宁夏引黄灌区猪粪还田对稻作土壤硝态氮淋失的影响

以宁夏引黄灌区稻田为例,探索猪粪还田条件下稻田土壤硝态氮淋失规律。试验设置3个处理:常规施肥300 kg纯N kg/hm2(CK)、常规施肥条件下施用4500kg/hm2(T1)和9000 kg/hm2(T2)猪粪。利用树脂芯法吸附稻田30cm、60cm和90cm土层的硝态氮流失量。结果表明:在常规施肥的基础上增施猪粪,可以减少稻田生育期内60cm与90cm处土壤硝态氮淋失量,与CK相比,T1、T2在两个土层处淋失量的减少比例分别为4.93%、13.92%与7.48%、13.77%。同一土层不同处理之间差异显著性比较看(P0.05),30cm处T1、T2与CK相比没有达到显著性差异;60cm处,T1与CK未达到显著差异,T2与CK达到显著差异;90cm处,T1、T2与CK相比达到显著差异;60cm和90cm土层处的T2与T1之间均达到显著差异。T1和T2在30cm处的淋失量高于CK,但增加不明显,处理之间以及处理与对照相比差异不显著。稻田生育期内不同土层硝态氮淋失量在13.61—17.77 kg/hm2(纯N)。硝态氮淋失集中在插秧至分蘖期(5月中旬—6月下旬),该阶段的硝态氮淋失量占生育期内总淋失量的61.62%—72.84%;后期淋失量明显减少。处理T1、T2的水稻产量增产率分别为15.86%与12.85%。由此可见,在引黄灌区稻田,一定数量的猪粪还田,不仅能够减少土壤硝态氮向深层淋失,防控地下水污染,还有利于水稻增产。     

基于秸秆还田条件下的黄灌区稻旱轮作土壤硝态氮淋失特征研究

宁夏引黄灌区农田面源污染较为严重,区内大部分排水沟水质为劣Ⅴ类,其主要污染物硝态氮与铵态氮。设置常规施肥(CK)、常规施肥条件下施用4500kg/hm~2(T1,半量还田)和9000 kg/hm~2(T2,全量还田)秸秆3个处理。利用树脂芯法吸附10、20、30、60、90cm土层的硝态氮流失量。2009—2013年的试验结果表明:秸秆还田能够减少土壤30cm土层的硝态氮淋失。与对照硝态氮淋失量(15.76 kg/hm~2)相比,T1(13.76 kg/hm~2)与T2(13.74 kg/hm~2)均达到显著差异(P0.05),淋失量分别减少12.71%和12.84%,T1与T2没有达到显著差异。秸秆还田对土壤硝态氮淋失的影响效应主要体现在30cm土层处,10、20、60与90cm土层处的处理与对照都没有达到显著差异。秸秆还田提高了30cm土层的土壤有机质与土壤总氮,与对照(13.78 g/kg)相比,T1与T2土壤有机质分别提高0.89 g/kg和1.24 g/kg;试验结束后,对照、T1和T2的总氮是达到0.64、0.66和0.69 g/kg,与对照相比,处理分别提高了2.76%和6.83%。秸秆还田有助于作物增产,T1与T2的水稻平均增产9.24%和10.37%,小麦增产10.11%和11.51%。     

宁夏引黄灌区猪粪还田对麦田土壤硝态氮淋失的影响

以宁夏引黄灌区为例,探索猪粪还田条件下冬小麦田土壤硝态氮淋失规律.试验设置3个处理:常规施化肥225 kg N·hm-2(CK)、常规施肥基础上施用4500 kg·hm-2(T1)和9000 kg·hm-2(T2)猪粪.利用树脂芯法吸附30、60和90 cm土层的硝态氮淋失量.结果表明:在常规施肥基础上增施猪粪,小麦生育期土壤硝态氮(纯N)淋失量为9.33~14.04kg·hm-2,占施N量的4.2%~6.2%.与CK相比,30 cm土层T1、T2的硝态氮淋失量增加2.6%和2.1%;60 cm土层增加1.5%和减少1.3%;90 cm土层减少8.7%和增加4.0%.增施猪粪与对照在30、60和90 cm土层处的硝态氮淋失量均无显著差异,而在深层土壤表现出减少趋势.硝态氮淋失主要发生在返青至灌浆期间,日均淋失量高于全生育期平均水平,该阶段的硝态氮淋失量占生育期内总淋失量的58.7%~75.3%.T1、T2春小麦产量比对照分别增加9.3%和12.5%.     

宁夏黄灌区稻田冬春休闲期硝态氮淋失量

对宁夏黄灌区稻田设置不同有机肥处理：常规施肥（CK）;常规施肥条件下分别施用4500 kg/hm2（T1）与9000 kg/hm2猪粪（T2）,采用树脂芯法测定了稻田冬春休闲期30 cm、60 cm、90 cm处的硝态氮流失量。结果表明,常规施肥条件下,90 cm处硝态氮淋失量最大,分别为T1、T2的1.10与1.13倍;在常规施肥基础上增施猪粪,硝态氮最大淋失量出现在60 cm土层,T1、T2的流失量分别为4.47 kg/hm2与4.21 kg/hm2,分别为该层CK淋失量的1.50与1.42倍。灌区稻田常规施肥基础上增施有机肥,能够减少硝态氮向深层淋失;但60 cm土层处硝态氮淋失量增加,为硝态氮的深层淋失提供了基础,但在灌区水旱轮作模式下,下季旱作灌水量明显减少,加之作物吸收,硝态氮淋失也将明显降低。     

有机肥对桃园土壤硝态氮分布的影响

于2004—2005年在北京市平谷区有机桃园设置不同有机肥处理：2年连续施有机肥,年均67 500 kg·hm^-2（T₁）;第一年不施肥,第二年施有机肥135 000 kg·hm^-2（T₂）;第一年不施肥,第二年施有机肥67 500 kg·hm^-2（T₃）;不施肥对照（CK）,并于2006年对0～120 cm土层土壤进行取样分析,研究施用有机肥对土壤硝态氮分布和淋失的影响.结果表明：对照土壤中硝态氮分布较均匀,T₁和T₃在0～120 cm土层硝态氮浓度变化呈单峰曲线,其中60 cm以上较高,在60～120 cm逐渐降低;而T₂土壤硝态氮浓度由浅到深逐渐增加,峰值出现在100～120 cm土层,其在60 cm以下土层的硝态氮浓度在所有处理中最高,说明过量施用有机肥易导致硝态氮的淋失.相关分析表明,土壤硝态氮的浓度和分布与多年施氮总量、最近一年施氮量和检测点与树的距离呈显著相关关系,并据此建立了有机肥施用与土壤剖面硝态氮浓度之间的相关模型.     

不同施肥条件下玉米田土壤养分淋溶规律的原位研究

利用排水采集器法结合田间原位试验,研究了夏玉米不同施肥处理对棕壤土养分淋失的影响.结果表明:在夏玉米生长期内,影响玉米田土壤水分淋溶的主要因素是大量降雨和灌溉,夏玉米生长前期的土壤淋溶水量较大,但随夏玉米生育进程的推进而递减,各处理差异也逐渐减小;与施氮肥处理相比,秸秆还田配施氮肥处理可加剧土壤水淋溶.在夏玉米生长期内,施肥处理的土壤淋溶水硝态氮浓度均呈"双峰"曲线变化趋势,而铵态氮浓度则呈先升后降的变化趋势.玉米田土壤氮素淋失以硝态氮形式为主,其累计淋失量为12.90～46.53 kg·hm-2,铵态氮的累计淋仅为1.66～5.11 kg·hm-2,两种形态氮的淋失量都随施氮量的增加而升高.秸秆还田配施氮肥处理的氮素淋失率比单施氮肥处理高6.53%～13.07%,低氮处理的氮素淋失率比高氮处理高3.66%～10.10%;玉米田土壤速效磷的累计淋失量较小,仅为0.148～0.235 kg·hm-2,而速效钾的累计淋失量较大,为7.08～13.00 kg·hm-2.在夏玉米生长后期,秸秆还田配施氮肥处理使土壤速效磷淋失量升高,并可加剧土壤速效钾的淋失,而单施氮肥处理作用不明显.     

不同作物对旱地农田残留硝态氮的利用差异

在黄土高原南部娄土上,通过2a田间试验研究了小麦和苜蓿对土壤中不同累积量的残留硝态氮的利用差异。研究包括0—3 m土壤残留硝态氮累积量(设N1、N2、N3、N4、N5和N6共6个水平,残留硝态氮量依次增加)和作物种类(冬小麦和苜蓿)2个因素,分别采用冬小麦-夏休闲-冬小麦和苜蓿连作种植方式。结果表明,不施用氮肥条件下,冬小麦-休闲-冬小麦轮作周期与苜蓿连作2a内,土壤残留硝态氮的消长有明显差异。在第1季小麦生长期间,小麦的氮素携出量(63.9—130.3 kg/hm2)、氮素携出量占播前残留硝态氮量的比例(18%—27%)及氮素携出量占该生长季硝态氮减少量的比例(29%—62%)均显著高于同期的苜蓿处理。在第2个生长季内,苜蓿的氮素携出量是小麦当季氮素携出量的近6倍,但由于苜蓿固氮作用强烈,至第2生长季结束后,0—3 m土壤硝态氮量与苜蓿播前相比平均只减少了72.4 kg/hm2,而麦田0—3 m土壤硝态氮量与小麦播前相比减少了158.3 kg/hm2。在短期内如果通过种植作物消耗土壤剖面的残留硝态氮,冬小麦比苜蓿更有优势。第1季小麦氮素携出量与小麦播前0—2 m(r=0.920**)和0—3 m(r=0.857*)土层残留硝态氮量呈显著或极显著正相关,与0—1 m土层残留硝态氮量没有显著相关性;第1生长季苜蓿氮素携出量与播前0—1 m土壤硝态氮累积量呈显著正相关关系(r=0.846*),而与0—2 m和0—3 m土壤硝态氮累积量的相关性并不显著。小麦比苜蓿能利用更深土层中的硝态氮。随着播前0—3 m土壤残留硝态氮的增加,小麦和苜蓿地上部氮素携出量呈增加的趋势,硝态氮表观损失也显著增加。     

华北平原冬小麦/夏玉米轮作体系土壤硝态氮的适宜含量

采用冬小麦季不同施氮处理(夏玉米季不施氮)研究了华北平原冬小麦/夏玉米轮作体系夏玉米季土壤硝态氮的适宜含量.结果表明:在播前土壤无机氮含量较高的条件下,冬小麦季施用150kgN.hm-2即可满足冬小麦/夏玉米两季作物的氮素需求;各氮肥处理在冬小麦季的氮肥施用当季的利用率仅为11%～23%,在夏玉米季氮肥残效利用率则高达30%～52%.当夏玉米播前0～90cm土层硝态氮含量达到82kg.hm-2时,无需施氮即可保证夏玉米十叶期的生长,达到151kg.hm-2时,无需施氮即可保证整个生育期的生长.夏玉米十叶期和收获后0～90cm土层硝态氮含量低于46和65kg.hm-2时,则影响作物正常生长.综合考虑产量和环境效应,冬小麦/夏玉米轮作体系中0～90cm土层硝态氮含量应控制在65～151kg.hm-2之间.     

水氮配合对绿洲沙地农田玉米产量、土壤硝态氮和氮平衡的影响

在黑河中游边缘绿洲沙地农田研究了不同的水氮配合对玉米产量、土壤硝态氮在剖面中的累积和氮平衡的影响.结果表明,施氮处理较不施氮处理产量增加48.22%～108.6%,施氮量超过225 kg hm-2,玉米产量不再显著增加.受土壤结构影响土壤硝态氮在土壤中呈"W"型分布,即土壤硝态氮含量在0～20 cm、140～160 cm和260～300 cm土层均出现峰值,并随施氮量增加,峰值增高.在常规高灌溉量处理硝态氮含量峰值最高值出现在260～300 cm土层,节水25%灌溉处理硝态氮含量峰值最高值出现在土壤表层0～20 cm土层.在常规高灌溉量处理0～300 cm土层中200～300土层硝态氮累积量所占比例最高,介于27.56%～51.86%之间;节水25%灌溉处理在0～300 cm土层中100～200土层硝态氮累积量所占比例最高,介于32.94%～38.07%之间;表明低灌溉处理下土壤硝态氮在土壤浅层累积较多,而高灌溉处理使更多的硝态氮淋溶至土壤深层.与2006年相比,2007年不施氮处理0～200 cm土层土壤硝态氮含量和积累量均明显减少;而施氮处理变化很小,在低灌溉处理甚至表现出硝态氮含量和积累量增加,表明施氮是土壤硝态氮累积的主要来源,而灌溉则使硝态氮向土壤深层淋溶.0～200 cm 土层土壤硝态氮累积量平均介于27.66～116.68 kg hm-2、氮素表观损失量平均介于77.35～260.96 kg hm-2,和施氮量均呈线性相关,即随施氮量增加,土壤硝态氮累积量和氮素表观损失量均增加,相关系数R2介于0.79～0.99之间,相关均显著.随施氮量增加,玉米总吸氮量和氮收获指数增加,氮的农学利用率降低,而灌溉的影响较小.施氮量超过225 kg hm-2时,地上部植株氮肥吸收利用率和籽粒氮肥吸收利用率开始有降低趋势.所以,在沙地农田,节水10%～25%的灌溉水平和225 kg hm-2的施氮水平可以在避免水肥过量投入的基础上减少土壤有机氮淋溶对地下水造成的污染威胁.     

半干旱区农田土壤无机氮积累与迁移机理

研究黄土旱塬区长期定位试验中 1 0个典型处理土壤剖面 (0～ 30 0 cm)水分和无机氮的季节变化 ,探讨在半干旱区农田无机氮的积累与迁移机理。结果表明休闲处理除表层外土壤剖面的水分、硝态氮和铵态氮的含量分别稳定在 1 7%～ 2 0 %、4～ 7mg N/kg和 6～ 1 0 mg N/kg土的范围。种植作物显著地改变土壤剖面水分和硝态氮的分布状况 ,并使其含量发生大幅度的季节变化。作物利用限制了农田土壤硝态氮向深层的迁移。小麦连作无化肥氮处理及苜蓿连作不施肥或氮、磷加有机肥处理土壤硝态氮主要集中在 0～ 40 cm土层。小麦连作单施氮肥 (1 2 0 kg N/(hm2· a) )处理经 1 7年后土壤剖面硝态氮积累总量达到施氮总量的55% ,40～ 60 cm和 1 4 0～ 2 2 0 cm土层出现两个高峰 ,并表现出随季节性变化向土壤深层迁移的趋势。氮肥与磷肥或有机肥施用大幅度减少了土壤剖面硝态氮积累 ,并使其限制在 1 60 cm以上的土层内 ,2 0 0 cm以下土层的硝态氮含量极低 (<1 mg N/kg土 ) ,因而不具向深层迁移的条件。土壤剖面的铵态氮含量不受作物、施肥和季节性气候变化的影响     

关中地区小麦/玉米轮作农田硝态氮淋溶特点

通过田间原位淋溶装置研究了不同施氮量和秸秆覆盖对关中地区小麦/玉米轮作农田90cm深处硝态氮(NO3--N)淋溶量、0～1m土层硝态氮累积及作物产量和氮平衡的影响.试验设不施氮(N1,0kg·hm-2·a-1)、常规施氮(N2,471kg·hm-2·a-1)、推荐施氮(N3,330kg·hm-2·a-1)、减量施氮(N4,165kg·hm-2·a-1)、增量施氮(N5,495kg·hm-2·a-1)和推荐施氮+秸秆覆盖(N3+S)6个不同施肥处理.结果表明:NO3--N淋溶量随施氮量的增加而增大,氮肥的过量施用及秸秆覆盖易造成NO3--N淋溶.N3+S处理90cm处年NO3--N流失量最大,为22.32kg·hm-2,施肥造成的氮流失量为16.44kg·hm-2,比相同施氮量不覆盖处理(N3)高158.9%.NO3--N主要累积在20～60cm土层,年施氮量330kg·hm-2(N3)时,秸秆覆盖与否不影响NO3--N的剖面分布.各施肥处理对作物产量没有显著影响,但减量施氮处理(N4)有减少作物产量的趋势.在本试验条件下,推荐施肥量(小麦施氮150kg·hm-2,玉米施氮180kg·hm-2)在保证作物产量的同时,可减少土壤NO3--N的淋溶和累积.     

典型农作措施对沙溪庙组壤质紫色土坡耕地径流氮流失的影响

明确典型农作措施对紫色土坡耕地径流氮(N)流失的影响可为优化面源污染防控措施提供科学依据。基于2019—2021年沙溪庙组发育的壤质紫色土坡耕地不同降雨等级次降雨产流事件,分析了常规施肥(CK),优化施肥(T1)和优化施肥+秸秆还田(T2)措施下径流、径流中总氮(TN)、硝态氮(NO₃-N)及铵态氮(NH₄-N)流失浓度和流失量的变化特征。结果表明,与CK相比,T1和T2的径流深分别减小了4.24%、12.71%,但减小程度不显著(P>0.05);CK与T1的径流系数相等,且比T2增加了12.5%(P>0.05);相比CK,T1和T2的TN浓度增加了19.35%、25.8%(P>0.05),TN流失量则均增加了11.54%(P>0.05),表明T1和T2的施用也有增加土壤N流失的潜在风险。与中雨、大雨和大暴雨事件相比,暴雨事件的径流深分别增加了6.5%—191.11%(P<0.05),而TN、NO₃-N及NH₄-N的流失量分别增加106.38%—177.14%(P>...     

Recovery of 15N-labeled urea and soil nitrogen dynamics as affected by irrigation management and nitrogen application rate in a double rice cropping system

A sophisticated soil microcosm system and ¹⁵N-labeled urea were used to investigate nitrogen (N) use efficiency and soil N dynamics in a rice monoculture system in two successive seasons. Topsoil (0 cm?C20 cm) and subsoil (20 cm?C50 cm) samples were collected from a traditional double rice cropping field in the Jiangxi Province, China, and these soil samples were derived from Quaternary red clay. Treatments were randomly assigned with two irrigation regimes and three N application rates (no application control, 80% traditional rate and 100% traditional rate noted as N0, N1 and N2, respectively). The levels of ¹⁵N recovery of plants, ¹⁵N and N remaining in soil were determined. Moreover, the N dynamic of soil solution from different layers of the soil profile was surveyed. The results showed that the effects of irrigation management and N application rate varied in different rice growing seasons. Irrigation regimes had remarkable effects on grain yield and chemical ¹⁵N fertilizers (CF-¹⁵N) uptake. When compared to flood irrigation (FI), the shallow water depth with wetting and drying (WD) increased grain yield up to 5.7%?C20%. Although the highest grain yield was obtained with reduced N application level, both N apparent recovery (NAR) and ¹⁵N use efficiency (the percentage of plant N uptake derived from applied N, %Ndfan) significantly decreased with increasing N inputs. However, the interaction between irrigation management and N application rate on grain yield and N use efficiency (NUE) of CF-¹⁵N were not significant. A survey of soil solutions every 5 days indicated that NH ₄ ⁺ -N was the main residual form of N, and high NH ₄ ⁺ -N leaching was observed. When compared to FI, WD decreased vertical NH ₄ ⁺ -N and TN leaching, especially at 10?C50 cm depths of soil profile in the second season. NH ₄ ⁺ -N was the main N residual form in the soil profile. Therefore, in this study, the WD irrigation regime and reduced rate (N1) was the optimal irrigation and fertilizer management strategy to increase the NUE of CF-N, increase the after effects of CF-¹⁵N, decrease leaching loss of CF-¹⁵N and minimize the shallow groundwater pollution risk, which were all beneficial for the ecological environment.     

高原鼠兔干扰对高寒草甸植物多样性与土壤养分间关系的影响

高原鼠兔干扰虽然能够改变高寒草甸植物多样性与土壤养分含量,但植物多样性与土壤养分间的关系对高原鼠兔干扰的响应尚不清晰。利用高原鼠兔有效洞口密度将高原鼠兔干扰程度划分为T_1(7个/625 m~2)、T_2(12个/625 m~2)、T_3(22个/625m~2)、T_4(38个/625 m~2)4个水平,运用RDA冗余分析法研究了高原鼠兔不同干扰程度下高寒草甸植物多样性与土壤养分间的关系。结果表明:随着高原鼠兔干扰水平的增加,优势种高山嵩草(Kobresia pygmaea)的重要值先增加后降低,而伴生种小花草玉梅(Anemone rivularis var.flore-minors)和莓叶委陵菜(Potentilla fragarioides)的重要值先降低后增加;当高原鼠兔干扰水平从T_1到T_2时植物多样性指数变化不显著,而高原鼠兔干扰程度超过T_2时则植物多样性指数具有降低趋势;土壤全氮和硝态氮含量随高原鼠兔干扰水平增加而降低,而土壤铵态氮含量则降低后增加,土壤有机碳和全磷先增加后降低;多样性指数与0—10cm土壤深度硝态氮、10—20cm土壤深度全钾间的相关性从T_1到T_3时为正相关,而到T_4时则变为负相关,而与0—10cm土壤深度全氮的相关性则表现T_1到T_3时为负相关,T_4时为正相关,与铵态氮间相关性只有T_1时为负相关,这说明高原鼠兔干扰改变了植物多样性与土壤养分间的关系,其变化阈值介于T_2和T_3。     

Effect of Rural Sewage Irrigation Regime on Water-Nitrogen Utilization and Crop Growth of Paddy Rice in Southern China

Reclaimed water irrigation has become an effective mean to alleviate the contradiction between water availability and its consumption worldwide. In this study, three types of irrigation water sources (rural sewage’s primary treated water R1 and secondary treated water R2, and river water R3) meeting the requirements of water quality for farmland irrigation were selected, and three types of irrigation water levels (low water level W1 of 0–80 mm, medium water level W2 of 0–100 mm, and high water level W3 of 0–150 mm) were adopted to carry out research on the influence mechanismS of different irrigation water sources and water levels on water and nitrogen use and crop growth in paddy field. The water quantity indicators (irrigation times and irrigation volume), soil ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃⁻-N), rice yield indicators (thousand-grain weight, the number of grains per spike, and the number of effective spikes), and quality indicators (the amount of protein, amylose, vitamin C, nitrate and nitrite content) of rice were measured. The results showed that, the average irrigation volume under W3 was 2.4 and 1.9 times of that under W1 and W2, respectively. Compared with R3, the peak consumption of rice was lagged behind under R1 and R2, and the nitrogen form in 0–40 cm soil layers under rural sewage irrigation was mainly NH₄⁺-N. The changes of NO₃⁻-N and NH₄⁺-N in the 0–40 cm soil layer showed the trend of declining and then increasing. The water level control only had a significant effect on the change of NO₃⁻-N in the 60–80 cm soil layer. Both irrigation water use efficiency and crop water use efficiency were gradually reduced with the increase of field water level control. The nitrogen utilization efficiency under rural sewage irrigation was significantly higher than that under R3. Compared with the R3, rural sewage irrigation could significantly increase the yield of rice, and as the field water level rose, the effect of yield promotion was more obvious. It was noteworthy that the grain of rice under R1 monitored the low nitrate and nitrite content, but no nitrate and nitrite was discovered under R2 and R3. Therefore, reasonable rural sewage irrigation (R2) and medium water level (W2) were beneficial to improve nitrogen utilization efficiency, crop yield and crop quality promotion.

     

不同秸秆填埋量对盐碱土水盐运移及垂柳反射光谱的影响

在宁夏西北盐化生态脆弱区的典型盐碱化土地,通过随机区组试验,探究在栽植穴填埋秸秆2000(T_1)、7000(T_2)、12000kg/hm~2(T_3)及17000 kg/hm~2(T_4)等作隔盐层对土壤水盐运移及垂柳(Salix babylonica)反射光谱的影响,将地下土壤水盐变化与地上植物生长及生理状况相结合,以期更准确的反映出各处理对盐碱土壤改良效果及地上植被恢复情况。研究结果表明:(1)填埋一定量的秸秆作隔盐垫层可以改变地下土壤水盐的剖面分布特征。T_2、T_3和T_4处理与对照组相比,20—80 cm土层土壤含水量都显著提高,填埋的秸秆层起到了蓄水保墒的作用;都明显降低了0—80 cm土层土壤盐分含量和盐溶质浓度;但这3种处理之间无显著差别。T_1由于填埋秸秆量过少,无显著蓄水控盐效果。(2)通过检测植物叶片反射光谱可以反映出地上植物生长及生理状况的变化。填埋一定量的秸秆作为隔盐垫层有助于改善垂柳的生理状况。T_2的垂柳叶片光合色素含量最高,光合特性及营养状况最好,其他光谱参数结果都显著提高。T_3显著提高叶绿素含量和光合特性,但效果均不如T_2,且营养状况差。T_4处理类胡萝卜素含量与叶片水分含量均处于最高水平,但叶绿素含量、营养状态以及光合特性都显著降低。T_1处理效果最差。(3)在地下填埋秸秆作隔盐层,会通过对地下土壤水盐运移及微域生态系统环境的调节,影响到地上植物生长及生理状况。综合地下水盐分布与地上植物叶片反射光谱的结果,T_2是宁夏引黄灌区盐碱地改良中最适宜的秸秆填埋量。     

Shallow depth placement of (NH4)2SO4 in submerged rice soils as related to gaseous losses of fertilizer nitrogen and fertilizer efficiency

Summary When nitrogen fertilizers are applied to rice, growing under submerged conditions, substantial gaseous losses of fertilizer nitrogen have been observed.Placement of the fertilizer at shallow depth greatly reduces these losses. A balance experiment using six different rice soils was carried out in a greenhouse. N¹⁵-labelled (NH₄)₂SO₄ (atom excess of 10% N-15) was applied on the surface and at 7 cm depth. Analysis of soil, roots and shoots showed that the difference in utilization of fertiliser nitrogen for surface and depth placement in pots could be accounted for by the difference in gaseous loss of fertilizer-N.