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Tuna Doğan 1, Gönül Aydın Bilgehan 2, İbrahim Yalçın 1 1 Department of Agr.Machinery, Faculty of Agriculture, Univ. of Adnan Menderes, Aydın/TURKEY 2 Department of Soil Science, Faculty of Agriculture, Univ. of Adnan Menderes, Aydın/TURKEY ABSTRACT Aydın is one of the cities where cotton farming is applied commonly. In Aydın, to practice the traditional tillage method in seedbed preparation and to obtain the optimum soil condition, the soil is over cultivated and crushed. Due to direct physical effects such as ploughing, seedbed preparation and cultivation, the structure of noncultivated soil display a great tendency to decay. Therefore, the effects of two tillage and seedbed preparation methods, (namely the traditional and the reduced tillage methods) have been examined in terms of their effects upon the soil structure when the cotton stalks are mixed and not mixed with the soil. The results of the research have shown that the aggregate strength and size, which indicate the soil structure, are badly affected when the traditional method is applied. INTRODUCTION Soil structure can be evaluated by determining the extend of aggregation and stability of the aggregates. These characteristics change with tillage practices a cropping system, they play a significant role in affecting soil-plant relationship. Problems, which are related to the soil structure, increase in natural soils when they are cultivated. Three causes of this are; 1-In soils, which are cultivated for vegetal purposes, destructive effects, increase and accumulate year by year due to the use of tractors and over dispersing tillage equipment. The destruction in the condition of the natural vegetation causes the soil to become weak against the destruction of the rain. 2-The mechanization process involving in soil loosing increases the air circulation within the soil and this increases the oxidation of the polymer complex which help the soil structure resistance. 3-Vegetal production applications at present decrease the production rate of products, which help to improve the soil structure. Breakdown of organic matters getting rapidly result in decrease of soil structure stability. (Brafield and Miller, 1954). The frequent tillage operations in the traditional method affect the soil negatively. Over tillage operations, not only increase the cost of the product but also disaggregate the organic matters in the soil. Production of some crops, which require over tillage, such as cotton, the soil aggregates are easily decomposed. Such decompositions cause soil erosion (Kayışoğlu et all., 1996). The changes occurring in the soil structure due to tillage mainly depend on the quantity of the soil moisture. Because of the soil contraction caused by over moisture in the soil. The soil structure is badly effected. In the case of soil compaction with minimum water content, crumbled structure with small pore forms. Then, this results in a reduction in the quantity of large pores, in total quantity of pores, in permeability and, at the and, in crop quantity (Utkayeva et all., 1986). In this study, it was tried to determine the effect of two different seedbed preparations on soil structure in a plot where cotton stalks are mixed or not mixed with soil. MATERIALS AND METHODS Soils on which the research was carried out are one of the parts belonging to the Great Meander Seri which is stretched out in the valley (Bilgehan Aydın, 1998).  Some characteristics of the machines and equipments applied in various tillage methods are shown in Table 2.  In this research, the cotton stalks were cut in 10 cm depth by moulboard without plough, and it was thought that those stalks could be picked by a straw baler (Yumak and Evcim, 1992; Anonim,1995). In addition to this, the stalks were cut into pieces by stalk cutting machine and disc harrow. Because of different tillage methods were applied on the plots with stalks and without stalks, the field on which the research was carried out had been designed split-plot pattern (Açıkgöz, 1993). Plot lengths were taken 25 meters and 8 rows of cotton seeds were planted on each variant. Between the variants 5 meters of vacant land was left and similarly 10 meters of land was left without cultivating between the repetitions so that the tractor could return easily. Two different tillage and seedbed preparation methods applied in the research; Traditional Tillage Method : Moulboard plough(autumn)+Moulboard plough+Trailed Disc harrow(x6)+Broadcaster+Field sprayer+Trailed Disc harrow+Scrubber Reduced Tillage Method : Moulboard plough(autumn)+Chisel+Mounted disc harrow+Broadcaster+Field sprayer+ Mounted disc harrow +Scrubber Evaluations are made according to 6 different methods consisted of various procedures (Table3).  The analytic method was used in obtaining the results containing time etudes. Throughout the tractor's operation united with the equipments, the time measurements for each procedure were done and values of effective work time requirements were found out. The results of this research were evaluated on the basis of the standard plot which has 150 m length, 66,67 m width and 1 ha size and was used in researches by Uçucu (1981) and Yalçın and Uçucu (1999). While calculating the values effective work time requirements in the fifth and sixth methods, the values related to the straw baler which could be referred in the application of the method were obtained from the literature (Evcim, 1990). 56 disturbed and undisturbed soil samples were taken from 6 different soil tillage practiced and non-tillage plots in research field at 4 different soil strata, namely 0-10, 10-20, 20-30 and 30-40 cm depths (2 repetition). Then, following analyses were carried out; Aggregation index: to determine the resistance of aggregates to water for soil samples sieved with 8 mm sieve (Yeşilsoy and Berkman, 1974). Total porosity (Vomocil, 1965) and volume weight (G.R.Blake, 1965). By sieving; using Retsch brand sieve, which is capable of sieving the materials of 19 mm, 4,5 mm, 2,36 mm, 2 mm, 1 mm and less than 1 mm diameter. During analysis, it was run for 4 minutes. Throughout the evaluation of all data obtained out of laboratory and plot tests the Turkish Statistical Software "TARİST" was used (Açıkgöz vd., 1994). DISCUSSIONS Structural and some structure related physical soil analysis were carried out for soil samples that were taken from research field. The results are given Appendix 1. Aggregation index refers to the resistance of aggregates to water. When these values are examined, it can be seen that 3 practices, where reduced tillage were applied, at first 0-10 cm stratum have greater aggregation index values than other 3 practices where traditional tillage were applied at first 0-10 cm stratum. This shows that surface soils are more crumbled by traditional tillage methods. Since the data at hand are the results of just 1-year trial, the differences seem too little in magnitude. But, as the research continues, the differences are expected to be clearer. If total porosity values and volume weights are examined, one can see that volume weight values of traditional tillage applied practices at 0-10 cm stratum are less than that of reduced tillage applied practices. Volume weight values generally increase from surface to deeper strata. The plot of non-tillage has greater volume weight values than others. At the strata with higher volume weight values, total porosity values decrease as expected. Due to intense soil tillage, higher volume weight values below surface are generally encountered throughout Meander Valley. In regards of dry sieving results, before tillage and methods used make no significant differences (Table 4). On the other hand, at 0-10 cm strata, sum of weight percentages of soil aggregates of 2 mm or below is more than 50 % for all methods. But, as a result of variance analysis between dry sieving values of different methods, F values at 5 % and 1 % levels are statistically in significant.  Intense soil tillage practices for seedbed preparation for, especially, cotton and second crop are a major problem in the Valley, because they result in crumbling of aggregates and decrease in their resistances. Moreover, that the valley soils contain less amounts of clay, organic matter and lime, which supports aggregate formation, and high amounts of sodium in some places is another major problem which decreases aggregate formation and resistance. Therefore, since maintaining physical productivity is of great importance, lessening the intense soil tillage in the Valley is indispensable in terms of both economy and soil conservation. Effective work time requirements for methods and their statistical groups are given in Table 5.  As the Table 5 implies, in terms of effective work time requirements by methods depending on machinery, the most suitable method is the Method-4. Generally, effective work time requirements of reduced tillage methods are less than that of the traditional tillage methods. Considering that different methods have no significant effect on soil characteristics and structure in respect of the results at hand, one can say that reduced tillage methods, which are more profitable in terms of effective work time requirement, can be employed without any hesitation.  REFERENCES Bradfield, R., Miller, R.D. (1954) Soil Structure. Transaction of the V. International Congress of Soil Sci. 1, 131-145. Blake, G.R., (1965) Methods of Soil Analysis. Part I. 371-373. Vomocil, J.A. (1965) Methods of Soil Analysis. Part I. 299-314. Yeşilsoy, M.Ş., Berkman, A. (1974) Islak Eleme Yöntemi İle Topraklarda Agregasyon İndeksinin Saptanması. Çukurova Üniversitesi, Ziraat Fakültesi Yıllığı. 1-2, 95-110. Uçucu, R. (1981) Buğday ve Arpa Hasat-Harmanında Uygulanan Değişik Sistemlerin Ege Bölgesi Koşullarında İş Başarıları, İşgücü Gereksinmeleri ve Maliyetleri. Doçentlik Tezi, E.Ü.Ziraat Fakültesi, İZMİR. Utkayeva, V.F., Sponzhinkov, P.M., Shchepotyev, V.N. (1986) The Compacting Effect of Agricultural Equipment on Soil Structure. Translated From Pochvovedeniye, 2:54-62. Evcim, Ü. (1990) Tarımsal Mekanizasyon İşletmeciliği ve Planlaması Veri Tabanı. Ege Üniversitesi Ziraat Fakültesi Yayınları, 495, İZMİR. Yumak, H., Evcim, Ü. (1992) Pamuk Saplarının Balyalanması Olanakları. Tarımsal Mekanizasyon 14.Ulusal Kongresi Bildiri Kitabı, S:223-231, SAMSUN. Açıkgöz, N. (1993) Tarımda Araştırma ve Deneme Metodları (III.Basım). Ege Üniversitesi Ziraat Fakültesi, 478, İZMİR. Açıkgöz, N., Akkaş, M.E., Moghaddam, A. ve Özcan, K. (1994) PC'ler için veritabanı Esaslı Türkçe İstatistik Paketi:TARİST. E.Ü.Ziraat Fakültesi, İZMİR. Anonim. (1995) Zirai Mücadele Teknik Talimatları. T.C. Tarım ve Köyişleri Bakanlığı Koruma ve Kontrol Genel Müdürlüğü, Cilt-2, ANKARA. Kayişoğlu, B., Taşeri, L., Bayhan, Y. (1996) İkinci Sınıf Toprak İşleme Aletlerinin Toprağın Bazı Fiziksel Özellikleri ve Agregat Stabilitesine Etkisi. 6.Uluslararası Tarımsal Mekanizasyon ve Enerji Kongresi Bildiri Kitabı, 594-603, ANKARA. Bilgehan Aydın, G. (1998) ADÜ Ziraat Fakültesi Araştırma ve Uygulama Çiftliği Topraklarının Bazı Strüktür Özellikleri. Ege Bölgesi 1.Tarım Kongresi, 2.Cilt, 478-485, AYDIN. Yalçın, İ., Uçucu, R. (1999) Comparison of Different Tillage and Sowing Techniques Applied in Cotton Farming in Terms of Time Requirements and Energy Consumptions. 7th International Congress on Mechanization and Energy in Agriculture, ICAME'99, p.332-337, ADANA. |