Water- and nitrogen-saving potentials in tomato production: A meta-analysis

Tomato cultivation is primarily limited by availability of water and nitrogen (N). Water and N have highly variable effects on tomato yield, water-use efficiency (WUE) and N-use efficiency (NUE), which may be due to the effect of cultivar, growing season and water and N inputs. Despite these strong effects, no systematic investigation had been conducted into the effects of N and water on yield, WUE, and NUE in tomatoes. The water-saving potential (WSP) and N-saving potential (NSP) have also not been systematically estimated. In this study, we use meta-analysis of 49 studies with 733 individual observations across 10 countries to determine the effect on yield, WUE, and NUE. The global average yield was 16.43-37.02 t ha−1, while the median yields ranged from 41.75 to 130.59 t ha-1. Median values for WUE and NUE were 7.09 to 34.63 kg m-3 and 208.1 to 2050 kg kg−1, respectively. Yield was correlated with temperature, water input and N input. Optimizing inputs of both water and N must consider their interaction to ensure consistency between high yield, WUE and NUE. Our results indicated that decreasing a supra-optimal water input to an optimal input would increase yield by 9.8%, WUE by 19.6% and NUE by 3.7% and that decreasing a supra-optimal N input to an optimal input would increase yield by 5.6%, WUE by 6.3% and NUE by 50.5%. WSP and NSP could be decreased by 41% (240 mm) and 37% (138 kg N ha−1), respectively, without decreasing yield. The present study is important for guiding the optimal use of water and N in tomato cultivation and can help to greatly save water and N resources.