阶段培养法测定稻田氮素矿化量的效果评价

传统原位培养法测定的氮素矿化量与无氮区水稻吸氮相关性不高。为此对传统培养方法进行改进,以期为准确测定土壤供氮提供方法。传统培养方法是在插秧前取土,按水土比约1:1装入自封袋中于田间原位连续培养,每隔约30 d取样测定土壤无机氮含量。改进培养方法则采取阶段培养的方法,在插秧前取土,同上法装入自封袋,再将自封袋放入装满水的离心管中于田间培养,在下次取土样(约30 d后)的同时取出上次培养的土袋,并测定土壤无机氮含量。2013—2015年的试验结果表明,随着培养时间的延长,传统培养方法测定的矿化氮先增加后降低,与最高值相比,矿化氮下降了6.7%~28.6%;而改进的阶段原位培养法测定矿化氮未出现下降情况,因此传统方法测定的矿化氮较改进方法降低了30.0%~67.7%(p0.05)。培养时间对矿化氮量影响显著,土样在田间连续培养约40 d就有抑制氮素矿化的风险,因此,每次培养时间不宜过长。改进培养方法测定的矿化氮量与田间无氮区水稻吸氮量之间具有正相关关系,决定系数R~2为0.621(p0.01)。在测定稻田土壤矿化氮时,应采用阶段培养法,每次培养时间不宜超过40 d。该方法测定矿化氮量可以作为评价土壤供氮能力的指标。

Effectiveness Evaluation of the Use of Phase Incubation Method to Determine N Mineralization in Paddy Soil

As not much correlation was observed between rice N uptake in Treatment N0(No N fertilizer applied)and N mineralization rate measured with the traditional in situ incubation method, modification was made of this method in an attempt to improve its accuracy in measuring soil N supplying capacity. The traditional one is a continuous incubation method,which goes like this:collect some soil from a paddy field before seedling transplanting,mix it with water at 1:1 in volume,pack the mixture in ziplock bags,put the bags back into the field for in situ incubation,and then sample the soil in the bag once every 30 days for measurement of inorganic N. The modified one adopts phase incubation and goes almost the same as the traditional one in preparation for incubation,and then put the bags in centrifuge tubes full of water and the tubes back into the field for incubation in situ and sample the soil in the bag for analysis of inorganic N once every 30 days,while removing the ziglock bags of the last phase of incubation. Results of the 2013-2015 experiment show that with the incubation going on,mineralized N content rose first and fell as was measured with the traditional method. Compared with the maximum value,cumulative mineralized N dropped by 6.7%~28.6%. However,the modified one did not see any decline. So the measurement using the traditional method was 30.0%~67.7%(p<0.05)lower than that using the modified one. Duration of the incubation is a major factor affecting the content of mineralized N. When incubation went on continuously over 40 days,it might pose a risk of inhibiting N mineralization. So,each incubation should not last too long or over 40 days. The content of mineralized N measured with the modified method was found to be closely and positively related to rice N uptake measured in Treatment N0,with R2 being 0.621(p<0.01). Therefore,it is suggested that when measuring soil mineralized N in paddy field,measurements using the modified one be cited as an indicator to evaluate soil N supplying capacity.