长江中游农田土壤微量养分空间分布特征

为了更好地掌握长江中游土壤肥力状况,运用地统计学和Arc GIS技术相结合的方法,对湖北、湖南、江西三省41 943个土壤样品的微量养分(铁Fe、锰Mn、铜Cu、锌Zn、硼B)含量的分布特征和空间变异进行研究。结果表明,长江中游土壤有效态Fe、Mn、Cu、Zn、B的平均含量分别为88.0、27.2、3.05、1.71、0.41 mg kg-1。空间分布特征表现为Fe、Mn均以江汉平原区较低,Zn以湖南省较低,Cu、B空间分布较为不均;与第二次土壤普查结果相比,土壤微量养分含量均有所提高,其中Fe、Mn、Cu含量为缺乏或严重缺乏的面积比例分别降至0.1%、2.2%和0.1%,而Zn和B分别为30.8%和17.7%。不同的土地利用类型、土壤类型和成土母质对土壤微量养分均有不同程度的影响。随着微量养分在农业生产中的贡献越来越突出,亟须根据土壤微量养分的分布特征进行分区管理。

Spatial Distribution of Micronutrients in Farmland Soils in the Mid-Reaches of the Yangtze River

AbstractObjective] The mid-reaches of the Yangtze River Valley is an important agricultural zone of China. The region is very high in multi-cropping index and dominated with a cropping rotation system, i.e. rotation of paddy/upland or rice/rapeseed. Long-term application of a large amount of chemical fertilizers in that system has resulted in imbalance of soil micronutrients.Method] To better understand nutrient status of the soil in the region,the five micronutrient elements(Fe,Mn,Cu,Zn and B)in the soil were cited as objects in the study and a total of 41 943 soil samples were collected from Hubei,Hunan and Jiangxi Provinces for analysis of contents of the five soil micronutrient elements and spatial distributions of the elements for plotting a farmland soil micronutrient element distribution map of the region,with the aid of the geostatistic function of ArcGIS.Result] The statistical results show that the soil available Fe,Mn, Cu,Zn and B contents averaged 88.0,27.2,3.05,1.71 and 0.41 mg kg-1,respectively,with coefficient variation(CV)lingering in the range from 63.1% to 112.2%,or at the medium or strong level. Among the five elements,B was the highest in variability. Distributions of the elements could be characterized by peaks that tended toward the right and to be medium or strong in variability,which was attributed to the joint effects of natural and human factors. Results of the semivariogram analysis via GS+ 9.0 show that the distributions of the nutrient elements appeared all to be in lognormal pattern,and the optimum theoretical model for all the five,except B,was the exponential model and that for B was the spherical model. The nugget and sill values in the model represented stochastic and structural deviations,respectively,and the mean nugget/sill ratio varied in the range of 50.1%~66.9%,indicating medium in spatial autocorrelation(25%~75%), and the variations of the micronutrient elements were attributed mainly to stochastic deviations. The spatial autocorrelation varied in the range from 99 km for Mn to 411 km for Zn,and disappeared when it went out of the range. Spatial distribution of the micronutrient elements could be visualized with the Kriging method,and properties,like content,of soil nutrients be assigned to evaluation units for farmland soils in the mid-reaches of the Yangtze region. Spatial distribution of soil micronutrient contents did not show any obvious tendency, but differed sharply between sub-regions. Fe and Mn contents were relatively low in the Jianghan Plain,Fe content relatively high in the center and south of Jiangxi,Mn content relatively high in the east and north of Hubei,Zn relatively low in Hunan,and Cu and B contents uneven in distribution. Soil micronutrient contents were sorted into five levels from extremely deficient to extremely rich according to the standard of the Second National Soil Survey(SNSS). Compared with the data of the SNSS,all the five soil micronutrients improved somewhat in content,especially Fe,Mn and Cu. Statistics by evaluation unit shows that the areas with soil Fe,Mn and Cu contents being sorted as rich or extremely rich were the highest in proportion,and the areas with Zn and B contents being sorted as moderate and rich were the highest. The areas deficient in soil available Fe,Mn and Cu accounted for merely 0.1%,2.2% and 0.1%,respectively,and the areas deficient in Zn and B did for 30.8% and 17.7%,respectively. On the other hand,when the contents of the soil micronutrients were too high,the risk of metal poisoning would rise. In this study,effects of land use,soil type and parent material were also analyzed on micronutrient contents. Fe content was obviously higher in paddy soil than in upland soil,while contents of the other soil micronutrients was not much affected by land use. Among the soils derived from different parent materials,the soil derived from weathered crystalline rocks was the highest in Fe content(106.0 mg kg-1),while the soil derived from river and lake alluvial deposits the lowest (74.7 mg kg-1);the soil derived from weathered crystalline rocks was also the highest in Fe content(25.9 mg kg-1);Cu,Zn and B contents in soils derived from different parent materials varied in the range of 3.03~3.11,1.70~1.86 and 0.36~0.45 mg kg-1,respectively.Conclusion] With the contribution of soil micronutrients to agricultural production becoming more and more prominent,it is essential to regionalize the management of farmlands in the light of the spatial distribution of soil micronutrients,which will surely be conducive to scientific application of macroelements fertilizers.