Field experiments were conducted in 2011 on an experimental farm at the Cotton Research Insti-tute, Chinese Academy of Agricultural Sciences, Anyang, China. We conducted experiments with a “SPAD-502” meter to quickly measure the relative value of chlorophyll content in the leaf blades of field cotton. Our goal was to seek a suitable leaf on a cotton plant to diagnose senescence status of crop plants at later stages of growth. We began by studying the dynamic change rule of the dis-tal-most four leaves of the cotton plant during the entire growth period with two early-maturing cultivars (CCRI 36, CCRI 50) and two mid-maturing cultivars (CCRI 41, SCRC 28). We also examined the effect of different nitrogen and potassium fertilizer rates on SPAD values of the leaves of SCRC 28. Our results suggest that SPAD values of the 1st distal stem leaves from two early cultivars can act as good indicators of senescence status in the plants, if they are measured between 10 d before the boll-opening stage and 10 d after boll opening stage. Differences of SPAD values of the 3rd distal stem leaves of two mid-maturing cultivars measured between about 15 d before the boll opening stage and 15 d after the boll opening stage can also be used to measure senescence status in these cotton cultivars. The conclusion can be used for cotton producer to manage N fertilizer better at later growth stage.
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Jiang B W, Dai J J, Wang C H, Wang L J, Jia W K, Chi F Q. (2010) Effect of N Management on the Relationship of Leaf SPAD with N Absorption of Corn in Cold Area. Soil and Fertilizer Sciences in China, 3, 41-44 (in Chinese with English Abstract).
Qiu Z J, Song H Y, He Y, Fang H. (2010) Variation Rules of the N Content of the Oilseed Rape at Growth Stage Using SPAD and Visible-NIR. Transactions of the Chinese Society of Agricultural Engineering, 3, 41-44 (in Chinese with English Abstract).
Hong J, Chen G, Zhang L H, Huang X, Ge M H, Wang H T, Yang H Q, Bi Q R. (2010) Study on N Nutrition Status of Citrullus Lanatus by Chlorophyll Meter. Journal of Changjiang Vegetables, 8, 82-85 (in Chinese with English Abstract).
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Li, L.L., Fang, W.P., Xie, D.Y., Ma, Z.B., Du, Y.F. and Zhang, D.L. (2010) Effects of N Application Rates on Photosynthetic and Physiological Characteristics and Yield and Quality of Hybrid Cotton. Plant Nutrition and Fertilizer Science, 16, 1183-1189 (in Chinese with English Abstract).
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Wang, L., Zhu, J.R., Yang, T., Wang, B., Yang, J.Y., Chen, B.Y., Liu, H., Xu, Y.M., Ma, X.W. and Zhao, D.C. (2010) Effects of N Fertilize Strategies on Chlorophyll Content in Leaf of Cotton under Mulch-Film Drip Irrigation. Cotton Science, 22, 454-459 (in Chinese with English Abstract).