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Base-cation saturation ratio (BCSR) is a method of interpreting soil test results that is widely used in sustainable agriculture, supported by the National Sustainable Agriculture Information Service (ATTRA)〔(NCat Soil Management )〕 and claimed to be successfully in use on over a million acres (4,000 km²) of farmland worldwide. The traditional method, as used by most university laboratories,〔McLean, E.O. 1977. Contrasting concepts in soil test interpretation: Sufficiency levels of available nutrients versus basic cation saturation ratios. p. 39–54. In T.R. Peck et al. (ed.) Soil testing: Correlating and interpreting the analytical results. ASA Spec. Publ. 29. ASA, CSSA, and SSSA, Madison, WI.〕 is known variously as the 'sufficiency level', sufficiency level of available nutrients (SLAN), or Index(UK) system. The sufficiency level system is concerned only with keeping plant-available nutrient levels within a well studied range, making sure there is neither a deficiency nor an excess. In the BCSR system, soil cations are balanced according to varying ratios often stated as giving 'ideal' or 'balanced' soil. These ratios can be between individual cations, such as the calcium to magnesium ratio, or they may be expressed as a percentage saturation of the cation exchange capacity (CEC) of the soil. Most 'ideal soil' theories stress both approaches. (See also – Cation exchange capacity) Strictly speaking, the 'base' cations are limited to calcium, magnesium, potassium, and sodium, and these are the primary nutrients that BCSR methods are most concerned with balancing. However, many proponents of 'ideal soil' theories also stress the importance of balancing the anions phosphorus, sulphur and chlorine as well as numerous minor and trace elements. The conventional SLAN system does not generally test for minor and trace elements unless there is sufficient cause to suspect a deficiency or toxicity. BCSR supporters argue that a soil balanced using their methods leads to greater crop yield and nutritional quality, as well as increasing the soil biological activity and the physical properties of tilth, aeration, and moisture retention. There is currently no publicly available research or trial data to support these claims,〔(Assessing soil fertility; the importance of soil analysis and its interpretation – Johnny Johnston, Lawes Trust Senior Fellow, Rothamsted Research )〕 but BCSR systems are fairly widely used in organic farms and many positive testimonials from farmers and gardeners can be found on the internet and in alternative agriculture literature. Under most circumstances following BCSR systems will not lead to negative effects. The main concern for farmers is simply the unnecessary expense of applying soil amendments beyond what the crop can actually utilise. ==History of BCSR methods== The cation exchange principle was discovered by Thomas Way and John Bennet Lawes at Rothamsted Experimental Station in the 19th century. In 1892 Oscar Loew observed that both calcium and magnesium can be toxic to plants when there is an excess of one and a deficiency of the other, thus suggesting there may be an optimal Ca:Mg ratio.〔Loew, O. 1892. Uber die physiolgischen funkton der kalzium- und magnesia-salze in planzen organisms. Flora 75:368–394.〕〔(Soil Science Society of America Journal – Article – A Review of the Use of the Basic Cation Saturation Ratio and the “Ideal” Soil Peter M. Kopittke * and Neal W. Menzies. Research before Circa 1930s )〕 In 1901 Oscar Loew and D.W. May did further testing and suggested an ideal Ca:Mg ratio of 5 to 4, though for several species maximum growth was obtained across a wide range of ratios. In 1916 Lipman reviewed the literature up to that point and concluded that while some researchers seemed to have identified 'optimal' Ca:Mg ratios for certain species, there was no evidence that the Ca:Mg ratio influenced growth. Later, in 1933, Moser also reviewed the literature and performed his own experiments, coming to the same conclusion as Lipman that there was no evidence for the Ca:Mg ratio influencing yield. He found that in high magnesium soils, low yields were due to a calcium deficiency, rather than an imbalance. This meant that liming would increase yield, but only up to the point where the deficiency was corrected. From the late 1930s, William Albrecht, the Chairman of the Department of Soils at the University of Missouri, began work at the Missouri Agricultural Experiment Station investigating cation ratios and the growth of legumes. Albrecht had been investigating cattle nutrition, having observed that certain pastures seemed conducive to good health, and at some point he came to the conclusion that the ideal balance of cations in the soil was "H, 10%; Ca, 60 to 75%; Mg, 10 to 20%; K, 2 to 5%; Na, 0.5 to 5.0%; and other cations, 5%".〔Albrecht, W.A. 1975. The Albrecht papers. Vol. 1: Foundation concepts. Acres USA, Kansas City.〕 At his death he left his papers to his friend Charles Walters who promoted the ideas by founding the magazine AcresUSA, which continues to be at the centre of the ideal soil movement. While Albrecht was a highly respected soil scientist,〔〔(A review of the use of the basic cation saturation ratio and the ideal soil – PMM Kopittke, W Neal )〕 he discounted soil pH, stating that "plants are not sensitive to, or limited by, a particular pH value of the soil." Instead, he believed that the benefits of liming soil stem from the additional calcium available to the plant, not the increase in pH. This belief has continued to be held by followers to this day, despite much evidence to the contrary.〔Bruce, R.C., Warrell, Edwards and Bell. 1988. Effects of aluminium and calcium in the soil solution of acid soils on root elongation of Glycine max cv. Forrest. Aust. J. Agric. Res. 39:319–338.〕〔Alva, A.K., Edwards, Asher and Suthipradit. 1987. Effects of acid soil infertility factors on growth and nodulation of soybean. Agron. J. 79:302–306.〕〔Foy, C.D. 1984. Physiological effects of hydrogen, aluminium, and manganese toxicities in acid soil. p. 57–97. In F. Adams (ed.) Soil acidity and liming. Agron. Monogr. 12. 2nd ed. ASA, CSSA, and SSSA, Madison, WI.〕〔Liebhardt, W.C. 1981. The basic cation saturation ratio concept and lime and potassium recommendations on Delaware's Coastal Plain soils. Soil Sci. Soc. Am. J. 45:544–549.〕 Like much of the early research into BCSR where soil pH was not controlled, it is difficult to draw solid conclusions from Albrecht's research in support of BCSR. At around the same time as Albrecht was working in Missouri, F.E. Bear in New Jersey was investigating whether calcium amendments could be used to limit the excess uptake of potassium in alfalfa plants in order to reduce fertiliser costs. From these studies he issued a bulletin with Prince and Malcolm in 1945 that tentatively proposed an 'ideal soil' ratio where the proportions of exchangeable cations were 65% Ca, 10% Mg, 5% K and 20% H.〔Bear, F.E., Prince and Malcolm. 1945. Potassium needs of New Jersey soils. Bull. 721. New Jersey Agric. Exp. Stn., New Brunswick〕 They confirmed their hypothesis with further experiments in 1948 (published with Toth). Though the details are obscure, it has been suggested that Albrecht was aware of these ratios and that they influenced his own. If true, because of the wide influence of Albrecht, it could be argued that the whole 'ideal soil' theory was founded on a mistaken interpretation, since the Bear and Toth ratios were intended to address one specific problem, not to act as a panacea. They explicitly stated that maximum yield of alfalfa occurs at a wide range of cation ratios. In 1959 E.R. Graham suggested a modification to Bear's ratios where calcium could range between 65% and 85% of the CEC.〔Graham, E.R. 1959. An explanation of theory and methods of soil testing. Bull. 734. Missouri Agric. Exp. Stn., Columbia.〕 Both Bear and Graham came to these conclusions after analysing various soils and noting a correlation between the ratios of cations and the productivity of the soils. Though deduction of this sort is generally eschewed by modern sciences in favour of testing in a more controlled environment, it is considered a valid method in agronomy and ecology where the complexity of the natural environment makes reductive techniques less useful. However, neither Bear nor Graham appear to have tested their theories by varying the ratios and studying the effects. In 1981, Baker and Amacher redefined the ideal ratio as 60–80% Ca,〔Baker, D.E., and M.C. Amacher. 1981. The development and interpretation of a diagnostic soil-testing program. Pennsylvania〕 10–20% Mg, 2–5% K. A decade later Neal Kinsey co-wrote a book with Charles Walters called "Hands on Agronomy" in which he defined the ideal ratios as 60–70% Ca, 10–20% Mg, 3–5% K, 1% Na, 10–15 H, 2–4% other cations. Kinsey's book has gone on to become the most widely known and influential work on the BCSR system. Certain studies conducted in 2008-2011 raise doubts about the efficacy of BCSR ()() 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Base-cation saturation ratio」の詳細全文を読む スポンサード リンク
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