| Management practices can influence agricultural water quality. This study quantitatively compared the fate of Escherichia coli, phosphorous, and nitrogen from non-incorporated and incorporated management systems with and without fall manure application, and incorporated spring manure. Water samples, analyzed for the three contaminants, were taken from overland flow collectors, zero tension pan lysimeters, tile drain flow monitors, and groundwater wells. Incorporation of fall manure can significantly reduce E. coli concentrations in lysimeters and groundwater wells. On the other hand, spring manure application, even with incorporation, significantly increased E. coli concentrations in soil water and groundwater. Neither manure application timing or incorporation influenced phosphorous concentration, mass, or total mass in agricultural drainage water. Peaks in total phosphorous levels were often seen following large rainfall events. The greatest total mass of phosphorous was lost in spring runoff from non-incorporated fall manure, and leached from the unsaturated zone when fall manure was incorporated. Generally, neither timing of application or incorporation of manure influenced nitrogen levels. Data from lysimeters was the most conclusive, with the incorporated spring manure having the lowest nitrogen transport to depth. Macropore flow likely contributed to the downward movement of these pollutants. This research has shown that management techniques that reduce potential bacteria transport (in particular, incorporation of fall manure) do not necessarily coincide with management practices designed to reduce nitrogen transport. However, incorporation of manure reduced ammonia losses, and bacteria transport in the fall, which lends credence to this manure management practice as environmentally sound. |
