Long-Term Fertilization Effect on Fertility of Salt-Affected Soils

The long-term effects of annual fertilizer applications on the fertility of salt-affected soils under the rotation system of wheat （Triticum aestivum L.） and maize （Zea mays L.） are not well documented. In 1984, research plots were established to test the effects of annual applications of different rates of nitrogen （N） and phosphorus （P） fertilizers on the fertility of a salt-affected soil （Typic Ustochrept） at the Quzhou Experimental Station, Quzhou County, Hebei Province, China. In October 2001, composite soil samples （0-20 and 20 40 cm） were collected from each plot and analyzed for soil fertility indices. Seventeen years of N and P fertilizer applications increased the soil organic matter （SOM） in the surface layer. With combined N, 270 （N1） and 540 （N2） kg N ha^-1 year^-1, and P, 67.5 （P1） and 135 （P2） kg P205 ha^-1 year^-1, fertilizer applications, total soil N mostly significantly decreased （P〈0.05）. Soil total P in the 0-20 cm layer of the P2 treatment significantly （P （0.05） increased as compared to those of the other treatments. Rapidly available P （RP） in the 0-20 cm layer of the N1P2 treatment was significantly higher than those in the other treatments except the P2 treatment; and RP in the 0-20 cm layer of the P2 treatment significantly increased as compared to those of the other treatments except the P1 and N1P2 treatments. RP in the subsurface soil layer （20-40 cm） of the P2 treatment （4.2 mg P kg^-1） was significantly （P〈0.05） higher than those in the other treatments. Nevertheless, long-term N fertilization did not significantly increase the alkali-hydrolyzable N in the soil. However, in the salt-affected surface soils the application of combined N and P fertilizers over 17 years significantly （P〈0.05） decreased rapidly available potassium （K）. The results suggested that while under long-term fertilizer applications some soil fertility parameters could be maintained or enhanced, careful monitoring of soil fertility was necessary as other nutrients such as K could become depleted.

Study on the Spatial Distribution of Resource-based Urban Land Based on Suitability Evaluation——A Case Study of Datong City in Shanxi Province

[ Objective] The study aimed at analyzing the spatial distribution of urban land based on the suitability evaluation of construction land in a resource-based city. [Methed] Firstly, the suitability of construction land in the center of Datong City was assessed; afterwards, according to the urban scale and spatial expansion mode in target years in the General Land Use Planning for Datong City （2006 -2020）, the spatial layout of new- ly-increased urban land and flexible construction land was carried out to determine the development boundary of Datong City in 2020. [ Result] In the evaluation area of Datong City, the most suitable construction land had an area of only 66.18 hm2, accounting for 10.40% of total area of evalu- ation region; the area of more suitable construction land was 117.51 hm2 and make up 18.47% of total area; moderately suitable land covered an area of 149.49 hm2, which took up 23.49% of total area; the area of unsuitable construction land （89.31 hm2 ） only made up 14.04% of total area. In the newly-increased urban construction land, the area of the most suitable and more suitable land accounted for 73.58%, while there was no un- suitable land. Meanwhile, in flexible construction land, the area of the most suitable and more suitable land made up 66.85%. In a word, the spa- tial layout of urban land was reasonable in Datong City. [Conclusion] The research could provide theoretical references for the spatial expansion and layout of urban land.

山东省耕地质量空间自相关分析与耕地保护分区研究

【目的】根据耕地质量等别差异及其空间特性,科学合理地划定具有空间调控与引导作用的耕地保护分区。【方法】将山东省133个区(县)耕地质量等别作为空间变量,采用自然断点法分析耕地质量空间分布,运用空间自相关的方法分析山东省耕地自然等、利用等、经济等的空间聚集关系,从而进行耕地空间分区。【结果】①山东省耕地自然等、利用等、经济等平均等别分别为6.67、8.30、9.53,耕地质量总体较优,空间上呈现“西高东低”的特征。②山东省耕地质量呈现显著的空间集聚特征,耕地质量自然等、利用等及经济等的空间集聚性呈递增趋势。③基于农业区位理论、空间极化理论,统筹考虑耕地质量空间内在联系与现实需求,将全省耕地划分为核心保护区、综合重构区、重点改良区、优先提升区4个耕地保护区并提出了相应耕地保护方案。【结论】山东省耕地质量空间差异性显著,可以利用空间集聚特征与农业区位来确定耕地保护分区与保护方案。

中国生态用地及生态系统服务价值变化研究

生态用地具有重要的生态系统服务功能,在维护生态平衡、保障国土生态安全、应对全球气候变化中具有特殊地位。论文在总结国内研究学者有关生态用地研究成果的基础上,从生态系统服务功能入手,界定了生态用地的概念,根据生态干扰度构建了生态用地分类体系,并将生态用地分类与土地利用分类进行衔接,对全国生态用地的生态系统服务价值进行了评估,分析其特征及规律。研究表明:1)广义的生态用地是指能发挥供给、调节、支持生态系统服务功能,以及对维持区域生态平衡和调节全球气候具有重要作用的土地类型;2)依据"生态干扰度"构建了生态用地分类体系,将生态用地分为3个一级地类、5个二级地类和31个三级地类;3)2012年全国生态用地的生态系统服务价值为280 483.80亿元,呈现"西高、中次、东低"空间格局。2009—2012年全国生态用地的生态系统服务价值整体呈下降趋势,变化幅度空间分布差异较大,呈现"中增、东西减"的格局特点;2009—2012年全国生态用地各项生态系统服务功能受到损失,呈下降趋势,生态系统稳定性不容乐观。

华北平原长期施肥和耕作对土壤氨挥发的影响

研究基于两个分别长达28年和26年的氮磷肥配比和免耕培肥定位试验,以冬小麦—夏玉米轮作体系为研究对象,采用通气法对土壤氨挥发进行原位监测。研究结果表明:氮磷肥配合施用降低了土壤氨挥发速率,同时也减少了土壤氨挥发损失量和氮肥损失率,试验中处理高量氮肥磷肥混施处理的氮肥损失率在轮作周期内最低仅为0.58%。在少耕培肥试验中发现表施秸秆促进氨挥发损失,将秸秆翻耕到30 cm可以降低土壤氨挥发。氮磷肥配比试验中施肥后连续测定的时间段内土壤氨挥发速率(y)与土壤铵态氮浓度(x)呈明显的线性相关性,y=0.0016x+0.0052,R^2=0.9263;在少耕培肥试验中二者在一定范围内呈现指数关系,y=0.0312e0.0164x,R^2=0.6557。在氮磷肥配比试验和少耕培肥试验中土壤氨挥发速率的机制模拟函数分别为Y=0.003e0.0015C+0.119W-0.06,R^2=0.559和Y=e0.0036C*(6.241ln T-55.924ln(1-W)-15.011)-4.225,R^2=0.412,可以解释40%～50%土壤氨挥发速率。并且土壤氨挥发速率与气温呈极显著相关(P <0.01),相关系数r=0.42。研究表明,气温对氨挥发有很大影响,通过氮磷肥配合施用以及秸秆翻耕深施都可以减少氨的挥发。