Senior consultant of Consulting Division, Japan Development Service Co. Ltd., Tokyo, Japan

Biograph
Dr. Kiyoko HITSUDA completed her PhD in 1982 from Hokkaido University, Japan, where she worked on analysis of crop growth limiting factors in acid soils with a scope of Brazilian central dry zone (Cerrado) development. She has worked as a researcher in Japan International Research Centre for Agricultural Sciences (JIRCAS), Soybean Research Centre of Brazilian Agricultural Research Corporation (EMBRAPA-Soja), or International Rice Research Centre (IRRI), and also as an agricultural consultant in Asian, Latin American, and African countries above 25 years. Although she has worked on various crop productions under different circumstances, she has kept her interest in application of scientific outcomes for practical agriculture throughot her carrier. At present, she works as a farming specialist in a Japan International Cooperation Agency (JICA) project for irrigated agriculture in West Bago region, Myanmar, targeting development of profitable cropping systems.

Speech Title: Percent Relative Cumulative Frequency Approach to Determine Micronutrient Deficiencies in Soybean

Abstract: Critical micronutrient concentrations in soils and plants have not been clearly determined for marginal soils where deficiencies are likely to occur. The objective of this study was to develop a reliable method for assessing micronutrient deficiency in soils and plants. Soybean plants [Glycine max (L.) Merr.] were grown in the A and B horizons of two Brazilian Ustoxes and watered with a complete nutrient solution (i.e., control) or solutions lacking one of the following micronutrients: Mn, Zn, B, or Cu. Soybean plants were repeatedly grown in the same soils until maturity. Th e cumulative frequency of defi cient plants where the relative seed dry weight was signifi cantly decreased was recorded. Th e percent relative cumulative frequency (PRCF) is calculated as: cumulative frequency ÷ total number of tested plants × 100. A linear-plateau regression line was fi tted to the PRCF as a function of the micronutrient concentrations in the soil, the uppermost mature leaf, or seed. Critical concentrations (mg kg−1) for deficiency indicated as transition points of regression lines are: 6.4 for Mn (reference), 1.0 for Zn, 0.2 for B, and 0.2 for Cu in the soil (Mehlich-I extraction for Mn, Zn, and Cu; hot 0.005 mol L–1 BaCl₂ extraction for B); 63 for Mn, 34 for Zn, 25 for B, and 4 for Cu in the uppermost mature leaf; 55 for Mn, 42 for Zn, 14 for B, and 5 for Cu in seeds. Thus, this determination method can clearly identify the critical values for micronutrient deficiency in soils and in plant tissues.