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Fikret EYÜPOĞLU, Naci KURUCU, İbrahim GÜÇDEMİR, Sedat TALAS Toprak ve Gübre Araştırma Enstitüsü - PK 54 - Yenimahalle ANKARA Abstract A soil survey study is conducted on rainfed cereal growing areas of Central Anatolian Plateau (CAP) in order to determine the Boron status of soils. Soil samples are collected at 278 locations from 0-25, 25-50 and 50-75 cm. Totally 830 soil samples are collected from three depths. The soils are extracted with hot water according to modified Berger and Troug (1944) as described by Sillanpaa (1990). Hot water extractable boron content of 0-25 cm depth soils varied between 0.01-11.0 ppm and the average value was 0.62 ppm. If 0.3 ppm is taken as the critical value for deficiency then the potential Boron deficient areas occupy 44.24 %, if the critical value is accepted as 0.5 ppm for deficiency then the potential Boron deficient areas occupy 62.59 % of the soils in the CAP area. If 2.5 ppm is accepted as the possible critical level for boron toxicity then 2.52 % of the soils in the CAP is potentially toxic for Boron. The average boron levels of the soils did not significantly differ along the soil depth. The average boron values were 0.62, 0.62 and 0.69 ppm in the soil depths of 0-25, 25-50 and 50-75 cm respectively. Boron toxicity was observed in the soils where the soil boron content varied between 0.86 - 4.86 ppm, and the average Boron values were 2.69 ppm. It is highly probable that Boron toxicity will be observed in the areas where average Boron values are around 2.69 ppm. Soil pH was determined as the most determining factor in assessing Boron toxicity. The average pH value of Boron toxic areas was 7.82. According to the results of the survey, Boron deficiency seems a greater problem than the boron toxicity in the rainfed cereal growing areas of the CAP, although deficiency synproms were not clearly observed. Introduction Boron is an essential element for the plant growth and taken into the plant as boric acid. Boron is one of the trace elements that cause a major problem in soil management. Only a small amount is necessary for optimal plant growth, while values slightly above this optimal optimal amount affect the plant growth negatively and reduce plant growth. Toxic and deficiency values are very close to each other. Boron is of interest in crop production both from the viewpoint of its effects in deficiency and excess. According to Reisenauer et all (1973) deficiencies of Boron occur in a wider range of crops and climatic conditions than deficiencies of any other trace element. Boron is also probably more important than any other micronutrient in obtaining high quality crop yields. The soils on which Boron deficiency occurs include those which are inherently low in B such as soils derived acid igneous rocks and podsolized soils. Sandy acid soils in particular need regular treatment of Boron fertilizers. The same treatment is also required when acid soils are limed, as excess amounts of lime can induce Boron deficiency (Walsh and Goulden, 1952). Boron availability decreases with increasing soil pH, Inadequate Boron availability has thus frequently on calcareous soils. High clay contents also impair Boron availability, probably due to borate adsorption (Welte 1955). Crop differs in their sensitivity to B deficiency. The most sensitive crops are sugar beets, mangolds and celery. Various Brassica crops such as turnips, cauliflower, cabbage, brussels sprouts also have a high Boron requirement. Of the fruit trees apples and pears are known to be particularly sensitive to Boron deficiency (Bradford 1966). (Gartel 1974) claims that Boron deficiency is one of the most severe non-parasitic diseases in wine growing and yield depression may be up to 80%. In general dicots have have higher Boron requirement than monocots . For this reason Boron deficiency in cereals is less common (Shive 1941). A series of various studies revealed that both the deficiency and toxicity of Boron exists in Turkey. Hakerler (1986), Çengel and Özkara (1989), Güneş et all (1997), Taban et all (1997) has reported Boron adequacy or toxicity as the major finding of their studies. But on the other hand Düzbastılar and Güleç (1995), Dikmelik (1995) reported wide distribution of Boron deficiency, Shorrocks (1997) also reported a significant yield increase of sugar beet and olive due to Boron applications in Turkey. Sillanpaa (1982; 1990) reported both severe toxicity and deficiency in his studies held in Turkey and attracted a special attention to Boron management. Bayraklı and Er (1988), Kacar and Fox (1967), Kacar et all (1979) also reported significant amounts of Boron deficiencies in Turkey as the results of their studies. Material and Methods Totally 830 soil samples representing rainfed cereal grown areas of Central Anatolıa are collected from 0-25, 25-50, 50-75 cm soils depths. Each soil depth is represented about 278 soil samples. Soil samples are air dried and passed through 2-mm sieves and prepared for further analyses. The soil samples are analysed for texture, pH, total salt level, organic matter and lime contents in order to identify the relationship of these factors with plant available boron status of the surveyed soils. Boron status of the soils are determined by hot water extraction method. Hot water soluble soil Boron content was determined by a modified Berger and Troug (1944) method.20 g. of air-dried soil and 40 ml of 0.01 M CaCl2 and about 0.5 g of activated charcoal was boiled for 5 minutes in a quartz flask and filtered immediately. 2 ml of this extract and 4 ml of buffer masking agent ( 250 g CH3COONH4 and 15 g Na2EDTA dissolved in 400 ml of water and 125 ml of 100% CH3COOH added) were mixed and 4 ml of azomethine reagent (0.9 g azomethine-H and 2 g ascorbic acid dissolved in 200 ml water, prepared daily). The colour was allowed to develop for one hour. Intensity was measured spectrophotometrically at 420 nm and compared to standards varying from 0-2 ppm Results and Conclusion The average Boron content of the rainfed cereal grown areas of Central Anatolıan region is determined as 0.62 ppm. The Boron content of the 278 soil samples that represent the 0-25 cm depth of the region varied between 0.01 ppm and 11.0 ppm.. 62.59 % of the samples have values less than 0.5 ppm which may be stated as the critical value for soil Boron deficiency. The percentage of soils that has boron content less than 0.5 ppm is highest in Karaman, while the percentage of soils that has boron content less than 0.5 ppm is lowest in Yozgat . 2.52% of the samples have values higher than 2.5 ppm which may be stated as the critical value for soil Boron toxicity (Table 1).Boron deficiency seems as a more critical problem than the Boron toxicity in the region. The average Boron content of 0-25, 25-50, 50-75 cm depth soils were 0.62, 0.62 and 0.69 ppm respectively. The boron content of the soils did not vary significantly by depth. Although the relation between the soil texture and boron content was not significantly important (Table 7), the average boron content was lowest in sandy soils (0.35 ppm), highest in clay soils (1.00 ppm) and steadily increased from sandy to clay soils. The percentage of potential boron deficient areas was highest in sandy soils (73.33%) (Table 2). Sandy soils can be taken as an indicator of Boron deficiency. Higher probability of Boron deficiency in sandy soils was reported by Gupta (1968) and Fleming (1980). Although the relation between the soil pH and boron content was not significantly important (Table 7), average Boron content of the soils were highest (1.19 ppm) when the soil pH was higher than 8.0 and lowest (0.41 ppm) when the soil pH varied between 7.0-7.5. The percentage of potential Boron deficient areas were lowest (25%) in acid reaction soils whose pH were lower than 6.0 and highest (63.83%) in 7.0-7.5 pH soils (Table 3). High pH seems as an indicator for boron toxicity. Similar results were presented by Berger and Troug (1945) Although the relation between the soil lime level and boron content was not significantly important (Table 7), the average boron content was lowest in soils whose lime content vary between 1-5 % (0.38 ppm) and highest (0.85 ppm) in soils whose lime content less than 1.0 ppm. The relation between the soil organic matter content and boron content was found significantly important (Table 7). The average boron value was lowest (0.43 ppm) in soils whose organic matter level was less than 1% and highest (2.11) in soils whose organic matter level was higher than 4%. Similarly the percentage of potential Boron deficient areas were highest (71.73%) in soils whose organic matter content was less than 1 % and lowest (42.86%) in soils where organic matter content was higher than 4% (Table 5). Similar relations between soil organic matter and boron content was reported by Elrashidi and O'Conner (1982) and Gupta (1968). The mineralisation of organic matter releases boron, resulting an increase in the boron content of the soil. Although the relation between the soil salt level and boron content was not significantly important (Table 7), the average boron content was lowest (0.33 ppm) in soils whose salt level was higher than 0.15% (Table 6). An area with clear indications of boron toxicity was observed during the survey. This area was sampled with extra 50 samples, to find out the soil conditions that create boron toxicity. The average soil boron content of these soils were 2.69 ppm, the pH was 7.82 and the average organic matter content was 3.07%, average lime content was 27.9%. Thus a special attention must be paid to high organic matter soils when they are coupled with high pH and lime content for possible boron toxicity. According to the results of the survey, boron deficiency seems a greater problem than the boron toxicity in the rainfed cereal growing areas of Central Anatolia, although deficiency symptoms were not clearly observed in cereals due to the reason that monocots require less boron than dicots. It is highly probable that the symptoms of deficiency will be more clear on legume crops, papaver, sugar beet and fruit trees grown in the area. A special attention must be paid to boron fertilisation in the region. Research and application studies must be initiated in the area.    References . Bayraklı, F.& Er,F., 1995. Boron content of vineyards and soils in Hadim Aladağ part of Konya . M.Şefik Yeşilsoy International Sympossıum on Arid region Soils 174-178. İZMİR . Berger, K.C & Troug, H., 1944. Boron tests and determination for soils and plants. Soil Science. 57:25 -36 . Berger, K.C & Troug, H., 1945. Boron availability in relation to soil reaction and organic matter content. Soil Science.Soc. Amer. Proc. 10: 113-116. . Bradford,G.R.1966. Boron in diagnostic criteria for plants and soils. p: 33-61. Ed. D.D Chapman, Uni. of California. . Çengel, M., Özkara,M., 1989. Toptakta bor ve mikrobiyolojik etkileri üzerine araştırma. . Düzbastılar,M., Güleç,I., 1995. Ege Bölgesi incir bahçelerinin beslenmesi açısından toprak ,özelliklerinin belirlenmesi. İlhan Akalın ve Çevre Sempozyumu. ANKARA . Dikmelik, Ü. 1995. Türkiyedeki zeytinliklerin bitki besin element seviyeleri ve gübre kullanımı. İlhan Akalın ve Çevre Sempozyumu. ANKARA. . Elrashidi, M.A& O'Conner, G.A., 1982. Boron Sorbtion and desorption in soils. Soil. Sc. Soc. Amer. Proc. 32: 45-48 . Gartel, W., 1974. The micronutrients-their importance for the nutrition of grapes with particular regard to deficiency and toxicity symptoms. Weinberg u. Keller 21: 435-507 . Gupta, U.C., 1968. The relation of total and hot water soluble boron and fixation of added Boron to properties to Podsol Soils. Soil Sc. Soc. Amer. Proc. 32: 45-48 . Güneş,A., İnal,A., Alpaslan, M., Taban,S.& Poyrazoğlu, S., 1997. Beypazarı yöresinde yetiştirilen havuçların beslenme durumları ve besin değerleri le toprak özellikleri arasında ilişkiler. TÜBİTAK 1638 nolu Proje Raporu. ANKARA . Hakereler, H., Anaç,D.&Düzbastılar.M., 1986. Menderes havzası pamuk tarlalarında bor'un , toprak ve bitkideki durumu. Toprak İlmi Derneği 9. Bilimsel Toplantı Tebliğleri . Kacar,B., Fox,R.L., 1967. Boron status of some Turkish soils. University of Ankara Yearbook of the faculty Agriculture 1966: 99-111. . Kacar,B., Prezemeck E.,Özgümüş A., Turan C., Katkat A.C., Kayıkcıoğlu I., 1979. Türkiyede Çay tarımı Yapılan yapılan toprakların ve çay bitkisinin mikroelement gereksinimi üzerine bir araştırma. TÜBİTAK. Proje No: 321. ANKARA . Sillanpaa, M., 1982. Micronutrients and the nutrient status of soils: a global study. FAO Soils Bull. No: 48.Rome . Sillanpaa, M., 1990. Micronutrient assessment at the country level: an international study. FAO Soils Bulletin No: 63.ROME . Shorrock,V, 1997. The occurrence and correction of boron deficiency. In Boron in Soil and Plants Ed: Dell,B., Brown, P.H., Bell., R.W. . Reısenauer,H. M., Walsh,L.M & Hoeft, R.G.,1973. Testing soils for sulphur, boron, molybdenum and chlorine p173-200 In: Walsh.L.M and J.D. Beaton ed:Soil Testing and Plant Analysis. Soil Science Soc. Of Amer. Inc. Madıson/Wısconsın. . Taban S., Alpaslan M., Hashemi, G. & E.Dürdane. 1997. Orta Anadoluda Çeltik tarımı yapılan toprakların bazı fiziksel ve kimyasal özellikleri. Pamukkale Üniversitesi Mühendislik Fakültesi Bilimleri dergisi. 3: 457-466. . Walsh,T.&Golden, J.D.,1952. The boron status of Irısh soils in relation to the occurrence of Boron deficiency in some crops, in acid and alkaline soils . Int.Soc.Soil Trans (Comm II and IV) II : 167 -171. |