Preferential Rooting in Biochars.

Low available phosphorus (P) in most soils is the greatest constraint to soybean (Glycine max.) production globally. Varying concentrations (4)of biochar will be applied to four different soybean cultivars (organic “Envy”, soybean cyst nematode resistant/Round Up Ready resistant, Round Ready, non-Round Up Ready/non-soybean cyst nematode resistant), each with specialized P acquiring efficiencies, root architectures, growth habits and responses to Pi fertilizers. Biochar is an old ‘new’ technology that has been studied in low P soils with compelling evidence of its ability to improve P availability after soil incorporation in five key effects: (i) root stimulation/growth, (ii) changes in soil biogeochemistry, (iii) altered microbial communities, (iv) increased presence of adsorbing surfaces, and (v) potential presence of signaling compounds. Beyond these indirect effects, little is known about the mechanisms controlling the interaction between roots and biochar. Biochars produced from oak at 450C, cedar at 1000C, and rice husks at 600C will be surface incorporated or banded at increasing application rates in custom-made rhizotrons to elucidate key mechanisms in the exploitative potential of P foraging of soybean roots in high and low P  environments, under moisture stresses and pathogenic pressure. In order to study how biochar influences in situ root morphology, a combination of approaches is required to first analyze directional root growth, root density, root volume, root plasticity, carbon (C) allocation, nodulation efficiency, nodulation phenology, root hair production, root elongation and overall root architecture. The capability of biochars to dampen or sorb root diffusates and other low molecular weight compounds will be investigated using soybean cyst nematodes (Heterodera glycines). Rhizotrons can provide frequent “snapshots” of root growth over temporal and spatial scales that can later be modeled in 3-D.Understanding root morphologies and direct interactions between biochar and plant roots is essential to predict growth responses to biochar in the field.