Effects of combined foliar application of amino acids with Zn increase the biomass, quality and zinc use efficiency of Chinese cabbage

Objectives Small molecular weight amino acids can be used directly by crops, fewer research have been done on their effect in growth and quality of crops. The study on their effect and the combined use with zinc will provide support for foliar application

Methods A pot experiment was conducted using Chinese cabbage as material. Three kinds of amino acids, glycine, glutamic and threonine were chosen and foliar sprayed in three concentrations:100 mg/L, 250 mg/L, 400 mg/L. The amino acids weresprayed individually in the three concentrations or combined with 0.1% ZnSO₄·7H₂O, twenty treatments in total, including water sprayed as control, were arranged with five replicates. We measured the biomass, the contents of nitrate, soluble sugar and vitamin C of Chinese cabbage after the harvest, and analyzed accumulation of zinc in plants.

Results 1) The foliar application of the three kinds of amino acids significantly increased the growth and zinc uptake, and improved quality of Chinese cabbage. Compared with spraying water (CK), the spraying of the amino acids increased the biomass by 32.0%, 19.8% and 16.6% in average, respectively, the contents of nitrate were decreased by 53.9%, 60.9% and 65.6%, respectively, the contents of soluble sugar were increased by 66.2%, 145.1% and 207.6%, and the contents of vitamin C were increased by 20.8%, 38.8% and 61.6%. The spraying of 100 mg/L glycine increased the zinc absorption by 12.0%, while all the treatments of spraying glutamic and threonine increased the zinc contents by 38.7% and 12.0%, respectively. 2) The combined spraying of amino acids with zinc effectively promoted the effectiveness of zinc. Compared with spraying ZnSO₄, the combined spray of amino acids with zinc increased the biomass of Chinese cabbage by 25.6%, 25.4% and 24.5% in average, decreased nitrate contents by 19.0%, 26.3% and 25.2%, enhanced the contents of vitamin C by 67.1%, 22.6% and 25.2%, enhanced the soluble sugar contents by 33.2%, 72.7% and 27.1%, and increased the accumulation amounts of total zinc by 26.7%, 50.0% and 67.8%, and the zinc use efficiency were increased by 14.3%, 10.2% and 19.2% which were under the statistically significant level.

Conclusions The combined use of glycine, glutamic and threonine with 0.1% ZnSO₄can effectively increase the biomass, quality and zinc absorption of Chinese cabbage. The optimal spraying concentrations of glycine, glutamic and threonine were 250-400 mg/L, 250-400 mg/L and 100-250 mg/L, respectively. The best effect is found in threonine with ZnSO₄, hinting a prospective combination for practical use.