Precipitation and irrigation dominate soil water leaching in cropland in Northern China

Studying the effects of precipitation and irrigation on soil water leaching are critical for maintaining agricultural environment in Northern China, where uneven irrigation has been applied coupled with a broad spectrum of climatic conditions. We conducted consecutive a 4-year field experiment from 2008 to 2011 with lysimeters buried 90 cm deep to determine soil water leaching. Results indicated that amounts of soil water leaching in greenhouse croplands were significantly higher than that in open field croplands. Rainy season is the key period for soil water leaching in semi-humid areas in open fields, accounting for 88.6% of the annual amount of leachate, while excess irrigation was a significant factor for soil water leaching in semi-arid areas. Irrigation pattern affects soil water leaching by determining irrigation volume. There was significant leaching with border irrigation, particularly in the Winter-Spring seasons (from Jan. to Jun.), while drip irrigation led to a 62-74% reduction of irrigation water with no leaching happened. With water-saving irrigation, the effects of fertilization on nitrogen leaching were not significant.