Diagnosis of Cassava Nitrogen Nutrition Status by Using Chlorophyll Meter SPAD-502
In this paper, taken the cassava variety of SC8 as tested materials, the change of cassava leaf SPAD value, fresh cassava yield and starch yield during different growth period were studied with nitrogen supply. The results showed that (i)at the root initiation stage and the root bulking stage, the leaf SPAD value varied with nitrogen fertilization levels in linear-plateau regression modes, and in linear regression modes at the root technical maturity stage; (ii) Fresh cassava yield and starch yield varied with the leaf SPAD value in a quadratic-function modes at root initiation stage, root bulking stage and the root technical maturity stage, and the threshold SPAD values of different growth stages of cassava were obtained by SPAD-502, which were critical for the instruction of nitrogen fertilization in cassava. SPAD values were 45. 19, 43. 09, 40.63, respectively, in the highest fresh cassava yield in above three stages and 44. 31, 42.49, 40. 51, respectively, in starch yield; (iii) when the observed SPAD value was less one unit than the critical SPAD value at the three stages,and the amount of nitrogen application was less than 1.98 kg/667m2 , the increasing amount of nitrogen apply were 0.42, 0.63 and 1. 34 kg/667m2 in the three stages. The amount of nitrogen application was more than 1.98 kg/667 m2 and the additional application amount would be studied in advance.
NETL
NSTL
万方数据
维普
