摘要
由于硝态氮(NO3--N)对于水稻的生长起到非常重要的作用,所以发生在水稻根际的硝化作用越来越受到人们的重视。试验采用根盒(3室)———速冻切片技术研究了常规籼稻(扬稻6号)和常规粳稻(农垦57)苗期根际土壤矿质态氮、硝化作用和氨氧化细菌数量的时空变异。结果表明,在淹水条件下,土壤矿质态氮主要为铵态氮(NH4+-N),NH4+含量随水稻生育期的推进变化不大,但随着距根区的距离增加其含量随之增加,两个水稻品种之间差异不显著;而NO3-的变化趋势与NH4+不一致,NO3-含量随水稻生育期的延长而显著下降,在培养58d时其平均含量约为0·05mgkg-1,同时在整个土体内呈均匀分布,两个水稻品种之间差异显著。土壤的硝化强度随水稻的生长而增强,且两种水稻的硝化强度均为根际土壤最高,然后依次为土体土壤和根区土壤。扬稻6号和农垦57硝化强度最大值分别出现在距根6mm和2mm处,最大值分别为0·88mgkg-1h-1和0·73mgkg-1h-1。土壤氨氧化细菌(AOB)数量随水稻生长时间的增加而增加,且其水平变异趋势与土壤的硝化强度一致,根际土壤AOB数量最多,土体土壤次之,根区土壤最少。相关分析结果表明,硝化强度和AOB数量呈显著正相关关系(r=0·86,p<0·01)。种植扬稻6号的土壤NO3-浓度、硝化强度以及AOB数量总是高于农垦57。
Increasing amounts of evidence is showing that nitrification in the rhizosphere is very significant for the nitrogen nutrition of rice plants. A rhizobox with three compartments and subsequent soil-slicing after quick freezing was used to measure simultaneously the spatiotemporal variations of mineral nitrogen, nitrification and AOB in the rhizosphere soil of two rice cultivars Yangdao 6 （Indica） and Nongken 57 （Japonica） growing at the N level of 30 mg N kg^-1 . The results obtained can be listed as follows： the main nitrogen form was ammonium （NH4^＋ -N） in flooded paddy soil and NH4^＋ -N concentrations in bulk soil showed almost no changes with incubation time, but NH4^＋ -N concentrations increased with the distance from root zone of both rice cultivars. The NH4^＋ -N concentration of both Yangdao 6 and Nongken 57 in the zone 40 mm from the root at 51 days after sowing, for example, achieved 13.8 and 14.6 mg kg^-1 soil, respectively. However, the nitrate （NO3^--N） concentration decreased significantly with the development of the incubation time, although the distribution of NO3^- -N was even in the bulk soil. The average NO3^- -N concentration for both cultivars was 0.05 mg kg^-1 soil. When the two varieties were compared, the NH4^＋ -N concentration was almost the same, while NO3^- -N concentration was significantly different at every sampling time. The nitrification activities of both rice cultivars increased with incubation time. Maximal nitrification activities were found in rhizosphere soil, followed by those in the bulk soil and in the root zone in every sampling. In the rhizosphere the nitrification activities decreased with increased distance from the root. The maximal nitrification activity measured at 44, 51 and 58 days after sowing of Yangdao 6 and Nongken 57 rice cultivars was at a distance of 6 mm and 2 mm from root zone, respectively. The maximal nitrification activity values measured were 0.88 and 0.73 mg kg^-1 h^-1 , respectively. The AOB in the root zone, rhizosphere （0 - 4 mm away from root zone） and bulk soil （ 〉 4 mm away from root zone） for both rice cultivars increased during the growth periods. The AOB in the root zone was always the lowest, while that in the rhizosphere soil was the highest in both cultivars. In these experiments, the nitrification activities measured were significantly proportional to AOB （ r = 0.86, p 〈 0.01）. The nitrate concentration, nitrification activities and AOB of Indica were always higher than those of Japonica rice.
出处
《生态学报》
CAS
CSCD
北大核心
2006年第5期1461-1467,共7页
Acta Ecologica Sinica
基金
国家自然科学基金资助项目(40471074
30390082)~~
关键词
籼稻
粳稻
淹水
根际
硝化微生物
Indica rice
Japonica rice
waterlogged
rhizosphere soil
nitrification microogganisms
