Synergistic effects of Arbuscular mycorrhizal fungi and silicon on greenhouse tomato under drought stress across irrigation regimes

Although arbuscular mycorrhizal fungi (AMF) and silicon (Si) have been separately reported to mitigate drought-related constraints in tomato production, their combined effects under different irrigation regimes in greenhouse tomato remain insufficiently quantified. This study evaluated the effects of AMF inoculation and Si application on yield, fruit quality parameters, and leaf nutrient composition of greenhouse-grown tomato under four irrigation regimes corresponding to 100, 80, 60, and 40% of cumulative Class A pan evaporation. The experiment compared control, AMF alone, Si at 30 kg ha −1 alone, and AMF combined with Si at 50, 100, or 150 kg ha −1 . The irrigation–yield relationship was significant ( p < 0.01) and was fitted by a second-order polynomial model (R 2 = 0.70). The highest yield was obtained from AMF × Si150 × I1.00 (115.45 t ha −1 ), whereas the lowest yield occurred in C × I0.40 (37.52 t ha −1 ). Relative to C × I1.00, AMF × Si150 × I1.00 increased yield, fruit length, fruit weight, puncture pressure, fruit number, and vitamin C by 43.5%, 7.6%, 6.9%, 6.0%, 5.3%, and 3.2%, respectively. Vitamin C was significantly affected by AMF and Si treatments, although the interaction with irrigation was not significant. For leaf nutrients, the interaction was significant for N and Mn, with maximum N under AMF × Si150 × I1.00 and maximum Mn under AMF × Si100 × I0.80. Overall, AMF × Si150 × I1.00 was the most effective treatment for maximizing yield and selected quality parameters under greenhouse conditions.