Effect of Pig Manure Compost or Sucrose Application on Recovering Chinese Cabbage from Ammonium Toxicity

This study was carried out to evaluate the effect of application of urea and combination of urea and pig manure compost (PMC) on the occurrence of and the recovery from ammonium ($NH_4{^+}$) toxicity in Chinese cabbage. To identify $NH_4{^+}$ toxicity of the crop four levels of urea at 0, 160, 320, and $480kg\;N\;ha^{-1}$ were applied, in addition, three levels of PMC at 10, 20, and $40M/T\;ha^{-1}$ was also applied with urea $320kg\;ha^{-1}$. For recovery $NH_4{^+}$ toxicity, six levels of sucrose were treated at the amount of 0, 600, 1,200, 1,800, 2,400, and $3,000kg\;C\;ha^{-1}$ at each level of combining treatments of urea and PMC. Our results showed that $NH_4{^+}$ toxicity was occurred at every urea application of $320kg\;N\;ha^{-1}$ regardless of PMC applied to the soils because $NH_4{^+}$ contents in the soils were more than $155mg\;kg^{-1}$ which was found to be the critical level to damage crop growth at 2 days after transplanting (DAT) in this experiment, the more sucrose was applied up to $1,800kg\;C\;ha^{-1}$ for the plants damaged by ammonium toxicity occurred at $320kg\;N\;ha^{-1}$, the greater extents recover the plants from the toxicity. PMC showed the similar effect with sucrose on recovering Chinese cabbage plants from $NH_4{^+}$ toxicity at 30 DAT.