HARNESSING PERENNIAL GRAIN-LEGUME INTERCROPS FOR AGROECOSYSTEM SUSTAINABILITY

Growing evidence indicates that increasing crop diversity by including cover crops, intercrops, or perennial buffers or forages in annual grain rotations can improve nutrient retention, soil carbon accumulation, and other ecosystem services. However, these practices still fall short of fully addressing the complex sustainability challenges posed by modern agriculture. This limitation motivates current efforts to develop perennial grain crops, which have traits expected to provision a wider suite of ecosystem services compared to adoption of conservation practices within annual cropping systems. Indeed, innovative management practices for perennial grains, designed based on knowledge of natural ecosystems, could support a highly multifunctional agriculture. Intercropping perennial grains with forage legumes, for instance, would increase farm enterprise diversity, alongside other benefits including reduced need for synthetic nitrogen inputs and reduced nitrogen losses from grain fields. Despite their potential importance, however, the specific impacts of diversified management approaches like intercropping are poorly understood within the context of perennial grain systems. To address this research gap, the proposed field experiment will determine links between perennial grain-legume intercrops and ecosystem services focused on nitrogen cycling and soil health. The experiment will quantify the potential for intercrops of intermediate wheat grass (IWG) and two perennial legumes, alfalfa and white clover, to meet the nitrogen needs of IWG through legume nitrogen fixation. Second, we will use a biomass transfer approach in the alfalfa-IWG intercrop to determinethe effects of alfalfa shoot and root inputs on IWG.Specifically, the proposed research project has three overarching objectives:(1) Understand the effects of intercropped legume species on intermediate wheat grass (IWG) yield, grain quality, and soil health.(2) Determine the relative contribution of above- and below-ground alfalfa biomass to fixed N inputs, soil nitrogen cycling capacity, and IWG performance.(3) Improve mechanistic understanding of the interactions between intercropped species that lead to potential yield gains or other ecosystem services.