Drip fertigation significantly increased crop yield, water productivity and nitrogen use efficiency with respect to traditional irrigation and fertilization practices: A meta-analysis in China

Improving irrigation and fertilization management for greater productivity is critical to address water scarcity. Drip fertigation can synchronize the water and nitrogen (N) supply with crop demand, offering the potential for enhanced water productivity (WP) and nitrogen use efficiency (NUE). To quantitatively assess the efficacy of drip fertigation and identify the main affecting factors, we used a meta-analysis to evaluate the effects of drip fertigation on the yield, WP and NUE under different conditions and to quantify the irrigation water saving potential (WSP) and N saving potential (NSP) of drip fertigation. Our results showed that, overall, drip fertigation led to significantly higher yields (12.0%), WP (26.4%) and NUE (34.3%), while significantly decreased crop evapotranspiration (ET) by 11.3%, compared to farmers' practices referring to traditional irrigation by furrow or flood and fertilization by broadcasting N fertilizer (broadcasting N fertilizer without irrigation in rainfed farming). However, the extent of improvement highly depended on crop types and was subject to edaphic, climatic and managerial factors. Among crop types, potato showed the highest increase in yield (40.3%) and WP (100.3%), and fruit showed the highest increase in NUE (68.2%). At a regional scale, drip fertigation performed best in semiarid regions. In addition, irrigation water inputs had large effects (P < 0.05) on the magnitude of yield, ET, and WP response, while N inputs had significant effects (P < 0.05) on yield and NUE but not on WP and ET. The results of WSP and NSP indicated that water input under drip fertigation for maize, wheat, potato, tomato and cotton could be further decreased by 14% (41 mm), 22% (87 mm), 20% (42 mm), 20% (59 mm) and 13% (50 mm), and N input could be further decreased by 23% (68 kg N ha(-1)), 26% (88 kg N ha(-1)), 33% (60 kg N ha-1), 21% (117 kg N ha(-1)) and 23% (66 kg N ha(-1)), respectively, without crop yield reduction.