土壤CEC的影响因子及Cokriging空间插值分析——以青岛市大沽河流域为例

运用地统计和多元回归分析方法,探讨大沽河流域土壤阳离子交换量(CEC)的空间变异和影响因子。结果表明,上下层土壤CEC与有机质、黏粒和粉粒含量有着显著的正相关,而与砂粒含量则存在显著的负相关,其中与黏粒含量的相关系数最大,与粉粒含量的相关性最弱;对CEC的贡献能力依次为黏粒有机质砂粒,黏粒的贡献能力平均为有机质的1.5～2.5倍;以黏粒为辅助变量的Cokriging(COK)较之Ordinary Kriging(OK)能提高插值精度,上下层均方根误差RMSE值分别减少了18.94%和41.05%,辅助变量与主变量的相关程度决定了估值的精度;大沽河流域中东、西北部及西南方向中部地区土壤CEC较高,而北部与西南角局部地区土壤CEC保肥能力非常弱,是以后土壤改良的重点地区,可通过增施有机肥以及改土培肥等措施来提高土壤肥力水平。     

红壤丘陵区坡地土壤颗粒组成的空间分布特征研究

通过分析红壤丘陵区农田坡面14个0~100 cm剖面的土壤颗粒组成,结合研究区土壤侵蚀等相关资料,拟阐明坡面尺度土壤砂粒、粉粒和黏粒含量的空间分布特征,揭示自然条件下土壤颗粒组成在水平和垂直方向上的分布规律。结果表明:坡面尺度土壤砂粒、粉粒和黏粒均呈现出中等的空间异质性,变异系数分别介于17.6%~23.2%、10.7%~15.8%和13.5%~17.0%。由于粗颗粒的沉积,花生地和橘园地均表现出坡下的砂粒含量显著高于坡上和坡中(P0.05),黏粒含量坡下显著低于其他坡位(P0.05);由于黏粒更容易随入渗过程向深层运动,两种植被类型均表现出土壤砂粒含量随深度增加而降低(P0.05)、黏粒含量随深度增加而增加的趋势(P0.05)。无论在水平方向还是垂直方向上,粉粒含量均无明显变化规律(P0.05)。砂粒含量随坡位和土壤深度的变化程度均大于粉粒和黏粒。植被类型及相应的耕作制度影响土壤颗粒的分布,土壤砂粒在水平方向上的运动在花生地表现得强于橘园地;橘园地土壤黏粒含量在垂直方向上的迁移速率大于花生地,而对粉粒含量的分布规律影响不大。     

水库消落带土壤颗粒组成分形及其空间分异特征

颗粒组成作为土壤的基本物理特性,对土壤结构、力学性质、肥力特征等均有明显影响。降雨径流、波浪和重力等多重营力作用下的消落带土壤侵蚀过程导致表层土壤颗粒发生了重新分布。为了研究水库消落带土壤颗粒组成的空间分异特征,以三峡水库典型消落带为研究对象,在不同海拔位置分别采集了0—10 cm和10—20 cm层的土壤用于测定颗粒组成,并利用分形理论计算出体积分形维数。结果表明:(1)三峡水库消落带土壤颗粒组成以粉粒为主,占总体积的72.6%～86.5%,且随着海拔的增加而升高; 从不同土层深度来看,0—10 cm层黏粒含量明显低于10—20 cm层。(2)消落带不同海拔位置的土壤体积分形维数具有明显异质性,且与海拔呈正相关(R²=0.74),而在不同土层之间具有弱变异性(C_v<2)。(3)体积分形维数与黏粒、粉粒含量均呈显著正相关(p<0.01),与砂粒含量呈显著负相关(p<0.01),且与黏粒的线性相关性最强。综上,消落带土壤颗粒组成在不同海拔存在较大差异(p<0.01),但在土层深度上无显著差异(p>0.01); 150～160 m海拔区间和0—10 cm层土壤具有明显的粗粒化现象。     

崩岗红土层土壤液塑限特性及影响因素研究

土壤液塑限可以反映土壤的入渗、抗冲、抗蚀和抗剪等情况,对崩岗的水土流失研究有重要的意义。通过对崩岗红土层土壤的液塑限研究以及颗粒分析和有机质测定,分析土壤有机质含量和土壤颗粒分布对土壤液塑限的影响。结果表明:崩岗红土层土壤为高液限黏土,土壤状态为坚硬;土壤液塑限值与粗砂粒、细砂粒和粉粒含量相关性不明显,与极细砂粒和黏粒含量呈二项式关系,其中极细砂粒含量与土壤液塑限呈负相关;黏粒含量与土壤液塑限均呈显著正相关关系,且模拟的方程可以较准确地描述土壤液塑限和各因素的相关关系。研究结果有利于丰富崩岗侵蚀机理的研究。     

荒漠绿洲过渡带土壤饱和导水率的空间变异特征

土壤饱和导水率(saturated hydraulic conductivity,Ks)是影响土壤水文过程的重要参数,反映了土壤的入渗性能与持水能力。为探究荒漠绿洲过渡带土壤Ks的空间分布特征及影响因素,基于网格法(2 km×2 km)在黑河中游荒漠绿洲过渡带不同景观类型布设27个样点,获取0—30 cm土层基本物理性质,并利用Hood-IL 2700入渗仪测定土壤Ks。采用经典统计学和地统计结合的方法分析土壤Ks空间分布特征及其影响因素,建立Ks的土壤传递函数。结果表明:(1)土壤Ks变异系数为1.21,属强变异,Ks和土壤水分(SW)、有机质、黏粒(clay)、粉粒含量呈极显著负相关(P0.01),与容重(ρ_b)、砂粒含量呈极显著正相关(P0.01)。(2)土壤水分半变异函数最佳拟合模型为指数模型,容重、黏粒含量均为球状模型,容重、土壤水分和黏粒的最佳采样距离分别为0.38～0.77,1.86～3.72,1.41～2.83 km。(3)建立的传递函数为log Ks=-2.914+2.772ρ_b-0.09SW+0.068clay,容重、土壤水分和黏粒含量可作为模拟区域饱和导水率空间分布状况的预测变量。研究结果为荒漠绿洲过渡带土壤水分运移及模拟提供重要的数据支撑。     

基于最小数据集的青藏公路沿线土壤质量评价

为明确青藏公路沿线土地土壤质量的基本特征,通过采集沿线3种不同土地利用类型(农地、草地和沙地)的土壤样品,采用主成分分析法(PCA,Principal Component Analysis)筛选最小数据集(MDS,Minimum Data Set)指标,并构建土壤质量指数(SQI,Soil Quality Index)定量评价其土壤质量。结果表明:(1)相较于农地和草地,沙地的土壤肥力较为贫瘠,其土壤有机质、全氮和有效磷的土壤肥力等级均为6级。9个土壤指标均为中低度敏感指标,沙地土壤黏粒和粉粒含量具有更强的空间分异性。(2)沿线土壤质量评价最小数据集由全钾、全磷、有机质、黏粒和粉粒组成,最小数据集能够较好地替代全数据集进行土壤质量评价(p<0.01)。(3)沿线农地的土壤质量指数SQI(0.535±0.043)高于草地SQI(0.499±0.044)和沙地SQI(0.449±0.066)。该研究发现沿线农地土壤质量为中等水平,沿线草地和沿线沙地土壤质量处于较低水平,土壤有机质是影响青藏公沿线土壤质量的主要因素。     

冀西山前冲积扇区土壤机械组成模型制图对比研究

探索适合地形平缓的山前冲积扇地区土壤机械组成的空间预测方法。以河北省灵寿、行唐、曲阳县400 m高程以下区域为研究区,结合地形因子、土壤类型、归一化植被指数、地表温度等环境变量,选择基于对称对数比（SLR）转换的普通克里格法（SLR-OK）、回归克里格法（SLR-RK）、随机森林法（SLR-RF）3种方法,对训练集114个样点表层土壤机械组成的空间分布进行预测,并通过验证集50个样点比较了3种方法的预测精度。（1）从空间预测图来看,砂粒呈现出西北低、东南高的空间分布趋势;粉粒和黏粒与砂粒相反。与SLR-OK法相比,SLRRK法和SLR-RF法能够更好地反映局部变异并减小平滑效应。（2）对于砂粒和粉粒,SLR-RF法对验证集含量预测的平均绝对误差（MAE）和均方根误差（RMSE）均低于其他两种方法,且决定系数最高,表明SLR-RF的预测精度最高;对于黏粒,SLR-OK法对验证集含量预测的MAE和RMSE均低于其他两种方法,且决定系数最高,表明SLR-OK法的预测精度最高。（3）线性回归预测模型的辅助变量包括高程、土壤类型和风力作用指数;随机森林法模型的辅助变量包括高程、土壤类型、归一化植...     

自然降雨条件下坡面侵蚀地表粗糙度的空间异质性

地表粗糙度是影响地表侵蚀的重要参数之一,也是土壤侵蚀研究的热点问题之一,研究自然降雨过程中砒砂岩区地表粗糙度的空间异质性,对其探索土壤侵蚀响应规律具有重要意义。以裸露砒砂岩为研究对象,采用地统计学和ArcGIS空间分析相结合的方法研究了坡面尺度次降雨过程下的地表粗糙度空间异质性特征。结果表明:地表粗糙度在次降雨过程中表现出中等变异性;地表粗糙度在次降雨过程中都具有较强的空间自相关性;由空间分布特征分析得出,地表粗糙度的增加量或者减少量在坡面下坡的数值变化较为明显,说明坡面的变化是坡顶被冲刷,坡底被填充;砂粒和粉粒含量均在坡下减小,而黏粒含量增大,地表粗糙度在坡下数值变化较明显,因此,地表粗糙度的变化随着土壤黏粒的变化而变化;降雨前后土壤黏粒与地表粗糙度表现出正相关,雨后的相关性更强烈,粉粒与其关系不显著,砂粒与其呈现负相关。     

沂蒙山区桃园棕壤斥水性对理化性质的空间响应

以沂蒙山区典型土地利用桃园棕壤为例,在分析降雨前后桃园棕壤斥水性与理化性质空间变异的基础上,探讨了棕壤斥水性对土壤含水量、有机质含量和土壤质地的空间响应特征。按照1 m×1 m网格等间距测定降雨前后土壤实际斥水性与含水量,同时采集表层0~3 cm土壤样品,分析其有机质含量与砂粒、粉粒、黏粒含量,并借助经典统计学、地统计学与空间自相关理论对土壤斥水性及理化性质进行空间格局与空间相关性分析。结果表明:沂蒙山区桃园棕壤的斥水程度强烈,雨后斥水性显著降低;降雨前后棕壤斥水性均具有中等变异水平和较强的空间自相关性,且呈指数模型分布,各向异性显著。受结构变异和随机变异作用,斥水性空间格局沿耕作方向呈条带状分布,在其垂直方向上最小变程为1.4 m。土壤质地是影响棕壤斥水性空间变异的主要因素,斥水性与粉粒含量呈空间正相关,与砂粒和黏粒含量呈空间负相关,相关程度粉粒砂粒黏粒;棕壤斥水性与含水量呈空间负相关,相关度雨前较弱,雨后显著。     

围栏种植红柳对川西北高寒沙地土壤颗粒组成和矿质养分的影响

为了揭示川西北高寒沙地生态修复过程中土壤颗粒组成和矿质养分的积累和变化特征,以川西北围栏种植红柳生态修复年限分别为0、2、4、6和8年的沙化土地作为研究对象,并结合土壤样品的采集和室内分析化验,研究了川西北沙化土地生态修复过程中土壤颗粒组成及磷、钾养分的变化特征。结果表明,生态修复过程中沙化土地0~20 cm土层土壤全磷和全钾含量略有增加,但不同生态修复年限之间土壤全磷和全钾含量差异未达显著水平(P0.05),而20~40 cm和40~60 cm土层土壤全磷和全钾含量无明显变化特征。随着生态修复年限的增加沙化土地0~20 cm、20~40 cm和40~60 cm土层土壤黏粒、粉粒、速效磷和速效钾含量均呈现逐步增加的趋势,而土壤砂粒含量呈现出逐步下降的趋势,其中0~20 cm土层变化最为明显,生态修复8年后沙化土地粉粒、黏粒、速效磷和速效钾含量分别增加了66.67%、96.30%和109.82%、102.61%,而土壤砂粒含量减少了5.57%,不同生态修复年限沙化土地0~20 cm土层土壤砂粒、粉粒、黏粒、速效磷和速效钾含量差异均达极显著水平(P0.01)。20~40 cm和40~60 cm土层土壤速效磷和速效钾含量增加幅度及差异显著性不及0~20 cm土层。沙化土地植被覆盖度与土壤全磷、全钾呈显著正相关关系(P0.05),与土壤速效钾、速效磷呈极显著正相关关系(P0.01);土壤速效磷、速效钾与土壤砂粒含量呈极显著负相关关系(P0.01),与土壤粉粒和黏粒含量呈极显著正相关关系(P0.01),土壤全磷、全钾含量与土壤颗粒组成相关性未达显著水平。     

黄土高原北部草地表层土壤水分状态空间模拟

为探明黄土高原北部草地表层土壤水分空间分布特征及其与环境因素的关系,该文用自回归状态空间模型和经典统计的线性回归模型对该区草地表层土壤含水率的分布状况进行了模拟。结果表明,状态空间方程可以应用于环境因素复杂的黄土高原水蚀风蚀交错区,其拟合效果优于线性回归模型。单因素中基于饱和导水率的模拟效果最佳（R2 = 0.936）;多因素模拟中以饱和导水率+海拔+凋落物模拟效果最佳（R2 = 0.976）,可以很好地解释表层土壤水分的变异状况。自回归状态空间模型可用于研究黄土高原北部水蚀风蚀交错区表层土壤水分与其他因素的空间关系。     

Evaluation of the spatial pattern of surface soil water content of a karst hillslope in Southwest China using a state-space approach

This study aims to evaluate the effects of soil physicochemical properties and environmental factors on the spatial patterns of surface soil water content (SWC) based on the state-space approach and linear regression analysis. For this purpose, based on a grid sampling scheme (10 m × 10 m) applied to a 90 m × 120 m plot located on a karst hillslope of Southwest China, the SWC at 0–16 cm depth was measured 3 times across 130 sampling points, and soil texture, bulk density (BD), saturated hydraulic conductivity (K_s), organic carbon (SOC), and rock fragment content as well as site elevation (SE) were also measured at these locations. Results showed that the distribution pattern of SWC could be more successfully predicted by the first-order state-space models (R² = 67.5–99.9% and RMSE = 0.01–0.14) than the classic linear regression models (R² = 10.8–79.3% and RMSE = 0.11–0.24). The input combination containing silt content (Silt), K_s, and SOC produced the best state-space model, explaining 99.9% of the variation in SWC. And Silt was identified as the first-order controlling factor that explained 98.7% of the variation. In contrast, the best linear regression model using all of the variables only explained 79.3% of variation.     

Estimation of spatial variability of soil water storage along the south–north transect on China’s Loess Plateau using the state-space approach

Purpose

Soil water is a critical variable for hydrological and biological processes in arid and semi-arid ecosystems. Information on regional spatial pattern of soil water storage (SWS) and its relationship with environmental factors is important for optimal water management and vegetation restoration in China’s Loess Plateau (CLP) region. State-space approach and artificial neural network (ANN) were used to analyze spatial variability of SWS in the CLP region.

Materials and methods

SWS in the 0–1, 1–2, 2–3, 3–4, and 4–5 m soil layers was measured during the period from June 2013 to September 2015 at 86 locations along a 860 km long south–north transect of CLP.

Results and discussion

The analysis showed that SWS in the 5 m soil profile generally decreased with increasing latitude, driven by decreasing precipitation and soil–water holding capacity. Using various combinations of variables, the state-space model gave a better spatial pattern of SWS than the ANN approach. The best state-space approach, which included clay content, mean annual precipitation, and slope gradient, explained 96.0% of the total variation in SWS. Then, the best ANN approach explained only 76.2% of the variation. Clay content, mean annual precipitation, and slope gradient was the most effective combination for large-scale estimation of SWS under the state-space approach.

Conclusions

The state-space model was recommended as an effective method for analyzing large-scale spatial patterns of soil water using soil, climatic, and topographic properties in the CLP region.

     

Prediction of soil properties using a hyperspectral remote sensing method

Quickly and accurately mapping soil properties is critical for agricultural, forestry and environmental management. In this study, a new hyperspectral remote sensing method of soil property prediction was developed and validated in Stipa purpurea dominated alpine grasslands located in Shenzha County of the Qiangtang Plateau, northwestern Qinghai-Tibet Plateau. Hyperspectral data were collected in a total of 67 sample points. At the same time, soil samples were obtained at the locations and soil properties including organic carbon, total nitrogen, total potassium and total phosphorus were measured. The correlations of the soil properties with original bands and enhanced spectral variables derived from both field and satellite hyperspectral data were analyzed. Regression models that explained the relationships were further developed to map the soil properties. The results showed that the stepwise regression models based on the satellite hyperspectral image derived enhanced spectral variables produced reasonable spatial distributions of the soil properties and the relative RMSE values of 68.9, 46.3, 31.4 and 45.5% for soil organic carbon, total nitrogen, total phosphorus and total potassium, respectively. Thus, this study implied that the hyperspectral data based method provided great potential to predict the soil properties.     

黄土高原水蚀风蚀交错带小流域土壤矿质氮空间变异性

为探明小流域土壤养分特性空间变异规律及其与环境因子的关系,以非均匀取样方法测定了黄土高原水蚀风蚀交错带小流域土壤表层（0～10、10～20、20～40 cm）的硝态氮和铵态氮,采用经典统计和地统计学方法分析了其空间分布特征及变异结构。结果表明：土地利用空间配置成混合利用结构拦截和减少径流侵蚀,形成了土壤矿质氮坡面斑块镶嵌格局。小流域内硝态氮和铵态氮呈中等的空间变异和自相关性,其变异性由土壤系统内部因素包括土壤质地、矿物、成土过程、地形特征和人类活动造成的外部因素包括施肥和耕作等共同控制。建立了土壤矿质氮多元回归预测模型,各回归模型的自变量不同,表明不同土层硝态氮和铵态氮的变异受不同环境因子控制。分析认为合理配置土地利用形成斑块状结构和增加养分投入可以改善研究区土壤质量。     

河北省表层土壤有机碳和全氮空间变异特征性及影响因子分析

【目的】在陆地生态系统中, 土壤全氮和有机碳是重要的生态因子。本研究基于土壤调查获得大量土壤剖面的空间和属性信息,研究河北的土壤有机碳和全氮的空间分布特征,为河北的土壤养分监测和管理提供科学依据,同时也为其他类似地区土壤采样提供参考,减少采样成本。【方法】运用传统统计学和地统计学分析方法,以变异函数为工具,初步分析了河北土壤全氮和有机碳的空间变异特征,并应用普通克立格法和回归克里格法进行插值, 得出全氮和有机碳含量的分布格局。【结果】研究区土壤有机碳和全氮的平均值分别为15.25 g/kg和1.23 g/kg,变异系数分别为0.73和0.63,属于中等强度变异。经对数转换后,土壤有机碳和全氮均符合正态分布。选择球状模型作为土壤有机碳和全氮的半方差函数理论模型,土壤有机碳和全氮的块金值/基台值的比值分别为1.8%和1.2%,有机碳和全氮的块金系数均小于25%,表明有机碳和全氮具有强烈的空间相关性。有机碳和全氮空间变异的尺度范围不同,分别为50.400 km和59.200 km。研究区的有机碳总体空间分布规律是有机碳在北部较高、南部较低,呈自北向南递减趋势,土壤全氮与有机碳的空间分布趋势相似,但有机碳的空间变异特征较全氮明显,这种空间分布格局主要受环境因子、 土壤质地、 土壤类型以及土地利用类型等的影响,其中环境因子中的气温和海拔对有机碳和全氮的影响较大。通过比较普通克里格和回归克里格的预测结果,回归克里格能较好地反映东南部有机碳和全氮较低地区的局部变异外,对于西北部的山区也能更好地反映碳、 氮与地形及气候等因素的关系。【结论】河北土壤有机碳和全氮的空间变异和分布特征较为类似,受地形地貌、 气候等因素的影响。通过比较普通克里格法和回归克里格法的空间预测结果,回归克里格法可以消除环境因子的影响,从而得到更准确的空间预测结果,因此建议使用回归克里格法进行预测,以期获得一个更为准确的土壤有机碳和全氮的空间预测结果。     

基于环境相关法和地统计学的土壤属性空间分布预测

土壤属性是土壤质量的重要决定因素,并强烈影响土地利用和生态过程。正确理解并充分考虑土壤空间变异,对于在景观尺度上建立生态、环境过程模型是必不可少的。在黄土高原横山县采集了254个样点,应用数字地形与遥感影像分析技术,获取相关地形因子与遥感指数,分析土壤属性（土壤容重、有机质和全磷）与环境因子相互关系,并利用环境变量进行空间预测。结果表明,土壤容重、有机质与地形因子和遥感指数之间存在较好相关性,而全磷与地形因子相关性不大;多元线性逐步回归模型对于土壤容重和有机质拟合较好,而对于全磷,预测结果较差;回归－克里格预测有效地减小了残差,消除了平滑效应,与实测值较为接近。     

典型喀斯特林地土壤养分空间变异的影响因素

为了探明喀斯特森林生态系统土壤养分空间异质性的成因及其对养分生物地球化学过程的指示意义,该研究以广西木论国家级自然保护区典型喀斯特峰丛洼地为研究对象,利用地统计学和经典统计方法分析了土壤养分的空间变异特征,并探讨了其主要影响因子。结果表明,研究区土壤有机碳(SOC)和全氮(TN)的块金值/基台值较大,分别为49.9%和28.6%,表现为中等程度的空间自相关,全磷(TP)和全钾(TK)的块金值/基台值较小,分别为10.4%和2.9%,表现为强烈的空间自相关,说明随机因素对TP和TK的影响相对较小;逐步回归分析表明,各环境因子对TK的方差解释最大,对SOC的方差解释最小。其中,土壤交换性Ca2+离子和凋落物中N含量是SOC和TN的主要控制因素,随着交换性Ca2+和凋落物中N含量升高,土壤SOC和TN积累增加;TP的控制因素比较单一,仅受凋落物中P含量影响。TK的影响因素比较复杂,除主要受交换性Ca2+控制外,凋落物N:P比、海拔高度和黏粒含量也有显著影响。     

SOIL EROSION,CONSERVATION, AND ECO‐ENVIRONMENT CHANGES IN THE LOESS PLATEAU OF CHINA

As one of the best‐known areas in the world, the Loess Plateau, has long been suffering from serious soil erosion. The present paper reviewed the historical variation of climate, vegetation cover, and environment changes in order to understand the causes of severe soil erosion. Documentary evidence indicated that climate changes and vegetation cover were the dominant natural factors influencing the soil erosion rates during the Holocene. Intensive human activities consisting of warfare, population growth, deforestation, and soil and water conservation measures were responsible for the changes of soil erosion during the anthropogenic period. Spatial and temporal changes of specific sediment yields presented significant decrease within the last several decades, which resulted from decreasing rainfall, large scale soil and water conservation measures, agricultural irrigation, and reservoir construction. Different phase of soil conservation measures demonstrated the development of policies and techniques on soil erosion control. Effective strategies of soil and water conservation, consisting of terracing, afforestation, natural rehabilitation, and check‐dams construction, were carried out on the Loess Plateau during the past six decades. The progress of soil conservation measures confirmed that the check‐dams systems might be suitable for Loess hilly Plateau, and natural vegetation rehabilitation is the best way for soil erosion control and should be implemented in other regions with emphasis of improving the quality of conservation measures based on natural rehabilitation. Copyright © 2013 John Wiley & Sons, Ltd.     

Variation of early growth and nutrient content of no‐till corn and soybean in relation to soil phosphorus and potassium supplies

Abstract

Knowledge of relationships between variation in early plant growth and soil nutrient supply is needed for effective site‐specific management of no‐till fields. This study assessed relationships between soil test phosphorus (STP) and potassium (STK) with early plant growth and P or K content of young corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] plants in eight no‐till fields. Composite soil (0–15 cm depth) and plant (V5‐V6 growth stages) samples were collected from 400‐m² areas at the center of 0.14‐ha cells of a 16‐cell square grid and from 2‐m² areas spaced 3 m along each of two 150‐m intersecting transects. Correlation, regression, multivariate factor analyses were used to study the relationships between the variables. Variability was higher for samples collected from the transects. Plant dry weight (DW), P uptake (PU), and K uptake (KU) usually were correlated with STP and STK but the correlations varied markedly among fields. Relationships between soil and plant variables could not always be explained by known nutrient sufficiency levels for grain production. Plant P concentration (PC) was not always correlated with STP and sometimes it increased linearly with STP, but other times increased curvilinearly until a maximum was reached. Plant K concentration (KC) usually was correlated with STK, however, and increased linearly with increasing STK even in fields with above‐optimum STK. The results suggest greater susceptibility of early growth to STP than to STK and greater plant capacity to accumulate K compared with P over a wide range of soil nutrient supplies. Variation in STK likely is a major direct cause of variation in KC over a wide range of conditions but variation in STP is not likely a major direct cause of variation in PC when high STP predominates.