Impacts of Phosphorus Application Methods on Rooting Dynamics in Corn in a Long-Term Strip Tillage Trial.

Phosphorus (P) is one of the most limiting nutrients in agricultural systems with half of P soil test levels from the eastern half of Kansas testing below the critical level of 20 mg kg^-1. Conservation tillage is becoming increasingly popular across the Great Plains for its many added benefits, however bringing additional concerns to producers regarding nutrient stratification especially with immobile nutrients such as P. Both P application methods and tillage practices impact root architecture as well as the distribution of P in the soil profile, thus impacting nutrient uptake. To better understand P fertilization in reduced tillage systems, we examined the impact of broadcast and deep band P application on rooting dynamics in corn (Zea mays L.) and P distribution in the soil profile. Replicated field trials were conducted in Manhattan, KS on a long-term strip till system. Three different P treatments were used, including a control (0 kg), 40 kg broadcast P, and 40 kg deep band P per hectare. Minirhizotron observation tubes were installed to observe in-situ root growth from shortly after emergence until tasseling. Images were analyzed using RootSnap! software. Volumetric soil cores were taken during grain fill with a manual hand-driven auger to obtain root dry weight biomass. Soil fertility samples were drawn after harvest both in the plant row and in the middle of the row at a depth of 60 cm. Mehlich-III P Analysis was ran by the KSU Soil Testing Laboratory.  Impacts of P treatments on temporal root distribution by depth will be discussed in detail.