Pesticide and Fertilizer Pollution Reduction in Two Alley Cropping Agroforestry Cultivating Systems

The efficiency of two common Mediterranean agroforestry systems, a potato-poplar and a maize-poplar, was assessed with respect to the uptake of nutrients and pesticides in an experimental plot located in Attica, Greece, during the cultivating period of 2016. Soil samples were collected on a monthly basis at different soil horizons and varying distance from the tree row. The monitored substances included all nitrogen ions (NO3−-N, NO2−-N, NH4+-N), phosphates (PO43−-P), potassium (K+), the insecticide chlorpyrifos, as well as the herbicides s-metolachlor, pendimethalin, and its metabolite M455H001. Experiments for the potato-poplar system exhibited reductions of more than 86% for K+, 90% for NO3−-N, 92% for NH4+-N, 85% for NO2−-N, and up to 100% for PO43−-P. Accordingly, for the maize-poplar system, reductions were more than 73% for K+, at least 77% for NO3−-N, approximately 77% for NO2−-N, 97% for NH4+-N, and up to 100% for PO43−-P. Regarding the examined pesticides, all substances reached more than 61.5% and up to 100% disappearance in the closest to the tree row points compared to the control points, thus also exhibiting the potential for tree uptake of the excess pesticides. As such, it was demonstrated that agroforestry alley cropping systems may act as a technique for pollution abatement, since tree roots that extend below the crops can uptake the excess of agrochemicals that would otherwise enter groundwater via leaching or surface water via runoff.