Controlled drainage and wetlands to reduce agricultural pollution: a lysimetric study.
Controlled drainage and wetlands could be very effective practices to control nitrogen pollution in the low-lying agricultural plains of northeast Italy, but they are not as popular as in other countries. An experiment on lysimeters was therefore carried out in 1996-1998, with the double aim of obtaining local information to encourage the implementation of these practices and to gain more knowledge on the effects involved. Controlled drainage + subirrigation and wetlands were all considered as natural systems where alternative water table management could ameliorate water quality, and were compared with a typical water management scheme for crops in the open field. Eight treatments were considered: free drainage on maize (Zea mays L.) and sugarbeet (Beta vulgaris L.), two treatments of controlled drainage on the same crops, and five wetland treatments using common reed [Phragmites australis (Cav.) Trin. ex Steud.], common cattail (Typha latifolia L.), and tufted sedge (Carex elata All.), with different water table or flooding levels. Lysimeters received about 130 g m 2 of N with fertilization and irrigation water, with small differences among treatments. The effects of treatments were more evident for NO3-N concentrations than for the other chemical parameters (total Kjeldahl nitrogen, pH, and electrical conductivity), with significantly different medians among free drainage (33 mg L(-1)), controlled drainage (1.6 and 2.6 mg L(-1)), and wetlands (0.5-0.7 mg L(-1)). Referring to free drainage, NO3-N losses were reduced by 46 to 63% in controlled drainage and 95% in the average of wetlands. Wetlands also reduced losses of total dissolved solids from 253 g m(-2) (average of crop treatments) to 175 g m(-2) (average of wetlands).
Borin
M
M
Dipartimento di Agronomia Ambientale e Produzioni Vegetali, Università di Padova, Legnaro (Pd), Italy. maurizio.borin@unipd.it
Bonaiti
G
G
Giardini
L
L
D000383:Agriculture; D004190:Disasters; D004784:Environmental Monitoring; D009584:Nitrogen / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis*; D014872:Water Movements; D014876:Water Pollution / Q000517:prevention & control*; D014881:Water Supply
D012989:Soil Pollutants; D009584:Nitrogen