Abstract

A new concept is presented which suggests that in stable plant/soil systems, plants control the soil environmental factors that affect plant growth and the interactions among those factors by controlling system structure. The concept is based on the plant-control hypothesis and rhizocentric model of soil structural development. The plant-control hypothesis declares that in plant/soil systems energy is the primary resource, and structure an essential regulator of energy flows. The rhizocentric model of soil structural development in grass-dominated plant/soil systems describes the process which results in plant-control of soil structure, and, consequently, of energy and nutrient flows for such systems. In conjunction, the plant-control hypothesis and rhizocentric model form a conceptual model of control in plant/soil systems. The conceptual model may help explain the self-regulatory capabilities of stable plant/soil systems, and the causes of instability in some agricultural plant/soil systems. Examination of published data from various sources has revealed no case in which application of the conceptual control model did not result in logically consistent, reliable prediction of experimental outcomes, plausible interpretation of previously uninterpretable results, and often, formulation of testable new hypotheses. It is concluded that the control model--and the plant-control hypothesis and rhizocentric model which it implies--has enough credibility to merit further critical examination as a potentially useful conceptual tool for soil and agricultural science, biology, and ecology