Tile drainage. Why tile drainage benefits wet land and increases farm income by King James A

Author:King, James A. [from old catalog] & Lynes, William S., 1893- [from old catalog] joint author
Language: eng
Format: epub, pdf
Tags: Drainage
Publisher: Mason City, Iowa, Mason City Brick and Tile Co.

SECTION V RESULTS AND DISCUSSION

This section discusses the average nutrient concentrations and discharges from tile drainage systems monitored. Emphasis is placed on long-term and short-term nutrient vsLrla-bility, seasonal eind areal variability, and variability due to agricultural practices, physiography, and soils. Indigenous nitrogen in virgin soils, irrigated soils, and parent materials is also discussed.

Average Nutrient Concentrations

The grand average concentration of nitrogen (nitrate-nitrogen) in composited drainage discharged from all systems intensively investigated throughout the entire period of study was 19.3 mg/l. This concentration is very close to the 21 mg/l value predicted in Bulletin No. 127 (l) by the Department of Water Resources.

Eighteen "satellite" systems, selected at random within the major tiled areas, were monitored to obtain "back-up" data and to determine the feasibility of monthly sampling. The composited drainage (individual nitrogen concentrations weighted by tile flow) averaged 23.6 mg/l for an eight-month period.

The composited drainage for all the tile systems monitored reguleirly in the major tiled areas, the isolated stations outside the areas, and the "satellite" stations averaged 20.0 mg/l nitrogen.

The average concentration of phosphorus (orthophosphate) in drainage composited from the intensively monitored major tiled areas averaged 0.09 mg/l, slightly less than the 0.15 mg/l predicted in Bulletin No. 12?.

Average Discharge

Tile drainage discharge averaged 1.^ acre-feet per acre for the same period of study; total dissolved solids (TDS) averaged 3,625 mg/l. The 1959-63 values were excluded from the grand average values given because the nutrient or TDS constituents could not be weighted by flow. They are presented in Table 7 for comparison.

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