Nitrogen application under aerated irrigation mitigated drought stress
by improving carbon and nitrogen reserves in greenhouse tomato
Abstract
Nitrogen (N) application can improve drought tolerance and water use
efficiency (WUE) in crops. Previous studies have shown that aerated
irrigation improves crop N absorption and utilization. However, the
mechanisms behind the interaction of water and N under aerated drip
irrigation and its impact on crop WUE remain unclear. This study
conducted a two-year greenhouse experiment with spring-summer and
autumn-winter tomato crops to investigate the effects of water and
nitrogen coupling on leaf carbon (C) and N content, photosynthetic
characteristics, dry matter accumulation, yield, and WUE. The experiment
included three irrigation levels (W1, 50% ET c; W2,
75% ET c; W3, 100% ET c) and three N
application rates (N1, 0 kg ha –1; N2, 150 kg ha
–1; N3, 250 kg ha –1). The results
showed that increased N application and irrigation levels significantly
increased leaf C and N content, net photosynthetic rate (P
n), and stomatal conductance (G s) (
P < 0.05). Under deficit irrigation, N application
increased leaf C content by 2.17% and N content by 9.34%, improving
leaf photosynthetic capacity and increasing P n by
15.57% and G s by 19.32%. The W2 treatment
demonstrated the most pronounced improvements compared to W1. The W3N3
treatment produced the highest dry matter accumulation for both tomato
types, with no significant difference from W2N3 ( P
> 0.05). The W2N3 treatment produced the highest yield,
8.67–9.13% higher than W3N3. The highest WUE occurred in W2N3 for
spring–summer tomato and W1N3 for autumn–winter tomato. Although W1N3
had 1.02% higher WUE than W2N3, it had a 15.25% lower yield. Thus,
W2N3 is recommended as the optimal water–nitrogen management strategy
for greenhouse tomato production. Correlation analysis revealed that
leaf C and N contents positively correlated with P n,
dry matter accumulation, and yield, while the leaf ratio of C and N
(C/N) negatively correlated with WUE, suggesting that leaf C and N
contents regulate tomato WUE. N application under deficit irrigation
enhanced leaf C and N contents, improving photosynthetic capacity (P
n, G s), dry matter accumulation, yield,
and WUE. Regression models suggest that the optimal water and N
application rates for greenhouse tomatoes are 192.30–225.67 mm and
205.93–243.43 kg ha -1 for spring-summer tomato, and
162.00–181.18 mm and 194.98–237.73 kg ha -1 and for
autumn-winter tomato crops. These findings provide a theoretical basis
for water-efficient agricultural practices and sustainable greenhouse
tomato production.