Study On A Quick Method To Determine The Contents Of Nitrogen And Phosphorus And Nutrition Characteristic In Fresh Rice

In order to meet the demand of the plant nutrient in timing and fit quantity, it is necessary to determine the kinds of nutrient of the soil and rice in time and precisely. At present, though there are routine methods to determine the nutrient of the soil and rices, the problem that how to determine the fresh samples of the soil and rices was not solved, especially not in the field. There have been many achievements about field fast test, such as the analysis of soil nutrient, the regular analysis, the chlorophyll diagnosis and the Hyperspectral Remote Sensing, etc. Compared to these methods, Wang Lin-xue from College of Resources and Environment Analysis Laboratory of Southwest University has designed a quick method of determination of the nitrogen and phosphorus, which just be proved fit for com yet..So this paper chose "3414" rice field test in Longshi town Hechuan borough as study object and adopting a method which was a suit of proper motion design and could combine determine nitrogen and phosphorus of fresh rice in the field to contrast determine the nitrate-N, ammonium-N and extractable phosphorus of lamina in the different growth stages of rice. At the same time, it compared the relativity about the content of nitrogen and phosphorus with the fertilization to ensure the feasibility of this method. And it was in purpose of provide a easy,fast and effective field test method of nitrogen and phosphorus of fresh rice sample. The main results were as follows:(1) 0.01 mol·L-1 EDTA was used as extractant and 1.0g activated carbon was used to decolor. The nitrate-N, ammonium-N and extractable phosphorus in the same extract were determined with portable high-strength photometer in the field. And the nitrate-N was determined with the nitrate-cadmium-deoxidize method, the ammonium-N was determined with ammonia nitrogen-salicylate method and the extractable phosphorus was determined with molybdate blue colorimetry. The result was steady and needed few equipment and reagent and it was easy to operate. It costed an hour to determine one sample. So it could carry out to determine the nitrogen and phosphorus in the field.(2) Under the field test conditions, the contents of NO3-N can be detected and the jointing stage was obviously higher than the heading date, sheaths higher than leaves. The contents of N03-N in sheaths were 1.50～21.0mg-kg-1(jointing stage) and 0.150～1.87mg-kg-1(heading date) and the difference was all significant at 1% levels through t-test (t=5.47,n=14) (3) The average contents of NH4+-N in fresh rice were far higher than NO3-N,and the difference between jointing stage and heading date was not significant. Though the contents of NH4+-N in sheaths were higher than leaves both in jointing stage and heading date and the difference was all significant at 1% levels through t-test (tJ=11.67, tH=14.18, n=14).(4) The results showed that the nitrogen application rate had a good correlation with the contents of NO3-Nin rice at jointing stage and heading date. The contents of NO3-N in sheaths were significantly positively correlated with the nitrogen application rate at jointing stage (rJS=0.763**, (r0.05=0.514, r0.01= 0.641, n= 14)), but the relativity of the leaves in rice were not obviously (rJL= 0.469). The contents of N03-N in sheaths and leaves were significantly positively correlated with the nitrogen application rate at heading date (rHL= 0.784**, rHs= 0.708**). So this paper suggested the sampling parts of the nitrate-N in primary growth stages in the field test were the sheath in jointing stage and the leaf in heading date.(5) The contents of NH4+-N in sheaths and leaves were significantly positively correlated with the nitrogen application rate at jointing stage, while contents of NH4+-N in leaves were significantly positively correlated with the nitrogen application rate at heading date, but the relativity of the sheaves in rice was not obviously(rHL= 0.581, rHS= 0.513). when low in phosphorus, there was no significant difference between contents of NH4+-N in leaves and sheaths at jointing stage and heading date; while medium phosphorus, there was a tendency of the contents of NH4+-N in sheaths were diminish with increase of nitrogen application rate. So this paper suggested the sampling parts of the ammonium-N in primary growth stages in the field test were the sheath in jointing stage and the leaf in heading date.(6) In the jointing stage and heading date, the contents of extractable phosphorus rised with the phosphorus application rate. Through the correlation test, in different periods the contents of extractable phosphorus in the leaves and sheaths of rice get to the notable level with every phosphorus application rate treats.(rJL=0.604*,rHL= 0.690**,rJS= 0.845**, rHS= 0.802**) In every growth stages, the sheath reached the extreme notable level with phosphorus application rate. However, when the amount of phosphorus and potash fertilizer were both in the middle level, the increased of nitrogen application rate maked the contents of phosphorus in plants raised first but then descended. It meanings that a suitable using of nitrogen fertilizer can promote the absorbtion of the rice to the phosphorus. But over the amount can restrain the absorbtion. So this paper suggested the sampling parts of the extractable phosphorus in primary growth stages in the field were leaf or sheath in jointing stage but sheath was better,the same as in heading date.