我国南方牧草生态系统氮素平衡与循环特征研究

通过在我国南方典型红壤早地种植牧草马唐,对大气N沉降、氨挥发、径流、淋溶等N素循环量进行了研究.结果表明,马唐的生长期内,不同N肥量处理,红壤旱地牧草生态系统通过肥料和大气沉降输入的N素量为26.28～256.28kg/hm2,通过氨挥发、径流、淋溶和牧草吸收输出的N素量为21.95～131.52kg/hm2,N素盈余4.33～124.76kg/hm2.其中,大气沉降N为26.28 kg/hm2, 占牧草生态系统总输入N的10.85%～22.60%; 氨挥发损失N为0.67～5.16 kg/hm2,占施入N的0.74%～2.24%;径流损失N为0.25～0.42kg/hm2,占施入N的0.44%～1.17%;淋溶损失N为0.28～2.86kg/hm2,占施入N的0.91%～1.24%.     

不同施氮量及施氮方式对水稻田氨挥发及氮肥利用率的影响

施用缓控释氮肥是降低稻田土壤氨挥发损失的常用措施之一。将缓控释氮肥与速效氮肥配施,可以解决水稻对氮素的需求与降低氮素损失之间的矛盾。在保证水稻产量的前提下,以减少稻田氨挥发损失、提高氮肥利用效率以及降低环境污染为目的,采用大田裂区试验的方法,设置不施氮肥和施氮量分别为60(N60)、120(N120)、180(N180)、240(N240)kg·hm-2 5个施氮水平,以及氮肥一次性施用(SF)及氮肥一基二追(TF)2种施肥方式,研究不同氮肥用量及运筹模式对水稻田氨挥发、氮肥利用率以及水稻产量的影响:结果表明,氮肥施用方式和施氮量对水稻田氨挥发损失量影响显著,同一施氮方式下,稻田土壤氨挥发损失量随着施氮量增加而增加,SF各处理氨挥发损失量为14.46～23.74 kg·hm-2,TF各处理的氨挥发损失量则为23.3～47.74 kg·hm-2,SF氨挥发损失量比TF降低37.9%～50.3%;氮肥施用方式显著影响氮肥表观利用率和氮肥偏生产力,SF和TF的最大氮肥表观利用率均出现在N180,分别为50.02%和38.68%;低施氮量(N60)和高施氮量(N240)时,TF氮肥偏生产力高于SF,而施氮量为120(N120)kg·hm-2、180(N180)kg·hm-2时,SF比TF氮肥偏生产力分别高出3.32和5.58 kg·kg-1;施氮量极显著影响水稻的氮素吸收量和氮肥农学利用率;SF和TF的最高产量分别出现在N180和N240,且SF高于TF,两者相差465.3 kg·hm-2。缓控释氮肥与速效氮肥配施一次性施肥可以有效降低稻田氨挥发损失,同时提升氮肥表观利用率和偏生产力,且能在施氮量较低的情况下获得较高产量,在水稻氮肥管理上具有应用价值。     

太湖地区氮磷肥施用对稻田氨挥发的影响

在太湖地区乌栅土上,采用田间小区试验连续两年研究了施氮(N)量为0、180、255、330kg hm-2,施磷(P2O5)量为0、309、0、180 kg hm-2的6个组合(对照N0P0、低氮N180P90、优化N255P90、低磷N255P30、高磷N255P180、高氮N330P90)以及三个施肥时期对稻田氨挥发损失的影响,氨挥发采用密闭室间歇通气法测定。结果表明,稻田氨挥发损失主要发生在施肥后6d内,基肥和第一次追肥后各处理氨挥发量占施氮量的0.4%~11.5%,而第二次追肥后氨挥发损失比例较大,对照、低氮、优化、低磷、高磷和高氮处理的氨挥发在2002年稻季分别占施氮量的5.8%、9.7%、25.6%、15.6%和11.6%,在2003年稻季则分别为27.4%、26.2%、30.0%、35.1%和27.6%。若施肥后遇阴雨天气或正值水稻拔节孕穗期,氨挥发量便降低。田面水中的NH4 -N浓度是氨挥发的决定因素之一,与氨挥发通量呈正相关。施磷量相同时,氨挥发随施氮量增加而增加;施氮量相同时,高磷和低磷处理氨挥发均高于优化处理,表明在氮磷不平衡施用时,氮肥氨挥发损失会加剧,从氨挥发损失方面考虑,稻田推荐施磷量不宜超过P2O590 kg hm-2。     

水稻基肥尿素干施与湿施对氮素损失及水稻氮素吸收的影响

运用大型原状土柱在田间条件下比较了水稻基肥干耕施(干施)与湿耙施(湿施)对氮素损失与水稻氮素吸收的影响,试验设尿素干施、湿施与对照3个处理,同步测定了施肥后小区的氨挥发、淋洗以及水稻的吸氮量。结果表明:(1)干施法氨挥发显著低于湿施法,模拟试验分别为40.1与68.8 kg hm-2,占施氮量的13.4%与22.9%,2004年的大田试验分别为19.2与26.2 kg hm-2,占施氮量的7.7%与10.4%;(2)而干施法的总氮(TN)淋洗量显著大于湿施法,分别为14.3与4.6 kg hm-2,占施氮量的4.8%与1.5%,氮的淋洗以NO3--N为主,占总量的73.7%～97.3%,两者的NH4+-N淋洗量差别很小;(3)与湿施法相比,干施法净减少氮肥损失19.0 kg hm-2,水稻吸氮量增加15.1 kg hm-2,氮肥利用率提高了5个百分点,产量略有提高,而土壤含氮量没有显著变化。因此,水稻基肥尿素干深施法是一项值得推广的施肥方法。     

春季有机肥和化肥配施对苹果园土壤氨挥发的影响

采用磷酸甘油-双层海绵通气法对旱地苹果产区不同有机肥和化肥配施下的氨挥发进行了研究。结果表明,不同有机肥和化肥配施显著影响了氨挥发速率和损失量。各处理氨挥发速率峰值大小和出现时间存在差异,纯化肥(100%N)处理峰值最高,达2.07kg N/(hm2.d),而纯有机肥(100%Y)处理峰值出现时间最早。氨挥发损失量以100%N处理为最大,达10.39kg N/hm2,占施氮量的3.46%,显著高于其它处理;50%N+50%Y处理氨挥发损失量和占施氮量的比例均为最低。有机无机肥配施可以有效减少氨挥发损失,以有机肥和化肥各半最好。     

秸秆全量还田与氮肥用量对水稻产量、 氮肥利用率及氮素损失的影响

【目的】在我国水稻生产中探讨秸秆全量还田与氮肥配施的理论与技术,阐明秸秆还田对水稻产量、 氮素利用率及氮素损失的影响,对于提高水稻产量和氮素利用效率、 减少氮污染具有重要意义。【方法】2009~2011年,以水稻南粳46为材料,在江苏常熟农业生态实验站进行原状土柱模拟试验。试验采用裂区设计,主区为秸秆全量还田(S)和无秸秆还田(S0); 副区为氮肥用量(N),设置N 120、 180、 240和300 kg/hm2 4个氮水平,以不施氮肥(N0)为对照。分析了水稻基肥期、 分蘖期、 穗肥期的氨挥发量和土壤80 cm处渗漏水全氮含量,土壤0—15 cm全氮含量,水稻产量,以及水稻籽粒和秸秆氮含量,计算水稻生育期氮肥的氨挥发损失率、 淋溶损失率、 土壤残留率以及水稻的氮肥利用效率。【结果】水稻产量随氮肥适宜用量增加而增加,与单施氮肥相比,秸秆还田下水稻平均增产6.3%,其中N 240 kg/hm2 处理产量最高; 水稻的氮肥利用率随施氮量的增加呈下降趋势,秸秆还田能够提高水稻的氮肥利用率,氮肥农学效率和氮肥表观利用率较单施氮肥分别提高1.4~3.4 kg/kg和1.8%~4.2%; 水稻田氨挥发损失量、 氮肥淋溶损失量和土壤残留氮量均随施氮量的增加而增加,在N 240 kg/hm2水平下,秸秆还田氨挥发损失量增加18.2%、 土壤残留氮量增加10.1 kg/hm2,减少氮素淋溶损失量30.9%,氮肥总损失率降低6.0%。【结论】在秸秆全量还田下,配施适量的氮肥,可以提高水稻对氮肥的利用率,增加产量,同时减少氮肥损失。本试验中,以麦秸全量还田配施N 240 kg/hm2为最优组合。     

春秋季红壤旱地氨挥发对氮施用量、气象因子的响应

通过红壤旱地种植牧草马唐和蔬菜冬萝卜轮作试验,研究了在春秋二季红壤旱地氨挥发对不同施氮量和气象因子的响应。结果表明,红壤旱地春季牧草实验,氮肥处理N90、N160和N230,氨挥发持续10~17d,在施肥后6~8d达到峰值,峰值(扣除对照N0)分别为N0.11、0.57和1.84kghm-2d-1。秋季氮肥处理N70、N130、N190和N250以基肥和以水带肥追施(基/追比为7∶3)氨挥发持续时间均为10~11d,基肥氨挥发峰值(扣除对照N0)分别为N0.02、0.05、0.06kghm-2d-1和0.09kghm-2d-1;追肥氨挥发峰值(扣除对照N0)分别为N0.05、0.22、0.38kghm-2d-1和0.72kghm-2d-1。不同施氮处理,春季累计氨挥发量为N0.67~5.16kghm-2,占施入肥料N的0.74%~2.24%;秋季累计氨挥发量为N0.37~3.04kghm-2,占施入肥料N的1.31%~3.69%。红壤旱地春秋二季氨挥发量(y)均随施N量(x)的提高而指数递增,其关系式分别为:y=0.1576e0.0146x和y=0.1826e0.0112x。显著性检验表明,春秋两季不同施氮量处理之间,土壤氨挥发量及挥发通量差异均达到显著水平。春秋二季基肥氨挥发总量和通量均与气温、气压、蒸发量和土温等环境气象因子有较好的相关性(p<0.05)。     

常规灌溉条件下施氮对温室土壤氨挥发的影响

为明确温室土壤的氨挥发特征,探讨适宜的减量施氮措施对氨挥发损失量及黄瓜产量的影响,在常规灌溉条件下设置了3个施氮（尿素）处理,采用通气法测定了冬春季黄瓜地中的氨挥发速率。结果表明：温室土壤在氮肥基施后7 d出现氨挥发速率峰值,但在氮肥追施后,施肥带与非施肥带的氨挥发速率峰值分别在第1 d与第5 d出现,氨挥发速率的峰值比氮肥基施时下降了8.6%～46.3%,施肥带的累积氨挥发量是非施肥带的0.91～1.54倍。冬春季黄瓜地的氨挥发损失量为16.7～26.6 kg/hm2,其中减施氮25%处理N900（900 kg/hm2）与减施氮50%处理N600（600 kg/hm2）与习惯施氮处理N1200（1 200 kg/hm2）相比,氨挥发损失量分别降低了22.1%和37.2%。而2 a黄瓜产量的平均值以处理N600（600 kg/hm2）最高,比处理N1200（1 200 kg/hm2）增加了6.52%。综合考虑氨挥发损失量、黄瓜产量及施氮量,在河北省的温室冬春季黄瓜生产中,比农民习惯氮用量（1 200 kg/hm2）减少25%～50%的措施是可行的。     

水氮耦合对水稻田间氨挥发规律的影响

在防雨棚池栽试验中应用通气法研究了水氮耦合对稻田土壤氨挥发速率的动态变化及损失量。结果表明,稻田施用氮肥后有明显NH3挥发损失,整个生育期累计氨挥发量为31.67～69.70kg·hm^-2,占施氮量的17.95%～28.64%;不同生育时期氨挥发量的大小依次为返青期〉拔节孕穗期〉分蘖期〉抽穗开花期〉乳熟期,挥发高峰出现在施氮肥后的1～3d内;随着施氮水平增加,田间氨挥发量显著增加。与此同时,稻田水分状况对NH3挥发损失具有重要影响,与常规灌溉模式相比,控制灌溉条件下氨挥发总量和氨挥发损失率均较小,且不同施氮水平间差异显著。就氨挥发损失率而言,在试验条件下水氮耦合效应显著,以控制灌溉模式下施氮量为180kg·hm^-2时的氨挥发损失率最低,为17.59%。     

基施氮肥对麦田冬前氨挥发损失的影响

通过田间原位测定农田氨挥发的方法，研究了京郊不同基施氮肥水平的麦田冬前土壤氨挥发情况及其时间变化规律。结果表明，麦田土壤氨挥发主要发生在施肥后1~2周内，以施肥后连续采样14 d的氨挥发累积量作为小麦冬前氨挥发总排放量，高施氮量处理的氨挥发总量大于低施氮量处理的氨挥发总量，50~400 kg·hm-2不同施肥水平下土壤的氨挥发总量（N）为1.83~14.29 kg·hm-2，占施氮量的2.04%~6.74%。温度回升也导致了氨挥发量小范围升高。     

基于文献分析的北方冬麦田氨挥发特性

中国北方地区是冬小麦-夏玉米种植体系的主要集约化农业区,过去30多年间化学氮肥投入量大和肥料利用率低的现象较为普遍,氨挥发等农业面源污染严重,需要对冬小麦生长过程中的氨挥发规律及测定方法等进行系统研究。该研究对1980年至2018年的华北平原冬小麦氨挥发文献进行研究总结,采用回归方程和T检验等统计学方法分析了不同施氮水平、施肥时期和测定方法对冬小麦氨挥发的影响。研究发现,随着化肥施氮量的增加,冬小麦氨挥发累积量呈现指数函数增加趋势(y=2.64e0.006 6x),净氨挥发量呈现幂函数增加特征(y=0.004 8x1.358 9)。不考虑激发效应的净氨挥发量比考虑激发效应的高估约21.8%。冬小麦生产中,基追比为1∶1的情况下,基肥期氨挥发量显著高于追肥期氨挥发量(P<0.05),占整个生育期氨挥发量分别为58.7%和41.3%。在180 kg/hm2氮肥水平时,海绵吸收法与真空抽气法测定的氨挥发数量无显著性差异。冬小麦季的氨挥发控制,应该重点通过优化氮肥施用数量,主要在基肥期进行控制。田间生产中,采用海绵吸收法和真空抽气法监测氨挥发应考虑不同施肥水平下的高估。     

Nitrogen Loss from Paddy Field with Different Water and Nitrogen Managements in Taihu Lake Region of China

High rates of nitrogen (N) fertilizer were applied to a paddy field in the Taihu Lake region of China to maximize crop production. Excessive N input has resulted in serious agricultural nonpoint pollution. Water and N management are two important approaches to regulating N loss from paddy fields. This study aimed to determine N losses through ammonia volatilization, runoff, and leaching from a paddy field during the rice-growing season in Taihu Lake region. Field experiments with two water and two N managements were conducted. The N exported to the environment through ammonia volatilization, runoff, and leaching from the paddy field was 37.2 kg N ha^?1 to 102 kg N ha^?1, with ammonia volatilization accounting for 69.6% to 83.5% of N loss. Ammonium and dissolved organic N significantly contributed to N loss through runoff and leaching. Controlled irrigation and site-specific N management (CS) significantly decreased N losses through ammonia volatilization, runoff, and leaching. Compared with the N and irrigation water inputs in traditional water and N management, those generated by controlled irrigation and site-specific N management were reduced by 34.6% to 43.0% and 59.2% to 63.3%, respectively. Moreover, the reduction in N and water input in the CS paddy field enabled the maintenance of high rice yield; it significantly increased N use efficiency by 15.1% to 34.9% and decreased the N exported to the environment by ammonia volatilization, runoff, and leaching by 53.1% to 56.1%. Therefore, the joint application of controlled irrigation and site-specific N management efficiently reduces agricultural nonpoint pollution through N loss from paddy fields.     

追施猪粪沼液对菜地氨挥发的影响

氨挥发是肥料氮素损失的主要途径之一。以厌氧发酵后的猪粪沼液为研究对象,通过蔬菜大棚小区试验,分析其作为追肥表施于冬季菜地(水芹(Oenanthe clecumbens L.)和扬花萝卜(Raphanus sativusL.Var.Radiculus pers.);追施氮量分别为72 kg hm-2和54 kg hm-2)及夏季菜地(小白菜(Brassica chinensisL.)和大叶茼蒿(Chrysanthemum carinatum Schousb.);追施氮量分别为42 kg hm-2和63 kg hm-2)后的氨排放特征及其影响因子。研究结果表明:(1)施用猪粪沼液后菜地氨挥发激增,沼液中氮素以氨挥发形态损失较快,通常发生在施入后48 h内;(2)冬季芹菜地和萝卜地施用沼液后的累积氨排放量分别为8.68 kg hm-2和9.90 kg hm-2,显著高于化肥处理(4.06 kg hm-2和5.59 kg hm-2);而夏季白菜地和茼蒿地则分别为10.40kg hm-2和11.61 kg hm-2,与化肥处理间差异不显著(9.81 kg hm-2和10.09 kg hm-2);(3)冬季菜地施用沼液后氨挥发损失率分别达到11.7%和17.7%,显著低于夏季菜地(23.3%和26.8%);(4)0～10 cm土层土壤温度、水分含量、可溶性有机碳含量、氮素水平及形态、微生物生物量及活性,均与菜地氨挥发有较高的关联度。沼液作为追肥施入农田后会因其自身氨挥发和激发效应而使氨排放增加,在施用过程中应特别注意温度的影响,同时应选择合适的施用方式。     

南京两种菜地土壤氨挥发的研究

在南京雨花区武警农场和栖霞区东阳科技站先后进行了秋季小青菜和秋冬季大白菜田间试验,研究菜地土壤施用氮肥后的氨挥发及其影响因素,氨挥发采用密闭室间歇密闭通气法测定。结果表明,小青菜试验地的pH为5 .4 ,施肥后土壤pH值也未高于6 .0 ,故氨挥发损失低(<0 .4 % ) ;而在pH为7.7的大白菜试验地上,控释尿素、低氮和高氮3个处理(施氮量分别为N 180、30 0和6 0 0kghm-2 )氨挥发率分别为0 .97%、12 .1%和17 1%。以上结果表明,土壤pH是影响菜地土壤氨挥发的主要因素,降低氮肥用量能明显减少氨挥发,而施用控释尿素是一种有效控制氨挥发损失的措施。大白菜不同施肥期的结果还表明,施尿素后降雨通过降低表层土壤氮的浓度而影响氨挥发,降雨离施肥期越近,雨量越大,氨挥发越小     

表施尿素的冬小麦土壤氨挥发损失

Ammonia volatilization was measured with a continuous air flow enclosure method from a winter wheat field in the Experimental Farm of Jurong Agricultural School to investigate its main influencing factors. The experiment with five treatments in triplicate, no N (control), 100, 200 and 300 kg N ha^-1 with rice straw cover at a rate of 1 500 kg ha^-1 and 200 kg N ha^-1 without rice straw, started when the winter wheat was sown in 1994. Sixty percent of the total amount of N applied was basal and 40% was top-dressed. The measurement of ammonia volatilization was immediately conducted after urea was top-dressed on soil surface at wheat elongation stage in spring of 1996 and 1997. The results showed that there was a diurnal variation of ammonia volatilization rate from the winter wheat field, which synchronized with air temperature. N losses through ammonia volatilization increased with increasing N application rate, but the ratio of N lost through ammonia volatilization to applied N was not significantly affected by N application rate. The coverage of rice straw had no significant effect on ammonia volatilization. Soil moisture and rain events after urea was top-dressed affected ammonia volatilization significantly.     

氮肥用量对太湖水稻田间氨挥发和氮素利用率的影响

Ammonia volatilization losses, nitrogen utilization efficiency, and rice yields in response to urea application to a rice field were investigated in Wangzhuang Town, Changshu City, Jiangsu Province, China. The N fertilizer treatments, applied in triplicate, were 0 （control）, 100, 200, 300, or 350 kg N ha^-1. After urea was applied to the surface water, a continuous airflow enclosure method was used to measure ammonia volatilization in the paddy field. Total N losses through ammonia volatilization generally increased with the N application rate, and the two higher N application rates （300 and 350 kg N ha^-1） showed a higher ratio of N lost through ammonia volatilization to applied N. Total ammonia loss by ammonia volatilization during the entire rice growth stage ranged from 9.0% to 16.7% of the applied N. Increasing the application rate generally decreased the ratio of N in the seed to N in the plant. For all N treatments, the nitrogen fertilizer utilization efficiency ranged from 30.9% to 45.9%. Surplus N with the highest N rate resulted in lodging of rice plants, a decreased rate of nitrogen fertilizer utilization, and reduced rice yields. Calculated from this experiment, the most economical N fertilizer application rate was 227 kg ha^-1 for the type of paddy soil in the Taihu Lake region. However, recommending an appropriate N fertilizer application rate such that the plant growth is enhanced and ammonia loss is reduced could improve the N utilization efficiency of rice.     

控/缓释肥料减少氨挥发和氮淋溶的效果研究

采用“静态吸收法”和“土柱淋溶法”室内模拟实验，分别研究了6种控／缓释肥料施入土壤中的氨挥发和氮淋溶情况。结果表明：6种控／缓释肥料处理都不同程度的降低了氨挥发量和N素淋溶量。与尿素比较，6种控／缓释肥料氨挥发量分别较普通尿素减少16．62％，23．78％，32．15％，0．11％，16．59％和37、78％，氮淋溶量分别较普通尿素减少15．84％，38．27％，68．87％，46．17％，52．51%和62．01％。试验还表明控／缓释氮肥氨挥发量与不同氮肥引起的土壤脲酶活性、pH值有密切关系。     

黄土高原旱地夏季休闲期~(15)N标记硝态氮的去向

夏季休闲是黄土高原旱地小麦常见的蓄纳雨水、恢复地力的措施。随着氮肥用量的增加,一季小麦收获后,旱地土壤剖面累积的硝态氮量不断增加,休闲期间降雨量高,残留硝态氮的去向是值得研究的问题。利用~(15)N标记法研究小麦收获后残留肥料氮在黄土高原旱地(陕西长武)夏季休闲期间的去向,即小麦收获后在微区土壤表层(0~15 cm)施入~(15)N标记的硝态氮肥(30 kg hm~(-2)(以纯氮计),约相当于当地小麦一季作物收获后土壤残留肥料氮量),休闲结束后,采集0~200 cm土壤样品,测定了土壤全氮、硝态氮含量及其~(15)N丰度。结果表明,小麦收获(即休闲开始)时0~200 cm土壤剖面硝态氮累积量在205~268 kg hm-2之间(平均244 kg hm~(-2)),累积量较高。夏季休闲期间降水量为157 mm,属欠水年,但休闲结束后,~(15)N标记肥料氮向下迁移已达80 cm土层,下移深度在45~65cm之间,说明,旱地休闲期间硝态氮的淋溶作用不可忽视。夏季休闲结束后,加入的~(15)N标记肥料氮平均损失率为28%,损失机理值得进一步研究。     

中国南方大棚蔬菜地氮平衡与损失

High rates of fertilizer nitrogen (N) are applied in greenhouse vegetable fields in southeastern China to maximize production;however,the N budgets of such intensive vegetable production remain to be explored.The goal of this study was to determine the annual N balance and loss in a greenhouse vegetable system of annual rotation of tomato,cucumber,and celery at five N (urea) application rates (0,348,522,696,and 870 kg N ha-1 year-1).Total N input to the 0-50 cm soil layer ranged from 531 to 1 053 kg ha-1,and N fertilizer was the main N source,accounting for 66%-83% of the total annual N input.In comparison,irrigation water,wet deposition,and seeds in total accounted for less than 1% of the total N input.The fertilizer N use efficiency was only 18% under the conventional application rate of 870 kg N ha-1 and decreased as the application rate increased from 522 to 870 kg N ha-1.Apparent N losses were 196-201 kg N ha-1,of which 71%-86% was lost by leaching at the application rates of 522-870 kg N ha-1.Thus,leaching was the primary N loss pathway at high N application rates and the amount of N leached was proportional to the N applied during the cucumber season.Moreover,dissolved organic N accounted for 10% of the leached N,whereas NH3 volatilization only contributed 0.1%-0.6% of the apparent N losses under the five N application rates in this greenhouse vegetable system.