Newly established, multifunctional woody polycultures preserve agroforestry soil health benefits of a widespread U.S. land retirement program

Soil degradation under intensive agriculture threatens the long-term economic viability of agricultural regions of U.S., in particular the U.S. Midwest Corn Belt. Agroforestry implemented through the Conservation Reserve Program (CRP) has substantially reduced soil degradation, but many landowners intend to return CRP lands back to maize and soybean production due to greater revenue potential. Expanding CRP guidelines to allow fruit and nut harvesting from a specialized type of agroforestry called multifunctional woody polycultures (MWPs) could incentivize landowners to remain in the program while achieving CRP conservation goals. We conducted a study in the heart of the U.S. Corn Belt to compare soil health metrics between newly established (<10-y) perennial agroforestry (PAF) and annual crop production (ACP) systems, and between two types of PAF treatments (CRP and MWP). We hypothesized that lack of soil disturbance via tillage in PAF would entail greater physical and biological soil health and soil organic carbon storage than ACP, and these benefits would be preserved across CRP and MWP. Our results showed soils under PAF were less compacted, had greater aggregation, and faster water infiltration compared to ACP, and greater activities of cellulase, chitinase, phosphatase, and sulfatase enzymes. Contrary to our hypothesis, we found no evidence for enhanced soil organic carbon storage under PAF, likely a result of the age of these systems being insufficient to accrue substantial soil carbon. Observed soil health benefits were largely preserved under CRP and MWP treatments. Our study demonstrates substantial and comparable improvements to soil physical and biological health under MWP and CRP can be achieved in a relatively short timescale. This supports expansion of CRP guidelines to include MWP establishment for soil health and conservation benefits while allowing landowners to transition to revenue-generating agroforestry systems in the North Central U.S.