Suitable sulfur concentrations in the nutrient solution used for Chinese chives in hydroponic production

Objectives Sulphur supply affects the yield and quality of Chinese chives. Study of the suitable sulfur concentrations in nutrient solution will provide basis for the optimization of nutrient solution for the hydroponic production of Chinese chives.Methods A Chinese chive hydroponic experiment was conducted using the Japan Chiba farming vegetable nutrient solution as base solution. Five levels of sulphur concentrations (1, 2, 3, 4, 5 mmol/L, noted as S1, S2, S3, S4 and S5, respectively) were setup with sodium sulfate as S source. The growth, yield, quality and sulfur compounds of chive were measured.Results Sulphur was found effective to stimulate the growth of chives. Compared with S1 treatment, the plant height, leaf length, stem diameter, leaf width, leaf number, single plant fresh weight and dry weight of S2 treatment were significantly increased by 2.6%, 4.5%, 5.6%, 10.8%, 7.2%, 6.9% and 10.1%, respectively. The peak root activity index was obtained in S3 treatment, which was 25.7% higher than the root activity index of S1 treatment, and the maximum chlorophyll a and chlorophyll a+b contents were obtained in S3 treatment, they were respectively 19.0% and 19.3% higher than those in S1 treatment (P 0.05). The content of Vc, soluble sugar and nitrate in Chinese chives were detected with the best quality in S3 treatment, with 18.8% more of Vc and 33.3% less of nitrate compounds than the S1 treatment (P 0.05). The maximum soluble proteins were detected in Chinese chive of S5 treatment. 29 sulfur-containing volatiles were identified in the chives, majority were shown as disulfide and trisulfide with small amount of tetra sulfide. The maximum total content of sulfur-containing volatiles was detected in the Chinese chive of S2 treatment. The highest yields were in the chive of S2 and S3 treatments, they were all significantly higher than that of S1 (3.6% and 5.6% higher, respectively).Conclusions Comprehensively considering the effect of growth, yield, quality and sulfur-containing volatiles, the optimum concentration of sulfur in Japan Chiba farming vegetable nutrient solution for Chinese chive is 2-3 mmol/L.