Effect of a Chemical Modified Urea Fertilizer on Soil Quality: Soil Microbial Populations Around Corn Roots

Slow‐release nitrogen (N) fertilizers are used to increase N‐use efficiency and extend N availability over a plant‐growing season. One formula of this fertilizer commonly used in turf and horticultural crops is methylene–urea–triazone. After this compound is applied in the soil, it is subject to bacterial degradation and becomes available for uptake by plants. The objective of this work is to elucidate the application of methylene–urea–triazone in the soil microbial population as well as effects on soil quality. Zea mays was planted in a silty loam soil. Urea and methylene–urea–triazone were incorporated into the soil. Two weeks and 6 weeks after inoculation, soil samples were collected and used to inoculate agar plates and for DNA extraction. Bacterial colony morphology was examined. Denaturing gradient gel electrophoresis (DGGE) was performed with the polymerase chain reaction (PCR) amplicons from the internal transcribed spacer (ITS) of the rRNA gene cluster. The Shannon Wiener index was determined for colony morphology and DGGE bands. There was a difference between urea and the slow‐release fertilizer on both plant responses and bacterial diversity. Although for the first 2 weeks DGGE did not show any difference in bacterial diversity, after 6 weeks, differences in the composition of the bacterial community were observed. There were concomitant effects on plant growth and microorganism population and diversity, probably reflecting changes in the richness and in the eveness of the bacterial population in the rhizosphere caused by the fertilizers. Therefore, both soil microorganisms and plant growth respond to environmental changes over time.     

不同大豆品种根瘤固氮酶活性与固氮量差异研究

大豆根瘤固氮酶活性与固氮量是衡量大豆固氮能力的重要指标,也是合理施用氮肥的依据.试验采用框栽方法,应用15N示踪技术,研究了不同大豆品种根瘤固氮酶活性与固氮量差异.结果表明:4个供试大豆品种根瘤固氮酶活性、根瘤干重及根瘤固氮潜力都呈现先升后降的变化趋势,但品种间有显著差异;生育期短的大豆品种根瘤固氮酶活性高于生育期长的品种,根瘤干重则相反,生育期越长,根瘤干重越大;根瘤固氮潜力随大豆品种生育期的延长而增加.大豆植株氮素构成品种间存在明显的差异性,随着品种生育期的延长,根瘤固氮所占的比例提高;在大豆品种黑河41氮素构成中,土壤氮和根瘤固氮所占比例相同,其他品种均以根瘤固氮为主,其次是土壤氮,肥料氮所占的比例很低.     

减氮配施缓释氮肥对棉田土壤酶活性和氮素吸收利用的影响

为探明减氮配施缓释氮肥对棉田土壤酶活性和氮素吸收利用的影响,通过试验研究减氮、配施不同比例缓释氮肥对棉花土壤理化性质、酶活性、无机氮含量、氮肥利用率及棉花产量的影响。试验选用新陆早64号棉花品种,设置2种施氮方式,分别为常规全施尿素(T2)和缓释氮肥与尿素不同比例配施(US),配施处理按照施氮量设3个水平,分别为不减氮U_0.8S_0.2(T3)、U_0.6S_0.4(T4),减氮20% U_0.6S_0.2(T5)、U_0.4S_0.4(T6),减氮40% U_0.4S_0.2(T7)、U_0.2S_0.4(T8),不施氮肥(T1)为对照,共8个处理。对棉花不同生育期内土壤的理化性质、酶活性、无机氮含量及成熟期棉花氮素含量和产量进行测定与分析,并计算氮肥利用率。结果表明:与常规全施尿素相比,配施缓释氮肥能显著提高土壤含水量和全氮含量,其中,以缓释氮肥与尿素4∶6配施(T4)处理的土壤含水量最大,较常规全施尿素(T2)在棉花苗期、蕾期、花期、铃期和吐絮期分别提高了14.07%,11.05%,7.58%,6.22%,6.65%;T4处理的土壤全氮在花期显著高于常规全施尿素(T2)处理,达到1.24 g/kg。减氮20%配施缓释氮肥(T5、T6)处理各生育时期的土壤脲酶活性、蔗糖酶活性、过氧化氢酶活性、碱性磷酸酶活性和铵硝态氮含量与常规全施尿素(T2)间无显著差异,减氮20%配施缓释氮肥(T5、T6)处理成熟期土壤脲酶活性与硝态氮含量较不减氮T4处理分别减少了28.20%,26.40%和11.13%,8.32%。此外,减氮20%(T5、T6)处理的氮肥利用率显著高于常规全施尿素(T2)处理,分别为62.09%和62.43%,产量及其构成因素与常规全施尿素(T2)间无显著差异。综上,减氮20%配施缓释氮肥(T5、T6)处理与常规全施尿素(T2)处理相比土壤酶活性、无机氮含量及产量差异不显著,氮肥利用率显著高于T2处理,可以确保棉花全生育期的氮素供给,避免[JP]氮素的大量浪费,达到棉花高产及氮肥高效利用的目的。     

Influence of Unflooded Mulching Cultivation on Nitrogen Uptake and Utilization of Fertilizer Nitrogen by Rice

Abstract

Through unflooded mulching in field plots and ¹⁵nitrogen microplot tracer experiments, nitrogen (N) uptake of rice and N utilization have been studied compared with normal irrigation cultivation. The results showed that N uptake of unflooded rice and N derived from fertilizer (NDFF) of root, stem, and grain under mulching cultivation were lower than that under cultivation without mulching. However, the NDFF of rice under unflooded cultivation was higher than that under normal irrigation cultivation. The N utilization has been greatly enhanced under unflooded cultivation without mulching and unflooded plastic film cultivation with mulching as compared with normal irrigation. At the same time, there was no significant difference on the N uptake of unflooded rice among different ways of mulching cultivations. During the growth period of rice, no prominent differences were found in the soil residue, recovery, and N losses of fertilizer except the N uptake of rice between unflooded mulching and normal irrigation. The yield of rice under film mulching and straw mulching cultivation was higher than that of cultivation without mulching in the condition of unflooded cultivation, whereas the yield of rice under irrigation cultivation was higher than that under unflooded cultivation.     

Iron Metabolism in Tomato and Watermelon Plants: Influence of Nitrogen Source

Abstract

Tomato and watermelon plants were grown in nutrient solutions in which nitrogen (N) was supplied as NO₃ ^? (6 mM‐N) or NH₄ ⁺ (6 mM‐N). The experiments were conducted to evaluate the effect which different N sources exert on iron (Fe) uptake and accumulation, on the enzymatic activities of aconitase (Aco), chelate reductase (FeCH‐R), peroxidase (POD), catalase (CAT), and Fe‐superoxide dismutase (FeSOD), and on biomass production. For both species of plants, fertilization with NH₄ ⁺ caused the total Fe concentration to be lower, in the roots and in the leaves in relation to the concentrations recorded in plants fertilized with NO₃ ^?. The response of the enzymes related to Fe correlated with their concentration. The plants treated with N?NO₃ ^? registered the highest activities in Aco, FeCH‐R, POD, and CAT for both tomato and watermelon. On the other hand, only in the tomato plants was the superoxide dismutase (SOD) activity appreciably influenced primarily by NH₄ ⁺, due possibly to the toxic effect of this N source. Finally, in relation to biomass production, fertilization with NH₄ ⁺ drastically reduced growth in the tomato plants, while in watermelon plants, no significant alteration was detected in dry‐matter production, regardless of the N form used. It was concluded that the response of the parameters analyzed to NH₄ ⁺ fertilization, in tomato and watermelon, compared to fertilization with NO₃ ^? was similar. By contrast, tomato plants, but not watermelon plants, were negatively influenced by NH₄ ⁺.     

氮素营养水平对小麦根际微生物及土壤酶活性的影响

在大田高产栽培条件下．研究了不同施氮水平对豫麦49-198根际微生物和土壤酶活性的影响。结果表明：豫麦49-198根系土壤蛋白酶活性和脲酶活性随生育时期推进均呈先上升后下降的变化趋势．蛋白酶活性、脲酶活性分别在拔节期和返青期达到最大值。在同一生育时期内，随着施氮水平的提高，蛋白酶活性呈先增加后降低的变化趋势．其中以N2（180kg／hm^2）处理的蛋白酶活性最高，但N4（360kg／hm^2）处理的蛋白酶活性仍大于对照N1（0kg／hm^2）；脲酶活性随施氮水平的提高呈上升趋势．以N4（360kg／hm^2）处理的脲酶活性最大。根际微生物总量随生育时期推进呈先增加后下降的趋势，在孕穗期达到最大值．开花期略有降低；在同一生育时期．随着施氨水平的提高，根际微生物数量呈先增加后下降的趋势，以N3（270kg／hm^2）处理的根际微生物总量最高．且各处理之间的差异都达到了显著水平。     

肥料~(15)N对烟叶氮和烟碱含量的影响

利用15N示踪技术在黄壤烟区研究了烤烟不同部位烟叶氮和烟碱含量的变化及肥料氮在烟碱中的分配。结果表明,不施氮肥的情况下,烟株第10片以上烟叶烟碱含量达到3.54%;施氮量为97.5kghm-2时,10片以上烟叶烟碱含量达到4.13%以上。烟碱积累在整个生育期是呈不断增加的趋势,于移栽后7周内积累较少,烟碱积累主要集中在9～15周,到烟叶采收结束17周为122.55kghm-2。烟叶进入成熟期后,烟碱含量与各部位烟叶来自土壤氮素比例呈正相关,其中与上部烟叶相关系数达0.88。烟碱总氮中来自肥料氮于下部、中部和上部烟叶分别占28.31%,26.63%和25.45%;相应构成烟碱的氮素中,下、中、上部烟叶中有来自土壤氮分别为71.69%、73.37%和74.55%。追肥氮占施氮总量30%条件下,烟碱中氮来自追肥氮在下、中和上部烟叶分别占14.25%、15.30%和14.94%,追肥氮是烟叶烟碱总氮主要氮源。     

Nitrogen fixation (C2H2 reduction) in a salt marsh: Its relationship to temperature and an evaluation of an in situ chamber technique

A temperature controlled chamber for the in situ measurement of nitrogen fixation (acetylene reduction) in a vegetated salt marsh is described. Rates of acetylene reduction activity (ARA) were linear during a 9 h incubation. Measurements of acetylene penetration into the sediment indicate that the chamber technique measures ARA within the top 2–4 cm of the sediment column. This depth of penetration accounted for approx. 60% of the total ARA in the sediment column. Measurements of in situ ARA in three zones of a vegetated salt marsh (tall, medium and short height Spartina alterniflora) over a year were positively correlated with seasonal temperature variations. About 70–80% of the seasonal variation in ARA was explained by the Arrhenius relationship: ARA (μmol C₂H₄m⁻²h⁻¹)=α exp(−β/fT); where T is the ambient air temperature (°C) and α and β are constants. The constant α in this model increased from 20.1 to 40.5 while β increased from 17.5 to 20.7 along a transect from the tall to short height-form S. alterniflora communities. These differences suggest that there is spatial variability within the salt marsh among the variables that affect nitrogen fixation.     

外源H2S对盐胁迫下红砂幼苗叶片和根系氮代谢的影响

H₂S作为新型气体信号分子在调控植物生长发育和抗逆境胁迫中发挥着重要作用。为探究外源H₂S对盐胁迫下红砂(Reaumuria soongorica)氮代谢的影响机制及最佳叶施浓度,以当年生红砂幼苗为材料,采用盆栽试验,以1/2 Hoagland浇灌为对照(CK)考察在300 mmol·L^-1NaCl胁迫(CK300)下,叶面喷施不同浓度(0、0.010、0.025、0.050、0.100、0.250、0.500、1 mmol·L^-1)H₂S供体硫氢化钠(NaHS)对红砂叶片和根系中硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合成酶(GOGAT)活性以及硝态氮、可溶性蛋白和游离氨基酸含量的影响。结果表明,盐胁迫下,红砂幼苗根、叶中可溶性蛋白、游离氨基酸、硝态氮含量以及NR、GOGAT、GS活性均较对照(CK)显著下降。经不同浓度外源H₂S处理后,红砂根、叶中可溶性蛋白含量与单独盐胁迫对照(CK300)相比显著降低,NR、GOGAT、GS活性和硝态氮、游...     

化学氮肥与绿肥对麦田土壤细菌多样性和功能的影响

基于渭北旱塬8年田间定位试验,利用高通量测序技术研究了化学氮肥和绿肥施用对麦田土壤细菌丰度、多样性及其功能的影响。结果表明:与对照(CK)相比,化学氮肥施用处理(FP)显著增加了土壤有机碳含量(8.0%),氮肥+绿肥施用处理(FGM)显著增加了土壤有机碳(20.0%)、微生物生物量碳(62.0%)、微生物生物量氮(35.9%)、可溶性有机碳(7.27%)和有机氮(56.3%)含量。不同处理麦田土壤细菌OTU(基本分类单元)数平均为3792,丰度和多样性指数在各处理间均无显著性差异。优势菌群为变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)、放线菌门(Actinobacteria)、芽单胞菌门(Gemmatimonadetes)和拟杆菌门(Bacteroidetes)等,各处理之间无显著性差异。但在属水平上,与CK相比,FP处理显著降低了Pseudoduganella、Steroidobacter、Adhaeribacter、Nordella、Ralstonia等细菌属的相对丰度,FGM处理则显著提高了Steroidobacter、Chryseolinea、Lentzea、Chitinophaga和降低了Lactobacillus细菌属的丰度。FAPROTAX细菌功能分组主要以化能异养、硝化作用、氨氧化、亚硝酸盐氧化作用、硝酸盐还原作用等为主,Tax4Fun功能分组主要以碳水化合物代谢、氨基酸代谢、膜转运、信号传导和能量代谢等为主,各处理之间无显著性差异。因此,化学氮肥和绿肥施用对该区域旱地麦田土壤的细菌多样性、群落组成和功能影响相对较小,但可在一定程度上提高土壤肥力。     

Effects of Inoculation of Phototrophic Purple Bacteria on Grain Yield of Rice and Nitrogenase Activity of Paddy Soil in a Pot Experiment

Phototrophic purple bacteria (PPB) are one group of dinitrogen (N₂)-fixing bacteria often found in the anoxic and photic zone of paddy soil. In the present study, the effects of inoculation of PPB on grain yield of rice and changes in their populations and nitrogenase activity were investigated with and without surface application of rice straw in a pot experiment. As an inoculant, Rhodopseudomonas palustris strain KN122 isolated from a paddy soil was selected, and the cell suspension was inoculated into the floodwater once or three times during the cultivation. As a result, the inoculation of PPB increased the grain yield of rice. Compared to the control, the grain yield was 9% higher in the inoculated plot without rice straw application. The treatment was more effective in combination with rice straw application. In the plots where PPB were inoculated with rice straw, grain yields were 21% (single inoculation) and 29% (triple inoculation) higher. Populations of PPB in the plots without rice straw application significantly increased by the inoculation, unlike those in the plots with rice straw application, except for the bulk soil. Phototrophic and heterotrophic nitrogenase activities (acetylene-reducing activity) associated with the soils or residues of the rice straw were not affected by PPB inoculation throughout the experiment. This indicates that the inoculation of PPB into floodwater may not be effective for enhancing N₂ fixation in paddy soils and that the beneficial effect of PPB inoculation on the grain yield of rice may be due to unidentified functions of PPB other than biological N₂ fixation.     

氮肥基追比例对测墒补灌小麦植株氮素利用及土壤氮素表观盈亏的影响

以中筋小麦济麦22为试材,在小麦拔节期和开花期0—40cm土层土壤相对含水量均补灌至70%和总施氮量为240kg/hm~2条件下,设置5个氮肥基追比例处理:0∶10(N1)、3∶7(N2)、5∶5(N3)、7∶3(N4)、10∶0(N5),研究测墒补灌节水栽培条件下氮肥基追比例对小麦植株氮素利用和土壤氮素表观盈亏的影响。结果表明:N3处理的植株氮素积累量、籽粒氮素积累量显著高于其他基追比例处理;营养器官氮素积累量、土壤矿质氮损失量、氮肥表观残留率和氮肥表观损失率显著低于其他处理。与N1、N2、N4、N5处理相比,N3处理的氮素生理利用率分别高33.22%,12.60%,11.54%,98.14%,籽粒氮素利用率高148.65%,56.48%,59.63%,229.29%,氮肥农学效率高96.52%,34.86%,37.64%,204.98%,氮素表观盈亏量分别低35.04%,13.82%,30.36%,29.30%。根据不同氮肥基追比例下各指标的相关系数分析表明,植株氮素积累量、籽粒氮素积累量、氮素生理利用率、籽粒氮肥利用率、氮肥农学效率与土壤硝态氮积累量、成熟期0—200cm土层土壤矿质氮残留总量均呈显著负相关。综上,氮肥基追比例为5∶5的N3处理为试验条件下的最优处理。     

氮形态和磷肥对红壤玉米根际解磷微生物群落和磷酸酶活性的影响

较低的土壤磷素有效性限制了酸性红壤生产潜力提升。作为磷素活化的主要执行者,解磷微生物对施肥和根际作用的综合响应尚不清楚。以玉米为试验材料,设置磷肥水平（施磷和不施磷）与不同氮形态（铵态氮肥和硝态氮肥）的交互试验,使用编码酸性磷酸酶和碱性磷酸酶的微生物phoC和phoD基因作为分子标记物,研究了施肥和根际作用对酸性红壤磷酸酶活性和相关功能微生物群落的影响。结果显示,根际作用显著提高了土壤磷酸酶活性,且作用强度大于氮形态和磷肥水平。氮形态、磷肥水平和根际作用均显著影响phoD细菌操作分类单元（OTU）数目和香农指数,然而仅有氮形态和根际作用影响phoC细菌OTU数目。根际作用对phoC和phoD细菌群落组成结构的影响程度显著高于氮形态和磷肥水平,而且对phoD细菌群落的作用更明显。根际磷酸酶活性提高与土壤有机质增加密切相关。phoC细菌群落组成和结构的变化主要与根际养分变化有关,而phoD细菌群落结构的变化可能是根系分泌物和养分变化共同作用的结果。总体而言,玉米根际作用对酸性红壤磷酸酶活性和相关功能细菌群落的影响大于氮形态和磷肥水平,但是其作用强度一定程度上依赖于上述施肥措施。     

Effects of Manure and Chemical Fertilizer on Nitrogen Transformations and Functional Bacteria in a Black Soil of the Song-nen Plain

Intensities of ammonification, nitrification, denitrification, and the numbers of functional bacteria were measured in a black soil of the Song-nen Plain under different fertilizer managements over a period of 3 years. The six fertilizer managements were as follows: no fertilizer applied, manure at low and high rates, chemical fertilizer at low and high rates, and manure and chemical fertilizers in equal ratio. Manure increased the numbers of ammonifying and nitrifying bacteria and the intensities of ammonification and nitrification, whereas chemical fertilizer increased numbers of denitrifying bacteria and intensity of denitrification. Average denitrifying intensities ranged from 52.5% to 61.1%. There might be some coupling relation between nitration and denitrification in black soil.     

施氮对紫色土硝酸根和盐基离子耦合迁移的影响

通过室内土柱模拟试验,研究氮肥种类及施用量对紫色土硝酸根离子和盐基离子淋溶特征的影响。结果表明:(1)施氮能增加土壤中NO3-和盐基离子(K+、Na+、Ca2+、Mg2+)的淋失量,且施氮量越大,土壤中的盐基离子淋失越多。(2)施用不同种类氮肥,土壤中NO3-淋失有一定差异,在施用浓度较低(纯氮100,200mg/kg)时,表现为硝铵>尿素>硫铵;在施用浓度较高(纯氮300,400mg/kg)时,则表现为尿素>硝铵>硫铵;在试验浓度范围内,淋溶液中盐基离子累积淋失量在3个施肥阶段均表现为硫铵>硝铵>尿素>空白。(3)3个施肥淋溶阶段,淋溶液中NO3-和K+、Ca2+、Mg2+浓度均呈极显著正相关,而NO3-与Na+的相关性只在施用100,200,300mg/kg尿素和硝铵的处理中达显著水平,在其他处理中均不显著。     

不同氮水平对甘蔗氮素利用及土壤氮素残留的影响

以新台糖22号(ROC22)为试材,设施用15N标记的尿素2.5 g pot-1、5.0 g pot-1及7.5 g pot-13个处理,研究施氮水平对甘蔗氮素利用效率及土壤氮素的影响。结果表明,随氮肥施用水平的提高,甘蔗干物质积累、氮素积累、来源于肥料氮素的比率不同程度增加,同时土壤碱解氮含量、硝态氮含量、肥料氮素残留量及肥料氮素残留率显著增加,但甘蔗氮肥利用率显著下降;施氮水平还明显影响甘蔗各器官的干物质分配、氮素分配、氮肥利用率及氮素在不同土层的分布。本试验条件下,甘蔗氮肥施用土层深度为20 cm、尿素施用量为5.0 g pot-1较为适宜。     

生物炭与氮肥对稻田甲烷氧化菌和产甲烷菌数量和潜在活性的影响

基于稻田中氮肥配施生物炭的田间定位试验,研究了施用生物炭与氮肥对旱季稻田土壤理化性质、甲烷氧化与产生潜势及甲烷氧化菌和产甲烷菌丰度的影响。田间试验共设置5个处理：单施生物炭、单施氮肥、氮肥配施生物炭（生物炭设置两个水平）以及对照。结果表明：施用生物炭三年后显著提高了有机碳和微生物生物量碳含量（p﹤0.05）,与单施氮肥处理相比,氮肥配施生物炭后可显著提高土壤pH。与对照相比,单施生物炭显著提高土壤甲烷氧化潜势。在施氮条件下,甲烷氧化潜势与生物炭施用量之间存在正相关关系,与氮肥配施20 t hm-2处理相比,40 t hm-2生物炭处理甲烷氧化潜势增长53.8%。氮肥配施高倍生物炭与配施低倍生物炭处理相比产甲烷潜势由0.001提高至0.002 mg kg-1 h-1;氮肥施用一定程度上抑制了甲烷氧化菌数量的增长,单施氮肥处理中产甲烷菌数量较对照处理显著增加了3.0%;单施或配施低水平生物炭显著增加土壤甲烷氧化菌数量。氮肥显著降低了甲烷氧化菌与产甲烷菌基因丰度比（pmoA/mcrA）。而在同氮肥水平下施加生物炭显著增加了土壤pmoA/mcrA比值,即生物炭对甲烷氧化菌的促进作用显著高于产甲烷菌,提高了旱季稻田土壤的甲烷氧化能力,因此有助于减少稻田土壤甲烷的排放。     

秸秆与氮肥配施对潮土微生物活性及团聚体分布的影响

为了探索秸秆还田与氮肥配施对砂质潮土微生物活性与土壤团聚体的影响.采用室内培养的方法,在定量秸秆条件下,通过控制尿素用量,研究不同氮肥用量与秸秆配施比例对砂质潮土的有机质、土壤微生物量碳、氮含量、土壤酶活性以及土壤团聚体的影响.结果 表明:与CK相比,秸秆配施适量氮肥,能显著提高土壤有机质(29.04％～41.90％)...     

减施氮肥下聚天冬氨酸对烤烟生理特性及氮肥去向的影响

针对烤烟种植氮素施用量过多、氮肥利用率不理想等问题,以聚天冬氨酸(PASP)为肥料增效剂、我国烤烟主要种植品种云烟87和贵州黄壤为供试材料,采用~(15)N同位素示踪技术,探索了减施氮肥30%情况下PASP施用对烤烟生理特性和氮肥去向的影响,为PASP应用于烤烟生产提供参考。结果表明:减施氮肥和添加PASP均可有效提高烤烟氮肥利用率,前者提高效果在烤烟生育后期尤为明显,后者在前者的基础上可进一步增强提高效果。常规施肥减氮30%条件下,烤烟根系生理和叶片光合特性受到显著影响;在此基础上添加PASP其烤烟根系生理、叶片生理形态及氮肥利用率皆得到显著促进。低水平PASP(100 mg/plant)可在一定程度上提高氮肥利用率,但对烤烟根系、叶片光合特性促进效果不显著;相比较而言,较高水平PASP(400 mg/plant)更有利于烤烟根系和叶片的生理代谢及肥料利用率的提高。相关分析表明,PASP的添加量与氮肥利用率之间存在极显著正相关关系(p0.01)。生育后期,各处理的~(15)N分配率均表现为地上部大于地下部,且随着PASP添加量的增加,植株分配到地上部的~(15)N的量相应增加;此外,施用PASP显著降低了氮肥损失率,提高了氮肥总回收率,表现为PASP用量越高效果越明显。综上可知,施用PASP促进了烤烟生理代谢和氮素的吸收,降低了氮肥损失,以施400 mg/plant PASP效果最佳。     

肥料增效剂对碳氮淋溶和CO_2排放量的影响

为了调控肥料养分在土壤中的转化、减少养分损失,研制和合理使用肥料增效剂具有重要意义。研究采用土柱模拟试验的方法,探讨添加不同数量肥料增效剂对土壤碳(C)、氮(N)养分淋失数量以及土壤呼吸强度的影响,从减少肥料损失、保护环境角度明确增效剂的最佳施用量,为增效剂的合理施用提供科学依据。结果表明:施用增效剂对N和C的淋洗损失和二氧化碳(CO_2)排放损失量具有显著的影响,该影响主要发生在肥料施用后的前60天左右。当增效剂按肥料投入总量的6‰和8‰加入时,淋洗液中无机氮的累积淋洗量降幅达到13%～41%(P<0.05);而淋洗的无机N以硝态氮(NO_3~--N)为主,NO_3~--N淋洗总量是NH_4~+-N淋洗总量的20倍左右。增效剂的添加对可溶性有机C无显著影响,但显著增加了土壤CO_2的排放,增幅达到14%～64%(P<0.05)。淋洗结束后,与不施增效剂处理相比,增效剂添加量为6‰和8‰处理能够显著增加土壤NH_4~+-N、NO_3~--N、全氮(TN)和可溶性有机碳(DOC)含量,而土壤有机碳(SOC)含量基本保持不变。说明肥料增效剂能够减缓肥料氮素水解速率,又能抑制NH_4~+-N转化为NO_3~--N过程,加之土壤和增效剂对NH_4~+-N的强吸附特性,致使氮素迁移总量降低,可有效减轻对地下水造成污染的风险。综合以上结果,从减少土壤C、N淋洗和保持、提升土壤C、N含量角度考虑,增效剂的最佳施用量应大于肥料投入总量的6‰。