ABSTRACT
The application of an extended form of von Bertalanffy's function to soybean hypocotyl elongation data is considered. Hypocotyl elongation of 'Forest 1975' soybean cultivar was recorded for 10 consecutive days at 48 combinations of soil temperature, soil moisture, and soil mechanical impedance. An approach to predicting soil compaction under tractor wheels was reported in the literature. The approach used Boussenesq's equation with Froehlich's concentration factor to predict the major principal stress σ1. It was assumed that the soil compaction was determined by σ1 alone and by substitution into a confined compression equation, the compaction in terms of bulk density could be determined. Soybean is frequently sown in paddy fields following rice harvest without any land preparation in Thailand, Taiwan and other Asian countries. It is sown by making on opening close to rice stubble with a hand trowel. Two to four seeds are dropped in each opening.
