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


15 Feb 2010

2009 Annual Interpretive Summary

Effect of Potassium Fertilizer Source and Rate on Yield and Heavy Metal Contents of Chinese Cabbage in Chongqing, 2009

This project is studying the effect of two sources of K fertilizer on yield and heavy metal content of Chinese cabbage planted in the suburban 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 sources of K fertilizers were potassium chloride (KCl) and potassium sulfate (K2SO4). The rates were 0, 75, 225, and 450 kg K2O/ha. All the treatments received 300 kg N/ha as urea and 150 kg P2O5/ha as single superphosphate. Both P and K fertilizers were applied as a single basal application, while N was split equally between the 4-leaf stage and leaf-ball formation.

Cabbage yield increased with increasing K rate regardless of source. Differences between two K sources were not statistically significant. At the lowest rate, both K sources significantly increased the content of amino acids compared to the check (CK), while all the other K treatments decreased amino acid content. Potassium sulfate applied at 75 kg/ha was the only treatment that enhanced vitamin C content. All rates of KCl produced lower sugar contents than K2SO4.

The effects of K source and rate on heavy metal uptake were not significant with the exception of KCl applied at 450 kg/ha, which significantly enhanced uptake of Pb (+20.4%) and Cd (+14.2%) compared to the CK. Mercury (Hg) uptake by cabbage was generally lower with larger rates of KCl, but increased under larger rates of K2SO4. Uptake of arsenic (As) was also positively related to increased rates of sulfate.

The study suggests that care must be taken to avoid excessive heavy metal uptake in vegetables grown on soil with risk of heavy metal pollution. The selection of the right source and rate of K fertilizer can prevent heavy metal uptake in these cases. Chongqing-BFDP-06