The effects of subsoiling and drainage treatments on soil and crop characteristics - Final report
The project compared conventional tile drainage with small bore, closely spaced tile drainage. It also evaluated subsoiling before and after tile installation versus conventional tile drainage. The project site was a level field of imperfectly drained Debert 22 soil which consists of 45 cm of friable sandy loam soil over compact subsoil. Four treatments, arranged in a completely randomized design with three replications, were as follows: (1) conventional tile (100 mm) at 10 m spacing, (2) subsoiling to a depth of 70 cm prior to installation of conventional tile at 10 m spacing, (3) subsoiling to a depth of 50 cm following the installation of conventional tile at 10 m spacing, and (4) closely spaced (3 m), small bore (50 mm) tile. Soil and crop parameters evaluated included: soil density, hydraulic conductivity, moisture, temperature, trafficability, watertable fluctuations, alfalfa yields, carrot yields and alfalfa plant counts. Tile drainage discharge and the potential obstruction of tile lines by alfalfa roots were also examined. High subsoil moisture prevented the optimum reduction in soil density from subsoiling. Although internal drainage was improved, no effect was noticed after the first winter. Drainage performance, soil characteristics and crop production showed no benefits as a result of subsoiling in the three growing seasons following subsoiling. The small bore, closely spaced tile treatment removed water quicker, especially when the soil was completely saturated, and kept the watertables about 5 cm lower than the conventional tile drainage with 10 m spacing. There was no significant differences in carrot production among the treatments but the small bore close spaced tile drainage produced significantly higher forage yields than the other treatments.