Overland flow will be collected by diverting water leaving each plot into a buried barrel (Fig. 4) positioned on the lower sloping. North corner of the plot (Fig. 1).
Sampling Methods for Measuring Nutrients and Bacteria in Subsurface Water Introduction:
Manure application to agricultural land is a potential source of subsurface water contamination. Two possible transport mechanisms include leaching through the soil matrix and preferential flow. A field experiment is being conducted to assess the leaching of nitrogen, phosphorous and E. coli as influenced by time of manure application and tillage practice.
Authors: S.J. Crittenden, J.D. Lauzon, G.W. Parkin and D.J. Fallow. Department of Land Resource Science University of Guelph Figure 3: Monitoring Well Sampling tube
Experimental Design:
Wells were installed in the
This experiment is being conducted at the Elora research station near Guelph, Ontario as a randomized complete block design with four replicates (Fig. 1).
spring of 2003 (Fig. 1) to monitor the depth of the water table throughout the experiment and to allow for the collection of water samples from the water table (Fig. 3).
Three approaches are being employed to collect drainage water. Tile drain flow monitors, and groundwater monitoring wells are used to sample the saturated zone. Pan lysimeters collect percolating water in the unsaturated zone. Overland flow collectors gather water traveling over the soil surface of each plot.
1-3
1-4
2-2
2-3
2-4
2-5
Bentonite
3m
1-1
1-2
1-3
1-4
designed to collect water moving through the unsaturated zone. A PVC “j” tube was attached to the spout of the lysimeter to collect the water (Fig. 3b). A pan lysimeter was inserted into each of the treatment plots as shown in Figure 1.
Laptop
TDR
Multiplexer
Battery
1-5
•Multiplexer (for TDR) •TDR nest (3 depths) 2-2
2-3
2-4
2-5
•TDR cable (underground in pvc pipe) •Main Multiplexer control and TDR cables
Pan lysimeters (Fig. 3a) are made of heavy gauge metal and were 3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
•Main shelter
1m 5m 10m15m
•Tile flow monitors 2-1
Figure 5a: TDR instrumentation
Well screen
•By-pass solid tile drain pipe
1-5
Soil surface
2-1
•Existing tile drain 1-2
volumetric water contents. The determination of the pathway of loss is assessed through monitoring of soil moisture content as a surrogate indicator of the pathway of flow. Nests of TDR probes at three depths (0-30 cm, 30-60 cm and 60-90 cm) are located in each plot (Fig. 5a). Row multiplexers (Fig. 5b) are connected to a main shelter (Fig. 5c) where a Tektronix 1502C, a central multiplexer, a computer and a battery are situated. Water content readings will be taken twice daily for the duration of the experiment.
Sand pack
Figure 1: Layout of tile drains and sampling wells
1-1
5 cm monitoring well
Time domain reflectometry (TDR) is used to measure soil
Figure 3a: Pan lysimeter
Figure 3b: Open trench with Figure 5b: Multiplexers
•Saturated zone monitoring wells
Figure 5c: Main shelter
•Overland flow collectors
60 cm
•Pan lysimeters 3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
1m 5m 10m 15m
60 cm
Tile monitors are composed of PVC pipe and pipe fixtures
(Fig. 2a and 2b). Each monitor acts as a reservoir collecting flow until a pre-determined volume has accumulated then the water is emptied into the by-pass tile (Fig. 1). The tile flow is quantified with sensors that record water levels.
Figure 2a: Tile drain flow monitor
Water height indicator leads
5 cm pipe elbow 5 cm pipe
Figure 2b: Tile drain flow monitor installed
15 cm PVC pipe cap
5 cm
5 cm
Overland flow will be collected
pan lysimeter (foreground) and tile flow monitor (centre) Figure 4: Overland flow collector
by diverting water leaving each plot into a buried barrel (Fig. 4) positioned on the lower sloping North corner of the plot (Fig. 1).
15 cm PVC pipe “T” connector
This fall the evaluation of the potential leaching of N, P, and bacteria from applied manure will commence. The treatments are listed in Figure 6. This combination of treatments gives 5 plots that will be replicated 4 times for a total of 20 plots (Fig. 6). Figure 6: Experimental Design
Soil surface Funnel
•No-till fall 1-1
1-2
1-3
1-4
1-5
•No-till fall + manure •Spring manure
Sampling tube
•Fall tillage + manure
15 cm PVC pipe 10 cm clay tile drain pipe
15 cm PVC pipe cap 10 cm plastic tile drain pipe
Treatments:
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
150 l rain barrel
Acknowledgements:
Presenter: Steve Crittenden
the authors acknowledge funding from Ontario Ministry of Agriculture and Food (OMAF), Ontario Cattlemen’s Association and the Ontario Pork Producers
