The adequacy of agriculture as our source of food depends upon production rates in crops and pastures. Part III considers important “production processes”. It begins with production and cycling of nitrogen (Chapter 8). Nitrogen has key roles in the structure of proteins and nucleic acids and thus can be considered, along with carbon, as one of the central elements of life. Nitrogen is subject to complex cycling and yet its supply is frequently limiting to performance of plant communities. Water is also commonly in scarce supply. Uptake of water from soils and its movement along the soil–plant–atmosphere continuum is the focus of Chapter 9, which gives particular attention to distinguish losses that occur through soil evaporation versus transpiration through plants. Acquisition of atmospheric carbon dioxide and its fixation and reduction (Chapter 10) are the central production processes. Photosynthesis is closely coupled with partitioning (pattern of use) of reduced carbon in respiration and growth (Chapter 11), which ultimately determines economic yield.