**3. Results and discussion**

There are research studies examining the effects of defoliation on seed and crude oil yields in sunflower. However, in all these studies, it was reported that leaf removal from plant gave rise to decreases in seed yield and crude oil yield. It was thought that these negative results were caused by the incorrect and incomplete application of the methods used in those researches. In some studies, all leaves in plant were removed [7–9], while 1/3 or 2/3 of leaves were removed in some other ones [9, 10]. Or defoliation was carried out in the lower, middle, and upper leaves of the plants [11, 12]. It was reported that effective leaves on yield were in top and middle of the plant [13]. In our study, a certain amount of defoliation (0 = control, two, four, and six leaves removed) was carried out in the middle of the plant and from the below of the head in "star-shaped head stage," which is the beginning of the reproductive period in the plant, and the results of photosynthesis are assimilated and transported to the seeds. When the amount of assimilation produced by photosynthesis is increased, the seed yield will also directly increase.

In this study, on the effects of different defoliation treatments on seed, crude protein, and crude oil yields per decare in "star-shaped head stage," which is the beginning of the reproductive period in sunflower, it was determined that different defoliation treatments, according to cultivars, significantly increased seed, crude protein, and crude oil yields compared to the control group with no defoliation treatment (**Table 1**).

For cv. "08-TR-003," the seed yield per decare was 385.4 kg in the control treatment in which no leaf was removed, while it was 431.2 kg in the four-leaf defoliation treatment in the plant. This means that the yield increased by 11.87%. An increase of 1.90% was observed in the crude protein yield obtained from a decare. When the oil yield per decare value was examined, it was 175.0 kg for the control treatment, while it was 207.7 kg — an increase of 18.67% — in the four-leaf defoliation group. The highest values for seed, crude protein, and crude oil yields in the cv. "08-TR-003" were obtained when four leaves per plant were removed (**Table 1**).

In cv. "TR-3080," the seed yield per decare in control treatment was measured as 398.3 kg, whereas there was an 8.64% increase to 432.7 kg when two leaves were removed at the beginning of the reproductive period. The protein yield was 66.2 kg in the control, whereas it increased by 6.40% up to 70.4 kg when two leaves were removed. Examining the crude oil yield per decare values, it was 184.8 kg for the control treatment, whereas it increased by 13.36% to 209.5 kg when two leaves were removed from the plant. In cv. "TR-3080," the highest values for seed, crude protein, and crude oil yields were obtained from the two-leaf defoliation treatment (**Table 1**).

Measurements were performed in totally 30 plants (10 plants per replication) in each defoliation treatments in all cultivars. Seed yield per plant (g/plant), seed yield per decare (kg/decare), protein and oil percentages, crude protein, and crude oil yields (kg/decare) were recorded.

**Figure 3.** Flowering in the head (on the left) and covering the head with paper bags to protect seeds from bird's damage

Experiments were arranged at "randomized complete block, split-plot" design with three replications. In the experiment, oil-type sunflower cultivars were main plots and four defoliation applications were subplots. Data were statistically analyzed by Duncan's multiple range test using "IBM SPSS Statistics 22." Data given in percentages were subjected to arcsine (√*X*)

There are research studies examining the effects of defoliation on seed and crude oil yields in sunflower. However, in all these studies, it was reported that leaf removal from plant gave rise to decreases in seed yield and crude oil yield. It was thought that these negative results were caused by the incorrect and incomplete application of the methods used in those researches. In some studies, all leaves in plant were removed [7–9], while 1/3 or 2/3 of leaves were removed in some other ones [9, 10]. Or defoliation was carried out in the lower, middle, and upper leaves of the plants [11, 12]. It was reported that effective leaves on yield were in top and middle of the plant [13]. In our study, a certain amount of defoliation (0 = control,

transformation before statistical analysis [6].

12 Physical Methods for Stimulation of Plant and Mushroom Development

**3. Results and discussion**

(on the right).

In cv. "TARSAN-1018," 407.3 kg/da seed yield determined for the control treatment was 451.6 kg/da when six leaves were removed from the plant. This indicates that in the six-leaf defoliation treatment, seed yield increased by 10.87% compared to the control. Crude protein yield per decare was found to be 75.6 kg for control treatment, while it was 85.1 kg for the six-leaf defoliation, an increase of 12.61%. The crude oil yield per decare value in the control group was 190.7 kg, while it was 215.3 kg for the six-leaf defoliation treatment, with an increase of 12.92%. In cv. "TARSAN-1018," the highest values for seed, crude protein, and crude oil yields were obtained from the six-leaf defoliation treatment (**Table 1**).

Leaves forming the surface for active photosynthesis in plants can be damaged due to environmental factors (such as storms and hail) and mechanical factors (tools and machines used in maintenance operations such as drilling and spraying). The extent of this damage is directly proportional to the amount of defoliation. In other words, as the number of defoliations increases in the plant, the agricultural characteristics decrease proportionally, based on the cultivar. This is confirmed by the lowest values for the seed yield per decare values obtained in our study for the six-leaf defoliation treatments for cvs. "08-TR-003" and "TR-3080."


Considering the general average values of the three cultivars used in this study, seed yield increased by 10.46%, crude protein yield increased by 6.97%, and crude oil yield increased by 14.98% compared to the control group when defoliation treatment was applied in "star-

The Effect of Leaf Removal–Based Physical Injury on High Seed and Crude Oil Yields…

http://dx.doi.org/10.5772/intechopen.71357

15

In 2014, we estimated that the Turkish population was 77,695,904 [14] and that annual consumption of vegetable oil per capita should be 21 kg, corresponding to 1,630,000 tons of vegetable oil needs. Accordingly, 800,000 tons of this was met with domestic production, and a shortage of 835,000 tons of crude oil was identified [15]. In 2014, 795,000 tons of crude oil was

Turkey paid 1194 US dollars for importing 1 ton of vegetable crude oil in 2014, and 835,000 tons of crude oil met by imports would be 996, 990,000 US dollars [15]. In 2014, oil-type sunflower seeds were sown over an area of 5,524,651 decares in Turkey and 1,480,000 tons of sunflower seeds were produced; the seed yield was 269.00 kg/da [16]. The crude oil yield in

According to the results obtained in this study, when leaves are reduced in sunflower cultivation, the seed yield per decare will increase from 269.00 to 297.13 kg, a 10.46% increase, and the crude oil yield will increase from 143.90 to 165.95 kg, a 14.98% increase. This means that crude oil production in Turkey from sunflower will be 914,054 tons (165.45 × 5,524,651). In other words, when the method described in the current study based on defoliation is applied to the production of sunflower, the production of crude oil in Turkey will increase to 119,054 tons (914,054–795,000). Considering that 1194 US dollars was paid for 1 ton of crude oil import, it is seen that 142,150,476 dollars (119,054 × 1194) will be retained domestically by applying the

Due to the increasing world population and the rapid consumption of natural resources, there is a need to increase crop production. Aside from increasing the agricultural lands to increase crop production, existing agricultural lands are decreasing day by day. In this case, it is necessary to develop new high-yielding cultivars and to apply agricultural techniques (fertilization, irrigation, and agricultural pest control) as the best way to increase crop production. However, with the rapidly increasing world population and ever-narrowing areas available for agriculture, the development of new cultivars resistant to biotic and abiotic stress factors (extreme heat, extreme cold, salinity, new pest culprits, and pest breeds) is extremely difficult due to time limitations and to the resistance characteristics being under the control of more than one gene. Therefore, it is necessary to develop new methods in order to increase the yield per unit area for plants that play an important part in human nutrition (wheat, corn, rice, sunflower, etc.).

shaped head stage," which is the beginning of the reproductive period.

**4. Economic analysis**

obtained from sunflower.

the sunflower was 143.90 kg/da.

method developed in our research.

**5. Conclusion**

Considering the general average values of the three cultivars used in this study, seed yield increased by 10.46%, crude protein yield increased by 6.97%, and crude oil yield increased by 14.98% compared to the control group when defoliation treatment was applied in "starshaped head stage," which is the beginning of the reproductive period.
