Effects of nitrogen reduction on the agronomic characteristics, quality, and water and fertilizer use efficiency of tomato (<italic>lycopersicon esculintum mill.</italic>) between drip fertigation and negative-pressure fertigation.

The aim of the study is to compare the agronomic characteristics, crop quality, water use efficiency (WUE), and fertilizer use efficiency (FUE) of tomato (<italic>Lycopersicon esculintum Mill</italic>.) between drip fertigation (DI) and negative-pressure fertigation (NPI). Four treatments were evaluated in a greenhouse plot experiment for their effects on soil moisture and soil available nitrogen and plant photosynthetic, nitrogen uptake, fruit quality, yield, irrigation water use efficiency (WUEi), and FUE: (1) NPI fertigation with no nitrogen fertilization (NPI-F0.00); (2) NPI fertigation with 75% conventional fertilization (NPI-F0.75); (3) DI fertigation with no nitrogen fertilization (DI-F0.00); and (4) DI fertigation with 100% conventional fertilization (DI-F1.00). Compared with those under NPI fertigation, the sugar-acid ratio (30%), vitamin C content (34%), soluble solids content (20%), and nitrate concentration (34%) of tomato fruits under DI fertigation decreased. In addition, the WUE across treatments significantly decreased in the order of NPI-F0.75 > NPI-F0.00 > DI-F1.00 > DI-F0.00; notably, compared with NPI, water consumption increased twofold-fold, and WUE decreased by 47% under DI. The apparent recovery efficiency of applied nitrogen, partial factor productivity from applied nitrogen, and agronomic efficiency of applied nitrogen under NPI-F0.75 were greater than those under DI-F1.00. Both DI and NPI were able to maintain a relatively high tomato yield, but NPI performed slightly better. The yield percentage increase from the soil fertility contribution under NPI and DI was greater than 90%. Compared with DI fertigation, NPI fertigation reduced the amount of fertilizer needed without reducing yield or fruit quality and improved WUE and FUE, resulting in better overall use of soil nutrients by tomato plants. [ABSTRACT FROM AUTHOR]