The effect of zinc application methods on seed cotton yield , lint and seed quality of cotton ( Gossypium hirsutum L . ) in east Mediterranean region of Turkey

The effect of different zinc application methods on seed cotton yield, yield components, lint and seed quality of cotton was investigated under east Mediterranean region conditions (Kahramanmaras, Turkey) in 2008. Experimental design was split plots with three replications. The cotton varieties: Agdas-3, Agdas-17 and Maras-92 (Gossypium hirsutum L.) were plant materials. Zinc application treatments were seed, soil surface, foliar application and untreated control. A commercial preparation of chelated zinc (EDTA Zn-17 %) was used as zinc fertilizer. It was determined that zinc application methods did not affect yield and yield components except plant height. While zinc application methods had no effect on lint quality traits except spinning consistency index (SCI), elongation and yellowness (+b), which are the best values, were taken from the soil surface and foliar application of zinc and control for spinning consistency index, and from the foliar application of zinc for yellowness. On the other hand, zinc application methods did not affect raw oil and protein ratio of cotton seeds, as well as the zinc content of cotton seeds and leaves. When the pH, organic matter, lime content and soil texture were taken into consideration, decreasing of pH value and lime content of soil and increasing of organic matter together with zinc fertilization in the experimental field were suggested.


INTRODUCTION
Cotton (Gossypium hirsutum L.) is an industrial crop which has an important place in the world agriculture and trade.A number of researches have been established on cotton that is valuable for many industries besides textile industry depending on the requirements of human being and rapid developments in the industry.In Turkey, cotton sowing area and seed cotton production is about 420.000 ha and 1.725.000tonnes, respectively.With this, lint cotton production is 638.250tonnes, seed cotton yield is 4.110 kg/ha and lint yield is 1.520 kg/ha.In Kahramanmaras, cotton sowing area is 7.048.4ha, seed cotton production is 23.266 tonnes, lint cotton production is 8608 tonnes, seed cotton yield is 3.380 kg/ha and lint yield is 1.220 kg/ha (Anonymous, 2009).
Nutrient elements must be sufficient enough in the growing environment of the plant to obtain high quality and more yield.Both plant growth and yield are negatively affected by deficiency of nutrient elements and lint quality is decreased as well.The amount of plant nutrient elements taken by cotton plant from soil varies depending on many factors.The species of Gossypium takes more nutrients from the soil.Cotton plant grown under irrigation conditions takes more nutrient elements.Among micro nutrient elements, cotton plant utilizes calcium (Ca) mostly followed by nitrogen (N) and potassium (K).Besides these elements, cotton plant needs zinc (Zn) which is a micro nutrient element and it can be sensitive in case of deficiency (Kacar and Katkat, 2007).Zinc is an indispensable element for healthy life of humans, animals and plants.It has important functions in protein and carbohydrate metabolism of plants.Furthermore, zinc is an element which directly affect yield and quality because of its function such as its activity in biological membrane stability, enzyme activation ability and auxin synthesis (Marschner, 1997;Oktay et al., 1998).In 49% of the soils in Turkey, zinc level is lower than 0.5 mg /kg which is at critical level.Also, in a large part of the soils in Turkey there are zinc deficiencies close to critical level.Linear relationship (Y = 0.16 + 0.362 X and R 2 ) between useful zinc quantity and organic matter content in the soils of Turkey were found positive and statistically significant (Eyupoglu et al., 1998a).Usefulness of zinc like the other micro elements is affected by organic matter quantity and properties of the soil.Organic matter affects usefulness of zinc by forming complex or making Zn adsorbtion with humic and fulvic acid fractions.The effect of Zn-organic matter complexes on usefulness of zinc depends directly on dissolution of this complex compounds (Tisdale et al., 1985).
Although, zinc as nutrient element is extremely important for plant production, its uptake from the soils can be easily blocked depending on many factors and its quantity decreased continiously.A study carried out in Turkey with 1511 soil samples showed that pH value was more than 7.0 in 91.8% of the soils.This finding has shown close relationship between zinc deficiency and soil pH value in Turkey soil (Ulgen and Yurtsever, 1984;Eyupoglu et al., 1998b).Because of adsorbtion of zinc by carbonates in lime soils or formation of compounds which has low dissolution such as ZnCO 3 and Zn(OH) 2, Zn +2 is transformed into unuseful form in the soil (Viets, 1966;Navrot and Ravikovitch, 1969;Trehan and Sekhon, 1977).Sodium and salt content increases where ground water is higher.In these lands, keeping the soils under water usefulness of zinc can be increased up to a period (Aydın et al., 1998).When these matters are taken into consideration, it can be said that zinc fertilization is necessary in the soils of Turkey.Maize, bean, cotton, flax, various fruits and walnut are more sensitive plants to zinc deficiency.On the contrary, sorghum, alfalfa, cereals, meadow grass and vegetables are less sensitive plant (Saglam, 1999).Symptoms of zinc deficiency include smaller young leaves, chlorotic inter-vascular leaves, red spots occurrence in leaf blade.Internodes become shorter; plants become dwarf and appear like shrub, in advance rosette (Anonymous, 2007).
In this study, the effect of different zinc application methods on seed cotton yield, yield components, lint and seed quality was investigated under east Mediterranean region conditions (Kahramanmaras-Turkey).

Materials
In this study, three cotton varieties Agdas-3 and Agdas-17 (G.hirsutum L.) brought from Azerbaijan and Maras-92 (G.hirsutum L.) developed in Kahramanmaras were used as the planting material.A commercial preparation of chelated zinc (EDTA Zn-17%) was used as zinc fertilizer in seed, soil and foliar application.Kahramanmaras is a province located in the east Mediterranean region of Turkey and it has typical Mediterranean climatic conditions comprises of hot and dry weather in summers and warm and rainy weather in winters.Some physical and chemical properties of soil Efe and Yarpuz 8783 samples taken from 0 to 30 cm depth in the experimental field are shown in Table 1.Soil texture of the experimental field was clay-loam with very high lime content (32.18%).The soil was not salty but alkaline (pH 7.95) with lack of organic matter, phosphorus, iron, and zinc.However, the soil contained sufficient amount of potassium and copper with high manganese (Table 1).

Methods
The study was carried out in 2008 in the experimental field of Kahramanmaras Sutcu Imam University, Faculty of Agriculture.The split plot experimental design was used with three replications.Application methods of zinc fertilizer were in main plots; cotton varieties were in subplots.The seeds of cultivars were sown by experimental mechanical planter in four-row plots of 10 m length at a planting space of 70 cm on 21 May 2008.After emergence, when plants had 4 to 5 leaves, they were thinned to 20 cm in rows.During the growing season, plants were hoed and harrowed 3 times to protect growing cotton seedlings from weeds, to prevent evaporation of soil water, and to aid development and deepening of roots of seedlings.Plants were furrow irrigated 7 times during the growing season as needed by the plants.Nitrogen was applied as one-third at presowing period, one-third at 36 days after sowing at presquaring period (prior to first irrigation), one-third at 54 days after sowing at the beginnig of flowering (prior to second irrigation) by using a fertilizer spreader in inter-rows at a total of 20 kg/da.Phosphorus was applied at presowing period at a rate of 6 kg/da P2O5.Composed fertilizer (20:20:0) and 46% of urea were used at presowing and surface fertilization, respectively.In this study, there were three different methods of Zinc (Zn) application and control (untreated): 1. Seed application: The seeds of tested cotton cultivars were kept overnight (10 to 12 h) before sowing in the solution of 10 L prepared using a commercial preparat of chelated Zinc (EDTA Zn-17%) at the rate of 100 g/kg seeds.2. Soil surface application: For each plots, 80 g of a commercial preparation of chelated zinc (EDTA Zn-17%) was dissolved in 12 L of water and sprayed using atomizer to the surface of soil of one plot (28 m 2 ).Immediately after application, seeds of cultivars were sown.3. Foliar application: Zinc fertilization was applied at three growing stages.At the first stage in which plants had 5 to 7 leaves in each plot, 80 g of commercial chelated Zinc (EDTA Zn-17%) was dissolved in the water of 12 L and the whole solution was sprayed using atomizer to the whole plants in one plot (28 m 2 ) early in the morning.Second application was made at 50% of squaring stage.Third application was made after 10 days from second application.4. Control (untreated): Zinc fertilizer was not applied to these plots.In foliar application and control, the seeds was not treated with water before sowing.
Before harvesting, 25 boll samples were taken at random from two rows in the middle of each plot when 50 to 70% of bolls opened (Efe, 2000).Plants were hand picked on 19, September and 08, October from two rows in the middle of each plot.Seed cotton yield, yield components, fiber quality traits, raw oil and protein ratio of cotton seed, zinc content in cotton seed and leaf were investigated.After ginning of the boll samples, fiber properties were determined by using HVI (high volume instruments) instrument.Raw oil ratio of cotton seed was determined by using the method of soxhlet extraction.Raw protein ratio of cottonseed was determined by using Kjeldahl method (AOAC, 1990).Zinc content in cotton seeds were determined by using microwawe and atomic absorbtion spectrophotometric method.Zinc content in cotton leaf was determined by using atomic absorbtion spectrophotometric method.
Table 1.Some physical and chemical properties of soil of the experimental field (Anonymous, 2008).The data obtained were analysed according to split plot design with three replications by using the SPSS statistical package program (Efe et al., 2000) and the means were compared by using Duncan multiple comparison test at 0.05 significant level (Bek and Efe, 1995).

RESULTS AND DISCUSSION
Statistically, differences were determined among different application methods of zinc for plant height (P<0.05),spinning consistency index (SCI) (P<0.05),elongation (P<0.05) and yellowness (+b) (P<0.01).Differences were also determined for brightness and yellowness among varieties.For plant height (P<0.01),fiber uniformity (P<0.01) and short fiber index (P<0.05),treatment x variety interaction was statistically significant.Means of zinc application methods, cultivars and treatment x variety interactions for seed cotton yield and yield components and groupings are given in Table 2.
As seen in Table 2, it was determined that zinc application methods did not affect the yield and yield components except plant height.Means of plant height for zinc application methods varied between 76.9 cm (seed application) and 71.4 cm (foliar application).Means of sympodial branch numbers for zinc application methods varied between 9.6 (seed application) and 8.7 (foliar application).Means of boll number per plant for zinc application methods varied between 14.0 (seed application) and 12.5 (foliar application).Means of seed cotton yield for zinc application methods varied between 3149 kg ha -1 (foliar application) and 2901 kg ha -1 (seed application).Means of ginning outturn for zinc application methods ranged from 41.4% (foliar application) to 40.4% (seed application) (Table 2).
For 100 seed weight and fiber quality traits, means of zinc application methods, cultivars and treatment x variety interactions and groupings are given in Table 3.
As seen in Tables 3 and 4, zinc application methods did not affect lint quality traits except spinning consistency index (SCI), elongation and yellowness (+b).Means of fiber length for zinc application methods varied between 29.3 mm (foliar application) and 28.8 mm (seed application).Means of fiber fineness for zinc application methods varied between 4.8 mic.(seed application) and 4.5 mic.(control application).Means of fiber strength for zinc application methods varied between 32.2 g tex -1 (soil surface and control application) and 30.7 g tex -1 (seed and foliar application).Means of spinning consistency index for zinc application methods ranged from 157.2 to 170.7.The best values were taken from soil surface and foliar application of zinc and control for spinning consistency index (Table 3).Means of elongation for zinc application methods varied between 5.6% (seed application) and 6.0% (foliar application) (Table 3).
For some lint quality traits means of zinc application methods, cultivars and treatment x variety interactions and groupings are given in Table 4.
The highest fiber uniformity index (87.4%)was obtained from cv Maras-92 for zinc fertilizer application to leaves.The lowest fiber uniformity index (84.3%)was obtained from cv Agdas-17 for zinc fertilizer application to seeds.The lowest short fiber index (5.8%) was obtained from cv Agdas-3 untreated control.The highest short fiber index (7.6%)was obtained from cv Agdas-17 for zinc fertilizer application to seeds.
Means of zinc application methods, cultivars and treatment x variety interactions for raw oil and protein ratio in seeds and zinc content in seeds and leaves are given in Table 5.
It was determined that zinc application methods did not affect raw oil and protein ratios of cotton seeds, zinc content in cotton seeds and leaves (Table 5).Means of raw oil ratios in seeds for zinc application methods varied between 18.4% (control application) and 20.2% (foliar application).Means of raw protein ratios in seeds for zinc application methods varied between 20.6% (seed application) and 23% (soil surface application).Means of zinc content in seeds for zinc application methods varied between 21.4 mg kg -1 (seed application) and 23.1 mg kg -1 (control application).Means of zinc content in leaves for zinc application methods varied between 44.0 ppm (foliar application) and 52.3 ppm (seed application) (Table 5).Raw oil ratios in seeds of the varieties were 19.0% (cv.Agdas-3), 19.3% (cv.Agdas-17) and 20% (cv.Maras-92) respectively (Table 5).Raw protein ratios in seeds of the varieties were 21.8% (cv.Agdas-3), 21.5% (cv.Agdas-17) and 22.1% (cv.Maras-92) respectively.Zinc content values in seeds of the varieties were 22.0 mg kg -1 (cv.Agdas-3), 19.7 mg kg -1 (cv.Agdas-17) and 25.0 mg kg -1 (cv.Maras-92).Zinc content values in leaves of the varieties were 44.9 ppm (cv.Agdas-3), 48.6 ppm (cv.Agdas-17) and 46.3 ppm (cv.Maras-92) respectively.When physical and chemical properties of soil from the experiment field (Table 1) was assessed, it was determined that the soil contain insuffient zinc that led to Zn deficient symptoms in the crops grown.In Table 1, it is shown that the pH degree of the soil is 7.95.Eyupoglu et al. (1998b) reported that the most zinc deficiency occur in the soils in which pH degree is between 7 to 8 and that useful zinc content decreases as soil pH increases.In Table 1, it is shown that organic matter content is 0.49%.In most zinc deficient soils, the organic matter content is lower than 1% and it is possible that zinc deficiency in the experiment field vary depending on the organic matter content.Zinc deficiency is highest in clay-loam soil (Marschner, 1997).Therefore, zinc deficiency in the experimental field may have been influenced by the soil texture.In this study, lime content in the soil of experiment field was 32.18%.Also, one of the reasons zinc deficiency in the field is very high lime content.Eyupoglu et al. (1998b) noted that zinc deficiency can occur in the soils in which zinc content is lower than 0.5 ppm.In this study, zinc deficiency (0.44 ppm) was determined in the soil of experiment field.Mert (2007) reported that effective root depth of cotton plant is 1 m depending on soil type, humidity, temperature and plant vigor.Based on this fact, it is possible that zinc may be present on seed coat and it could not be uptaken because it could not be transfered to effective root zone while plant germinate and grow.
As a result, it was determined that zinc application methods did not affect yield and yield components except plant height.While zinc application methods had no effect on lint quality traits except spinning consistency index (SCI), elongation and yellowness (+b), the best values were taken from soil surface and foliar application of zinc and control for spinning consistency index, from foliar application of zinc for yellowness.It was determined that zinc application methods did not affect raw oil and protein ratio of cotton seeds, zinc content in cotton seeds and leaves.Among varieties, the brightest (78.3) and the least yellow (8.5) fibers were taken from cv.Maras-92.Inconclusion, when pH, organic matter and lime content and soil texture are taken into consideration, it can be suggested decreasing of pH value and lime content of soil and increasing of organic matter together with zinc fertilization in the experimental field.Because there was iron deficiency in the experimental field it can be necessary iron fertilization besides of zinc.Moreover, zin cfertilization of cotton with increased zinc and iron doses should also be tried fo rbetter results in further studies.

Table 2 .
Means of zinc application methods, cultivars and treatment x variety interactions for seed cotton yield and yield components and groupings.

Table 3 .
Means of zinc application methods, cultivars and treatment x variety interactions for 100 seed weight and fiber quality traits and groupings. a

Table 4 .
Means of zinc application methods, cultivars and treatment x variety interactions for some fiber quality traits and groupings.

Table 5 .
Means of zinc application methods, cultivars and treatment x variety interactions for raw oil and protein ratio in seed and zinc content in seed and leaf.