Effects of nitrogen supply on tomato yield, water use efficiency and fruit quality: A global meta-analysis

Nitrogen, one of the essential nutrients for tomato growth, has significant influence on tomato cultivation. Yield, water use efficiency (WUE) and fruit quality are widely considered as the most important indicators in the production of tomato. However, reported effects of nitrogen application on tomato yield, WUE and fruit quality vary greatly, mainly due to differences in experimental and environmental factors. Besides, until now, there is no systematic analysis to discuss the effects of nitrogen application on tomato yield, WUE and fruit quality. Therefore, we adopted a global meta-analysis of tomato yield, WUE and fruit quality, including 1096 data pairs from 76 publications from eight countries. We concluded that the optimal nitrogen rate was between 236 and 354 kg ha(-1) with the potential of significantly increasing tomato yield by 59.9%, enhancing Vitamin C (VC), sugar/acid ratio (SAR), soluble sugar (SS) and total soluble solids (TSS) by 18.8%, 33.5%, 23.5% and 11.9%, respectively, but decreasing lycopene by 10.8% and increasing nitrate content by 60.4%. Namely, the optimal nitrogen rate could obtain relatively higher tomato yield, VC, SAR, SS and TSS compared with no nitrogen supply. Tomato yield and SS were not significantly different between greenhouse/pot and field at the optimal nitrogen rate. Average annual temperature of 12-23 degrees C improved most tomato quality indicators (TSS, VC, SS, SAR, nitrate content and lycopene) and yield at the optimal nitrogen rate. There was no significant effect of soil pH on TSS and SS at the optimal nitrogen rate, and tomato yield, VC, SAR and nitrate content were improved more in soils with pH<7, while organic acid (OA) showed the opposite result. Our meta-analysis offered greater understandings of the effects of nitrogen supply on tomato yield, WUE and fruit quality in various experiment sites, average annual temperatures, soil textures, pH and irrigation water depths to produce higher tomato yield and fruit quality as much as possible.

Automated summary

This study examined the effects of nitrogen supply on tomato yield, WUE, and fruit quality through a global meta-analysis. The optimal nitrogen rate was found to significantly increase tomato yield and improve fruit quality indicators such as Vitamin C, sugar/acid ratio, soluble sugar, and total soluble solids. The study also analyzed the impact of factors like soil pH and average annual temperature on tomato production.