稻田土壤养分空间变异与合理取样数研究

以嘉善县陶庄农场内一块0.52hm2的水稻田为研究区,采用地统计方法和常规统计方法进行土壤pH及养分(全氮、全碳、速效钾、速效磷、速效镁、速效锰、速效铜、速效锌)的空间变异及其合理取样数目研究。结果表明,各土壤养分在田间尺度均存在一定的空间变异,全氮、全碳、速效钾、速效磷等主要养分的空间格局呈南北向条带状,与农户经营田块的方向基本一致;不同农户耕种、管理下的4田块的土壤养分差异显著;反映土壤肥力的土壤全碳、全氮等养分的合理取样数目在95%的置信度和5%的相对误差条件下为45～个,基本上每个农户经营田块为1个,即可反映土壤养分的真实情况。因此,试验区以N素管理为主的精确田间管理的土壤采样可以采用以农户经营地块为单位的混合样采样方式,以减少土壤采样量和分析成本。

Spatial variability of soil nutrients in paddy field and their appropriate sampling sizes

An understanding of the spatial components of variability in soil nutrients is essential,before any decision can be made as to how many fertilizer rates are likely to be appropriate for the field.The objectives of the present study were to examine the spatial variabilities of soil pH and nutrients,and to determine their appropriate sampling size by the means of conventional statistics and geostatistics.The area selected for this study was a 0.52 hectare paddy field divided into four blocks,which were cultivated separately by four farmers,at Taozhuang farm in Jiashan county.The soil nutrients analyzed consisted of total N,total C,available K,available P,available Mg,available Mn,available Cu,available Zn.The results showed that the data sets of soil properties except pH and total N were all normally distributed,and the data set of total N was also normally distributed through log transformation.All the soil nutrients were found to vary across the field to some extent.And that soil pH had the least difference within the field,whilst available Mn had the greatest one.The spatial patterns of main nutrients,such as total N,total C,available K and available P,were zonal in south-north direction,same as the direction of the blocks.The difference among 4 blocks cultivated by four farmers was prominent.For a 95% confidence with 5% of population mean,the estimated number for pH would be only one,which meant that only one sample was needed for the whole area.Those for soil total N and total C would be 4 to 5 samples,i.e.,one block needed only one sample.All these results indicated that the farmers' fertilization habits could affect the spatial variability of those soil nutrients.It was concluded that soil could be sampled in farmer unit for site-specific management to N fertilization at this farm.