成都平原土壤氮素的空间分布特征及其影响因素研究

Spatial distribution characteristic and its influential factors of soil nitrogen in Chengdu Plain

根据2002年117个随机格网和分层抽样样点的耕层(0—20 cm)土壤氮素含量数据,在ArcGIS9.0平台上运用地统计学、缓冲区分析和叠置分析等方法,研究了成都平原区土壤氮素的空间分布特征及其影响因素。结果表明,该区土壤全氮含量达1.29±0.50 g/kg,碱解氮含量达72.2±40.9 mg/kg。土壤全氮含量高值区(>2.00 g/kg)位于崇州中部,并以此为中心向两侧呈带状减少,在郫县—温江一带和龙泉驿的西南部形成两个低值区(<0.85 g/kg);土壤碱解氮含量以崇州为中心向东和向西均呈先增后减的趋势,向南和向北都逐渐增加,其高值区(>110 mg/kg)主要位于彭州、新津和新都的部分地区,低值区(>30 mg/kg)位于崇州东南部和平原西南部边缘的大邑—邛崃一带。影响因素分析表明,在成都平原主要的4种第四系成土母质中,灰棕色冲积物上发育的土壤全氮含量极显著高于成都粘土和老冲积物,但与灰色冲积物差异不明显;菜地和水田的全氮含量显著高于花卉地和旱地。由近年来施氮量的统计可知,土壤全氮和碱解氮含量高值区的施用量明显高于低值区;缓冲区分析表明,在距成都市主城区3.0 km以内的城乡交错带,土壤全氮和碱解氮含量均随距离的增加呈极显著的增加。

Nitrogen is a vital nutrient to enhance plant growth. Nevertheless, when nitrogen fertilizer application exceeds the plant demand, nitrogen can leach to ground water and contaminate environment. Chengdu Plain, as one of the agricultural bases in China, is confronted with a series of environmental issues which are caused by extensive or irrational use of nitrogen fertilizer, According to the data of soil nitrogen content collected from 117 random grid and hierarchical sampiing points in topsoil in 2002, the spatial distribution characteristics and their influential factors of soil nitrogen in Chengdu Plain were analyzed using the software ArcGIS 9.0 with geostatistics, buffer analysis and overlay analysis. The results indicated that the content of soil total nitrogen （TN） and available nitrogen （AN） were 1.29 ± 0.50 g/kg and 72.2 ±40.9 mg/kg, respectively. The regions with high TN content （ 〉 2.00 g/kg） were mainly distributed in the middle part of Chongzhou, and declined gradually towards to the periphery, presenting a zonal shape. The regions with low TN （ 〈 0.85 g/kg） were located in Pixian-Wenjiang and the southwest of Longquanyi. Taking Chongzhou as the center, the AN content first increased and then decreased towards east and west, and gradually increased towards south and north. Further more, the regions with high TN （ 〉 110 mg/kg） were mainly distributed in some parts of Pengzhou, Xinjin and Xindu, while the two lowest value regions （ 〈 30 mg/kg） were distributed in the southeast of Chongzhou and some part of Dayi-Qionglai which was near the southwest edge zone of the plain. The analysis of influential factors showed that,regarding four main parent materials of Quaternary System in Chengdu Plain,TN content of grey-brown alluvium was highly significantly higher than that of Chengdu clay and old alluvium, whereas there was no significant difference observed between the grey-brown alluvium and grey alluvium; TN content of the vegetable and paddy field were both significantly higher than that of flower land and dryland; Based on statistical data of the nitrogen fertilizer application lately, the N application rate at the regions with high TN and AN contents were obviously higher than that region with low TN and AN. Buffer analysis showed that： at the rural-urban fringe of 3.0 km outside the Chengdu downtown, both TN and AN contents were highly significantly increased with the distance.