Effects of nitrogen fertilizer forms on growth and chromium accumulation of Leersia hexandra Swartz
In order to optimize the nitrogen application efficiency of Leersia hexandra Swartz in soil chromium(Cr)remediation,the effects of five nitrogen fertilizer forms(calcium nitrate,urea,ammonium chloride,ammonium nitrate and ammonium sulfate)on Cr remediation efficiency,growth index,and root index of L.hexandra were assessed in pot experiments.The results showed that,compared with the control,the five nitrogen fertilizer forms promoted the growth and the root activity of L.hexandra and changed its root morphological characteristics;these changes improved Cr content,rate of Cr accumulation,bioconcentration factor(BCF),and the soil Cr removal rate of itself.The biomass and average root diameter of L.hexandra were greatest under ammonium sulfate treatment,with values 5.54 times and 1.51 times of the control,respectively,and the root activity increased by 108% compared with the control.The total root surface area and total root volume were greatest under ammonium nitrate,with values that were 2.17 times and 1.99 times of the control,respectively(P<0.05).The results of correlation analysis showed that the biomass,average root diameter,total root surface area,total root volume,and root activity of L.hexandra were related to the efficiency of soil Cr remediation.Among these factors,the BCF and soil Cr removal rate were highest under ammonium sulfate treatment,with values that were 1.45 times and 5.56 times of the control,respectively.Therefore,the application of ammonium sulfate is more conducive to improve the remediation efficiency of Cr-contaminated soil than other forms of nitrogen fertilizer.
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