頁籤選單縮合
題名 | 桃園紅壤磷鉀含量與水稻營養及肥料效應之關係=Correlations among Soil PK Values, Plant Analysis and Response of Rice to Aded Fertilizers in Taoyuan Latosols |
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作者 | 盛澄淵; 蘇楠榮; 林銅鐘; 馮明彬; | 書刊名 | 中華農學會報 |
卷期 | 48 民53.12 |
頁次 | 頁18-34 |
關鍵詞 | 紅壤; 水稻營養; 肥料效應; 磷鉀含量; |
語文 | 中文(Chinese) |
英文摘要 | 1. Twenty rice PK trials were laid out in 1963, 2nd crop and 1964, 1st crop, on selected representative Reddish Brown Latosols and Yellowish Brown Latosols of Taoyuan Prefecture, for the purpose of studying the quantitative relations among the soil PK values, plant PK contents and the response of rice to applied potash and phosphate, as affected by the types of soil and cultural factors. 2. The correlations between the value of soil exchangeable potassium (by neutral N-NH4 extraction) before transplanting and the potassiom content of rice straw at harvest as well as at the stage of full ear elongation were highly significant; the correlation coefficient was particularly high for straw samples taken at full ear elongation (r=0.850). This indicates that the exchangeable form of potassium is a reliable index of soil potassium status for latosol paddies. 3. The relation between the exchangeable potassium content of soil and the responsiveness of rice to added potash (in term of the percentage yield value of K0 plots) may be represented, in both of the two crops, by semilogarithmic curves. The relation may also be expressed by straight lines when the exchangeable potassium values are not high. The correlation coefficients were 0.784 and 0.810, for the 2nd crop of 1963 and the 1st crop of 1964, respectively, being both highly significant statistically. For both crops 70 ppm K (on air dry basis) is the critical value for soil exchangeable potassium, provided 98% of maximum yield is taken as the economic margin. For a maximum yield, however, the exchangeable potassium should be maintained above 90 ppm. 4. Neither the pedolongical difference between the two distinct groups of soils nor the differences in rice variety interfered with the above correlations. 5. On the other hand, differences in farmers' custom of water management seems to have been responsible for the deviations in the relationship between soil potassium and rice response to applied potash. The percentage yield of K0 tended to deviate upwards from the regression curve, in the case of the fields where the water supply was abundant and the irrigation water was allowed to flow in and out rather freely, and also where the farmers preferred to drain water more frequently, while in the cases where water was not at all drained, owing to deficiency of new water supply, the percentage yield of K0 tended to deviate downwards from the regression curve, showing a higher effect of potash than would be expected from the soil potassium content. 6. The critical concentration of potassium in rice straw was found to be about 1.8% (as K) of dry matter at harvest and 1.7% at the stage of full ear elongation. Below this concentration, an economical return from application of potash may generally be expected. The stage of full ear elongation seems to be more reliable as sampling date for analysis of potassium. 7. The soil available phosphorus values tested by the Bray's No.1 and No. 2 methods were both highly correlated with the phosphorus content of the straw. Since the difference between the correlation coefficients for two methods is small, both methods can be used for testing the phosphorus status of latosol paddies. 8. There were no correlations between any of the two soil phosphorus values and the yield response of rice to applied phosphate, when the data of the two crops were treated separately. Nevertheless, the facts that the available phosphorus contents of the soils in P0 showed a marked decrease during the lapse of the two crop periods and that the effect of applied phosphate was generally higher in 1964 1st crop than in the 1963 2nd crop together are the proof that there exists a rough correlation between the soil phosphorus status and the rice response to added phosphate. From diagramatical study of combined data from the two crops, it was perceived that the critical values of soil available phosphorus for rice on these latosols were 15-20 ppm P for Bray's No. 1 method and around 30 ppm P for Bray's No. 2 method. 9. Neither the differences in the two tested groups of soil, in varieties nor in the water management, within the common range, of variation, were observed to interfere appreciably with the correlation between the soil phosphorus and yield response to phosphate. However, a serious water shortage was assumed to be responsible for the abnormally high response of rice to added phosphate in two fields. In addition, damage by unseasonable hot wind to rice in phosphate-fed plots on the day of flowering, which came earlier than that in the P0 plots in some fields, also caused a large error to occur in one field. Separatin of such interfering factors as stated above is highly important in the correlation studies. 10. The relationship between the straw phosphorus concentration and the effect of applied phosphate is not so clear as in the case of potassium. For majority of the cases, the critical concentration of phosphorus in the straw seems to be aroung 0.075% at harvest time. For the sample taken at full ear elongation, the value seems to be at least 0.3%. (The figure for the harvest stage should be regarded as more reliable.) 11. Based on the economic appraisal of potash rates in the two crops for each field--the experiment employed 0, 40 and 100 kg/ha of K2O-- the amounts of K2O for latosols are resommended according to their soil exchangeable K values as follows: < 50 ppm: 60-100 kg/ha, 51-70 ppm: 40 kg/ha, 71-100 ppm: 0-40 kg/ha, > 100 ppm: 0 kg/ha. |
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