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| Transformations of Fractions of Exogenous Chromium（Ⅲ） in Manural Loess Soil After Long-term Fertilization |
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| KeyWord:manural loess soil; long-term fertilization; bio-available chromium; fraction of chromium |
| Author Name | Affiliation | | LI Yu-hui | College of Natural Resources and Environment，Northwest A＆F University, Yangling, Shaanxi 712100, China | | ZHANG Shu-lan | College of Natural Resources and Environment，Northwest A＆F University, Yangling, Shaanxi 712100, China | | FENG Yong-tao | Agricultural Technology Extension Service Center, Baoji, Shaanxi 712100, China | | SUN Ben-hua | College of Natural Resources and Environment，Northwest A＆F University, Yangling, Shaanxi 712100, China | | YANG Xue-yun | College of Natural Resources and Environment，Northwest A＆F University, Yangling, Shaanxi 712100, China |
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| Abstract: |
| Fractions and bioavailability of heavy metals in soils varied among different soils, thus impacting soil resilience to heavy metal contamination. We spiked two levels of Cr（Ⅲ）（0 and 500 mg·kg-1） to soils subjected to different fertilization for 23 years and incubated the soils for three months. The fertilizer treatments included （1）no fertilizer（CK）, （2）mineral nitrogen, phosphate and potassium（NPK）, and （3）organic manure integrated with NPK（MNPK）. Soil Cr fractions were measured with sequential extraction. Spiking Cr decreased soil pH by 0.4 to 0.6 units. Long-term fertilization significantly reduced bioavailability of exogenous Cr. Compared with no fertilizer（CK）, soil bioavailable Cr was 34% lower in NPK and almost 100% lower in MNPK. In NPK soil, iron and manganese oxides bounded and organic bounded fractions increased by 12% and 38%, respectively; exchangeable Cr contents decreased by 27%; no significant changes were observed in carbonates bounded and residual Cr fractions, as compared with the CK. In MNPK soil, contents of exchangeable, carbonates bounded, iron and manganese oxides bonded Cr were 100%, 44% and 29% lower; whereas organic bounded and residual Cr were 72% and 17% higher than in NPK, respectively. These results suggest that long-term organic-inorganic fertilizer management can significantly improve the resilience of loess soil and thus alleviate the impairment of chromium contamination. |
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