The major objective of a crop production system is the interception, fixation, and storage of sunlight energy. There are many components of a system that will accomplish that objective. The most important are early planting, narrow rows, productive varieties that resist disease, the control of weeds, insects, and diseases that rob energy from the system, and providing soil nutrients in adequate amounts. Other inputs to the system must not limit energy fixation or slow the process. Following is a discussion of the effects, interactions and relationships of various inputs of an efficient soybean production system.