A model describing chemical interference caused by decomposing residues at different densities of growing plants

In literature, the biological response of plants to phytochemicals has been modelled and then used to simulate phytotoxicity caused by plant residues during decomposition. According to the resulting residue allelopathy model, stimulation dominates in the beginning of the residue decomposition process for a short while. Thereafter, severe inhibition is predicted to occur rapidly, until stimulation gradually re-emerges at the later stages of residue decomposition. Also in literature, direct chemical interference has been shown to be density-dependent; with increasing target plant density, the effects of phytochemicals are diluted. As a result, inhibition is the most probable outcome in density-dependent phytochemical interactions at low target plant densities, but phytotoxic effects often become stimulatory as target plant density increases. In this paper, these models that have been reported in literature are combined. While the original residue allelopathy model predicts inhibitory effects in most cases, the new density-dependent extension of the residue allelopathy model predicts that the density of target plants determines whether or not inhibition occurs. According to the new model, the intensity of inhibition decreases and the final stimulatory period begins earlier if target plant density increases. Therefore, combining the effects of density-dependency to the residue allelopathy model enhances our understanding of chemical interference. In addition, the new model may partially explain why several field studies have not observed chemically driven inhibitory effects similar to those observed in laboratory experiments.