Root Growth and Morphology, Nutrient Uptake, and Nutrient Status of Soybeans as Affected by Soil K and Bulk Density 1

Due in part to the difficulty of isolating roots from soil and measuring them, little research has been conducted on root growth and morphology and its relation to shoot growth, nutrient status of shoots, and net nutrient influx. A soil experiment was conducted to measure the effect of increasing soil K and soil bulk density on the above parameters and their interaction. A 2 × 2 × 3 factorial experiment (soil bulk density × K added × date of harvest) was conducted in a greenhouse using soybeans [ Glycine max (L.) Merr.] grown in Raub silt loam soil (Aquic Argiudoll). Increasing soil K increased root and shoot growth but had a variable effect on net nutrient influx and plant nutrient content. Increasing soil bulk density reduced root growth, shoot growth, and nutrient composition of shoots but increased net nutrient influx. The detrimental effect of increasing soil bulk density on shoot growth and nutrient status of soybean plants may have been caused by decreased root growth, coarser roots, and lower root surface area/g shoot. Changes in nutrient influx and root surface area/g shoot in some cases counteracted each other in determining plant nutrient status.