Relating sediment and phosphorus movement at multiple scales using fallout cesium-137, phosphorus sorption dynamics and precision conservation technology

This dissertation examines cross-scale linkages between source, transport, and management factors affecting sediment and phosphorus (P) movement within an agricultural subwatershed in Dane County, Wisconsin. Chapter 2 summarizes the results of a sediment and P delivery study using natural rainfall-runoff data from two alfalfa swards monitored from 2004-2005 at hillslope scales. Sediment and P delivery in natural rainfall-runoff was evaluated by standardizing loads by rainfall erosivity after verifying that linear relationships existed between these parameters for the data collected in this study. Results from this study are then used to compare sediment and P delivery movement at the hillslope scale to the coarser scale of the subwatershed in which it is nested. Research for Chapter 3 employed an integrated precision monitoring system for tracking the location and application rates of the manure spreader used on the farm where the study was conducted. One of the major observations emerging from this study was the identification of an elevated application zone that occurs when liquid manure slurry falls from the expulsion port at the initiation of the manure spreading process. This condition resulted in elevated soil test P levels among the spatial pattern of P accumulation, exemplifying how disproportionately influential environmental conditions develop as a result of management actions that may be considered as outliers. Chapter 4 summarizes sediment and P movement between erosional and depositional areas at the study site, with a particular emphasis on depressional landscape positions where colluvial sediments are stored. The central hypothesis was that P delivery from these zones may be occurring as infrequent pulses from soils that are highly saturated with P relative to their sorption potential. Although these sediment and P may be hydrologically immobilized and buffered by depressional zone for long periods, infrequent spillage events may activate P movement. This condition may then result in temporally lagged contributions from landscape positions that regularly act to store sediment and P.