Effect of balanced fertilization on yield and quality of Chinese cabbage and lettuce in Chongqing


03 Feb 2011

2010 Annual Interpretive Summary

Effect of Two Sources of Potassium Fertilizer on Yield and Heavy Metal Contents of Chinese Cabbage in Chongqing, 2010

This project was initiated in 2009 to study the effect of potassium chloride (KCl) and potassium sulfate (K2SO4) on yield and heavy metals contents of Chinese cabbage grown in the suburb region of Chongqing City. Project results will guide K fertilizer application and nutrient management in this and similar areas under intensive vegetable cultivation. The two fertilizers were applied in equal rates of either 0, 75, 225 and 450 kg K2O/ha in combination of 300 kg N/ha as urea and 150 kg P2O5/ha as single superphosphate.

Results showed that cabbage yield increased with K input regardless of sources. Yields were highest at 225 kg K2O/ha and no significant differences were noted between the two K sources. Except for lead (Pb), all other heavy metal concentrations in cabbage tissue were all far below the permissible levels regulated by the S rate, regardless of K source or rates. Application of KCl significantly reduced concentrations of Pb, arsenic (As), cadmium (Cd), and mercury (Hg), particularly at the highest rate (450 kg/ha), which brought the Pb concentration down to a safe level (≤ 0.2 mg/kg). Potassium sulfate acted differently on heavy metal uptake by cabbage. The concentrations of As and Pb significantly increased with K2SO4 rate, while Hg concentration responded the opposite. Concentration of Cd in cabbage was not affected by K rate.

The study suggested that care can be taken to avoid harmful levels of heavy metal accumulation in vegetables grown on soil with risk of heavy metal pollution by selecting the right sources and rates of K fertilizers. Chongqing-BFDP-10