カリ肥料の有効性に及ぼす鉄塩類の障碍作用に就て

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While the available quantity of potash in soils is not insufficient for the crop production, this element, occasionally, does not display its desirable nutritive effect. It is doubtlessly considered that there should be some factors which reduce the availability of potash as plant food. The present paper deals with a study of the case in Tozan Vicinity, Rato-gun, Taihoku-shu. 1) The soil in Tozan Vicinity is alluvial clay-loam formed from clay-slate rocks. It shows slightly acid, as its pH value is 5.33 or the total acidity is 3.27. Quantity of K_2O, soluble in strong HCl, is 0.11% and easily soluble K_2O is more than 7 mg per 100 g soil. The latter has been determined in extracts obtained by distilled water, 1% citric acid solution, electro-dialysis and CaCl_2 solution. 2) According to the fertilizer experiment in the puddy field, vegetative growth and grain yield of rice noticeablly diminish in the plots with no potash, comparing with those in the other plots with this element. The soil requires 76.64kg of K_2O per hectare in order to produce the maximum yield of the grains when it is calculated from Pfeiffer's yield equation y = ax^2 + bx + c, applying the real yields of five crops and variable quantities of K_2O used as fertilizer. 3) The natural formation of soil layer in Tozan Vicinity is a little different from other places, as a thick gravel layer is accumulated under the soil. Through out the gravel layer underground water comes out, everywhere, in the puddy fields during the wet season. It separates very significant sediment of iron rust from the water on the soil surface. Since, the water contains a great deal of FeSO_4 which ultimately changes into red rust or Fe(OH)_3 obtaining oxygen from the atmosphere. 4) The soil contains 6.27% Fe_2O_3,soluble in strong HCl. Amongst, 0.6% is soluble by 1% citric acid solution and 0.02% is dialysable by means of the electricity. 5) Ashes of straw and grains of rice cropped from the different experiment plots have been analysed. The results show that the straw contains more amount of K_2O according to heavier application of that fertilizer, but it reversely contains less quantity of Fe_2O_3. It seemingly suggests there is a certain mutual relation or an antagonistic action between potash and iron in the plant body from the physiological view point. 6) Changes of the solubility of FeSO_4,on the other hand, have been tested, when an excess of FeSO_4 crystals has been added over saturation into every solution of different concentrations of K_2SO_4 and the mixtures have been kept at 30℃ shaking for a week. The test has been done by determinations of cations and anion in the mixed solutions. It is known by this way that thc solubility of FeSO_4 gradually decreases according to an increment of concentration of K_2SO_4,accompanying diminition of solubility of this salt to an extent. By mixing both sulphate solutions, it should be recognized the formation of a double salt, (K_2SO_4・FeSO_4・nH_2O, ) which will crystallizes and precipitates over saturation point. 7) The electro-conductivity of such solutions as above mentioned, at the same time, has been measured. The conductivity of mixed solutions accordingly increases to an increment of concentration of K_2SO_4,but it is smaller than sum of that of each solution. This indicates that dissociation of the salts in the solution diminishes by mixing, forming a new compound or the double salt in molecular equivalent. 8) From the result of various experiments, the authors may conclude that : (a) The available potash in the soil, as if it is not insufficient for plant growth is reduced its availability by mutual action with soluble iron which is excessively contained in the soil water. (b) The available potash forms a double salt with iron, under a certain condition, as both elements combine with the same kind of anion. (c) Formation of the double salt in the mixed solution diminishes the electro-conductivity of the solution, or it decreases the disaociation degree of the electrolytes. The potash contained in the soil, consequently, becomes less available and diminishes its nutritive effect for the plant growth. (Laboratory of Soils and Fertilizers, Taihoku Imperial University)
社団法人日本土壌肥料学会の論文
1935-03-20

カリ肥料の有効性に及ぼす鉄塩類の障碍作用に就て

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