The long-term effects of annual fertilizer applications on the fertility of salt-affected soils under the rotation system ofwheat (Triticum aestivum L.) and maize (Zea mays L.) are not well documented. In 1984, research plots were establishedto test the effects of annual applications of different rates of nitrogen (N) and phosphorus (P) fertilizers on the fertilityof 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 fertilityindices. 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 P2O5 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 theP2 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 P2treatment; and RP in the 0-20 cm layer of the P2 treatment significantly increased as compared to those of the othertreatments except the P1 and N1P2 treatments. RP in the subsurface soil layer (20-40 cm) of the P2 treatment (4.2 mg Pkg-1) was significantly (P < 0.05) higher than those in the other treatments. Nevertheless, long-term N fertilization didnot significantly increase the alkali-hydrolyzable N in the soil. However, in the salt-affected surface soils the applicationof combined N and P fertilizers over 17 years significantly (P < 0.05) decreased rapidly available potassium (K). Theresults suggested that while under long-term fertilizer applications some soil fertility parameters could be maintained orenhanced, careful monitoring of soil fertility was necessary as other nutrients such as K could become depleted.
在第二次全国土壤普查的基础上,于2002年10月对研究区域———河北省曲周县的耕地进行了全面的调查和分析,并将GPS、GIS技术应用到耕地质量调查工作中。研究结果表明:随着盐碱地综合治理的深入、外源物投入数量的增加和质量的改进、作物布局的调整,盐渍土改造区土壤养分在时间和空间上发生了很大的变化。在时间上,耕层土壤有机质平均含量从8.4 g kg-1增加到13.89 g kg-1,全氮平均含量达到0.937 g kg-1,速效磷平均含量从5.45 mg kg-1增加到23 mg kg-1,速效钾含量从34~285 mg kg-1之间逐步变化为67~191 mg kg-1之间的高肥力农业土壤;在空间上,土壤养分的分布与养分的地球化学过程、农业产业结构布局及采用的相应措施有密切关系。主要表现在:土壤有机质、全氮及速效磷含量随着农业集约化程度的提高、外源物质投入的增加而相应增加;土壤速效钾含量则由原来的随地球化学过程而变化,转变为随着农业集约化程度的提高而相应变化。
