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Phosphorus Losses through Agricultural Tile Drainage in Nova Scotia, Canada

^a Dep. of Animal Sciences, Nova Scotia Agricultural College, Truro, NS, Canada, B2N 5E3
^b Dep. of Environmental Sciences, Nova Scotia Agricultural College, Truro, NS, Canada, B2N 5E3
^c Dep. of Engineering, Nova Scotia Agricultural College, Truro, NS, Canada, B2N 5E3
^d Agriculture and Agri-Food Canada, P.O. Box 550 Truro, NS, Canada, B2N 5E3

View larger version (17K): [in this window] [in a new window]   Fig. 1. Sample total P (TP) evolution over 21 mo of observations and represented by four selected fields from various texture classes and manure histories.

View larger version (25K): [in this window] [in a new window]   Fig. 2. Monthly mean total P (TP) and soluble reactive P (SRP) concentrations and discharge flow rates from tile drainage of 39 fields in Nova Scotia, Canada from April 2002 through December 2003. Variability between fields is indicated by standard error bars and the dashed line marks the USEPA (1994) guideline for TP in rivers and streams.

View larger version (27K): [in this window] [in a new window]   Fig. 3. Total P (TP) and soluble reactive P (SRP) response to increasing flow rate. Fields are shown in order of increasing flow rate. The data on each of the plots represent the overall mean for the corresponding field for the study period. The regression lines have the following equations: TP = 0.304 + 0.001(Flow); SRP = 0.027 + 0.0018 (Flow).

View larger version (22K): [in this window] [in a new window]   Fig. 4. The proportion of unavailable P (UP) in total P (TP) relative to soil texture and TP. The fields are shown in order of finest to coarsest texture based on sand content; the actual value can be found in Table 1. The data on each of the plots represent the overall mean for the corresponding field for the study period. The regression lines have the following equations: %UP = 91.1 – 0.273(%Sand); %UP = 89.7 – 36.7(TP).

View larger version (54K): [in this window] [in a new window]   Fig. 5. Tile drainage total P (TP, gray) and soluble reactive P (SRP, black) concentrations as affected by: (A) soil test P (STP), (B) manure type, and (C) crop cover. Fields are shown within each subcategory in order of finest to coarsest soil texture based on % sand. Soil test P categories were chosen based on the agronomic guideline suggested as "high" for field crops (75 mg kg–1) by NSDAF (2001), and the environmental STP threshold (200 mg kg–1) suggested by Sharpley et al. (2003). The data on each of the plots represent the overall mean for the corresponding field for the study period.