^(15)N交叉标记有机与无机肥料氮的转化与残留

Nitrogen transformation and its residue in pot experiments amended with organic and inorganic ^(15)N cross labeled fertilizers

有机无机肥配施能够培肥土壤,改善土壤氮素供给,但目前有机无机肥配施主要集中在化肥氮的研究,忽略秸秆氮对化肥氮转化的影响。为了解秸秆还田对不同氮源转化和残留的影响,采用15N对尿素和水稻秸秆进行交叉标记,在两种不同肥力水稻土(粘土矿物类型为1∶1型红黄泥和2∶1型紫潮泥)进行水稻盆栽试验。设置对照(CK),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)4个处理。结果表明,水稻吸收的氮素60%以上来自土壤氮,土壤氮素肥力相对较低的红黄泥较之紫潮泥对肥料氮的依赖更强;水稻生长期间微生物同化的尿素氮占标记底物的百分数红黄泥为1.8%-8.3%,紫潮泥为1.8%—19.2%;微生物同化的秸杆氮占标记底物的百分数红黄泥为1.7%-5.0%,紫潮泥为2.0%-6.2%。而粘土矿物固持的尿素氮占标记底物的百分数,红黄泥为0.3%-2.1%,紫潮泥为3.5%-18.7%;粘土矿物固持的秸杆氮红黄泥为0.2%-0.9%,紫潮泥为1.7%-5.0%。水稻成熟期尿素氮的残留率,红黄泥15NU处理、15NU+S分别为14.5%和17.0%,紫潮泥分别为16.9%和17.1%。秸秆氮的残留率分别为红黄泥38.8%、紫潮泥41.5%;有机无机肥配施提高了微生物同化化肥氮的能力,降低了粘土矿物晶格固持化肥氮的水平。有机无机配施提高了化肥氮利用率同时,提高了有机形态氮残留,降低了无机形态氮(矿质氮+固定态铵)的残留。

Application of chemical fertilizer incorporated with rice straw can improve soil fertility and N supply.In most of such experiments,however,attention was mainly paid to the function of chemical fertilizers while the effect of the straw N on the transformation of N from chemical fertilizers was to certain extent neglected.In order to investigate the effect of rice straw application on the transformation and residue of N from different fertilizers,pot experiments with two different types of soils（Reddish yellow clayey soil,1 ∶ 1 type,low fertility level and Purple alluvial clayey soil,2：1 type,high fertility level） were conducted by applying the 15N cross labeled technique with urea and rice straw as the N sources.The designed experiments included four treatments and 8 replications（total 64 pots including pots for sampling）： the control（CK with no N application）,labeled urea（15NU）,combination of labeled urea and rice straw powder（15NU-S） and the combination of labeled rice straw power and urea（15NS-U）.The results obtained from the experiments indicated that the uptake rate of the soil native N by rice exceeded 60% while that of the applied N in the low fertility level soil（Reddish clayey soil） was higher than in the high fertility level soil（Purple alluvial soil）.During the rice growth period,the assimilation percentages of the labeled urea N by microorganism in reddish clayey and purple alluvial soils were 1.8%-8.3% and 1.8%-19.2%,respectively,while those of the labeled rice straw N in these two types of soils were 1.7%-5.0% and 2.0%-6.2%,respectively.The fixation percentages of the labeled urea N by soil clay were 0.3%-2.1% and 3.5%-18.7% while those of the labeled rice straw N were 0.2%-0.9% and 1.7%-5.0% in reddish clayey and purple alluvial soils,respectively,.The residue percentages of the labeled urea N of 15NU in reddish clayey soil and purple alluvial soil and were 14.5% and 16.9% respectively;while those of 15NU＋S in both soils were 17%.The residue percentage of the rice straw N in reddish clayey soil and purple alluvial soil were 38.8% and 41.5%,respectively.In conclusion,the combined application of urea and rice straw increased the assimilation rate of urea N by microorganism and decreased the fixation level of urea N by soil clay.In addition,the combined application increased both the N uptake rate by crops and the residue quantity of organic N from exogenous N associated with decreased inorganic N residue from exogenous N.