Effect of combined application of low-level potassium fertilizer with nano-Mg(OH)₂ on Chinese cabbage quality

Objectives To evaluate the effect of low-level potassium fertilizer and nano-Mg(OH)₂combination application on growth and K use efficiency of Chinese cabbage.

Methods A pot experiment was conducted using purple soil and Chinese cabbage as test materials in Southwest University. At the base of applying N 200 mg/kg and P₂O₅100 mg/kg soil,five treatments were set as:low K (K₂O 75 mg/kg soil), proper K (K₂O 105 mg/kg soil), low K plus 1.13 and 1.88 mg/kg of nano-Mg(OH)₂, and no K control. After 68 days growth, the Chinese cabbages were harvested and the yield, chlorophyll content, antioxidant resistance, nutrients uptake were analyzed, the nutrient use efficiency was calculated.

Results The combined application of low K and nano-Mg(OH)₂significantly increased the yield of Chinese cabbage, with the highest yield-increasing of 21.5% in treatment of addition ofMg(OH)₂0.3% (1.13 mg/kg).With the two addition dosages of Mg(OH)₂, the contents of chlorophyll a, chlorophyll b, chlorophyll and chlorophyll a/b were increased by 5.3%-10.3%, 4.0%-6.1%, 4.8%-8.9% and 4.3%-8.7%; the contents of carotenoid, total phenol and lavonoid were increased by 7.6%, 6.2% and 6.8%-20.0%, the nitrogen uptake, phosphorus, potassium and magnesium uptakes were significantly increased by 9.1%-10.2%, 13.2%-32.3%, 8.4%-14.4%, 26.6%-39.7%; the partial factor productivity of K, agronomy efficiency of K, K physiology efficiency and utilization efficiency were increased by 20.6%-23.7%, 74.5%-77.6%, 27.4%-36.5% and 14.6%-25.0%. The highest potassium fertilizer use efficiency was observed in the treatment of low K plus 0.3% of Mg(OH)₂. The contents of nitrate were reduced by 11.5%-12.9%, the content of soluble sugar was little affected by the addition of nano-Mg(OH)₂.

Conclusions The yield, chlorophyll content, antioxidant resistance, nutrients uptake, K use efficiency of Chinese cabbage were significantly increased with low-level potassium fertilizer and nano-Mg(OH)₂combination application. The added nano-Mg(OH)₂treatment with the 0.3% dosage of NPK was perfect treatment for combined effect.