水稻、黄瓜幼苗生育及氮素代谢的研究——低pH无机态氮的同化

采用培养液pH自动调节装置,研究水稻、黄瓜11个品种,在低pH条件下,幼苗生育及无机态氮的同化。结果表明:不同处理6个水稻品种的干物质增长量比较接近;5个黄瓜品种对pH较为敏感;水稻、黄瓜对NH_4-N的吸收速率比较稳定。pH3.8处理水稻对NH_4-N的吸收速度约占pH6.0的1/2;黄瓜对NO_3-N的吸收易受pH的影响。水稻Rieciasominon品种体内可溶性~(15)N含量占吸收~(15)N总量的百分比顺序为:AL[pH3.8(~(15)NH_4)_2SO_4]>NL[pH3.8Na~(15)NO_3]>AH[pH6.0(~(15)NH_4)_2SO_4]>NH[pH6.0Na~(15)NO_3];黄瓜幸风品种为:AH>AL>NH>NL。     

Nitrate-N loadings through subsurface environment to agricultural drainage ditches in two flat Midwestern (USA) watersheds

A study was conducted to understand the contributions of tile flow and baseflow to total nitrate-N (NO₃-N) loadings in two subsurface (tile)-drained watersheds, namely the Big Ditch (BD) and the Upper Embarras River (UER) watersheds in Illinois. Two stream sections were selected in the watersheds and rectangular cutthroat flumes were installed at the upstream and downstream ends of the stream sections to calculate the flow mass balance for separating baseflow. The stream section at BD site had two tile outlets draining into it. The stream section at UER watershed did not have any tile drain. Tile flow was also measured along with stream flow. Water samples were collected not only from the stream sections using auto-samplers but also manually from the tile drains. Average baseflow rates per unit lengths of the stream sections at BD and UER sites were 3.5 × 10⁻⁰⁴ and 9.4 × 10⁻⁰⁵ m² s⁻¹, respectively. At BD site, for six study periods, the percentages of baseflow and tile flow contributions of NO₃-N loads within the stream section were 90 and 10%, respectively. Annual NO₃-N contributions by the upstream subwatersheds for BD and UER stream sections were 61,819 and 16,155 kg, respectively. Annual NO₃-N loss from these two subwatersheds within BD and UER watersheds was 42.9 and 7.0 kg ha⁻¹, respectively. For the stream section at BD site, baseflow seemed to play a more important role than tile flow in raising the NO₃-N concentration level in the stream water. Land use seemed to play a major role in the significant difference in NO₃-N concentrations at the two subwatersheds upstream from the project sites. Nitrate-N loadings primarily depended on precipitation, antecedent moisture condition (AMC), fertilizer application time, and evapotranspiration (ET).     

微生物菌剂对连栋大棚土壤养分及硝态氮累积的影响

笔者利用微生物菌剂对长期废弃的2hm2大棚进行改良处理,通过测定试验前土壤重金属、农药残留情况和土壤基本理化性状,以及处理后土壤pH、EC、有机质、有效磷、硝态氮含量的变化,分析不同施肥处理对土壤养分的改良效果以及对硝态氮累积的影响。研究结果表明：农村废弃大棚土壤重金属含量低于《土壤环境质量标准》的二级限值和《农用污泥中污染物控制标准》的限值,农药残留含量小于《土壤环境质量标准》的二级限值;对照、有机肥和菌剂复合处理使0~5cm表层土壤pH上升;有机质、菌肥、有机肥和菌剂复合处理能提高土壤EC值以及土壤养分含量,且与对照存在着差异;3个施肥处理增加了表层的硝态氮含量,存在着表聚现象,但在5~30cm土层中,各处理土壤硝态氮含量比试验前均减少。可得出结论,该地块没有受到重金属和农药残留污染;在不同施肥处理中,施用有机肥+菌剂复合处理能显著提高土壤pH、有机质、有效磷含量,降低5~30cm土层中硝态氮含量。     

不同施氮方式对玉米田土壤无机氮动态变化的影响

研究不同施氮方式对玉米田土壤水分动态变化和土壤无机氮变化特征的影响。结果表明,玉米生育期不同施氮方式下,0~100 cm土壤水分变化趋势相似,非雨季0~20 cm土壤含水量施肥处理比不施肥(CK)低2~4个百分点,雨季由于降雨的补给各处理各层土壤水分无明显变化。施氮显著增加了0~100 cm土层无机氮含量。习惯施肥处理土壤硝态氮含量受降雨影响较大,表现出向土壤深层迁移的趋势;缓控释肥、优化施肥和优化施肥+秸秆还田处理可降低土壤硝态氮的残留。0~40 cm土壤铵态氮含量受基肥和追肥影响较大,41~100 cm土壤铵态氮含量为3~5 mg/kg,变化幅度较小,趋于稳定。合理的氮肥用量及施氮方式,可有效减少土壤硝态氮的残留,减轻浅层地下水硝态氮污染的风险。     

两种作物对土壤不同层次标记硝态氮利用的差异

 利用15N层标记的土柱试验法，研究了蔬菜和大田种植体系中菠菜、小麦两种作物及小麦的两个品种对土壤不同层次标记硝态氮利用的差异。结果表明，菠菜对土壤10～20、40～50、70～80 cm层次标记硝态氮的利用率分别为40.7%、29.9%、23.4%，小麦两个品种小偃54和京411利用率分别为45.5%、16.1%、7.7%和32.5%、12.4%、4.7%。菠菜对土壤不同层次标记硝态氮的利用率显著大于小麦，小偃54对土壤不同层次标记硝态氮的利用率显著高于京411。作物的根长密度与相应土层标记硝态氮的利用率呈显著的正相关关系。作物收获后土壤剖面NO-3-N含量分布的总体趋势是菠菜小于小麦，小麦品种间为小偃54小于京411。土壤10～20 cm层次的标记NO-3-N峰下移到40～50 cm， 40～50 cm层次标记NO-3-N没有发生明显移动，而70～80 cm层次标记NO-3-N可见较为明显的上移趋势，并在60 cm左右出现累积峰。菠菜和小麦之间、小麦品种之间土壤不同层次标记NO-3-N的移动距离没有显著差异。     

An evaluation of plant-available soil nitrogen in selected sandy soils by electro-ultrafiltration, KCl, and CaCl2 extraction methods

 Improving the precision in estimating the nitrogen (N) requirement for citrus trees on sandy soils is important for increasing N efficiency by the trees and minimizing potential losses of N in commercial citrus production areas. In this study, representative Florida soils were sampled from major citrus production areas and the electro-ultrafiltration (EUF) technique was used to measure the concentrations of total EUF-extractable nitrogen (EUF-N_t), ammonium-N (EUF-NH₄ ⁺–N) and nitrate-N (EUF-NO₃ ^––N). Available organic N (N_org) was calculated as: EUF-N_t–(NH₄ ⁺–N+NO₃ ^––N). The N concentrations in the EUF extraction were greater than those by the KCl or CaCl₂ method. The N_org fraction, estimated by the EUF method, varied from 4.4 to 40.8 mg kg^–1 soil, equivalent to 10 to 91 kg N ha^–1 (for the top 15 cm depth soil) and was positively correlated with the total soil N determined by the Kjeldahl method. The presence of appreciable amounts of N_org in these soils indicates that these soils contain high proportions of the total soil N in easily mineralizable N_org forms. This study demonstrates that the EUF-extractable organic bound N must be considered in developing N fertilizer recommendations for citrus. Received: 13 January 1999     

冬小麦—夏玉米轮作体系优化施氮对土壤硝态氮的影响

为了建立小麦/玉米轮作体系下的作物营养诊断推荐施肥技术体系,确定最佳施肥方案,对不同施肥方式下每一季作物进行硝态氮、产量、施肥量进行观测。结果表明,不同的施肥处理对作物产量影响显著,优化施肥产量提高2.73%~6.39%。不施肥处理条件下,二、三季作物产量显著降低,四季作物减产幅度趋于平衡;长期优化施肥使0~60 cm土壤硝态氮含量维持在同一个水平,而长期习惯施肥则使土壤硝态氮含量有增高的趋势;长期不施肥使土壤硝态氮含量稳定在较低水平;优化施肥节约化肥36.84%~52.97%。上述三种施肥方式以优化施肥最佳。     

硝态氮与铵态氮对西伯利亚百合生长的影响

[目的]研究不同氮素形态对西伯利亚百合生长的影响。[方法]用营养液培养法,先对健康植株进行缺氮培养,再提供NO3--N与NH4+-N2种不同形态的氮肥,待生长稳定后测定相关生理指标。[结果]不同形态的N对植物各项生理指标的影响不同。NO3--N对硝酸还原酶活性有促进作用,其活性除在最高施用水平50 mmol/L受到抑制外,随着施用水平的升高而增强;NH4+-N对硝酸还原酶活性有一定的抑制作用。NO3--N处理百合叶片中的可溶性糖含量、可溶性蛋白含量、淀粉酶活性普遍高于NH4+-N处理,但NH4+-N处理百合叶片中还原性糖含量普遍高于用NO3--N处理。[结论]硝态氮是西伯利亚百合生长较好的氮素形态。     

氮素对不同来源大豆氮代谢相关指标的影响

在田间条件下,以12个不同来源大豆品种为试验材料,采用二因素裂区设计,研究了不同大豆品种间叶片氮代谢相关指标的差异,以及氮素对叶片氮代谢相关指标的影响.结果表明:氮肥处理对不同来源大豆品种叶片氮代谢指标影响不同,不同生育时期大豆对氮肥的反应也有所差别.施肥处理会降低开花期辽宁当代品种叶片的谷氨酰胺合成酶(GS)活性;中等肥力处理(100 kg hm-2)会提高结荚期俄亥俄当代品种叶片的GS活性,而高肥处理则会降低该酶的活性;辽宁当代品种和辽宁老品种叶片GS活性随着施氮量的提高而降低.在鼓粒期,中等肥力处理会提高俄亥俄当代品种和辽宁当代品种叶片的GS活性,而施肥处理会降低辽宁老品种的GS活性.在开花期,三组不同来源品种叶片的硝态氮含量均随着施氮水平的提高而增加.施肥处理能显著提高叶片的氨态氮含量.     

太湖地区水稻土的硝态氮穿透曲线及影响因素

用模拟土柱的方法对太湖地区三种主要水稻土的硝态氮垂直运移穿透曲线和影响因素进行了研究。结果表明:对同一种土壤而言,土层由上往下土层的出流速度减慢,硝态氮的穿透过程推迟。对这三种土壤而言,乌栅土的各土层的平均流量最小,穿透时间最长。在水分饱和和充分淋洗的条件下,硝态氮能完全穿透土柱,硝态氮的垂直运移过程主要受土壤粘粒含量的影响,随着粘粒含量的增加出流速度减小,硝态氮的穿透开始时间推迟,硝态氮的穿透曲线峰值变低、峰面分布变宽,穿透曲线变化平缓。所有的穿透曲线都显得不对称,粘粒含量越高的土壤越有明显的拖尾现象。土壤容重和有机质含量对硝态氮的垂直运移有很大的影响;容重越小、有机质含量越高,出流的流量就越大,穿透开始的时间也就越提前;有机质与穿透总时间有极显著的相关性;有机质含量越高,穿透总时间就越短。