P − Dr − Rf ± s

(2)

where ET is the canola crop evapotranspiration (mm), I is the irrigation water applied during the growth period (mm), P is the effective rainfall plus capillary rise (mm), Dr is the drainage water amount (mm), Rf is the runoff amount (mm), and s is the change in soil moisture content (mm) determined by gravimetric sampling. During the irrigation periods of both study years, there was no precipitation, excess irrigation and runoff; therefore, P, Rf and Dr were assumed to be zero, reducing the equation to ET = I ± s

(3)

The treatments used in this study included 0, 25, 50, 75, and 100% of full (control) irrigation amounts. Once plants reached maturity, 2 m × 3 m (6 m2 ) sections from all plots were hand harvested, and plant height, 1000-seed weight, crop yield, and biomass values

E. Dogan et al. / Agricultural Water Management 98 (2011) 1403–1408

Fig. 1. Relationship between seasonal applied irrigation water and crop height for 2006–2007 and 2008–2009 seasons.

were measured. In addition, harvest index, Water Use Efficiency (WUE) and Irrigation Water Use Efficiency (IWUE) values of all treatments were calculated with the following equations (4, 5, and 6), HI =

Yt BM

WUE = IWUE =

(4)

Yt − Yc ETc

(5)

Yt − Yc I

(6)

where HI is the harvest index, Yt is the yield (kg ha−1 ) of each irrigation treatment, BM is the biomass value (kg ha−1 ) of each treatment, WUE is the water use efficiency, Yc is the yield (kg ha−1 ) of the control (full irrigated, I100 ) treatment, ETc is the seasonal crop water use (mm) of each treatment plot, IWUE is the irrigation water use efficiency, and I is the irrigation amount (mm). This experiment was based on a complete randomized design with 3 replications. Differences among main treatments (irrigation) were analyzed using ANOVA and regression tests and were considered significant at p < 0.05 level. Seasonal irrigation amounts were regressed against each of the measured crop parameters, and a linear regression was considered. Both, the coefficient of determination (R2 ) and the significance of each regression (P) were considered for evaluating the validity of regression equations. 3. Results and discussion A total of 250 and 225 mm irrigation water (IW) was applied to full irrigation treatment plots in the first and second crop seasons, respectively. The total crop water use (ETc), including soil water deficit (s) plus the applied irrigation water (IW), from sowing to harvest of all treatments was 295, 312, 362, 396, 462 mm and 239, 275, 338, 387, 449 mm for the first and the second crop growing seasons, respectively. Abuelos et al. (2002) applied 359 mm of irrigation water to full irrigated canola under central California conditions, and those values were higher than our full irrigation rates,

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Fig. 2. Relationship between seasonal applied irrigation water and 1000 seed weight for 2006–2007 and 2008–2009 seasons.

which is probably due to climatic differences. In the first season of the study, the applied irrigation amount was higher than the amount applied in the second season, mainly due to slightly severe climatic conditions in the first season. On average, monthly maximum, minimum and average temperatures in first season were 2.5, 2.9, and 1.2 ◦ C higher than in the second growing season (Table 2). The lowest and highest plant heights of both crop growing seasons were obtained in the I0 and I100 treatments, and they were 147.7 and 164.0 cm in the first and 141.3 and 159 cm in the second study year. The statistical analysis of the data indicated no difference between years; however, there were differences among treatments. In general, I0 , I25 , and I50 were not significantly different (p > 0.05), but there was a significant difference between I100 and the other treatments. Similarly, Tahir et al. (2007) reported plant height values ranged from 112.6 to 180.6 cm; the slight difference compared with our data could be due to the use of a different cultivar and environment conditions. Plant height measurements indicated that to obtain 1 cm of crop height difference, 15.3 and 12.7 mm of irrigation water was required in the first and second years, respectively (Table 3). The regression analysis indicated a strong linear relationship between irrigation and crop height for both years (Fig. 1). Likewise, the regression analysis indicated that, on average, each extra millimeter of irrigation water resulted in approximately 1.7 mm increase in crop height. The effect of irrigation on 1000-seed weight in both years was similar to the effect on crop height, and the values ranged from 2.8 to 3.3 g in 2006–2007 and from 2.5 to 3.2 g in 2008–2009. Similar to our study, Tahir et al. (2007) reported values from 3.01 to 3.93 g, depending on the number of irrigations. Overall, there was no statistical difference between years, among low irrigation treatments (I0 , I25 , and I50 ) and among high irrigation treatments (I75 and I100 ). However, there was a difference between low and high irrigation treatments (p < 0.05; Table 3). Similarly, there was a positive linear relationship between irrigation amount and 1000 seed weight for both study years (Fig. 2). Canola crop yield in 2006–2007 ranged from 1094 (I0 ) to 3944 (I100 ) kg ha−1 , and the yield varied from 1333 to 3880 kg ha−1 in 2008–2009. There was no significant difference between years;

Table 1 Some of the selected soil physical and chemical properties of the study area. FC, Field capacity; PWP, Permanent wilting point; BD, Bulk density, OM, Organic water. Depth (cm)

20 40 60 90 120

FC (cm3 cm−3 )

0.39 0.39 0.39 0.39 0.39

PWP (%)

0.23 0.23 0.23 0.23 0.23

BD (g cm−3 )

1.35 1.35 1.36 1.36 1.35

pH

7.3 7.3 7.4 7.4 7.4

Soil particle distribution (%)

Texture class

Sand

Silt

Clay

7.3 7.1 7.7 34.3 34.3

34.7 32.6 29.2 19.3 19.3

58.0 60.3 63.1 46.4 46.4

Clay Clay Clay Clay Clay

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Table 2 Some of the weather data from crop development months of the study area. Parameters

Min. air temp. (◦ C)

Max. air temp. (◦ C)

Av. temp. (◦ C)

Precipitation (mm)

Relative hum. (%)

Solar radiation (MJ m−2 day−1 )

November December January February March April May June

2006 2006 2007 2007 2007 2007 2007 2007

3 −4.3 −3.7 −4 3.8 4 11 17.8

21 19.5 17.5 17.4 21.4 25.5 38 41.5

11.4 6.8 4.8 7.7 11.5 13.1 25.3 30.4

26.2 23.3 57.5 93.2 56.6 49.2 8.8 0.8

57.5 49.5 67.3 71.7 62.7 66.5 53.9 36.8

257.8 206.4 207.1 266.4 489.1 531.5 600.0 771.6

November December January February March April May June

2008 2008 2009 2009 2009 2009 2009 2009

6 −1.7 −4.7 0.1 1.5 5.9 10 17.8

24.7 19.5 15.7 17.3 23 27.5 37 40

14 7 5.7 8 10 15.8 22.7 29.6

35.3 37.7 29.8 54.5 55.3 48.8 4.7 9.2

62.3 58.6 59.1 72.2 65.6 53 36.3 29.1

255.4 199.3 213.9 253.9 460.1 627.2 755.8 754.7

however, there were differences among all treatments, except between treatments I25 and I50 in 2008–2009 (p < 0.05; Table 3). Similarly, canola seed yield decrease due to water stress as reported by Rahnema and Bakhshandeh (2006). Likewise, up to a 62.9% decrease was reported with lower irrigations by Hati et al. (2001). In addition, Tahir et al. (2007) conducted a study to determine the effect on canola seed production of different irrigation practices in spring months and reported yield values of 1610 and 3650 kg ha−1 in the lowest and the highest irrigation treatments, respectively. Moreover, Wahid et al. (2009) reported similar yield results, of approximately 2500 kg ha−1 , under semiarid climatic conditions. As expected, the regression analysis indicated a strong positive linear relationship between irrigation treatments and crop yield with high R2 values (Fig. 3). Both equations were significant for yield and irrigation amounts (p < 0.01). A yield analysis of the study years indicated that, on average, 1 mm of irrigation water increase resulted in approximately 11.36 kg ha−1 of additional yield (Fig. 3). Above ground biomass values of the first and second growing seasons varied from 6.7 (I0 ) to 17.9 t ha−1 (I100 ) and from 7.5 (I0 ) to 18.3 t ha−1 (I100 ), respectively. Similar to the yield results, the analysis of biomass data indicated a significant difference among treatments (p < 0.05) but not among years. Likewise, canola biomass values of all irrigation treatments of the same year were significantly different (p < 0.05), except the values of treatments I25

Fig. 3. Relationship between seasonal applied irrigation water and crop yield for 2006–2007 and 2008–2009 seasons.

and I50 . In contrast to our results, Wahid et al. (2009) reported higher biomass values, of approximately 10 t ha−1 , in dry land and semiarid climatic conditions. Sinaki et al. (2007) conducted a study to determine the effect of water stress on canola crop and reported approximately 11.0 t ha−1 of biomass, while Wahid et al. (2009) reported 10.0 t ha−1 of biomass. In addition, the regression analysis of our biomass data with irrigation showed a significant

Table 3 Results of measured canola parameters and statistical analysis. Parameters

Total irrigation amount (mm) Seasonal crop ET (mm) Crop height (cm) 1000 seed weight (g) Yield (kg ha−1 ) Biomass (t ha−1 ) Harvest index Water use efficiency (kg ha−1 mm−1 ) Irrigation water use efficiency (kg ha−1 mm−1 )

Year

2007 2009 2007 2009 2007 2009 2007 2009 2007 2009 2007 2009 2007 2009 2007 2009 2007 2009

Treatments I0

I25

I50

I75

I100

0.0 0.0 295.2 239.4 147.7a 141.3a 2.8a 2.5a 1094a 1333a 6.747a 7.52a 0.16a 0.18a 3.7 5.6 NA NA

62.5 56.3 312.4 275.3 156.7ab 144.7a 2.6a 2.7ab 1441b 1528b 9.283b 8.41b 0.16a 0.18a 4.6 5.5 23.1 27.1

125.0 112.5 362.4 337.8 158.3bc 144.3a 2.9a 3.0bc 2102c 2360c 10.866bc 10.99b 0.19ab 0.21ab 5.8 7.0 16.8 21.0

187.5 168.8 396.0 387.0 166.6c 152.3ab 3.1ab 3.1c 2771d 3204d 13.150c 14.24c 0.21b 0.23c 7.0 8.3 14.8 19.0

250.0 225.0 462.4 449.5 164.0c 159.0b 3.3b 3.2c 3944e 3880e 17.900d 18.31d 0.22b 0.21ab 8.5 8.6 15.8 17.2

Values at the same rows fallowed by different letters are significantly different at 0.05 level.

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Fig. 4. Relationship between seasonal applied irrigation water and above ground biomass for 2006–2007 and 2008–2009 seasons.

relationship between those two parameters, with high R2 values (p < 0.05; Fig. 4). The calculated harvest index values of 2006–2007 and 2008–2009 ranged from 0.16 to 0.22 and from 0.18 to 0.23, respectively. In general, higher harvest index values were reached with higher irrigation, and a statistical difference occurred in the I75 and I100 treatments. The average WUE in the first and second seasons ranged from 3.7 (I0 ) to 8.5 (I100 ) and from 5.6 (I0 ) to 8.6 (I100 ) kg ha−1 mm−1 , respectively. Similarly, Wahid et al. (2009) reported harvest index values of canola between 0.22 and 0.26 under the semiarid climatic conditions of Pakistan. However, Huhn (1991) reported a wider range of harvest index values, from 0.19 to 0.32. In general, the effect of irrigation treatments on WUE, which ranged from 3.7 to 8.5 kg ha−1 mm−1 and 5.6 to 8.6 kg ha−1 mm−1 in the first and second study years, respectively, was obvious and significant (p < 0.05). The values of the first season seemed to be lower than the second ones; the reason for this difference was probably more severe climatic conditions that resulted in higher crop water use and lower yield. In contrast to the WUE values, the irrigation water use efficiency (IWUE) values were higher in low irrigation treatments (I25 and I50 ), and lower IWUE values were obtained in high irrigation treatments (I75 and I100 ). IWUE values from the first and second crop seasons ranged from 14.8 to 23.1 kg ha−1 mm−1 and 17.2 to 27.1 kg ha−1 mm−1 , respectively. 4. Conclusions A two-year experiment was conducted to determine the effect of supplemental irrigation on winter canola crop yield and yield components under semiarid climatic conditions. The results of the study indicate the following: • In the first and second year, a total of 250 and 225 mm of irrigation water was applied to full irrigation treatment fields, which indicate that, under similar climatic conditions, the irrigation amount should be no less than 250 mm. • Any level of supplemental irrigation significantly increased crop height, 1000-seed weights, yield and biomass. • Depending on environmental conditions and water management strategies, full irrigation of canola under conditions similar to the present study would result in approximately 4 t ha−1 of seed yield and 18 t ha−1 of above ground biomass. Even though canola is considered a dry land plant, irrigation during rapid plant growth stages had a significant effect on yield and yield components. This effect would be more pronounced in dry years. Therefore, if water is available, supplemental irrigation should be applied to ensure an economically viable crop development and yield in canola.

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