Objectives This study aimed to investigate the effects of pig blood-derived amino acid-chelated calcium (PC) on growth and fruit quality of tomato under salt stress conditions, in order to provide an effective technical measure for enhancing the resistance to saline stress and growth of crops, as well as to find a high-value utilization path of abundant pig blood resources.

Methods A pot experiment was conducted using a tomato cultivar ‘Dahong’ as the test material. Four treatments were set up: CK (no salt stress + foliar spraying distilled water), NaCl (salt stress + foliar spraying distilled water), PC (salt stress + foliar spraying pig blood-derived amino acid chelated calcium), and CC (salt stress + foliar spraying calcium chloride). Tomato plants were harvested at the complete maturity of the third cluster fruits to measure indicators related to plant growth, photosynthesis, nutrient uptake, and fruit quality.

Results Compared with CK, the three salt stress treatments significantly reduced tomato biomass and fruit yield, while the decreases in PC and CC treatments were significantly lower than those in the NaCl treatment. Compared with the NaCl treatment, the PC treatment significantly increased the total fresh weight, total dry weight, root surface area, leaf area, and fruit yield of tomato plants by 15.5%, 15.7%, 31.2%, 19.7%, and 42.7%, respectively. The CC treatment only significantly increased the total dry weight and leaf area, with a significant 13.6% increase in fruit yield. The PC treatment significantly enhanced the N and K accumulations in tomato roots as well as the P and K accumulations in leaves, and increased chlorophyll a, chlorophyll b, and total chlorophyll contents by 30.5%, 76.9%, and 44.5%, respectively, along with significant increases in net photosynthetic rate and stomatal conductance by 31.7% and 36.1%, respectively.The CC treatment only significantly increased leaf P accumulation. Compared with the NaCl treatment, the PC treatment not only significantly improved fruit firmness, color (L* value), transverse diameter, and longitudinal diameter, but also significantly increased glutathione content in the third fruit cluster, ascorbic acid contents in the second and third fruit clusters, and Ca content in the second fruit cluster by 16.2%.

Conclusions Foliar spraying of pig blood-derived amino acid-chelated calcium effectively mitigates the oxidative damage induced by salt stress, boosting photosynthetic rate, nutrient uptake, and calcium accumulation in tomato fruits. These changes significantly improve tomato yield and fruit quality. Despite its superior salt-resistance effect to that of calcium chloride, the tomato yields still fall short of those achieved in non-stress soil conditions. Thus, further research is required to enhance its efficacy.