Using Chlorophyll Meter To Estimate N Status Of Potato Plants

The potato variety xipodi was planted under membrane drip irrigation in xinhe and sanjianfang, Wu Chuan County in2010. Then another potato variety kexin1was planted under the same irrigation mode in xiatuhai, Wu Chuan County and Lin Xi County, Chifeng city in2011. This research was conducted to ensure the trend of the SPAD values under varies of conditions, such as different regions, different varieties, different planting mode and different measuring time and so on. And the SPAD values were measured from the youngest fully expanded leaves of each plant, generally the top of each apex lobule under the different nitrogen level. And then the potato nitrogen nutrient diagdednosis index and nitrogen dynamic diagnosis model were determined. The results are as follows:1. The SPAD values were significantly affected by the potato genotype and the planted location.2. The SPAD values measured from the top of each apex lobule had the positive correlation with N rates. SPAD values became saturated and to be nonsensitive to the nitrogen application when the N rate the value reached the threshold values of375kg/hm2.3. The SPAD values measured from the top of each apex lobule were significantly affected by the growing season.4. When the seedlings emergence had been determined, the relatively SPAD values could eliminate many affecting factors, such as the region, the year and the potato varieties and so on. The relatively SPAD values were calculated by the SPAD values in the testing field divided that of in N rich field. Potato dynamic diagnosis model was determined:y=-0.00004(?)x2+0.0027x+0.9223(x:the days after emergence; y:the relatively SPAD threshold value).5. When the seedlings emergence had not been determined, the relatively SPAD value can only eliminate region factors, and there were different dynamic diagnosis model in different potato varieties. The dynamic diagnosis model of xipodi is:y=-0.00090x2-0.002365x+0.7987, the dynamic diagnosls model of Kexin1is:y=-0.0009x2-0.0182x+0.8559(x:the amount of potato compound leaves; y:the relatively SPAD threshold value).