| When the crop nitrogen deficiency will typically show the leaf chlorophyll content caused by lower leaf color becomes shallow, and nitrogen is overmuch, leaf color dark and some obvious symptoms. Therefore, you can through the plant leaf nitrogen content and leaf chlorophyll content close relevance and similarity to monitor changes in plant nitrogen status. And crop leaf optical reflection characteristics and quantitative relationship in the leaf color shades, and plants in the reflectivity of visible light band was mainly affected by chlorophyll, according to the principle of Japan has developed a portable chlorophyll meter(SPAD502) for crop nitrogen nutrition diagnosis and guiding fertilization, and in the field crops such as corn, wheat, rice and soybean were applied.This study through field experiment and indoor biochemical determination of the way of combining the field measurement of corn rice leaf SPAD values, laboratory determination of leaf nitrogen content and kao, according to the results of experiment and investigation, clear SPAD value under different conditions and the relationship between maize, rice nitrogen nutrition, so that the user can according to the practical cultivation conditions, determine the right amount of fertilizer and fertilizer time, at the same time, provide technical support for further popularization and application. Main conclusions are as follows:(1) The increase of N application in rice yield showed a trend of first increased and then tend to be stable, showing a quadratic function curve, the calculated as N application rate of 170 kg N/ha in the highest yield can reach 7078 kg/ha.(2) Rice SPAD value under the condition of different fertilizer effect is different, but the trend of dynamic monitoring SPAD value, low amount of nitrogen in the earing fertilizer fertilizer effect is much better than that at high n application effect.(3) Rice leaf SPAD value, 38, 40 when topdressing nitrogen optimal, 3 days and not more than 15 days, the latest simultaneous determination date should be controlled before the young flowering.(4) When the rice leaf SPAD value of 40, total N application rate of 180 kg N/ha, divided into basal(accounting for 40% of the total amount of nitrogen), jointing fertilizer(accounting for 30% of the total amount of nitrogen) and earing fertilizer(accounting for 30% of the total amount of nitrogen) three highest trendy rice nitrogen utilization, respectively.(5) With the increase of n application rate of corn leaf SPAD value increased significantly, during the whole monitoring of corn leaf SPAD values have an obvious increase stage, late maize leaf SPAD value basically tends to equilibrium state.(6) Corn leaf leaf base to tip in different location SPAD value accords with quadratic function curve, starting from the leaf base measured value variation minimum 40% ~ 70% of the area, the average value of 58.5. So when the leaf SPAD value is measured by chlorophyll meter should be started along the direction of the blade tip every leaf middle position 1 cm continuous determination of 5-8 point it is advisable to take the average.(7) With the increase of N application corn yield showed increasing trend and then stabilised, then present a quadratic function curve, the calculated as N application rate of 181 kg N/ha in the highest yield can reach 13800 kg/ha.(8) Through the corn SPAD values of continuous determination of leaf SPAD value is 52 start fertilizer for corn fertilizer best time. In a normal year should be appropriate in the maize jointing stage topdressing nitrogen fertilizer to improve the yield in small quantities. |
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