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Seasonal Nutrient Uptake and Accumulation Patterns in Soybeans¹

Field hydroponic gravel culture systems were used to determine nutrient uptake and accumulation in soybeans (Glycine max (L.) Merr.). Uptake of N, P, K, Ca, and Mg were low during the first 30 days after emergence. At initial flowering, nutrient uptake increased sharply, reaching maximum uptake rates between full bloom and midpod fill. Uptake of N, P, and K generally declined through later development stages while Ca and Mg uptake remained high or even increased. The difference in uptake patterns of the macronutrients during later development stages appeared to reflect differences in mobility and translocation of the nutrients.

Percent N in the total tops gradually declined from the seedling stage and leveled off shortly after full bloom. Phosphorus concentration increased during the first 30 days after emergence, peaked at initial flowering, declined until mid-pod fill, and leveled off through the remaining sampling dates. Phosphorus toxicity symptoms were evident at initial flowering with the highest nutrient level imposed. Percent K increased slightly from the seedling stage until full bloom and then declined. Calcium concentration increased until initial flowering, then declined and leveled off during later growth stages while the Mg concentration decreased gradually from the seedling stage through the green bean stage. The concentration of micronutrients (Fe, Mn, Zn, Cu, and B) generally declined from the seedling stage through the green bean stage.

Key Words: Field hydroponic system • Nutrient solution analysis • Gravel culture • Production • Glycine max (L.) Merr.

² Plant Physiologist, Plant Science Research Division, Agricultural Research Service, U. S. Department of Agriculture, Urbana, Illinois 61801.

Received for publication September 16, 1970.