玉米南繁基地土壤速效氮空间变异性对采样间距的响应研究

Response of Soil Available Nitrogen Spatial Variability to Sampling Spacing in Maize Propagation Base

【目的】探明玉米南繁基地土壤速效氮含量的空间变异性及其尺度效应,确定合理的采样间距,为精确土壤采样设计提供理论依据。【方法】以玉米南繁地块为试验样地,按10 m采样间距采集土样且为原始尺度,并以20、30、40 m距离依次抽样形成不同采样间距数据集,再利用空间自相关莫兰指数、半方差函数及分形维数分析不同采样间距条件下土壤速效氮含量的空间结构变化规律。【结果】试验地的土壤速效氮平均含量为90.24 mg/kg,属中等水平,变异系数为19.77%,属中等变异范围;在10、20、30、40 m等采样间距中,土壤速效氮样本数据结构变化不大,仅变异系数差异较大,其中以20m采样间距的变异系数最大、为29.37%,其他采样间距相差不大;随着采样间距增大,土壤速效氮含量的空间自相关莫兰指数呈减少趋势,其空间聚集性变弱,而块金值、块基比和分形维数呈增加趋势,表明随机因素所引起的空间变异逐渐增多,随机因素逐渐削弱结构因素引起的空间变异,使空间相关性逐渐变弱;20 m采样间距的土壤速效氮含量空间分布与10 m采样间距原始尺度一致,其空间预测的均方根误差值最小,空间预测精度为最高。【结论】随着采样间距增大,土壤速效氮含量的空间自相关性逐渐减弱,表征出随机因素所引起的空间变异性逐渐增强,结构因素引起的空间变异性逐渐削弱,其中20m采样间距的土壤速效氮含量空间变异特征和空间分布与10m采样间距原始尺度相似,且空间预测精度最高,是较为合理的采样间距,本研究可为玉米南繁基地的氮肥精准施用管理提供技术支撑。

【Objective】The spatial variability and scale effect of soil available nitrogen content in maize propagation base were investigated,and reasonable sampling interval was determined to provide a theoretical basis for accurate soil sampling design.【Method】Taking the perennial southern maize propagation plot as the test plot,soil samples were collected at 10 m sampling interval with original scale,and sampled successively at 20,30 and 40 m to form different sampling interval data sets.Spatial autocorrelation Moran index,semi-variogram and fractal dimension were used to analyze the spatial structure changes of soil available nitrogen content under different sampling interval conditions.【Result】The average content of soil available nitrogen in the test site was 90.24 mg/kg,belonging to the medium level,and the coefficient of variation was 19.77%,belonging to the medium range of variation.At the sampling intervals of 10,20,30 and 40 m,the data structure of soil available nitrogen samples did not change notably,only the coefficient of variation was different greatly.The coefficient of variation at the sampling interval of 20 m was the largest 29.37%,while that at the other sampling intervals was little different.With the increase of sampling interval,the spatial autocorrelation Moran index of soil available nitrogen content decreased and its spatial aggregation became weaker,while the nugget value,block base ratio and fractal dimension showed an increasing trend,indicating that the spatial variation caused by random factors gradually increased,while the spatial variation caused by random factors gradually weakened the spatial variation caused by structural factors,making the spatial correlation gradually weakened.The spatial distribution of soil available nitrogen content with a 20 m sampling interval was consistent with the original scale of a 10 m sampling interval,and the root mean square error value of spatial prediction was the smallest,indicating that the spatial prediction accuracy was highest.【Conclusion】With the increase of sampling interval,the spatial autocorrelation of soil available nitrogen content gradually weakened,indicating that the spatial variability caused by random factors gradually increased,and the spatial variation caused by structural factors gradually weakened.The spatial variation characteristics and distribution of soil available nitrogen content at 20 m sampling interval were similar to those of 10 m sampling interval with the original scale and the spatial prediction accuracy was highest,which was a reasonable sampling interval in this study.It provided technical support for precise application and management of nitrogen fertilizer in maize propagation base.