【作者】 吕丽红；

【导师】 李世清；

【作者基本信息】 西北农林科技大学 ， 植物营养学， 2004， 硕士

【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，在位于半干旱和半湿润地区的陕西关中、陕北和甘肃的定西，我们采取不同土地利用方式、不同试验处理条件下的土壤剖面，系统研究了残留NO3- -N的累积强度及其影响因子。通过研究，获得的主要研究结果和新见解有：1. 在半干旱半湿润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的差异不大，而且在不同生态系统和管理条件下土壤剖面中的差异也不大，其含量显著小于残留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，0～100cm土层残留NO3- - N累积量小于50 kg N/hm2的有26个，占20%, 大于70 kg N/hm2的有86个，占66.7%，大于100 kg N/hm2的有47个，占36%，大于140 kg N/hm2的有13个，占10%，每季作物吸氮量大约是70kg N/hm2，说明在目前施肥和生产水平下，有66.7%田块0～100cm土层中的残留NO3- - N最少与1季作物吸氮量相当；在杨陵、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）土壤剖面中残留的NO3- - N，甚至有些不施氮肥对照小区中的残留NO3- - N也与1季作物的吸氮量基本一致。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。2. 从我们在关中地区采取的100个土壤剖面看，NH4+ - N含量和在一定土层中的累积量与岐山129个土壤剖面的情况基本一致，不受土层深度和不同土地利用方式的影响，硝态氮累积量不仅在不同土地利用方式下有很大差异，而且在相同土地利用方式下也存在一定差异：农田土壤0-100cm土层硝态氮累积量变化在56～1582kgN/hm2，果园土壤变化在93～6791kgN/hm2，菜地土壤变化在124～3459kgN/hm2。菜地和果园土壤剖面中的残留NO3- - N的累积量平均占可浸取态总矿质氮（NO3- - N+NH4+ - N）累积量的75%以上，在农田土壤中NO3- - N的平均累积量占可浸取态总矿质氮（NO3- - N+NH4+ - N）累积量的54%左右，由于菜地和果园施氮量远大于农田，土壤剖面中的残留硝态氮累积量较高，因此，残留硝态氮所占可浸取态总矿质氮比例较农田土壤高。随着果园年限的延长，0-100cm土层土壤剖面中累积的残留硝态氮呈显著增加的趋势，5～6年园龄果园硝态氮的累积量大部分分布在287~675 kg N/hm2之间；对10年以上园龄的果园，其硝态氮的累积大部分分布在708~3038 kg N/hm2之间。对于菜地土壤，大棚种植和露地种植土壤剖面中硝态氮的累积也存在明显差异：大棚种植平均为1388kgN/hm2(n=15)，而露地种植平均为866kgN/hm2(n=13)。在不同利用方式下0-100cm土层土壤中NH4+ -N的累积量相差不大，而且各个剖面中的变化幅度也比较小，在农田土壤中的变化范围为101～577 kg N/hm2；平均300 kg N/hm2，在菜地土壤中的变化范围为255 ～802 kg N/hm2；平均362 kg N/hm2，在果园土壤中的变化范围为178 ~1332 kg N/hm2，平均459 kg N/hm2；与农田土壤和菜地土壤相比，果园土壤中铵态氮的累积量和变化范围较大，但从总体上看，不同土地利用方式土壤剖面中铵态氮的累积量和变化范围较硝态氮小。 <WP=8>3. 在不同试验区进行的所有试验结果表明，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；在杨陵长达25年的长期定位试验中，NP处理0-120cm土层残留NO3- - N累积量（163.4kg N/hm2）比不施肥对照（51.8kg N/hm2）增加111.6 N/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 N/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。在安塞进行的长期定位试验表明，经过14年连续施用不同配合的肥料后，土壤剖面中硝态氮的残留累积存在显著差异，在只施用氮肥的情况下0-100cm土层中残留硝态氮的累积量（136.7kg N/hm2）最高，比对照（41.7kg N/hm2）增加95kg N/hm2；如果在施用氮肥的基础上配施有机肥，则残留硝态氮的累积量（99.4kgN/hm2）与只施氮肥相比有一定程度的降低，比对照增加57.8kg N/hm2；如果在施用氮肥的基础上同时配施有机肥和磷肥，则残留硝态氮的累积量（79.6kgN/hm2）进一步降低，比对照增加37.9kgN/hm2；仅施有机肥，残留硝态氮的累积量（70.4kgN/hm2）仍然高于对照，比对照增加28.7kgN/hm2；如果氮磷配合施用，残留硝态氮的累积量（41.0kgN/hm2），与对照相差不大；如果仅施磷肥，残留硝态氮的累积量（34.7kgN/hm2），与对照相比有一定程度的降低。安塞的试验结果与杨陵的试验结果基本相同，配施磷肥对土壤剖面中残留硝态氮的影响主要与促进了作物生长以及对土壤中硝态氮的吸收利用有关；配施有机物料对土壤剖面中残留硝态氮的影响主要与有机肥对土壤中氮素转换过程的影响有关。更多还原

【Abstract】 For utilizing nitrogen fertilizer effectively and reducing the accumulation of residual NO3--N in the soil profile, soil profiles under the different experimental treatments and different soil utilities were collected in Guanzhong of Shaanxi province, Shanbei of Shaanxi province and Dingxi of Gansu province situated in semiarid and semihumid areas，the accumulation intensity of residual NO3--N and influence factor was studied systematically. By research, the results and new viewpoints are as follow: 1. Large quantities of residual NO3--N were accumulated in calcareous soil of semiarid and semihumid agro-ecological system. In all the measured soil profiles, the content and cumulative quantity of NH4+-N was not significant diffference not only in different soil layers but in the soil profile under the different ecological system and management condition, the content is less than residual NO3--N remarkably. The NO3--N accumulative quantity, on average, occupied more than 75% of that of total mineral nitrogen, and it was the principal parts of extracting mineral nitrogen. In the 129 measured soil profiles of Qishan county, there are 26 profiles（0～100cm layers）that its accumulative quantity of residual NO3--N was less than 50kgN/hm2 occupied 20%, the 86 profiles that its accumulative quantity of residual NO3--N was more than 70 kg/Nhm2 occupied 66.7%,the 47 profiles that its accumulative quantity of residual NO3--N was more than 100kgN/hm2 occupied 36% and the 13 profiles that its accumulative quantity of residual NO3--N was more than 140 kg/Nhm2 occupied 10%, the nitrogen uptake of crops of every growing season was about 70 kg/Nhm2. These results indicated that the content of residual NO3--N was equal to nitrogen uptake of crops of one growing season in 0～100cn layers of 66.7% fields at lest; in Yangling, Dingxi county and so on, the content of residual NO3--N in soil profile of most of trial plot, even that of some plots of control plots of no nitrogen application were equal about to the nitrogen uptake of crops of one growing season. These results show fully that the content of accumulative residual NO3--N in calcareous soil profiles of semiarid agro-ecological systems are available nitrogen pool not to be ignored. So residual NO3--N in soil profile must be considered at determining supply capacity of soil nitrogen, or application of nitrogen fertilizer, or the method of determination of soil supply nitrogen index in these areas.2. See from the 100 soil profile samples collected from Guanzhong region, the content and cumulative quantity of NH4+-N are similar to the 129 measured soil profiles of Qishan county, not influenced by soil depth and land utilize. The accumulation of residual NO3--N in soil profile not only in different land utilize but also in same land utilize appeared notable differentia: the residual NO3--N accumulation of 0-100cm in cropland soil profiles changed from 56kgN/hm2 to 1582kgN/hm2; the residual NO3--N accumulation of 0-100cm in orchard soil profiles changed from 93kgN/hm2 to 6791kgN/hm2; the residual NO3--N accumulation of 0-100cm in vegetable land soil profiles changed from 124kgN/hm2 to 3459kgN/hm2. The <WP=11>NO3--N accumulative quantity in orchard or vegetable land soil profiles, on average, occupied more than 75% of that of total mineral nitrogen, but in cropland soil profiles, the NO3--N accumulative quantity , on average, occupied 54%. Because of the applied N fertilizer in orchard or vegetable land soil profiles is much more than that in cropland soil profiles, and the residual NO3--N accumulation of 0-100cm is higher than that in cropland soil profiles, as a result, the proportion of the residual NO3--N accumulation of 0-100cm in orchard or vegetable land soil profiles is higher than that in cropland soil profiles. With the years long, the residual NO3--N accumulation of 0-100cm in orchard appeared increasing trends, the residual NO3--N accumulation of 0-100cm in orchard soil profiles about 5～6 years mostly changed from 287kgN/hm2 to 675kgN/hm2，but to the orchard more than更多还原