李世清,王瑞军,李紫燕,李凤民,邵明安,李生秀.干旱半湿润农田生态系统不可忽视的土壤氮库-土壤剖面中累积的硝态氮[J].干旱地区农业研究,2004,(4):1~13
干旱半湿润农田生态系统不可忽视的土壤氮库-土壤剖面中累积的硝态氮
Soil nitrogen pool not to be ignored residual NO-3-N Accumulated in soil profile in semiarid and semihumid agro-ecological system
  
DOI：10.7606/j.issn.1000-7601.2004.04.01
中文关键词:  半干旱区  半湿润区  农田生态系统  土壤残留硝态氮
英文关键词:semiarid area  semihumid area  agro-ecological system  residual nitrate nitrogen in soil
基金项目:青年科学基金项目(面上项目);重点项目;科学部主任基金项目;委主任基金项目;地区科学基金项目(面上项目);自由申请项目(面上项目);高技术新概念新构思探索项目;重大项目;重点实验室研究项目基金（专项基金）;研究成果专著出版基金（专项基金）;国家杰出青年科学基金（专项基金）;数学天元基金（专项基金）;科学仪器基础研究专款（专项基金）;委托任务;国家基础科学人才培养基金
作者单位
李世清 中国科学院水利部水土保持研究所,黄土高原土壤侵蚀与旱地农业国家重点实验室,陕西,杨凌,712100
西北农林科技大学资源环境学院,陕西,杨凌,7121003 
王瑞军 西北农林科技大学资源环境学院,陕西,杨凌,7121003 
李紫燕 西北农林科技大学资源环境学院,陕西,杨凌,7121003 
李凤民 中国科学院水利部水土保持研究所,黄土高原土壤侵蚀与旱地农业国家重点实验室,陕西,杨凌,712100 
邵明安 中国科学院水利部水土保持研究所,黄土高原土壤侵蚀与旱地农业国家重点实验室,陕西,杨凌,712100 
李生秀 西北农林科技大学资源环境学院,陕西,杨凌,7121003 
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中文摘要:
      为了有效利用氮肥,减少残留NO-3-N在土壤剖面中的累积,在位于半干旱半湿润地区的陕西岐山、杨凌、澄城和甘肃的定西,我们连续几年对不同试验处理条件下土壤剖面中残留NO-3-N的累积强度及其影响因子进行了系统研究.研究结果表明,在半干旱半湿润农田生态系统石灰性土壤剖面中累积着大量的残留NO-3 -N.在所有测定土壤剖面中,NH4+ -N含量和累积量不仅在不同土层中差异不大,而且在不同生态系统和管理条件土壤剖面中的差异也不大,其含量变化在1～3 μgN/g 之间,累积量相当于14～42 kg/hm2, 平均28 kg/hm2,显著小于残留NO-3-N.残留NO-3-N累积量平均占总矿质氮(NO-3-N+NH4+ -N)累积量的75%以上,是土壤剖面中可浸取态矿质氮的主体.在岐山测定的129个土壤剖面中,0～100 cm土层残留NO-3-N累积量小于50 kg/hm2的有26个,占20%, 大于70 kg/hm2的有86个,占66.7%,大于100 kg/hm2的有47个,占36%,大于140 kg/hm2的有13个,占10%,每季作物吸氮量大约是70 kg/hm2,说明在目前施肥和生产水平下,有66.7%田块0～100 cm土层中的残留NO-3-N最少与1季作物吸氮量相当;在杨凌、澄城、定西等地大部分试验小区(与当地一般施肥水平相当的小区),甚至有些不施氮肥对照小区土壤剖面中残留的NO-3-N与1季作物的吸氮量也基本一致.这些结果充分说明,在半干旱农田生态系统石灰性土壤剖面中残留累积的NO-3-N是不可忽视的有效氮库.因此,在估计土壤供氮水平和确定施氮量,或者在制定这一地区土壤供氮指标测定方法时,必须要充分考虑在一定土层土壤剖面中的残留NO-3-N.土壤剖面中的残留NO-3-N通过对流(Convection)和扩散(Diffusion)等途径,逐渐向深层移动, 脱离根区.在杨陵灌溉试验站和蔬菜试验站的测定结果表明,0～1 000 cm土层累积的NO-3-N分别高达1 295.6 kg/hm2和710.4 kg/hm2, 0～600 cm土层累积的NO-3-N分别为706.1 kg/hm2和435.1 kg/hm2.在200 cm土层以下累积着大量NO-3-N.在以上观测的2个剖面中,200～400 cm、400～600 cm、600～800 cm和800～1 000 cm各土层累积的NO-3-N数量显著大于0～200 cm土层,说明在上层(特别是在耕层)以各种途径增加的NO-3-N,通过长期淋溶,完全有可能脱离根区,淋溶到1 000 cm 以下土层.在不同试验区进行的所有试验结果均表明,与不施氮对照小区相比,施氮小区在作物收获时,土壤剖面中残留NO-3-N累积量呈增加趋势,并随施氮量增加,残留累积量增加.在杨凌和澄城进行的长期定位试验表明,连续施用氮肥,特别是高量氮肥田块,土壤剖面中残留NO-3-N与不施氮对照之间的差异很大:在杨凌长达25 a的长期定位试验中,NP处理0～120 cm土层残留NO-3-N累积量(163.4 kg/hm2)比不施肥对照(51.8 kg/hm2)增加111.6 kg/hm2,如果在施NP的基础上休闲,残留NO-3-N增加效果更加突出,比对照增加156.5 kg/hm2;试验还发现,在施NP的基础上,配施玉米秸秆,一定程度上能够降低残留NO-3-N累积量,并随秸秆用量增加,残留NO-3-N累积量下降;在澄城,连续4季作物施用氮肥后,从2个灌水处理平均结果看,与不施氮对照相比,在每季作物施氮量低(＜75 kg/hm2)时,不会发生NO-3-N残留累积,而当施氮量高于112.5 kg/hm2时,在0～120 cm土层中残留NO-3-N累积量显著增加.在杨凌进行的2次大田试验表明,无论是在降雨丰富年份,还是在干旱年份,休闲都能够显著增加土壤剖面中NO-3-N的累积量,并且不管在任何采样时期,休闲小区100～120 cm土层的NO-3-N含量均比复种玉米小区高,复种玉米能够减少残留NO-3-N在土壤剖面中的累积.由于地膜覆盖改变了土壤水热状况和生物性质,因而也必然影响土壤氮素转化过程,从而影响NO-3-N在土壤剖面中的累积.在定西进行的2 a试验结果表明,如果在春小麦播种后全生育期覆膜,能够显著增加收获时土壤剖面中残留NO-3-N的累积:1999年,不施氮时,增加9.4 kg/hm2,施氮后,增加88.9 kg/hm2;2000年,不施氮时,增加17.9 kg/hm2,施氮后,增加39.9 kg/hm2;定西试验还表明作物生育前期覆膜,后期揭膜,有利于减少残留NO-3-N在土壤剖面中的累积.在作物生长后期,地膜覆盖处理耕层土壤水分条件较好,温度较高,有利于土壤有机氮的矿化.而在这一时期,小麦对NO-3-N的吸收能力减弱,需要量减小,因而在土壤剖面中易产生残留NO-3-N的大量累积.小麦收获后,值降水较多期,累积的NO-3-N非常容易通过淋溶和反硝化损失,从这一角度考虑,在春小麦栽培中,不宜提倡全生育期地膜覆盖。
英文摘要:
      For effectively utilizing nitrogen fertilizer and reducing the accumulation of residualNO-3-N in soil profile, the accumulation of residual NO-3-N was studied systematically in Qishan, Yangling, Chengcheng of Shaanxi province and Dingxi of Ganshu province situated in semiarid and semihumid areas. In these experiments, the soil profiles under the different experimental treatments were collected. The results showed that quantities of residual NO-3-N were accumulated in calcareous soil of semiarid agro-ecological system. In all the measured soil profiles, the aontent and cumulative quantity of NH4+-N was not significantly diffferent not only in different soil layers but in the soil profiles under different ecological systems and management conditions, its content changed from 1 to 3μgN/g and the accumulative quantity was from 14 to 42 kgN/hm2, averaging 28 kgN/hm2, and the accumulative quantity was significantly less than that of NO-3-N. The NO-3-N accumulative quantity, on average, occupied more than 75% of that of total mineral nitrogen, and it was the principal parts of extracted mineral nitrogen. In the 129 measured soil profiles of Qishan county, there were 26 profiles(0～100 cm soil)whose accumulative quantity of residual NO-3-N was less than 50 kg N/hm2occupied 20%, the 86 profiles whose accumulative quantity of residualNO-3-N was more than 70 kg/Nhm2occupied 66.7%, the 47 profiles that its accumulative quantity of residual NO-3-N was more than 100 kgN/hm2occupied 36% and the 13 profiles whose accumulative quantity of residual NO-3-N was more than 140 kg/Nhm2occupied 10%, the nitrogen uptake of crops of every growing season was about 70 kg/Nhm2. These results indicated that the content of residual NO-3-N was equal to nitrogen uptake of crops in one growing season in 0～100 cm soil of 66.7% fields at least; in Yangling, Chencheng, Dingxi county and so on, the content of residual NO-3-N in soil profiles of most trial plots, even that of some plots in control plots of no nitrogen application were about equal to the nitrogen uptake of crops in one growing season. These results showed fully that the content of accumulative residual NO-3-N in calcareous soil profiles of semiarid agro-ecological systems were available nitrogen pool not to be ignored. So residual NO-3-N in soil profile must be considered in determining supply capacity of soil nitrogen, or application of nitrogen fertilizer, or the method of determination of soil supply nitrogen index in these areas. The residual NO-3-N of soil profile gradually moved to the deep layers through convection and diffusion and so on, gotten out of root region. The determined results in the Vegetable Experimental Station and Irrigation Experimental Station showed that the content of NO-3-N accumulation in 0～1 000 cm soil layers was respectively 1 295.6 kgN/hm2and 710.4 kgN/hm2, that in 0～600 cm soil layers was respectively 706.1 kgN/hm2and 435.0 kgN/hm2, a large amount of NO-3-N was accumulated under 200 cm soil layers in two observed soil profiles, the amount of NO-3-N accumulation in 200～400 cm, 400～600 cm, 600～800 cm and 800～1 000 cm soil layers were significantly higher than that of NO-3-N accumulation in 0～200 cm soil layers. This indicated that the added NO-3-N in surface soil by all the ways could completely take off root region and leach to the soil layers under 1 000 cm through long-term leaching. All the trial results in different experimental areas showed that, compared with plots of no nitrogen fertilizer application plot, the contents of accumulative residual NO-3-N in nitrogen fertilizer application plot soil appeared increasing trends when crops were harvesting, and it increased with the rate of nitrogen fertilizer application. The long-terms experiment in Yangling and Chengcheng showed that the difference between residual NO-3-N in soil profiles and the plot of no nitrogen fertilizer application was bigger when nitrogen fertilizer was successively applied, especially applying the high rate of nitrogen fertilizer; In the long-term experiment of Yangling in 25 years, the amount of residual NO-3-N accumulation of 0～120 cm layer in the treatment of N+P was 163.4 kgN/hm2increased by 111.6 kgN/hm2compared with CK of no fertilization 51.8 kgN/hm2, If combining N+P treatment with fallow, the effect of increasing of residual NO-3-N was more significantly and increased by 156.5 kgN/hm2compared with the CK. The experiment also showed that the amount of residual NO-3-N accumulation could be reduced to some extent if combined N+P treatment with corn straws, and the amount of NO-3-N accumulation decreased with increasing of the amount of corn straws, compared with CK of no nitrogen fertilizer application, the residual NO-3-N couldn't accumulate when the rate of nitrogen fertilizer application in every season was low through successive nitrogen fertilizer application for crops in 4 慳捥捡畳浯畮汳愠瑩敮搠?楨湥?瑧档敨?獮潧椠汣?灵牮潴晹椻氠敢獵???晨瑥攠牣?睮桴敥慮瑴?桯慦爠癲敥獳瑩??牡慬椠湎晏愼汳汵?椾猭?愯汳獵潰￣瘼敳牵祢￣爳椼振桳??猾漭?爠敡獣楣摵畭慵汬?乴佥?猠畩灮????猲田瀠??猠畳扯????獡畹扥??丠?睮慣獲?敡慳獥楤氠祳?汧潮獩獦敩摣?瑮桴牬潹甠杷桨?汮攠慴捨桥椠湲条?慥渠摯?搠敮湩楴瑲牯楧晥楮挠慦瑥楲潴湩??智牥潲洠?瑰桰楬獩?灡潴楩湯瑮?潷晡?瘠楧敨睥??灴汨慡獮琠椱挱′昮椵氠浫?济甯汨捭格楳湵杰￣昲漼爯?瑵桰放?睔桨潥氠整?杯爠潦睩楥湬杤?灥數牰楥潲摩?獥桮潴畳氠摩湮?瑙?扮敧?慩摮癧漠捳慨瑯敷摥?椠湴?瑡桴攬?捩畮氠瑴畨牥攠?潥晡?睳栠敥慩瑴?er of enough rainfall or arid, fallow can significantly increase the quantity of residual NO-3-N in soil profiles, and the content of NO-3-N in 100～200 cm layers of fallow plot was higher than that in multiple corn plots, so multiple corn could reduce the content of residual NO-3-N accumulation in soil profile. Film mulching must relate to the soil nitrogen transformation processes which have significant relationship with soil biological process, thus it also affected the accumulation of residual NO-3-N in soil profile. The results of 2-year experiment in which spring wheat was used as indicating crop showed that plastic film mulching for the whole growing period after harvest could significantly increase accumulation of residual NO-3-N in soil profiles after harvest; it increased by 9.4 kgN/hm2in 1999 and 17.9 kgN/hm2in 2000 under no nitrogen fertilizer application condition; it also increased by 88.9 kgN/hm2in 1999 and 39.9 kgN/hm2in 2 000 under nitrogen fertilizer application condition; but plastic film mulching at the former growth stage and no mulching at the latter growth stage had advantage to reduce the accumulation of residual NO-3-N in soil profiles. At the latter growth stage, soil water condition in tilth layers was better and temperature was higher, so it also was beneficial to the mineralization of soil organic nitrogen, but at this stage, the uptake power of wheat to NO-3-N became weak and the requirement of NO-3-N became low, therefore, the amount of residual NO-3-N was
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