Coupling among applied,soil, root,and top components for forage crop production

Abstract

This analysis establishes linkage among (a) applied nutrients nitrogen (N), phosphorus (P), and potassium (K), (b) available soil nutrients, (c) root dry matter and nutrient content, (d) top dry matter and nutrient content, and (e) leaf area and carbon dioxide (CO₂) concentration. It was previously shown that (a) and (d) are coupled by logistic equations with a common response coefficient c between dry matter and plant nutrient uptake with each applied nutrient. As a consequence of the common c, it has been shown that dry matter and plant nutrient removal are coupled by a hyperbolic equation. Furthermore, a model has been developed which includes N, P, and K as inputs. In the present work, (a) and (b) were coupled by a logistic equation as were (a) and (c). It was then shown that plant nutrient removal was coupled to available soil nutrients through a hyperbolic equation. The hyperbolic relationship was also shown to link dry matter between roots and tops, as well as plant N removal between roots and tops. As a consequence of the results above, it was then concluded that root nutrient content is related to available soil nutrient through a hyperbolic equation. The detailed mechanism of this coupling was not identified. Leaf area of soybeans followed a hyperbolic relationship with CO₂ concentration in the canopy.