干旱区生态环境知识资源中心(Arid): 半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

Arid

	半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
其他题名	Soil nitrogen pool not to be ignored residualNO3--N Accumulated in soil profile in semiarid and semihumid agro-ecological system
	李世清 1; 王瑞军 2; 李紫燕 2; 李凤民 1; 邵明安 1; 李生秀 2
来源期刊	干旱地区农业研究
ISSN	1000-7601
出版年	2004
卷号	22 期号:4 页码:1-14
中文摘要	为了有效利用氮肥,减少残留NO3--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NO3--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NO3- -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 mugN/g 之间,累积量相当于14～42 kg/hm2, 平均28 kg/hm2,显著小于残留NO3--N.残留NO3--N累积量平均占总矿质氮(NO3--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NO3--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NO3--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NO3--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NO3--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NO3--N.土壤剖面中的残留NO3--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NO3--N分别高达1 295.6 kg/hm2和710.4 kg/hm2, 0～600 cm土层累积的NO3--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NO3--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NO3--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NO3--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NO3--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NO3--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NO3--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NO3--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NO3--N累积量,并随秸秆用量增加,残留NO3--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NO3--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NO3--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NO3--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NO3--N含量均比复种玉米小区高,复种玉米能够减少残留NO3--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NO3--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NO3--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NO3--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NO3--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NO3--N的大量累积.小麦收获后,值降水较多期,累积的NO3--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 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 re-sults showed that quantities of residual NO_3~--N were accumulated in calcareous soil of semiarid agro-eco-logical system. In all the measured soil profiles, the aontent and cumulative quantity of NH_4~+- N was not significantly diffferent not only in different soil layers but in the soil profiles under different ecological sys-tems and management conditions, its content changed from 1 to 3mugN/g and the accumulative quantity was from 14 to 42 kgN/hm~2, averaging 28 kgN/hm~2, 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 ctnsoiDwhose accumulative quantity of resid-ual NO_3~--N was less than 50 kg N/hm~2 occupied 20%, the 86 profiles whose accumulative quantity of residual NO_3~--N was more than 70 kg/Nhm~2occupied 66. 7%, the 47 profiles that its accumulative quan-tity of residual NO3~-N was more than 100 kgN/hm~2 occupied 36% and the 13 profiles whose accumula-tive quantity of residual NO_3~--N was more than 140 kg/Nhm~2 occupied 10%, the nitrogen uptake of crops of every growing season was about 70 kg/Nhm~2. 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 accumu-lative residual NO_3~--N in calcareous soil profiles of semiarid agro-ecological systems were available nitro-gen 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 Veg-etable Experimental Station and Irrigation Experimental Station showed that the content of NO_3~--N accu-mulation in 0~l 000 cm soil layers was respectively 1 295. 6 kgN/hm~2 and 710. 4 kgN/hm~2, that in 0~600 cm soil layers was respectively 706.1 kgN/hm~2 and 435. 0 kgN/hm~2, a large amount of NO_3~--N was ac-cumulated 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~l 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 fertil-izer 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 fertilizers In the long-term experiment of Yangling in 25 years, the amount of residual NO_3~--N accumu-lation of 0~120 cm layer in the treatment of N+P was 163. 4 kgN/hm~2 increased by 111. 6 kgN/hm~2 com-pared with CK of no fertilization 51. 8 kgN/hm~2, 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/hm~2 compared 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 de-creased 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 seasons in Chengcheng county; but the content of residual NO_3~--N accumulated in 0~120 cm soil layers increased significantly when the rate of nitrogen fertilizer application was gher than 112. 5 kgN/hm~2. The two field experiments in Yangling showed that, in the years either 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 pro-cesses which have significant relationship with soil, biological process, thus it also affected the accumula-tion 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 sig-nificantly increase accumulation of residual NO_3~- -N in soil profiles after harvest; it increased by 9. 4 kgN/hm~2 in 1999 and 17.9 kgN/hm~2 in 2000 under no nitrogen fertilizer application condition; it also in-creased by 88.9 kgN/hm~2 in 1999 and 39. 9 kgN/hm~2 in 2 000 under nitrogen fertilizer application condi-tion; 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 min-eralization 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 accumulat-ed in the soil profiles. After wheat harvest, rainfall is also very rich, so residual NO_3~-- N was easily lossed through leaching and denitrification, from this point of view, plastic film mulching for the whole growing period shouldn’t be advocated in the culture of wheat.
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
语种	中文
国家	中国
收录类别	CSCD
WOS类目	AGRICULTURE MULTIDISCIPLINARY
WOS研究方向	Agriculture
CSCD记录号	CSCD:1802025
来源机构	西北农林科技大学 ; 中国科学院水利部水土保持研究所
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/204989
作者单位	1.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, 杨凌, 陕西 712100, 中国; 2.西北农林科技大学资源环境学院, 杨凌, 陕西 712100, 中国
推荐引用方式 GB/T 7714	李世清,王瑞军,李紫燕,等. 半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]. 西北农林科技大学, 中国科学院水利部水土保持研究所,2004,22(4):1-14.
APA	李世清,王瑞军,李紫燕,李凤民,邵明安,&李生秀.(2004).半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.干旱地区农业研究,22(4),1-14.
MLA	李世清,et al."半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".干旱地区农业研究 22.4(2004):1-14.