Olsen法有效磷对提取温度的响应及量化关系

Response and quantification of Olsen method’s available P to extraction temperature

Olsen法有效磷受到提取温度的显著影响,在严格标准温度25℃下用0.5 mol/L NaHCO_(3)(pH=8.5)提取测定的有效磷不能良好反映田间实际温度下的土壤磷有效性。探明不同提取温度下的Olsen法有效磷对提取温度的响应并建立其与Olsen-P的量化关系,为评价田间不同温度下土壤磷的有效性提供依据。选择具有广泛Olsen-P含量(4~280 mg/kg)的24个黑土样品,采用Olsen法分别于10、15、20、25、30和35℃下测定其有效磷含量;统计分析其与Olsen-P的比值、线性响应关系系数等,随机选取16个黑土数据采用系数直接代入法、系数间接代入法、提取率拟合法、最小二乘法拟合法和两种二阶拟合法共6个换算方程,拟合和建立不同温度下Olsen法有效磷与Olsen-P的量化关系,通过剩余的8个黑土数据对换算方程验证对比,获得将Olsen-P换算成任意温度下土壤Olsen法有效磷含量的方程。结果表明,Olsen法有效磷均随提取温度的升高而显著增加,温度每升高1℃,Olsen法提取的土壤有效磷增加量为0.2~5.4 mg/kg;土壤Olsen-P含量越高,Olsen法提取有效磷的增量越大。不同温度下Olsen法提取有效磷的相对提取率也随温度升高而增加,10、15、20、30和35℃下的平均提取率分别为69.8%、76.1%、87.5%、113.7%和138.7%;并受Olsen-P含量的影响。构建的Olsen法提取有效磷量与提取温度和Olsen-P含量的双因素换算方程,通过方程预测值与实测值的决定系数(R^(2))、残差均方根(RMSE)和相对误差(RE)3个主要指标判断,并考虑简单易行,对比明确了系数直接代入法的换算方程[PT=(0.019×P_(25)+0.170)×T+0.545×P_(25)-3.247]最优,其R^(2)、RMSE和RE分别为0.996、6.18和1.28(n=48)。该方程可用于土壤Olsen-P在4~280 mg/kg范围内,10~35℃不同温度下,进行土壤Olsen-P与Olsen法有效磷含量间的换算。

The available phosphorus(AP)determined by the Olsen method was significantly affected by the extraction temperature,and the available P(Olsen-P)was extracted and determined with 0.5 mol/L NaHCO3(pH=8.5)at 25℃,which could not well reflect soil phosphorus availability at actual field temperature.Exploring the response of Olsen method’s AP to extraction temperature and establishing a quantitative relationship between the Olsen method’s AP with Olsen-P analyzed could provide a basis for evaluating the Olsen method’s AP at different temperatures in the field.The 24 black soil samples with a wide range of Olsen-P contents(4~280 mg/kg)were selected.And the AP was determined by the Olsen method at 10,15,20,25,30 and 35℃.The ratio and linear response coefficient of Olsen-P were analyzed.The correlation between Olsen-P and Olsen method’s AP at any temperature was converted by six conversion equations(direct coefficient substitution,indirect coefficient substitution,extraction rate fitting,least-square fitting,and two second-order fitting methods)to obtain any temperatures equation by verifying and comparing the conversion.The results showed that the Olsen method’s AP increased significantly with the increase in extraction temperature,and the increase of AP was 0.2~5.4 mg/kg for every 1℃increase in extraction temperature.The Olsen-P in soil was positively correlated with the increment of the Olsen method’s AP.The amount of Olsen method’s AP and the relative extraction rate of Olsen-P affected by the Olsen-P was also positively correlated with the increase in temperature.And the average extraction rates at 10,15,20,30 and 35℃were 69.8%,76.1%,87.5%,113.7%and 138.7%,respectively.Based on the above,a two-factor conversion equation was established for the extraction of available phosphorus by Olsen method,extraction temperature,and Olsen-P content.The predicted value and measured value were compared according to the equation determination coefficient(R^(2)),root mean square of residual error(RMSE)and relative error(RE).The simpler conversion equation was chosen.The conversion equation[PT=(0.019×P_(25)+0.170)×T+0.545×P_(25)-3.247]with R^(2) of 0.996,RMSE of 6.18,and RE of 1.28(n=48)could be used for the conversion of Olsen method’s AP with Olsen-P at 10~35℃in the range of 4~280 mg/kg soil Olsen-P.