Controlled drainage and crop production in a long-term experiment in North-Eastern Italy

Crop productivity under controlled drainage was studied in long-term field experiment with shallow fluctuating water table in North-Eastern Italy. Fourteen years of hydrological and yield data, including winter wheat, su- garbeet, soybean and maize, were collected over two monitoring periods (1995–2002 and 2006–2013). Controlled drainage (CD) and free drainage (FD) were tested in combination with open ditches (O) and sub- surface pipes (P) systems. CD reduced outflow waters by 69%, respect to FD. Wheat produced on average 4.9 t ha−1. P system was more productive (up to 14.2%) in drier years characterized by sparse and more intense spring rainfalls, due to reduced runoff and increased infiltration. O system was more productive (up to 27.9%) in wet years with frequent rainfalls after sowing, as water was removed faster from soil surface avoiding water- logging. Soybean produced on average 3.2 t ha−1, with higher yield (5.7% more) in P, probably due to better and more uniform topsoil moisture conditions. Sugarbeet sucrose production showed no univocal response to CD, as a great variety of factors were involved in determining root growth and sucrose concentration. Maize yield had great variability among the years, depending on weather. However, the best results were always obtained with CD (up to 14.5 t ha−1 of grain), showing a definite increase in productivity (on average, with CD grain maize produced 27.3% more, and silage maize 4.0% more). The benefits of CD on maize yield were more pronounced in years with wet springs followed by summer droughts. Subirrigation in CD helped to achieve higher yields when soil moisture content was declining due to prolonged dry periods. In our environment, CD proved to be extremely helpful in reducing water outflows and increasing maize yield, mitigating drought stress.