盆栽条件下红黄泥微生物量氮和固定态铵的动态变化

Dynamics of Soil Microbial Biomass Nitrogen and Fixed Ammonium in Reddish Clayey Soil During Pot Experiment

目的研究盆栽条件下红黄泥微生物和晶格对有机、无机氮源的固定以及土壤微生物量氮(SMBN)和固定态铵的动态变化。方法采用15N示踪技术对有机无、机氮源交叉标记进行盆栽试验,设置单施尿素(15NU)、标记尿素与稻草配施(15NU-S)和标记稻草与尿素配施(15NS-U)3个处理。结果在水稻生育期内,SMBN和固定态铵占全氮比例分别为2.20%～4.00%和4.77%～8.37%;SMBN在孕穗期出现最低值,各处理固定态铵在分蘖期出现最低值。水稻成熟时,SMBN和固定态铵各处理间差异不显著。微生物和晶格固定的尿素氮分别为4.01～15.14和0.47～4.82 mg.kg-1,占施用尿素氮的1.76%～8.83%和0.28%～2.11%;固定的秸秆氮分别为0.97～2.85和0.09～0.50 mg.kg-1,占施用秸秆氮的1.69%～4.98%和0.15%～0.87%。有机无机肥配施促进了微生物对尿素氮的固定,降低了晶格的固定。单施尿素处理和有机无机肥配施处理SMBN的最大释放率为66.04%和69.15%,固定态铵最大释放率为87.75%和87.64%。结论盆栽水稻条件下,土壤微生物和矿物晶格对外源氮的固定和释放是一个动态的过程,有机无机肥配施对SMBN和固定态铵有明显影响。

[ Objective ] The study looked at immobilization of nitrogen by microbe and crystal cell in reddish clay soil. The soil was examined after amending urea and straw. The study investigated the dynamics of soil microbial biomass nitrogen （SMBN） and fixed ammonium during rice growth. [ Method] A flooded pot experiment was conducted during rice growth and three treatments were installed, i.e., labeled urea,group （15NU）, labeled urea plus rice straw powder group （^15NU-S） and labeled rice straw power plus urea group （^15NS-U）. [Result] During rice growth, the percentage of SMBN and fixed ammonium to total nitrogen were 2.20%-4.00% and 4.77%-8.37%, respectively. SMBN was minimum at rice booting stage and fixed ammonium was minimum at rice tillering stage. For SMBN, there was no significant difference between three treatments at rice matured stage and the same to fixed ammonium. The immobilization of urea nitrogen by microbe and crystal cell were 4.01-15.14 mg·kg^-1 and 0.47-4.82 mg·kg^-1, respectively. The percentage of labeled substrate SMBN and labeled substrate fixed ammonium to urea nitrogen were 1.76%-8.83% and 0.28%-2.11%, respectively. The immobilization of rice straw nitrogen by microbe and crystal cell were 0.97-2.85 mg·kg^-1 and 0.09-0.50 mg·kg^-1, respectively. The percentage of labeled substrate SMBN and labeled substrate fixed ammonium to rice straw nitrogen were 1.69%-4.98% and 0.15%-0.87%, respectively. Urea plus rice straw powder groups （URSP, including ^15NU-S and ^15NS-U） increased the assimilation of microbe, decreased the immobilization of crystal cell. The maximum releasing rate of SMBN in ^15NU and URSP were 66.04% and 69.15%, respectively. Those of fixed ammonium in ^15NU and URSP were 87.75% and 87.64%, respectively. [Conclusion] During rice growth under flooded pot experiment, the immobilization and release of amended substrate nitrogen by microbe and crystal cell was a dynamic process. URSP obviously influenced the sink of SMBN and fixed ammonium.