Abstract: Water-nitrogen partially decoupled drip fertigation (DF) was proposed to cut nitrate leaching loss often associated with conventional water-nitrogen coupled drip fertigation (CF) in greenhouse soils. To investigate the performance of DF in a silty loam soil (thickness 28 cm), the distance between drip irrigation loci, the relative ratio of irrigation or nitrogen fertilization on water-more-nitrogen-less (WM) and water-less-nitrogen-more (WL) rootzone soil were set at 15 cm, 2, and 0.67, respectively. The reduction in soil nitrogen leaching without the presence of plants was small at an average daily irrigation intensity of 12.8 mm (<10%) after a switch from CF to DF. With an average daily irrigation intensity of 22.2 mm and the presence of densely planted cucumbers (plant spacing 25 cm), such switch slightly reduced water leaching intensity (10.8%) but significantly reduced the content of nitrate-dominated (averagely 82.0%) dissolved nitrogen in leachate averagely by 35.6% (P<0.05), resulting in significant reduction in dissolved nitrogen leaching by 42.8% (P<0.05), significant increases in soil residual nitrate level and cucumber yield (16.1%; P<0.05). DF promoted water absorption from the WM rootzone soil to weaken the lateral diffusion of water and nitrate in opposite direction in soil, and subsequently reduced dissolved nitrogen content in leachate mainly derived from the WM rootzone soil to reduce the leaching loss of dissolved nitrogen without much change in water leaching.

Key words: rootzone soil, lateral diffusion, nitrate