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Winter application of manure is commonly practiced in the northeastern and north-central U.S. Potential nutrient losses from winter-applied manure are difficult to predict due to uncertainty in weather forecasting and limited knowledge on soil-nutrient-hydrology interactions during the winter. The objective of this study was to extend the understanding of nutrient cycling and transport processes associated with manure application methods during winter months. Specifically, the influence of manure position within the snowpack on nutrient losses, was examined using a laboratory approach. Dairy manure was applied either before, midway through, or upon completion of an artificial snowfall. Runoff and leachate were subsequently collected throughout a snowmelt event and rainfall simulations. Manure application prior to the snowfall increased the losses of total N and NH4-N in snowmelt runoff and resulted in larger losses of both N and P in runoff during the rainfall simulation. Manure application on top of the snow reduced the amount of NH4-N losses but increased the losses of organic N, DRP, and total P in snowmelt runoff. The results of this research show that the relative position of manure within the snowpack plays a significant role in the fate of N and P from winter-applied manure. [ABSTRACT FROM AUTHOR]

The laboratory study of water movement and nutrient dynamics associated with agricultural soils has been limited within an experimental setup to either surface investigation or leaching analysis. This study was conducted to develop a laboratory system for simultaneous investigation of surface and subsurface hydrologic and nutrient dynamics within a soil block. The system consists of a square steel casing 61 cm wide and long by 61 cm deep that is driven into the ground with a 1.1 Mg drop hammer, excavated, and undergirded with a 12.7 mm thick PVC plate to capture an undisturbed soil block. Unique features of the lysimeter system include the use of petrolatum (petroleum jelly) to suppress side wall bypass flow and potential chemical interaction with the steel lysimeter walls, and the capability to investigate overland and subsurface flows in one assemblage. [ABSTRACT FROM AUTHOR]

Nitrate nitrogen (NO3-N) leaching from animal production systems in the northeast USA is a major non-point source of pollutionin the Chesapeake Bay. We conducted a study to measure NO3-N leaching from dairy slurry applied to orchardgrass (Dactylis glomerata L., cv. Pennlate) using large drainage lysimeters to measure the direct impact of four rates of slurry (urine and faeces) N application (0, 168, 336, 672 kg N ha-1 yr-1) on NO3-N leaching on three soil types. We then used experimentally-based relationships developed earlier between stocking density and NO3-N leaching loss and leachate NO3-N concentration to estimate the added impact of animal grazing. Nitrate N leaching losses from only dairy slurry applied at the 0, 158, 336, and 672 kg N ha-1 yr-1 rates were 5.85, 8.26, 8.83, and 12.1 kg N ha-1 yr-1, respectively with corresponding NO3-N concentrations of 1.60, 2.30, 2.46, and 3.48 mg l-1. These NO3-N concentrations met the 10 mgl-1 US EPA drinking water standard. However, when a scenario was constructed to include the effect of NO3-N leaching caused by animal grazing, the NO3-N drinking water standard was calculated to be exceeded. [ABSTRACT FROM AUTHOR]

A field study site was installed in east-central Pennsylvania to examine processes controlling groundwater recharge. It was instrumented to monitor climatic inputs, soil water dynamics and groundwater response. Characterization of the layered fractured bedrock underlying thesite by rock coring, seismic surveys and interval packer testing showed consistencies between layer depths, fracture frequencies, seismicvelocities and hydraulic conductivities. Monthly summaries of rainfall and percolate over two years showed that percolate rates were generally high and closely related to precipitation during the dormant season. During the growing season, however, the relationship became erratic with large variabilities occurring between individual lysimeter measurements. Eight dormant season rainfall events were examined in detail. Smaller events produced similar responses from 1 m deep percolate lysimeters. Approximately 10-15 mm of rain was required to initiate percolate, with the time delay in response dependent on how long it took this depth to accumulate; 5 to 6 mm of the rain was retained in storage, with the remainder becoming percolate. Larger rains, from 30-110 mm, caused correspondingly larger depths of percolate and larger water table responses, but generally similar patterns of site response. Groundwater at the site was typically about 6 m below the land surface during the dormant season. It responded 1-2 hours after the onset of percolate, and reached its maximum elevation anywhere from 4 to 16 hours after that, even though percolate was still occurring. Based on causative depth of recharge and amount of water level rise in wells, the specific yield of the aquifer was found to be of the orderof 0701. This value is characteristic of fracture geometry rather than matrix properties of the bedrock. [ABSTRACT FROM AUTHOR]

Understanding the dynamics of phosphorus (P) transport in agricultural drainage ditches is essential to their improved management for water quality protection. Seven ditches draining soils with a 20+ year history of receiving poultry litter were monitored: two for five years and five for one year. Ditches receiving runoff from point sources (e.g., barns) exported 4.3 to 25.3 kg total P ha-1 (3.8 to 22.6 lb total P ac-1) from 2005 to 2006, while ditches draining areas with only nonpoint source contributions exported 2.6 to 4.8 kg total P ha-1 (2.3 to 4.3 lb total P ac-1) during that period. High concentrations of P in field soils (Mehlich-3 P averaged 441 nag kg-1, or parts per million) and ditch soils (Mehlich-3 P averaged 171 mg kg-1 suggest that desorption is the key nonpoint source process controlling P in ditch flow. Over five years, annual total P losses from two ditches with only nonpoint source P contributions were 1.4 to 26.2 kg ha-1 (1.3 to 23.4 lb ac-1). Overland flow from the fields to these two ditches accounted for ≤ 8% of annual ditch P export, pointing to groundwater as a key pathway for P transport to ditches. Because P export from ditches was primarily in storm flow and groundwater sampling was primarily during base flow, this study does not provide compelling insight into the role of groundwater in ditch P transport. Only occasionally did dissolved P concentrations in groundwater and ditch flow correspond, and P export from the ditches occurred primarily in storm flow. Sampling of algal mats formed on the bottom of ditches suggests that floating algae may exacerbate sediment-related P transport. Results point to the need for new ditch management practices that can sequester dissolved forms of P and trap floating sources of P, in combination with traditional methods that primarily address sediment-bound P. [ABSTRACT FROM AUTHOR]