The Characteristics of Soil N Accumulation and Movement in Different Farmlands in the Yellow River Irrigation Region of Ningxia, China

• Main Authors: KE Ying, GUO Xin-nian, JI Hong-jie, ZHANG Wei-li, ZHAO Ying
• Format: Article
• Language: zho
• Published: Agro-Environmental Protection Institute, Ministry of Agriculture 2014-02-01
• Series: Journal of Agricultural Resources and Environment
• Subjects: the Yellow River Irrigation Region of Ningxia; greenhouse fields; open fields with rotation of paddy-upland crops soil N accumu-lation; shallow groundwater
• Online Access: http://www.aed.org.cn/nyzyyhjxb/html/2014/1/20140104.htm

The greenhouse fields(n=4)and open fields with rotation of paddy-upland crops(n=4)were chosen in the Yellow River Irrigation Region of Ningxia. A method of multiple-points field sampling investigation and laboratory analysis was conducted to study the charac-teristics of soil N accumulation and distribution in different soil profiles and its movement effect on N content in the shallow groundwater from two different farmlands. The results indicated that total soluble N(TSN), NO3--N and soluble organic N(SON)contents in 0~150 cm soil in greenhouse fields were significantly higher than that in open fields, and the average contents in the former fields were 1.5~5.6, 1.5~3.4, 1.6~9.8 times as that in the latter fields, respectively. Different forms of N were mainly accumulated in 0~5 cm and 5~20 cm soil depth in green-house fields, and which were accumulated in 40~100 cm soil depth in open fields. Soil TSN accounted for TN by 5.4%~11.5% and 2.2%~4.9% in the greenhouse and open fields, respectively, and the former had a higher risk of soil N leaching losses. Different forms of dissolved N accumulation amount were SON>NO3--N>NH4+-N in 0~150 cm soil in greenhouse fields, and with the order of NO3--N>SON>NH4+-N in open fields. The TSN, NO3--N and SON contents in the shallow groundwater in greenhouse fields were also significantly higher than that in open fields, the former were 9.5, 13.8, 7.0 times as that in the latter, respectively. Therefore, both NO3--N and SON could be important soil N accumulation forms in these two different farmlands, and that may pollute the shallow groundwater in these two different fields.