THE VON LIEBIG PRODUCTION-FUNCTIONS WITH DECREASING YIELDS

Despite the fact that crop response to agricultural materials since a long time has been researched, there are several issues that are still waiting for answer. The importance of the issue is that a more realis tic crop response model, with biological meaning, would allow a better interpretation of experimental results. The law of the minimum was st ated by Justus von Liebig circa 1840. This law explains the crop respo nse by the production factor that is most scarce to the plant. The pro blem associated to this law is that some researchers avoid to use it b ecause the algebraic formulations commonly used to express the law do not allow a decreasing yields phase. Results gotten show that von Lieb ig models allow to have decreasing yields. Consequences of these new v on Liebig models are associated with greater plateau production levels , suggesting greater use of input to get them. The von Liebig framewor k using the square-root polynomial regimes and the plateau, with or wi thout specific BP (back-plan) regime is strongly suggested. Results go tten also corroborate the idea that curvilinear response functions, wh ich characterize marginal decreasing yields, are more suitable specifi cations to interpret experimental data.