Nitrogen application levels based on critical nitrogen absorption regulate processing tomatoes productivity, nitrogen uptake, nitrate distributions, and root growth in Xinjiang, China

The unreasonable nitrogen (N) supply and low productivity are the main factors restricting the sustainable development of processing tomatoes. In addition, the mechanism by which the N application strategy affects root growth and nitrate distributions in processing tomatoes remains unclear. In this study, we applied four N application levels to a field (including 0 (N0), 200 (N200), 300 (N300), and 400 (N400) kg/hm(2)) based on the critical N absorption ratio at each growth stage (planting stage to flowering stage: 22%; fruit setting stage: 24%; red ripening stage: 45%; and maturity stage: 9%). The results indicated that N300 treatment significantly improved the aboveground dry matter (DM), yield, N uptake, and nitrogen use efficiency (NUE), while N400 treatment increased nitrate nitrogen (NO3--N) residue in the 20-60 cm soil layer. Temporal variations of total root dry weight (TRDW) and total root length (TRL) showed a single-peak curve. Overall, N300 treatment improved the secondary root parameter of TRDW, while N400 treatment improved the secondary root parameter of TRL. The grey correlation coefficients indicated that root dry weight density (RDWD) in the surface soil (0-20 cm) had the strongest relationship with yield, whereas root length density (RLD) in the middle soil (20-40 cm) had a strong relationship with yield. The path model indicated that N uptake is a crucial factor affecting aboveground DM, TRDW, and yield. The above results indicate that N application levels based on critical N absorption improve the production of processing tomatoes by regulating N uptake and root distribution. Furthermore, the results of this study provide a theoretical basis for precise N management.

Automated summary

This study investigated the effects of nitrogen (N) application strategy on root growth and nitrate distributions in processing tomatoes. The results showed that appropriate N application levels can improve aboveground dry matter, yield, and nitrogen use efficiency, while excessive N application can result in nitrate nitrogen residue in the soil. Temporal variations of root dry weight and root length showed a single-peak curve, and the N application strategy had an impact on secondary root parameters. The correlation analysis indicated that root dry weight density in the surface soil and root length density in the middle soil had strong relationships with yield. The path model demonstrated that N uptake is a critical factor affecting aboveground dry matter, total root dry weight, and yield.