Effect of timing of application of municipal solid waste compost on N availability for crops in central Spain

To calculate the correct nitrogen fertilizer rate for crops and the possibility of using municipal solid waste (MSW) compost as an organic amendment, nitrogen mineralization rates were studied by laboratory incubation and field measurements in a soil in central Spain. Nitrogen mineralization rates were studied in a 250-day laboratory soil incubation with two treatments: with and without compost, incubated at 28°C and a moisture content of 70% of field capacity. Three phases are described: (1) no increase in the mineral nitrogen content, (2) a linear increase in the mineral N fraction and, finally, (3) a linear, parallel increase in both mineral N and easily mineralizable organic N fractions. Incubation data were fitted to three different equations. The exponential model proposed by Stanford and Smith (1972) was selected to predict field N mineralization rates. The field experiment was performed using a crop of maize with three treatments: compost applied in February (before sowing), compost applied during sowing and a control (without compost application): sampling was carried out over 14 months. Soil water content was measured periodically. Soil with compost applied in February showed 1.9 and 1.4 times more available nitrogen than soil without compost and compost at sowing, respectively, for the month of maximum accumulation. These results suggest that compost amendments must be applied before sowing. Compost applications were shown to supply the available nitrogen for spring crops. A simulation model showed satisfactory agreement with field data, after correction for soil temperature and water content. Received: 22 July 1996     

长期施肥潮土在玉米季施肥初期的有机碳矿化过程研究

以黄淮海平原长期定位试验地2007年玉米播种期土壤为研究对象,通过室内37天的培养实验并选择4个应用比较广泛的方程对土壤有机碳矿化过程进行拟合,其目的主要是为了比较研究长期不同施肥土壤在玉米季施肥初期有机碳矿化过程及主要矿化参数的差异,并评估矿化参数和主要土壤性质之间的相关关系.结果表明,37天培养期内各施肥处理土壤CO2-C累积释放量与土壤有机碳、全氮含量和微生物活度均呈显著正相关,大小依次为OM＞1/2OM+1/2NPK＞NPK＞NP＞PK＞CK＞NK,有机碳矿化过程均呈曲线形式,与Jones(1984)改进的一级动力学方程拟合效果最好.拟合所得土壤潜在可矿化有机碳量(C0)、易矿化有机碳量(C1)和初始潜在矿化速率(C0k)均表现出有机肥处理高于化肥处理,施肥处理高于不施肥处理(NK处理除外),与土壤有机碳、全氮和土壤微生物活度均呈显著正相关;有机碳矿化速率(k)和土壤潜在可矿化有机碳占土壤总有机碳的比例在处理间差异均不显著,除k与有机碳呈显著负相关外,其他与土壤性质均无显著相关性.因此,我们推测有机肥和化肥的平衡施用均能显著增强土壤有机碳的矿化作用,有利于土壤无机养分的释放,同时使部分有机碳在土壤中积累.     

Laboratory vs. in situ resin‐core methods to estimate net nitrogen mineralization for comparison of rotation and tillage practices

Properly estimating soil nitrogen (N) mineralization as a consequence of different agronomic practices would result in better soil N fertility management. In this study, we tested the differences between laboratory and in situ resin‐core incubation methods for estimating soil net N mineralization for long‐term burley tobacco (Nicotiana tobacum L .) tillage and rotation systems. The laboratory incubation method used crushed, homogenized, litter‐free soil samples, and the in situ resin‐core incubation method used an intact soil core with the inclusion of any plant residue below or above ground. Comparisons showed that no‐tillage had significantly increased soil net N mineralization compared to conventional tillage with the laboratory incubation method, while there was no significant difference between tillage methods with the in situ resin‐core method. This indicates that soil pretreatment in the laboratory incubation method can create an “artificial tillage effect” for soil previously managed with no‐tillage, resulting in overestimated soil net N mineralization. The rotation comparison showed that different crop sequences had no impact on measured net N mineralization with the laboratory incubation method. However, a preceding soybean crop did significantly increase net soil N mineralization compared to preceding corn when measured with the in situ resin‐core method. This suggests that discarding plant residue in the laboratory incubation method can neglect the potential effect of plant residue on soil N mineralization. Therefore, it is important to be aware that soil pretreatment may influence soil N mineralization estimates, potentially resulting in flawed decisions for soil N fertility management.     

Study of the Potentially Mineralized Nitrogen Content and Nitrogen Supply by Soil Incubation Method in a Long-Term Field Experiment in East Hungary

The formation and fate of soluble nitrogen (N) forms and their response to organic-matter mineralization is not obvious yet, and results are often inconsistent despite intensive research. The available N supply of the soil is very important for plant nutrition and environmentally sound N fertilization. The determination of actual N supply is very important for sustainable agriculture in Hungary, especially in acidic sandy soils, which are very sensitive to environmental effects and inefficient human treatment. Therefore, the aim of this article is to provide further information about N mineralization processes and organic–mineral interactions of soil. To establish the potentially mineralized N content and available N supply of soil, a biological (incubation) method was carried out an acidic brown forest soil of the Nyírlugos long-term field experiment in Hungary. The incubation was carried out in the laboratory with differently treated soils of the long-term field experiment to investigate the effect of treatments on N mineralization processes of soil. The incubation period was 16 weeks long. The pH and the easily soluble mineralized and organic N fractions of soil were measured periodically from leached solution (0.01 M calcium chloride; CaCl₂). The leaching process was repeated after 2, 3, 5, 7, 9, 12, and 16 weeks. The potentially mineralized N content of soil and the actual rate of N mineralization were calculated from periodically collected data. The results of the incubation method can be summarized as follows: the kinetics of incubation of 0.01 M CaCl₂ soluble organic N is similar to mineral N; 0.01 M CaCl₂–soluble N fractions were mainly in inorganic forms in the incubation period but the content of the organic form was significant too; and the mineralization rate is greater where the microbiological activity of the soil is expressed and the soil properties are more favored as a result of applied treatments.     

安太堡煤矿区不同复垦年限和复垦模式土壤氮矿化及硝化特征

为揭示煤矿复垦区土壤氮素内循环中的矿化及硝化特征,探索不同复垦模式与不同复垦年限下复垦土壤的氮素转化效率,采集山西安太堡露天煤矿中复垦3年、9年、21年苜蓿地及3年荞麦地表层（0~20 cm）土壤,并以3年自然恢复和未复垦新排土为对照,采用间歇淋洗好气培养法与恒温培养法研究各采样地土壤矿化与硝化过程,利用一级反应动力学模型与Logistic方程对有机氮素的矿化与硝化数据进行拟合。结果表明,3年苜蓿地的矿化速率最高,21年苜蓿地的矿化速率最低,且土壤氮素快速矿化主要在培养前7 d,之后逐渐平缓,并在28 d趋于稳定。经一级动力学方程拟合可知,氮矿化势（N_o）的变化范围为89.28~124.51 mg·kg^-1,21年苜蓿地 > 3年自然恢复地 > 3年苜蓿地 > 3年荞麦地 > 未复垦新排土 > 9年苜蓿地;矿化速率常数（k）的变化范围为0.022 6~0.051 9,3年苜蓿地 > 9年苜蓿地 > 未复垦新排土 > 3年自然恢复地 > 3年荞麦地 > 21年苜蓿地。氮矿化势与土壤有机质含量显著正相关（r=0.91）。复垦区各土壤随培养时间的延长硝态氮含量大致为"S"型曲线且可分为3个阶段：前期阶段（0~5 d）-上升阶段（5~14 d）-稳定阶段（14~28 d）;Logistic方程拟合结果显示：复垦年限显著影响硝化高峰出现的时间（不同复垦年限苜蓿地最大相差6.85 d）,21年苜蓿地硝化过程剧烈而短促,3年自然恢复地的硝化过程缓慢而漫长;耕地较草地有更大的硝化速率与更长的硝化时间。长期的种植苜蓿复垦显著提高了土壤的氮库容量,矿化过程更为平稳。     

沼泽湿地土壤氮矿化对温度变化及冻融的响应

通过室内控制培养试验方法,研究了不同温度和冻融循环过程对沼泽湿地土壤有机氮矿化影响。结果表明,湿地土壤中无机氮以铵态氮为主,温度和培养时间显著影响土壤有机氮的矿化,在温度-25~30℃之间,N的矿化速率、硝化速率随温度增加而增加,30℃时矿化速率（1.17mg.kg-1.d-1）和硝化速率（0.79mg.kg-.1d-1）最大。沼泽湿地土壤有机氮矿化培养时间以4~5周较为适宜。冻结温度和冻融次数显著影响土壤有机氮矿化过程,且-25~5℃冻融循环比-5~5℃冻融循环矿化累积量高。冻融循环促进了土壤有机氮的矿化,有利于土壤中有效氮的累积,为春季植物生长提供足够的氮素,对维持生态系统稳定有重要意义。     

Die N-Mineralisierung von Böden im Laborbrutversuch

N mineralization in soils under laboratory incubation conditions The potential rate of release of nitrogen by the organic matter in agriculturally used soils was determined under laboratory conditions by means of incubation. Mineralization of the more resistant soil organic matter proceeded linearly with time during an incubation period of 2–3 weeks, when field-moist and air-dried samples were used and at the beginning of the incubation experiment sufficient water was added to bring them to saturation. Mineralization was taking an exponential course in soils with additions of easily decomposable organic matter or in soils with a higher proportion of organic residues from crops. For the 14 investigated arable and grassland soils great variations in the average daily rate of mineralization were found ranging from 5–60 μg N_min/10 g DM. The data correlated very well with the biomass (r = 0.96) and the cell-free protease activity (r = 0.98) of the soils. Different measures of soil management (preceding crops, application of sewage sludge, addition of heavy metals) had a more or less pronounced influence on the rate of mineralization. The optimum temperature was 50°C for N mineralization and 26°C for nitrification. Contrary to nitrification, the soil reaction had only little influence on mineralization and proved also independent of the N_min content of soils. The results indicate that ammonification of organic N compounds may largely proceed via the microbial biomass.     

稻田土壤氮素矿化的几种方法比较

结合盆栽实验,对稻田土壤氮素矿化的几种方法进行了比较,结果表明:KC I煮沸法和碱解氮法是很好的测试土壤供氮能力的方法,淹水培养法矿化氮量与植物全氮含量相关性不高;而采用淹水培养间歇淋洗法和淹水密闭连续培养法对稻田土壤进行土壤氮素矿化的淋溶试验,结果表明:淋洗有利于土壤氮素的矿化过程。     

丹江口水库库滨带典型植物群落氮矿化特征

为明确库滨带典型植物群落矿化特征,探究植物化学性质与土壤氮矿化的关系,选取丹江口水库库滨带的苘麻和蛇床群丛.试验采取单一叶处理、单一根处理和根+叶混合等9种处理,分别测定第1、3、7、14、21、31、41、51和61 d的土壤氮矿化量,系统分析添加植物后土壤氮矿化特征.结果表明:1)添加植物后,土壤氮矿化可分为3个阶段,即前期(1 ～7d)各处理矿化量均减小,中期(7 ～41 d)各处理矿化量都有所增加,幅度变化较大,后期(41 ～61d)基本保持平衡,所有处理的土壤矿化量均小于对照(CK)的79.53 mg/kg,单一处理中,苘麻叶(QL)矿化量最高,达到71.62 mg/kg,混合处理最高为苘麻叶+蛇床根(QL+ SR) 26.43 mg/kg;2)添加植物后,土壤微生物的质量分数显著增加(P＜0.05),QL＞4个混合处理＞另外3个单一处理;3)整个试验期间,土壤氮矿化量与植物全碳和全氮质量分数显著相关(P＜0.05),主成分分析(PCA)结果显示全氮质量分数对土壤有机氮矿化影响最明显,重要程度为全氮＞C∶N＞纤维素＞L∶N＞多元酚;4)所有混合处理中,实测氮素矿化量均显著小于预测值(P＜0.01).说明添加苘麻和蛇床后,土壤氮矿化表现为抑制作用,根茎混合处理没有激发效应.该研究为区域植被生态恢复、水土保持与非点源污染治理提供参考依据.     

不同施肥措施对稻田土壤氮矿化的影响

采集田间通过不同施肥处理的水稻土为研究对象,在室内采用淹水培养方法,研究不同施肥措施对水稻土氮矿化的影响。结果表明:与不施肥处理相比,施加氮肥和饼肥能提高土壤的氮矿化能力;与常规施氮处理相比,采用新型施肥措施,氮肥+木质素、一次施用的水稻缓释肥、氮肥+有机碳源均降低土壤的氮矿化作用,其中氮肥+有机碳源处理与常规施氮处理相比,土壤全氮增加了16.7%,但淹水培养期间土壤的氮矿化量却减少了18.5%,这一结果说明,采用这些新型施肥措施有利于增加土壤对氮的固持,降低氮素向环境损失的风险。     

模拟氮沉降对小兴安岭地区人工红松林土壤氮转化的影响

以我国小兴安岭地区凉水国家级自然保护区30年林龄的人工红松林为研究对象,建立对照(0 kg hm~(-2)a~(-1))、低氮(20 kg hm~(-2)a~(-1))、中氮(40 kg hm~(-2)a~(-1))和高氮(80 kg hm~(-2)a~(-1))四种模拟氮沉降水平的样地;采用室内培养试验,研究了短期模拟氮沉降对人工红松林土壤氮净矿化、净硝化速率和氧化亚氮排放的影响。结果表明,与对照处理相比,经过2年的模拟氮沉降处理,土壤的净矿化、净硝化速率都有降低趋势。与对照相比,低氮、中氮、高氮土壤净矿化速率分别降低了16.9%、20.6%和25.2%,土壤净硝化速率分别降低了16.7%、20.9%和25.5%,但是处理间差异没有达到显著水平。净硝化速率与净矿化速率呈显著正相关关系(P0.05),表明净矿化速率降低减少铵态氮供应量可能是氮沉降处理降低净硝化速率重要原因。另外,模拟氮沉降处理导致土壤p H降低也不利于硝化作用。中氮和高氮处理土壤氧化亚氮累积排放量分别比对照高84%和40%,但是差异不显著。高的氮沉降量使硝化过程中氧化亚氮的排放比例增加,可能是中氮和高氮处理下净硝化速率下降而土壤氧化亚氮排放量却增加主要原因。研究结果表明,氮沉降会影响我国小兴安岭地区森林土壤氮矿化和硝化过程,但是由于实验开展观测时间较短,其影响规律还需长期实验验证。     

长期施肥对黑土氮素矿化与硝化作用特征的影响

采用培养试验研究了长期施肥对黑土矿化与硝化作用特征的影响。结果表明,黑土的矿化作用和硝化作用都较强,长期施肥对黑土矿质态氮量有显著影响,施用化肥能够增加矿质态氮量,在施用NPK肥基础上增施有机肥,矿质态氮量进一步增加,表明在土壤管理上如果增加有机肥的施用,可以提高土壤的供氮能力。长期施肥黑土的硝化率与施N肥相关性较好,其次是施用PK肥。有机肥与无机肥配施可使土壤硝化率显著提高;硝化率高低取决于黑土可矿化态氮素含量和土壤pH。     

不同利用方式下土壤有机氮素矿化特征的研究

采用长期淹水密闭培养-间歇淋洗法(30℃),测定了长期(16年)定位的水田、旱地和林地土壤有机氮素的矿化氮数量,利用一级反应动力学模型对有机氮素的矿化过程进行了拟合,并探讨了不同利用方式下土壤有机氮素的矿化特征。结果表明,3种利用方式下土壤有机氮素的矿化过程均可用一级反应动力学模型很好地拟合;任意两种土壤利用方式之间的N0值差异均达1%显著水平,水田与旱地、林地之间的k值差异均达1%显著水平,而旱地与林地之间的k值差异则达5%显著水平,林地土壤氮素矿化势最大(72.96 mg kg-1),约为旱地和水田土壤的1.3倍和7.4倍,水田土壤氮素矿化速率最大(0.0908 d-1),约为旱地和林地土壤的4.1倍和2.3倍;旱地和林地土壤供氮能力大小相接近,分别为88.24 mg kg-1和89.11 mg kg-1,约为水田土壤的2倍左右。由此可见,长期(16年)不同利用方式对土壤有机氮素矿化特征影响显著,水田土壤可供矿化的有机氮数量最少且矿化时间最为短暂,旱地土壤可供矿化的有机氮数量较多且矿化时间最为缓慢持久,林地土壤可供矿化的有机氮数量最多且矿化时间较为缓慢持久。     

水分条件对不同类型土壤氮矿化及酶活性的影响

针对凉攀烟区立体气候特征明显，干湿分明特征，从水分变化角度研究植烟土壤氮素矿化及其酶活变化特征，为合理调控土壤氮素供应提供科学依据。以凉攀烟区土壤为研究对象，通过室内培养法研究了不同水分条件培养下（60%田间持水量（60%WHC），淹水状态（FS）），土壤（红壤、紫色土）氮矿化动力学及酶活性特征。结果表明，（1）与60%WHC相比，FS培养条件提高了土壤NH4+-N含量，且培养期内紫色土NH4+-N平均含量较红壤增加6.0%~9.0%； 60%WHC培养下土壤NO3--N含量明显高于FS，且培养期内红壤NO3--N平均含量（40.7~64.1 mg/kg）高于紫色土（38.0~56.4 mg/kg）；（2）FS培养提高了土壤氨化速率，紫色土平均氨化速率均高于红壤，60%WHC培养提高了土壤硝化速率，且红壤平均硝化速率高于紫色土；（3）培养期内，60%WHC培养下土壤无机氮累积矿化量明显高于FS，红壤氮矿化潜力强于紫色土，其中红壤在60%WHC培养下的土壤无机氮累积矿化量最大（42.12~394.06 mg/kg），其次是同一水分条件培养下的紫色土；（4）土壤脲酶、蛋白酶和亚硝酸还原酶的活性与土壤无机氮矿化累积量存在显著的相关性，红壤的脲酶活性强于紫色土，尤其是在60%WHC培养的效果更为显著；紫色土的蛋白酶活性和亚硝酸还原酶活性高于红壤，尤其是在FS培养下的效果显著。总体上，凉攀烟区红壤氮矿化潜力强于紫色土，尤其是在60%WHC条件下，在推荐氮肥施用量时，不仅要考虑不同土壤类型，而且还应该注意土壤水分状况的调控，防止烤烟生长后期氮素供应能力过强，影响烟叶成熟落黄和香气物质形成。     

水稻生长对土壤氮素矿化的影响

淹水条件下,土壤氮素的矿化是土壤有效积温的函数.用淹水密闭培养法,预测田间种稻下土壤氮素的矿化量和矿化过程时,其准确性受到许多因素的影响.为了明确水稻生长对土壤氮素矿化的影响程度,以及不同季别的水稻在这方面的异同,我们进行了下述试验.     

土壤微生物体氮与可矿化氮关系的研究

同时应用大田试验和室内培养试验研究土壤微生物体氮与可矿化氮之间的相关性。试验结果表明,田间条件下,土壤微生物体氮与可矿化氮之间的关系不密切,但在培养试验中,微生物体氮与淹水培养法、硝化培养法和Stanford短期淋洗通气法测定的可矿化氮间有显著的线性关系,相关系数在0.767(p<0.01,n=12)以上。田间试验结果和室内培养试验结果的不一致性,与试验条件的差异有关。新形成的微生物体氮易降解,而原有土壤微生物体氮却相对稳定。     

土样制备和保存方法对亚热带土壤反硝化的影响

比较了两种土样制备和保存方法对厌氧培养1周内土壤反硝化及矿化的动态影响。试验结果表明,强烈风干后并经长期存放过的土样显著促进了NO3--N浓度降低速率和N2O排放速率的提高,其反硝化速率和矿化速率分别较稍微风干后无存放时间(即立即开始培养试验)的土样提高了47.3%和31.0%。强烈风干土有机C矿化作用的增强以及易矿化有效态C含量的提高是促进反硝化作用增强的主要原因。风干程度和存放时间对反硝化的促进程度取决于其对有机质矿化影响的相对大小,对有机质矿化的影响越大,反硝化强度增加的幅度也越大。由试验结果可推测,利用风干土的实验室培养方法测定得到的土壤反硝化势可能会过高估计田间原位测定的反硝化势。     

长期有机培肥模式下黑土碳与氮变化及氮素矿化特征

土壤氮的矿化是土壤氮素肥力的重要指标,是影响作物产量至关重要的因素。本研究依托黑土长期定位试验,通过取样分析研究了32 a不同培肥模式下黑土碳、 氮及主要活性组分的变化,采用淹水培养法研究了不同施肥模式下黑土氮素的矿化特征。结果表明,施肥显著提高黑土可溶性碳（DOC）、 氮（DON）的含量及其比例。在氮、 磷、 钾化肥的基础上配施有机肥,显著降低了土壤微生物量氮（SMBN）占土壤总氮的比例,提高了土壤微生物量的C/N比值（SMBC/SMBN）,促进了土壤氮的生物固持。施肥32 a后,单施常量和高量有机肥处理的土壤氮的矿化量（Nt）显著提高,分别相当于不施肥的8.2倍和10.2倍,而单施氮或氮磷钾化肥对黑土氮素矿化量无明显影响。施用有机肥显著提高了土壤氮素的矿化率（Nt/TN）,但有机肥配施化肥（氮或氮磷钾）的处理与单施有机肥相比,黑土氮的矿化率显著降低,降低幅度分别为23.5%~32.1% 和14.1%~17.8%。土壤氮素矿化量与土壤有机质、 全氮储量、 活性碳、 氮组分均呈极显著线性相关,但氮素的矿化率随着有机质和全氮含量的提高而提高至0.4% 后基本稳定。表明尽管土壤氮的矿化与有机质的含量直接相关,但土壤有机质的品质同样决定着土壤氮素的矿化能力。施有机氮是提高土壤供氮能力的重要途径。     

苏打盐碱化稻田土壤氮素矿化和硝化特征及其影响因子

  【目的】  为探明土壤盐碱化对氮素转化的影响,研究了不同盐碱化条件下氮素的矿化和硝化特征以及这些特征与土壤盐分、养分含量的关系,为盐碱化土壤养分的科学管理提供理论依据和数据支撑。  【方法】  随机采集了30个不同盐碱化程度的稻田土壤 (0—20 cm)样品,根据盐碱化程度将采集的土壤样品划分为轻度(含盐量0.1%～0.3%,碱化度5%～15%)、中度(含盐量0.3%～0.5%,碱化度15%～30%)和重度(含盐量0.5%～0.7%,碱化度30%～45%)盐碱土3类,每个类别中依据最小归类样品数选取盐碱化程度接近的3个土样作为3次重复,进行氮素矿化和硝化室内培养试验(25℃,24 h光照)。于培养的第0、3、6、9、15、21天取样测定土壤铵态氮、硝态氮含量及脲酶和碱性蛋白酶活性。通过相关性分析研究土壤各指标与氮素矿化、硝化过程间的相关关系,采用逐步回归分析筛选影响氮素矿化和硝化过程的主要因子。  【结果】  随着土壤盐碱化程度的加剧,氮素矿化和硝化作用显著下降(P<0.05)。与轻度盐碱土相比,中度和重度盐碱土的氮素最大净矿化速率分别低12.7%和29.8%,累积矿化氮量分别低15.7%和25.2%,最大净硝化速率分别低15.4%和23.1%,累积硝化氮量分别低15.4%和23.1%,最大脲酶活性分别低16.0%和34.8%,最大碱性蛋白酶活性分别低6.0%和15.6%。逐步回归分析表明,土壤电导率(EC)、pH、CO₃2–、Na+、全氮和有机质是影响土壤氮素矿化作用的主要因子,EC、pH、CO₃2–、Na+和有机质是影响土壤氮素硝化作用的主要因子。  【结论】  随着土壤盐碱化程度的增加,土壤氮素净矿化速率、净硝化速率、累积矿化氮量、累积硝化氮量、脲酶和碱性蛋白酶活性不断下降,土壤盐碱化显著抑制了氮素的矿化和硝化作用。     

施用猪粪条件下重金属对土壤氮素净转化的影响

以东北耕作黑土为研究对象,在25℃和70%WHC水分条件下进行为期35天的室内培养试验,研究了施用猪粪条件下重金属Cu、Cd对土壤氮素净转化的影响。结果表明:添加单一重金属显著抑制了土壤的硝化作用和矿化作用。与对照处理相比,添加重金属Cu、Cd处理培养结束后土壤铵态氮含量分别增加了5.83和5.39倍,硝态氮含量分别下降了84.3%和79.5%,且土壤净氮矿化速率和净硝化速率均显著低于对照处理。添加重金属的同时施用猪粪加剧了重金属对硝化作用和矿化作用的抑制,土壤净硝化速率和净氮矿化速率均显著低于单一重金属处理。添加重金属抑制了土壤反硝化作用,但同时添加猪粪在一定程度上降低了重金属离子的活性和毒性,进而减轻重金属离子对反硝化作用的抑制程度。