冻融影响下黑土耕层剖面速效氮动态变化

为了探明冻融过程对东北典型黑土耕层氮(N)生物有效性的影响,试验利用室内模拟方法,探究了不同冻结温度、土壤容重、含水量、冻融循环次数影响下耕层土壤剖面速效氮(AN)的时空分布规律。结果表明,经冻融循环后,土壤AN含量随土层深度增加呈现波动性下降;冻结温度越低,AN随土层深度增加下降的波动性越大,AN峰值、AN土柱平均值越低;冻结温度-15℃时整个土柱AN平均值比-10℃降低9.3%~44.6%;容重增高,AN含量降低,AN/TN值升高,土壤容重1.1 g/cm³时整个土柱AN平均值比容重1.0 g/cm³降低13.0%~18.6%,容重1.1 g/cm³整个土柱AN/TN平均值比容重1.0 g/cm³显著提升0.6~4.7倍;随着含水量的提高,低容重(1.0 g/cm³)表层(0—8 cm)AN越高,底层(20—30 cm)AN越低,而高容重(1.1 g/cm³)土柱表层(4—8 cm)AN越高,表层(0—4 cm)AN、底层(20—30 cm)AN越低;在各个变量中,pH大小与AN累积趋势呈负相关关系,含水量、TDS、电导率、冻结温度均与AN含量成正相关,是否冻融循环对AN垂直分布影响最大,其次是恒温及冻融循环次数(p<0.05)。研究结果可为黑土区冻融过程土壤N素管理、提升土壤肥力、减少N损失等问题提供理论依据和技术支撑。

Dynamics of Soil Available Nitrogen Influenced by Freeze Thaw Cycling in the Profiles of Plough Layer in Mollisol

In order to clarify the effects of freeze-thaw cycling(FTC)on the nitrogen(N)bioavailability in the cultivated layer in the mollisol,incubation method was explored to detect the vertical distribution of soil available nitrogen(AN)in the profile of different freezing temperatures,soil bulk density(BD),soil moisture,and FTC frequency.The results showed that after FTCs,soil AN contents decreased with the increasing soil depths.The lower the freezing temperature was,the greater the fluctuation of AN with increasing depth was.The lower the freezing temperature was,the lower the peak value and mean value of AN in soil column were.The mean value of AN in the entire soil column(0—30 cm)at-15℃was 9.3%~44.6%lower than that at-10℃;the increase of BD resulted in the AN value decreased and the AN/TN value increased.Compared with BD of 1.0 g/cm³,AN of BD 1.1 g/cm³ was reduced by 13.0%~18.6%in 0—30 cm soil depth,while AN/TN of BD 1.1 g/cm³ significantly increased by 0.6~4.7 times.When the soil water contents increased,the AN increased in surface layer(0—8 cm)and decreased in low soil layer(20—30 cm)under low BD treatment(1.0 g/cm³);while the AN increased in the layer of(4—8 cm)and decreased both of 0—4 cm and 20—30 cm soil depth under high BD treatment(1.1 g/cm³).AN was negatively correlated with pH,while positively correlated to the soil moisture,TDS,conductivity,and freezing temperature.Both the FTC happened or not influenced vertical distribution of AN,followed by temperature and FTC frequency(p<0.05).This study aimed to provide the theoretical basis and technical support for soil N management during FTCs in mollisol areas,e.g.improving soil fertility and reducing N loss.