The primary concern in this discussion is the influence of weather on crops and on crop production.
Weather is the major uncontrollable factor that influences the development of crops.
Initially, we will look at some of the historical trends in crop yield. We often hear about deviation from yield trend. This is a concern as we have been seeing greater deviation from yield trends during the past few years than were experienced during the 1960s and the early 1970s. We attribute much of this to changing weather patterns and the interaction of the weather with the soils and the crops. Notice the change in yield thoughout the century.