No fertilizer N is recommended for soy beans as they are capable of meeting the majority of their N requirement through symbiotic nitrogen fixation. Root infection by Rhizobium japonicum bacteria results in root nodules which make atmospheric nitrogen available for plant growth in exchange for sugars produced by the plant. Mineralized nitrogen and residual N present in a medium textured soil will be sufficient to sustain the crop during the first three to four weeks while the crop is being established and the root nodules begin to function. Applied nitrogen generally will reduce the amount of nitrogen fixed symbiotically in direct proportion to the amount applied. The exception would be in the case of very sandy soils where available N levels are low and very small amounts of applied N may be useful to help with the establishment of crop growth until the root nodules can become effective.
Indeterminate plants are generally taller than determinate plants of comparable maturity.
In contrast, Determinate plants flower over a relatively brief period. Indeterminate plants have a maximum of one to three small pods at the uppermost node while Determinate plants have a terminal raceme or cluster of pods. Indeterminate plants continue vegetative growth while flowering progresses up the main stem, hence the uppermost pods are developmentally younger and smaller. Because of the more nearly-uniform flowering pattern of Determinate soybeans, pod number and size are more nearly uniform from top to bottom on the plant. An extreme example of delayed planting is to double crop soybeans after wheat harvest.