| A pot experiment was carried out to investigate the effects of potassium application on the dynamic characteristic of potassium content and accumulation in different winter wheat (Ningmai No.9) organs on the basis of8types of soils differentiated in potassium content. It was also studied the feasibility of Plant K nutrition diagnosis based on the absolute K content and the ratio of K content in different sampling parts. The best diagnosis period, sampling parts and the critical K level were determined. At the same time, the extraction method of soil available potassium which was closely correlated with plant growth was determined. With this extraction method, the critical valve of soil potassium was calculated at the condition of pot experiment. The results are as follow:1. The K content in wheat plant gradually decreased during the growth period. It was increased with K application, and the degree was different with the soil K-supply ability. The lower ability of soil K supply, the larger degree of K content increased in the plant after K application. The K content in different organs was different in different developing stages and the level of K supply in soil. At jointing stage, the K content in different organs showed stem>leaf> sheath under low K supply condition, while in high K supply condition, the K content in sheath was higher than that in leaves. At booting stage and heading stage, however, the K content in wheat organs showed wheatear> leaf>stem> sheath under low K supply condition while in high K supply, K content in leaves was highest, and then wheatear.2. Cumulative K accumulation in the plant gradually increased with the growth of wheat. The ratio of K accumulation in the above ground part from seeding to heading stage reached58.0%-93.0%, which suggested that potassium supply before heading stage was very important. In this stage, the absorbed K was mainly accumulated in leaves, then came sheathes, and then stem, in which the ratio of accumulated K was lowest. From shooting stage to heading stage, under low soil K supply, the K mainly accumulated in wheatear, then came stem, and the distribution ratio in leaves and sheath were lowest. But under the condition of high soil K supply, K was distributed mainly in stem, and then came wheatear, while less was distributed in the leaves and sheath, which suggested that the re-use degree was different with soil K supply.3. The diagnosis of plant K nutrition was studied in order to indicating the K level and the critical value in plant with pot culture. According to the coefficient between the K content in different sampling parts and the total K content of above-ground part and the absorption of K in maturation (indicator index), there was close correlation between the leaves content of K both in jointing stage and booting stage, while lower correlation was found between heading stage. It was indicated that the content of K in single leaf might efficiently predict the plant K nutrition stage. It was proved that the content of K in the second and third leaf were both good indicator for the prediction of K nutrition. The critical value of wheat K diagnosis in the2nd and3rd leaf was calculated as31.6g/kg and23.6g/kg in jointing stage and17.1g/kg and14.6g/kg in booting stage.4. Six extraction methods of soil available K(2h-NaBPh4、1h-NaBPh、30min-NaBPh4、2mol/L cold HNO3、1mol/L NH4OAc and ASI) was studied to determine the soil available K. The correlation between K amounts extracted by30min-0.2mol L-1NaBPh4and2mol L-1cold HNO3was found to be closely correlated with plant K content and the total K absorption in maturation. The critical level of soil available K was estimated by Linear Regression Models at the relative yield of90%. It was calculated that the critical level of K was388mg/kg and190mg/kg, with the method of cold HNO3and NaBPh4, respectively. |
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