Irrig Sci (2006) 24: 279–289 DOI 10.1007/s00271-006-0028-x
O R I GI N A L P A P E R
Ali Osman Demir Æ Abdurrahim Tanju Go¨ksoy Hakan Bu¨yu¨kcangaz Æ Zeki Metin Turan Eyu¨p Selim Ko¨ksal
Deficit irrigation of sunflower (Helianthus annuus L.) in a sub-humid climate Received: 6 February 2004 / Accepted: 9 January 2006 / Published online: 26 January 2006 Springer-Verlag 2006
Abstract The response of sunflower (Helianthus annuus L.) to 14 irrigation treatments in a sub-humid environment (Bursa, Turkey) was studied in the field for two seasons. A rainfed (non-irrigated) treatment as the control and 13 irrigation treatments with full and 12 different deficit irrigations were applied to the hybrid Sanbro (Novartis Seed Company) planted on clay soil, at three critical development stages: heading (H), flowering (F) and milk ripening (M). The yield increased with irrigation water amount, and the highest seed yield (3.95 t ha1) and oil yield (1.78 t ha1) were obtained from the HFM treatment (full irrigation at three stages); 82.9 and 85.4% increases, respectively, compared to the control. Evapotranspiration (ET) increased with increased amounts of irrigation water supplied. The highest seasonal ET (average of 652 mm) was estimated at the HFM treatment. Additionally, yield response factor (ky) was separately calculated for each, two and total growth stages, and ky was found to be 0.8382, 0.9159 (the highest value) and 0.7708 (the lowest value) for the total growing season, heading, and flowering-milk ripening combination stages, respectively. It is concluded that HFM irrigation is the best choice for maximum yield under the local conditions, but these irrigation schemes must be re-considered in areas where water resources are more limited. In the case of more restricted irrigation, the Communicated by E. Christen A. O. Demir (&) Æ H. Bu¨yu¨kcangaz Department of Agricultural Structures and Irrigation, Agricultural Faculty, University of Uludag, 16059 Bursa, Turkey E-mail:
[email protected] Tel.: +90-224-4428970 Fax: +90-224-4428775 A. T. Go¨ksoy Æ Z. M. Turan Department of Field Crops, Agricultural Faculty, University of Uludag, 16059 Bursa, Turkey E. S. Ko¨ksal Lodumlu, Rural Affairs Research Institute, 06583 Ankara, Turkey
limitation of irrigation water at the flowering period should be avoided; as the highest water use efficiency (WUE) (7.80 kg ha1 mm1) and irrigation water use efficiency (IWUE) (10.19 kg ha1 mm1) were obtained from the F treatment. Keywords Sunflower Æ Deficit irrigation Æ Evapotranspiration Æ Water use efficiency Æ Irrigation water use efficiency Æ Crop water production function Æ Yield response factor (ky)
Introduction The objective of well-regulated deficit irrigation is to save water by subjecting crops to periods of moisture stress with minimal effects on yields. The water stress results in less evapotranspiration (ET) by closure of the stomata, reduced assimilation of carbon, and decreased biomass production. The reduced biomass production has little effect on ultimate yields where the crop is able to compensate in terms of reproductive capacity. In some cases, periods of reduced growth may trigger physiological processes that actually increase yield and/ or income (Smith et al. 2002). In sunflower, crops stressed before anthesis regulate transpiration by reduction of interception of radiation (IR) mediated by reduced leaf expansion. In contrast, it is difficult to identify a dominant factor in the regulation of transpiration of crops subjected to water deficit after anthesis. In that case there seems to be an interplay between reduced IR, by faster leaf senescence and wilting, and reduced canopy conductance. More work at the crop level is necessary for an accurate determination of the relative effect of each of these factors on crop transpiration under various timings and intensities of water deficits (Connor and Sadras 1992). Sunflower (Helianthus annuus L.) is one of the four most important oil crops in the world. Because of its moderate cultivation requirements and high oil quality, its acreage has increased in both developed and
280
undeveloped countries (Sˇkoric´ 1992). Sunflower oil is highly demanded not only for human consumption, but also for chemical and cosmetic industries. The total area of sunflower production is 510,000 ha in Turkey. Of Turkey’s sunflower production of 610,000 t, 13% of this is produced in southern Marmara region (DIE 2001). In respect of total yield produced, water requirements of sunflower are relatively high compared to most crops. Despite its high water use, the crop has an ability to withstand short periods of severe soil water deficit of up to 15 atmosphere tensions. Long periods of severe soil water deficit at any growth period cause leaf-drying with subsequent reduction in seed yield. Severe water deficits during the early vegetative period result in reduced plant height but may increase root depth. Adequate water during the late vegetative period is required for proper bud development. The flowering period is the most sensitive to water deficits which cause considerable yield decrease since fewer flower come to full development. Yield formation is the next most sensitive period to water deficit, causing severe reduction in both yield and oil content (Doorenbos and Kassam 1979). Although sunflower is known as a drought tolerant crop or grown under dryland conditions, substantial yield increases are achieved by irrigation. There is no research on sunflower irrigation in the region (southern Marmara) where the study was carried out. Despite the region situated in a sub-humid climatic zone, rainfall amounts are extremely low in the summer period which is the main growing season of sunflower. Therefore, irrigation is vital for some periods during growing season. Major decreases in sunflower yields have been experienced in some water shortage years in southern Marmara. Yield may increase with deficit irrigation for dry years in that region. The objective of this study was to determine the effects of rainfed (non-irrigated) treatment as the control and 13 irrigation treatments with a full and 12 different deficit irrigations applied at heading, flowering, and milk ripening stages on the growth, yield response, water use
efficiency (WUE), and irrigation water use efficiency (IWUE) of sunflower grown on an alluvial soil in a subhumid environment.
Materials and methods The experiment was carried out during the growing season of 2000 and 2001, between the months of April and September, on the experimental field of Research and Application Centre of Agricultural Faculty of Uludag University, situated in Bursa (Turkey), latitude 4015¢ 29¢¢N, longitude 2853¢39¢¢E, and altitude 72 m above sea level. The local climate is temperate, summers are hot and dry, and winters are mild and rainy. According to longterm meteorological data (1929–1991), annual mean rainfall, temperature, and relative humidity are 697 mm, 14.6C, and 69%, respectively (Anonymous 1992). A sub-humid climate prevails in the region according to mean rainfall amount (from 600 to 700 mm of annual precipitation) (Jensen 1980). The climate of the region is sub-humid, but rainfall amounts are extremely low in the summer period. Seasonal rainfall amount is 73 mm, which coincides with 10% of total annual rainfall, for the summer period (June, July, and August). Additionally, total annual evaporation is nearly twofold of annual rainfall, and seasonal evaporation in the summer months is much higher than seasonal rainfall amount (Table 1). Climatologic data of trial years (in 2000– 2001) were measured at the meteorological station nearby the experimental area. The soils of the trial field are Typic Xerofluvent according to American Taxonomic Classification, and Calcaric Fluvisol according to FAO/UNESCO Classification System in which soils are alluvial and unregulated calcareous with profile. The soil is very fine (average 45.6% clay content), and having 0.1% total nitrogen content (Kjeldhal method), 0.40 kg ha1 phosphorus (Olsen method, P2O5), 5.70 kg ha1
Table 1 Mean air temperature, relative humidity and total monthly rainfall in 2000–2001 and between 1929 and 1991 at Bursa Years
Jan Feb March Temperature (C)
2000 2001 Long-term average
3.3 7.4 5.3
2000 2001 Long-term average
Relative humidity (%) 79 68 66 71 79 61 74 73 70
2000 2001 Long-term average
Rainfall (mm) 29 105 96 9 66 49 92 75 68
Long-term averagea
Evaporation (mm) (class A pan) 40.8 47.2 64.7 102.3
a
5.2 6.3 6.2
29-year average of evaporation values
7.6 14.0 8.3
April
May
June
July
Aug
Sep
Oct
15.0 13.7 13.0
17.7 18.2 17.6
21.8 23.6 22.1
25.5 27.7 24.5
24.8 26.4 24.1
21.2 22.6 20.1
14.8 16.8 15.6
12.5 10.9 11.2
72 72 70
65 65 69
61 48 62
51 51 58
56 53 60
60 59 66
78 60 72
74 64 75
84 – 74
109 86 59
49 65 52
16 17 31
9 2 25
11 13 17
82 42 39
129 – 58
22 93 78
50 128 103
104.3
213.5
256.1
232.7
161.2
89.8
Nov
54.5
Dec 6.2 – 7.6
50.6
Average 14.6 17.0 14.6 68 62 69 Total 707 570 697 1417.7
281
exchangeable potassium (ammonium acetate method, K2O), 1.9% organic matter (Walckey–Black method), 0.08% total salt, and a bulk density of 1.45, 1.53, and 1.50 g cm3 in 0–0.30, 0.30–0.60, and 0.60–0.90 m profile, respectively. The soil pH was 7.2. The water holding capacity (WC) of the experimental site was observed as 122 mm in a 0.90 m soil profile. WC was determined by the difference between the water content at field capacity (FC) and at permanent wilting point (PWP). There is no waterlogging problem in the area. The hybrid cultivar Sanbro variety (Novartis Seed Company) was planted. It is a variety of an earlier single hybrid, medium tall, large table, and high oil percentage. It has high resistance to Orobanche, Verticilum, and Sclerotinia Sclerotiorum. In the experiments, plot size was 20.8 m2 (8.0·2.6 m2) at harvest; row spacing was 0.65 m; plant–plant spacing was 0.30 m. The crops were sown on 4 April 2000 and 6 April 2001, and harvested on 11 September 2000 and 5 September 2001. After plots were harvested, seed and stem yield, oil percentage, and oil yield were recorded. Crude oil percentage was determined by the Soxhlet extraction technique (Pomeranz and Clifton 1994). Oil yield was calculated as a function of seed yield and crude oil percentage. Irrigation water was supplied from the deep wells drilled in the same area. Pressurized water was delivered to the plots with polyethylene pipes, 60 mm in diameter, and was applied to the trial plots as controlled by a water meter. Required irrigation water was applied to the plots by short blocked-end furrows. Perforated PVC pipe was used to ensure uniform water distribution to each furrow in a plot. There are no recorded problems with water quality. The crop phenological cycle was divided into the three critical growth stages which were considered to be the most relevant from the point of view of their response to irrigation, i.e., heading (H), flowering (F), and milk ripening (M), to determine the irrigation scheduling (Doorenbos and Kassam 1979). Irrigation was applied at each of these stages as full and deficit according to the treatments listed in Table 2. The individual irrigation application depths were determined on the basis of soil water storage depletion. Under full irrigation condition, irrigation water was applied to 0.9 m of the soil profile to achieve FC. There is no irrigation applied under non-irrigated or control condition, and irrigation was applied in as much as 40 and 60% of soil moisture deficit at three growth stages. Additionally, full irrigation was only applied at one and two growth stages. The total irrigation water applied over the season for each treatment to achieve FC was recorded. The layout of the experiments was a completely randomized block design with four replications. Soil water contents were monitored gravimetrically in 300 mm depth increments to 0.9 m prior to and after irrigation at three growth stages (heading, flowering, and milk ripening), and weekly from the plots of the second replication (block) throughout the growing season.
Table 2 A list of irrigation treatments and description Treatments
Description
Control H F M HF
Rainfed (non-irrigated) treatment Irrigation applied only at heading stage Irrigation applied only at flowering stage Irrigation applied only at milk ripening stage Irrigation applied at heading and flowering stages Irrigation applied at heading and milk ripening stages Irrigation applied at flowering and milk ripening stages Irrigation applied at all the stages (full-irrigated). No water stress The same as HFM, but a 40% of water deficit was applied at heading stage The same as HFM, but a 60% of water deficit was applied at heading stage The same as HFM, but a 40% of water deficit was applied at flowering stage The same as HFM, but a 60% of water deficit was applied at flowering stage The same as HFM, but a 40% of water deficit was applied at milk ripening stage The same as HFM, but a 60% of water deficit was applied at milk ripening stage
HM FM HFM H60FM H40FM HF60M HF40M HFM60 HFM40
Crop evapotraspiration was estimated using the following form of the water balance equation: ET ¼ I þ P DS R D where ET is evapotranspiration (mm), I is the irrigation water (mm), P is the precipitation (mm), DS is the change in soil water storage (mm), R is the runoff, and D is the drainage below the root zone. In the equation, I was measured by a water meter, P observed at the Meteorological Station of Agriculture Faculty, DS obtained from gravimetric moisture observations in the soil profile to a depth of 0.9 m. Runoff was eliminated by earthen embankments and blocked-end furrows. Since the clayey soil characteristics are fully dominant in the field, deep percolation (drainage) was assumed to be negligible so that only estimated water (field capacity minus available soil moisture content) was applied to 0.9 m soil profile to reach field capacity. Relationships between yield and ET, irrigation water or transpiration are called production functions. A large number of models were developed to define those relationships in recent decades. Stewart’s equation is the most frequently used model (Stewart et al. 1976; Doorenbos and Kassam 1979). In this study, the Stewart model has contributed to define the relationships between yield and ET. ð1 Ya Ym1 Þ ¼ ky ð1 ETa ET1 m Þ where Ya is the yield under water deficit conditions, Ym is the maximum yield under full irrigation regime, ETa is the ET under water deficit conditions and ETm is the maximum ET related to the full irrigation treatment.
282 Table 3 Applied irrigation water amounts (mm) and irrigation dates for irrigation treatments Treatments 2000
2001
Dates
Total Dates
16.06 28.06 19.07 Control H F M HF HM FM HFM H60FM H40FM HF60M HF40M HFM60 HFM40
– 129 – – 129 129 – 129 77 52 129 129 129 129
– – 118 – 118 – 118 118 118 118 71 47 118 118
– – – 129 – 129 129 129 129 129 129 129 77 52
Total
WUE was calculated as the ratio of seed yield (YLD) to ETa, given as WUE = YLD/ETa (kg ha1 mm1). IWUE was estimated by following equation: IWUE ðkg ha1 mm1 Þ ¼
13.06 27.06 11.07 – 129 118 129 247 258 247 376 324 299 329 305 324 299
– 123 – – 123 123 – 123 74 49 123 123 123 123
– – 91 – 91 – 91 91 91 91 54 36 91 91
– – – 129 – 121 121 121 121 121 121 121 73 48
YLD YLDrainfed IRGA
Where YLDrainfed is the seed yield obtained from the rainfed treatment or dryland yield and IRGA is the seasonal irrigation amount used in millimeter. All data were subjected to analysis of variance for each character using MSTAT-C (version 2.1-Michigan State University 1991) and MINITAB (University of Texas at Austin) software. The significance of irrigation treatments and treatment · year interactions were determined at the 0.05 and 0.01 probability levels, by the F test. The F-protected least significant difference (LSD) was calculated at the 0.05 probability level according to Steel and Torrie (1980).
– 123 91 129 214 244 212 335 286 261 298 280 287 262
Results and discussion Values of ky indicate the sensitivity of sunflower to deficit irrigation. The WUE was determined to evaluate the productivity of irrigation in the treatments. WUE and IWUE are two terms used to promote the efficient use of irrigation water at the crop production level (Bos 1980).
Irrigation water applied and ET The amounts of applied irrigation water for each treatment in 2000 and 2001 are given in Table 3, and monthly and seasonal ET values are given in Table 4.
Table 4 Monthly and seasonal calculated evapotranspiration (mm) Treatments
Control H F M HF HM FM HFM H60FM H40FM HF60M HF40M HFM60 HFM40
Months
Total
Years
Aprila
May
June
July
August
Septembera
2000 2001 2000 2001 2000 2001 2000 2001 2000 2001 2000 2001 2000 2001 2000 2001 2000 2001 2000 2001 2000 2001 2000 2001 2000 2001 2000 2001
97 44 90 33 94 43 101 43 103 45 103 74 125 52 111 48 101 27 119 79 98 43 110 59 109 39 100 53
127 167 133 182 118 146 114 148 105 154 118 212 93 149 122 161 142 175 87 140 121 162 126 155 133 159 124 156
88 57 189 145 128 79 97 68 239 177 196 69 107 34 236 196 186 128 179 74 201 189 185 138 232 185 240 164
34 11 63 26 100 74 90 117 111 95 104 145 182 222 175 174 141 216 141 226 195 173 139 189 129 170 141 157
0 22 0 42 9 29 45 24 25 28 50 23 55 17 44 37 79 14 77 14 16 23 49 21 63 14 23 12
10 0 11 0 0 6 6 0 2 1 20 0 15 21 0 0 8 0 29 6 24 0 19 0 0 8 7 0
a Evapotranspiration was estimated for 24 and 26 days in April 2000 and 2001; for 11 and 5 days in September 2000 and 2001, respectively. Total vegetation periods are 160 and 152 days in 2000 and 2001, respectively
356 301 486 428 449 377 453 400 585 500 591 523 577 495 688 616 657 560 632 539 655 590 628 562 666 575 635 542
283
Irrigation dates are similar for each year. As Table 3 shows that the crop was irrigated in the middle of June in the heading period, toward the end of June in the flowering period, and in the second half of July for 2000 and in the first half of July for 2001 in the milk ripening period. The largest amount of irrigation water was applied to the HFM treatment in both years (376 mm for 2000 and 335 mm for 2001). Monthly and seasonal ET of sunflower was different for each treatment and between years (Table 4). Highest seasonal ET values were recorded for the HFM treatment with no water stress. Seasonal ET values of this treatment were estimated as 688 and 616 mm for 2000 and 2001, respectively. Highest monthly ET values varied with treatments and years. Highest monthly ET values for the HFM treatment were estimated as 236 mm in June of 2000 and 196 mm in June of 2001 (Fig. 1). Heading and flowering growth stages correspond to this period. Doorenbos and Kassam (1979) stated that the percentage of total crop water use over the different growth periods is about 20% during vegetative period, 55% during the flowering period and the remaining 25% during the yield formation and ripening periods. When considering all treatments, the highest monthly ET values were found as 240 mm in June of 2000 for the HFM40 treatment, and 226 mm in July of 2001 for the H40FM treatment. The main reason for differences was that the total rainfall amount was 310 and 201 mm in April and in the previous months (February and March) for 2000 and 2001, respectively. The largest amount of irrigation water was applied in the irrigation season of 2000 (May, June, July, and August) which was drier than 2001. Total rainfall amount was 85 and 97 mm in this period of 2000 and 2001, respectively. Estimated ET values for sunflower (688 mm for the full irrigation treatment in 2000 and 616 mm for the same treatment in 2001) are compatible with ET values pointed out by Doorenboos and Kassam (1979). The authors stated that the water requirements of sunflower vary from 600 to 1,000 mm, depending on climate and length of total growing period. There are many different
results given by many authors. In similar experiments elsewhere, ETc of sunflower was found between 500 and 950 mm (Paltineanu and Sipos 1973; Browne 1977; Demiro¨ren 1978; Ayla 1984; Yakan and Kanburoglu 1989; Karaata 1991; Karaata and Aran 1998; Kadayıfcı and Yıldırım 2000). It was observed that the mean monthly ET values (2-year average) of all irrigation treatments, full or deficit, at three phenological stages (H, F, and M) were different from each other. The differences on ET values of the irrigation treatments depend mainly on the different irrigation water amounts applied. The peak ET of almost all treatments with irrigation at three growth stages occurred at June, whereas ET values of only two treatments (H60FM and H40FM) reached to the peak value at July more likely due to deficit irrigation at the first phenological stage (H). Mean monthly ET (2-year average) changes of the HFM treatment are shown in Fig. 2. In Fig. 2, ET change is relatively slow at the beginning of the growth period and then tends to increase after mid-May. According to the graph, the peak value of 216 mm in mean monthly ET were obtained for the second half of June, and ET of sunflower gradually decreased until harvest time. When considering the average of 2 years, the highest daily on average ET was 7.2 mm in June (corresponding to heading and flowering period). Doorenboos and Kassam (1979) reported that ET increases from establishment to flowering, and can be as high as 12–15 mm day1, and high ET rates are maintained during seed setting and early ripening period. ET increased till flowering stage, then slightly decreased till milk ripening stage, and considerably decreased after milk ripening stage in both years of our study. Our findings for ET correspond to those of previous works. Stem and seed yield In this study, stem and seed yield were examined. According to variance analysis results, the differences
2000 2001
200
250 Evapotranspiration (mm)
Evapotranspiration (mm)
250
150 100 50
200 150 100 50
0 April
May
June
July Months
August
September
Fig. 1 Monthly ET values of the HFM treatment for individual years
0 April
May
June July Months
August
Fig. 2 Mean monthly ET values of the HFM treatment
September
284
between irrigation treatments were statistically significant at 1% level of probability for stem and seed yield in individual years (2000 and 2001) and in the analysis of combined data. Also, the years significantly affected stem and seed yield. On the other hand, ‘‘year · treatment’’ interactions were significant at the 5% level of probability for stem and seed yield. Mean stem and seed yield results for experimental years and 2-year combined data were summarized in Table 5. The results indicate that the highest stem yield was obtained from the HFM treatment (7.04 t ha1), in which crop water requirement was fully applied for the total growing period and the lowest stem yield was obtained from control (5.29 t ha1), where no irrigation water was applied for the total growing period. The treatments H60FM, HF60M, HF40M, HFM60, and HFM40 were placed in the same statistical group of HFM and their stem yields were also higher than the other limited irrigation treatments. It was concluded that stem yield considerably decreased as the irrigation frequency and the amount of irrigation water decreased. Similar results were obtained in individual experimental years as well. In other studies elsewhere, it was also reported that stem yield increased with frequent irrigation (Turner and Rawson 1982) and irrigation applied at heading (Harman et al. 1982) and flowering (Unger 1982) periods. Karaata (1991) found that full irrigations applied at heading, flowering and milk ripening stages and limited irrigation at milk ripening stage (treatment HFM60, HFM40) gave the highest stem yield, whereas non-irrigated treatments and irrigation at milk ripening stage produced the lowest stem yield. Our results were compatible with those experiments given above. Unger (1990) reported that water stress at critical stages has a marked influence on sunflower growth, achene yield, and achene quality factors. Early stress (before budding) reduced the leaf area per plant and leaf
numbers (Muriel and Downes 1974; Marc and Palmer 1976). Besides affecting leaf numbers and areas, early stress reduced plant height (Karami 1977; Selvaraj et al. 1977; Patel and Singh 1979; Unger 1982, 1983). The full and deficit irrigation at three growth periods (heading, flowering, and milk ripening) gave the highest seed yield. The mean of 2-year data indicated that seed yield of the HFM, H60FM, H40FM, HF60M, HF40M, HFM60, and HFM40 treatments were 3.95, 3.83, 3.80, 3.73, 3.86, 3.83, and 3.74 t ha1, respectively. The lowest seed yield was obtained from the non-irrigated treatment (2.16 t ha1). These results indicate that deficit irrigations applied at three growth stages can maintain seed yield in sunflower. Our findings are in agreement with those of Doorenboos and Kassam (1979) who reported that seed yield ranges from 2.50 to 3.50 t ha1 under irrigation. In addition, when considering a single irrigation at each critical growth stage, seed yield was especially increased with irrigation at flowering stage. Full irrigation (HFM) produced 82.9% higher seed yield, compared to the non-irrigated treatment. The seed yield increases for deficit-irrigation treatments were: 31.0% for H; 49.1% for F; 29.2% for M; 50.5% for HF; 56.5% for HM; 51.9% for FM; 77.3% for H60FM; 75.9% for H40FM; 72.7% for HF60M; 78.7% for HF40M; 77.3% for HFM60; 73.1% for HFM40. In previous studies, Muriel (1974) reported that the highest seed yield was obtained from a treatment having no water stress (full irrigation), whereas the lowest yield was produced from a non-irrigated application. Osman and Talha (1975) reported that seed yield increased as the amount of water and irrigation number increased in a study in Egypt. Unger (1982) reported that the seed yield was the highest with an irrigation treatment in which no water stress was applied. The author stated that a higher seed yield was obtained for irrigation treatments applied at flowering or at the end of the flowering stages, whereas increase in stem yield and
Table 5 The effects of irrigation treatments on stem and seed yield in 2000–2001 and combined years Treatments
Control H F M HF HM FM HFM H60FM H40FM HF60M HF40M HFM60 HFM40 Mean LSD (0.05)
Stem yield (t ha1)
Seed yield (t ha1)
2000
2001
Average of years
2000
2001
Average of years
5.94 e 6.44 de 6.57 de 6.79 de 7.12 cd 7.24 bcd 7.28 bcd 8.44 a 8.37 a 7.33 bcd 8.10 ab 8.08 ab 7.79 abc 7.78 abc 7.38 a 890.2
4.63 d 4.62 d 5.44 ab 4.87 d 5.48 ab 4.91 cd 5.38 ab 5.64 ab 5.65 ab 5.29 bc 5.37 ab 5.49 ab 5.71 a 5.49 ab 5.29 b 391.5
5.29 f 5.53 ef 6.01 de 5.83 f 6.30 cd 6.08 d 6.33 bcd 7.04 a 7.01 a 6.31 bcd 6.74 abc 6.79 ab 6.75 abc 6.64 abc – 478.6
2.21 f 2.96 e 3.20 cde 2.99 de 3.23 cd 3.26 c 3.53 b 3.98 a 3.93 a 3.73 ab 3.91 a 3.77 ab 3.79 a 3.81 a 3.45 a 253.8
2.11 g 2.69 ef 3.23 cd 2.59 f 3.27 cd 3.50 bc 3.03 de 3.92 a 3.72 ab 3.86 ab 3.54 bc 3.95 a 3.87 ab 3.67 ab 3.35 b 375.1
2.16 d 2.83 c 3.22 b 2.79 c 3.25 b 3.38 b 3.28 b 3.95 a 3.83 a 3.80 a 3.73 a 3.86 a 3.83 a 3.74 a – 222.9
The values with the same letter are statistically homogeneous in LSD test
285
plant height was observed under irrigations at germination and heading stages. Yakan and Kanburoglu (1989) suggested that one irrigation at flowering stage produced the highest net income and irrigation applied at 30% level of available moisture produced highest seed yield in the Thrace region of Turkey. Karaata (1991) found that seed yield was the lowest in a non-irrigated treatment, whereas higher yields were obtained with full and deficit irrigation treatments at heading, flowering, and milk ripening stages of sunflower in the same region. On the other hand, the same researcher reported that in the case of limited irrigation, water stress should be scheduled on two growth stages (heading and milk ripening of grain) instead of one growth stage (flowering). Quality components Oil percentage and oil yield were investigated as quality components in this study. According to the results of the analysis of variance for quality components, differences between irrigation treatments were not statistically significant for oil percentage in individual year and 2-year combined data. However, years for oil percentage were significant at a confidence level of 1%. Differences between irrigation treatments were statistically significant at 1% level of probability for oil yield in a single year and in the analysis of combined data. On the other hand, years and ‘‘year · treatment’’ interactions for oil yield were significant at 5% level of probability. Mean oil percentage (%) and oil yield (t ha1) results for experimental years and 2-year combined data were summarized in Table 6. Oil percentage was not affected by irrigation treatments applied at different growth stages. Mean oil percentages varied from 43.9 to 45.9% in all irrigation treatments.
Our findings for oil percentage do not correspond to those of Muriel (1974), Jana et al. (1982), Decau and All (1973), Flagella et al. (2002), who reported that oil percentage increased with irrigation. Muriel (1974) reported that oil percentage was found as 47.8, 47.3, and 42.3% for treatments in which applied water was 199% of ET, 50% of ET, and non-irrigated, respectively, in a study carried out in Romania. Unger (1982) found that irrigation at flowering and at the end of flowering stage gave the highest oil percentage (48.8%), whereas irrigation at germination and heading stages produced the lowest (43.4%). Ferri and Losavio (1982) reported that oil percentage was decreased by limited irrigation between seed formation and milk ripening stages. Karaata (1991) reported that oil percentage did not significantly increase as the amount of irrigation water increased, but increased with irrigation applied at flowering and milk ripening stages. Since oil percentage is determined by several environmental factors (especially temperature) as well as genotypic structure (Fick and Zimmerman 1973; Harris et al. 1978), it is likely that the differences between the various studies are mainly due to environmental conditions. In this study, the highest mean oil yield (1.78 t ha1) was obtained in the HFM treatment and the lowest mean oil yield (0.96 t ha1) was obtained from the nonirrigated (or control) treatment. As similar to results of seed yield, oil yield increased as the amount and frequency of irrigation water increased. When compared as a percentage, full irrigation at three growth stages (HFM) produced 85.4% more oil yield compared to the non-irrigated treatment. The oil yield increases for deficit-irrigation treatments were: 30.2% for H; 47.9% for F; 29.2% for M; 50.0% for HF; 59.4% for HM; 57.3% for FM; 79.2% for H60FM; 78.1% for H40FM; 77.1% for HF60M; 80.2% for HF40M; 78.1% for HFM60;
Table 6 The effects of irrigation treatments on oil percentage and oil yield in 2000–2001and combined years Treatments
Control H F M HF HM FM HFM H60FM H40FM HF60M HF40M HFM60 HFM40 Mean LSD (0.05)
Oil yield (t ha1)
Oil percentage (%) 2000
2001
Average of years
2000
2001
Average of years
42.9 42.7 42.3 43.5 42.9 43.1 44.4 43.5 43.2 44.0 44.7 43.3 43.1 43.9 43.4 b –
46.0 45.3 45.7 45.7 45.5 47.0 47.5 47.3 47.0 46.3 46.3 46.5 46.0 46.3 46.3 a –
44.4 43.9 44.0 44.6 44.2 45.0 45.9 45.3 45.0 45.1 45.5 44.9 44.5 45.0 – –
0.95 e 1.27 d 1.36 cd 1.30 cd 1.38 cd 1.40 c 1.57 b 1.71 a 1.69 ab 1.64 ab 1.75 a 1.63 ab 1.63 ab 1.67 ab 1.50 b 132.5
0.97 f 1.22 e 1.48 cd 1.18 e 1.49 cd 1.65 abc 1.44 d 1.85 a 1.75 ab 1.78 ab 1.64 bcd 1.83 ab 1.78 ab 1.70 ab 1.56 a 206.4
0.96d 1.25 c 1.42 b 1.24 c 1.44 b 1.53 b 1.51 b 1.78 a 1.72 a 1.71 a 1.70 a 1.73 a 1.71 a 1.69 a – 120.7
The values with the same letter are statistically homogeneous in LSD test
286
1 – ETa . ETm-1 0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.00 0.05 0.10 0.15 0.20
Crop water production functions
0.25
Water production functions for sunflower were obtained by plotting observed yield on the Y-axis and the ET on the X-axis in 2000 and 2001 (Fig. 3). A linear relationship was found between seasonal ET and seed yield at 99% level of confidence. Seed yield responded linearly to applied water. To determine the yield response factor (ky), relationships between proportional ET decreases and proportional yield decreases were calculated. Adjusted maximum yield values (Ym) were calculated versus maximum evapotranpiration (ETm) by using linear equations (from Fig. 3) for each single experimental year. Crop water production function and yield response factor (ky) were given below for total growth stage. ½1 ðYa Ym1 Þ ¼ 0:8382 ½1 ðETa ET1 m Þ; r ¼ 0:9169 The slope of line (ky) that was given in the function was found as 0.8382 for the total growing period and is illustrated in Fig. 4. Additionally, crop water production
0.30
ky = 0.8382
1 – Ya . Ym-1
76.0% for HFM40. Our results are in agreement with those of Osman and Talha (1975), Browne (1977), Jana et al. (1982), and Kadayıfc¸ı and Yıldırım (2000) who reported that oil yield increased as the amount of irrigation water increased.
0.35 0.40 0.45 0.50
Fig. 4 Relationship between relative seed yield decrease and relative ET deficit for sunflower throughout the total growing season during 2 years (2000–2001)
functions were calculated for each individual growth stage (heading, flowering, and milk ripening). Crop water production functions obtained for each growth stage were given below: Heading (H) ½1 ðYa Ym1 Þ ¼ 0:9159 ½1 ðETa ET1 m Þ; r ¼ 0:9826 Flowering (F) ½1 ðYa Ym1 Þ ¼ 0:7859 ½1 ðETa ET1 m Þ; r ¼ 0:9160 Milk Ripening (M)
5
Yield (t ha-1)
4
½1 ðYa Ym1 Þ ¼ 0:8971 ½1 ðETa ET1 m Þ; r ¼ 0:9734
2000
The graphs of these equations are shown in Fig. 5. To present wider options to irrigation planners, obtained results from treatments in which deficit irrigation was spread over two growth stages. Crop water production functions obtained for two growth stages are given below and graphs of those functions are shown in Fig. 6.
3 y = 0.4649x + 76.529 r = 0.9405
2 1 0 200
300
400
500
600
700
800
1 – ETa . ETm-1
Evapotranspiration (mm) 0.6
0.5
0.4
0.3
0.2
0.0 0.00
0.1
5
0.05
2001
0.10 0.15
3
0.20 0.25
2
ky = 0.7859 (F)
y = 0.5589x + 55.808 r = 0.8966
1
ky = 0.9159 (H) ky = 0.8971 (M)
0 200
300
400
500
600
700
H
0.30
F
0.35
M
1 – Ya . Ym-1
Yield (t ha-1)
4
0.40 0.45 0.50
Evapotranspiration (mm) Fig. 3 Relationship between seed yield and evapotranspiration for sunflower during two seasons (2000–2001)
Fig. 5 Relationship between relative seed yield decrease and relative ET deficit of sunflower for the individual growth stages during two seasons (2000–2001)
287
1 – ETa . ETm-1 0.5
0.6
0.4
0.3
0.2
0.1
0.0
0.00 0.05
0.15 0.20 0.25
ky = 0.7708 (FM) HM
ky = 0.9022 (HF)
HF
ky = 0.8945 (HM)
FM
0.30
1 – Ya . Ym-1
0.10
0.35 0.40 0.45 0.50
Fig. 6 Relationship between relative seed yield decrease and relative ET deficit of sunflower for two growth stages during two seasons (2000–2001)
Heading–flowering (HF) ½1
ðYa Ym1 Þ
¼ 0:9022 ½1
by Doorenboos and Kassam (1979). The deviation may be attributed to differences in phenological stages and in irrigation water amounts depending upon the different soil and climatic conditions. Yield response factor (ky) at some calculations for individual growth stage was found to be higher than those calculated for the total growing season (0.8382). For example; ky is 0.9159 for heading, 0.8971 for milk ripening, 0.8945 for heading–milk ripening, and 0.9022 for heading–flowering stages. When comparing the results for individual growth stages, it was concluded that ky for milk ripening stage (0.8971) is close to ky for yield formation stage (0.8), ky for flowering is smaller than one (0.7859
