【作者】 郝晓晖；

【导师】 胡荣桂；

【作者基本信息】 华中农业大学 ， 土壤学， 2008， 博士

【摘要】 选取分布在湖南省不同县市的8个稻田长期定位施肥试验点,以不同施肥小区（无肥、化肥、有机肥、秸秆还田）的耕层土壤作为研究对象,通过室内分析和培养实验,对土壤有机碳、活性有机碳、有机氮组分、微生物生物量、微生物多样性、土壤酶活、有机碳氮的矿化作用等进行测定分析,揭示涉及土壤有机质积累转化过程中的土壤微生物学特性及土壤有机质组分的特征。主要结果如下:一、稻田土壤碳氮积累特征1、各试验点耕层土壤有机碳（TOC）含量范围为16.18～38.65 g/kg,长期不施肥处理（CK）土壤TOC的含量保持在一个较为稳定的水平上,在17年的试验过程中,土壤TOC有上升趋势。单施化肥（NPK）对土壤TOC含量的影响不显著（仅在桃江和临澧试验点显著提高）;化肥配施有机肥处理（MOM、HOM）均显著提高了土壤TOC的含量,秸秆还田处理（STR）也对土壤TOC含量的提高作用明显。2、各试验点耕层土壤全氮（TN）含量范围为1.07～3.93 g/kg,CK处理土壤TN的含量与试验初始时相比基本持平。各施肥处理对土壤TN的影响与TOC相似,NPK处理对土壤TN含量的提高有一定的效果,且在3个试验点上影响显著;MOM、HOM和STR处理均显著提高了土壤TN的含量。3、稻田土壤碳氮比（C/N）在9:1～17:1之间,各施肥处理对其影响不显著,只在半数试验点上的MOM、HOM处理对其提高显著。4、各试验点土壤pH值变化在5.07～8.00之间,除南县和武冈试验点的土壤是偏碱性外,其余试验点土壤pH值均呈酸性。与稻田土壤初始值相比,长期种植水稻后土壤的pH值均表现出下降的趋势;与CK处理相比,长期施肥后稻田土壤pH值有明显的下降。二、稻田土壤活性有机碳特征1、各试验点耕层土壤可溶性有机碳（SOC）含量范围为23.73～122.77 mg/kg。NPK处理对SOC含量的影响不显著;MOM、HOM、STR处理均显著提高SOC的含量,且影响效果是HOM＞MOM＞STR。土壤SOC占TOC含量的0.13%～0.32%,新化和南县点土壤SOC所占的比例较高,MOM、HOM和STR处理除个别试验点外均显著提高其比例。2、各试验点耕层土壤轻组有机碳（LFOC）含量范围为0.62～6.08 g/kg。NPK处理可以提高LFOC的含量;MOM、HOM、STR处理均显著提高了LFOC的含量。土壤LFOC占TOC含量的3.80%～17.40%,MOM、HOM和STR处理均显著提高了土壤LFOC占土壤TOC的比例。3、土壤易氧化有机碳（ROOC）含量范围为5.87～18.60 g/kg。土壤ROOC占TOC的比例变化范围在49.02%～58.31%之间,与CK处理相比,不同施肥处理之间的比例差异均不显著。4、土壤活性有机碳各组分均与土壤TOC有显著的正相关性,可以作为表征稻田土壤有机碳的指标。三、稻田土壤有机氮组分特征1、各试验点耕层土壤酸解总氮（TAHN）的含量范围为822～3102 mg/kg,占土壤TN的64%～92%,是土壤氮的主体。长期不同施肥处理对TAHN含量及其组分有显著的影响。与CK处理相比,各施肥处理可以提高土壤TAHN及其组分中的氨基酸氮（AAN）、氨基糖氮（ASN）和酸解氨态氮（AN）的含量,但在个别试验点上影响未达显著水平。不同施肥处理使土壤酸解未知氮（HUN）和非酸解性氮（NHN）的含量有不同的变化规律,总体上施肥后HUN的含量有所降低,而使NHN有所增加。2、不同施肥处理土壤TAHN各组分所占TN比例的变化规律不尽相同,各处理间差异不太显著,大致上讲ASN和AAN的比例有所增加,AN和HUN的比例有下降趋势。AAN所占份额较大,对施肥处理的响应最为显著,ASN所占份额最小,且所占份额对不同施肥措施不敏感。3、土壤可溶性有机氮（SON）含量的变化范围为6.19～30.86 mg/kg,占土壤TN的0.32%～0.96%。NPK处理对土壤SON的影响不显著,化肥配施有机肥显著提高SON含量及其所占TN的比例。土壤SON与酸解有机氮各组分均存在显著的正相关性。四、稻田土壤微生物量、群落功能多样性及酶活性特征1、各试验点稻田土壤微生物量碳（MBC）、微生物量氮（MBN）含量的范围分别为261～968 mg/kg和25～109 mg/kg。NPK处理对半数试验点的土壤MBC、MBN含量影响不显著,MOM、HOM、STR处理则均有显著提高。土壤MBC占TOC的1.3%～4.5%,平均为2.1%;MBN占TN的1.3%～3.7%,平均为2.5%。施肥对微生物量占土壤TOC和TN的比例影响不太显著。土壤MBC与TOC、MBN与TN之间的关系呈显著正相关。各试验点稻田土壤微生物量碳氮比变化范围在6.5～13.5之间,除株洲和武冈试验点值较大外,其余都在7～9左右。与CK处理相比,各施肥处理降低了微生物碳氮比,但差异不显著。2、各试验点不同施肥措施在Biolog测定的细菌单一碳源利用模式上区分明显:Biolog盘中每孔的平均吸光值AWCD随培养时间的延长而增加,即土壤微生物碳源利用率在提高;不同施肥处理土壤微生物在碳源的利用能力上存在显著差异;土壤微生物群落利用的碳源主要为氨基酸类和糖类,但不同施肥处理碳源利用类型有差异。Shannon和Simpson指数的结果显示所有施肥处理均有利于维持微生物群落多样性,但秸秆还田使土壤微生物群落均匀度（McIntosh指数）降低。3、不同施肥处理下稻田土壤与碳循环有关的酶活（蔗糖转化酶、淀粉酶、纤维素酶、）,与氮循环有关的酶活性（蛋白酶、脲酶）以及参与磷循环的酶活性（酸性磷酸酶）,与CK处理相比,活性均有显著的提高,其中HOM处理的促进作用最大,STR的影响在新化试验点上最为明显。五、稻田土壤有机碳氮矿化作用特征1、在淹水条件下,不同施肥处理土壤有机碳矿化速率总趋势基本相似,CO₂的产生速率在前期保持较高水平,之后迅速下降直至稳定水平;CH₄的产生速率呈现为先缓慢升高后迅速降低的动态变化;土壤CO₂累积排放量范围为448.64～1516.77μg/g,CH₄累积排放量在范围15.60～33.34μg/g,化肥配施有机肥处理显著增加CO₂和CH₄的累积排放量;在培养期内土壤有机碳累积排放总量占TOC的3.6%～5.6%;土壤不同碳形态的含量与累积排放总量之间极显著正相关性,而仅ROOC、HC和FC的比例与累积排放总量呈显著正相关性;土壤有机碳累积排放总量所占TOC的比例与各碳形态相关性不显著。2、在不同温度条件下,土壤有机碳矿化在培养前期土壤CO₂产生速率较快,后期逐渐趋于平缓,其速率变化符合对数函数。升温促进了稻田土壤有机碳的矿化,以MOM、HOM和STR处理土壤有机碳矿化总量较高。土壤矿化总量与不同形态碳含量呈显著正相关关系。土壤的Q₁₀值变化在1.01～1.53之间,与土壤微生物代谢商和酶活显著正相关性,与土壤C/N比和Kos呈负相关。3、土壤有机氮矿化实验中,初始阶段矿化作用较强,矿化速率最大,有机氮矿化量迅速增加;但随着时间的延续,矿化作用减弱,矿化速率不断下降,矿化量达到最大值后变化平缓。10～30℃范围内,土壤有机氮矿化作用逐渐增强,65%田间持水量比淹水状态更有利于土壤氮素的矿化。长期化肥配施有机肥施用可以促进土壤氮素的矿化作用,使氮矿化量和矿化速率增大。综上,化肥配施有机肥对稻田土壤有机碳、氮及其各组分,有机碳、氮的矿化作用,土壤微生物量、活性和群落多样性都有明显促进作用,显著提高土壤碳氮肥力。不同有机肥之间的效果有所差别,秸秆还田措施不及施用猪粪处理,因此合理选择有机肥管理措施,可以提高土壤健康质量,增加土壤有机碳库,对缓解温室效应、发展可持续农业有重要的现实意义。更多还原

【Abstract】 Soil organic matter,soil microbial biomass,soil microbial community functional diversity,and soil organic matter mineralization affected by the applications of inorganic fertilizers and organic amendments in subtropical paddy soils were investigated.Soil samples were collected from the plough layer of 8 long-term field experiments at Xinhua, Ningxiang,Taojiang,Zhuzhou,Hanshou,Linli,Nanxian,and Wugang counties in Hunan Province,China.The long-term field experiments began in 1986,with the sites receiving the treatments:（1） no fertilizer[CK]（2） inorganic NPK fertilizer[NPK]（3） medium rate manure along with NPK fertilizer[MOM]（4） high rate manure along with NPK fertilizer [HOM]（5） rice straw along with NPK fertilizer[STR]（6） inorganic NK fertilizer[NK]（7） inorganic NP fertilizer[NP].Results showed that:1.Compared with initial levels,soil total organic C（TOC） in CK treatment increased at all sites,and total N（TN） increased at three sites.Compared with CK,application of NPK alone showed no significant effects on soil TOC and TN.NPK plus manure or straw significantly increased soil TOC and TN content.Ratio of C to N of paddy soils were ranged from 9:1～17:1.The different treatments had no significant effects on these values,except the MOM and HOM treatments.In comparison with initial levels,long-term plantation altered the soil pH; Application of inorganic fertilizers or organic amendments caused a soil pH decrease, compared with CK.The observed pH changes were due to the acidification of inorganic fertilizer and additional organic amendments to soils.2.Compared with CK,application of manure or straw along with inorganic fertilizer significantly increased the contents of soluble organic C（SOC）,light fraction organic C （LFOC）,readily oxidation organic C（ROOC）.The percentages of TOC presented as SOC, LFOC and ROOC were ranged from 0.13%～0.32%,3.8%～17.4%and 49.0%～58.3%, respectively.There was significant difference in these percentages for different treatments. There were highly significant correlations between SOC,LFOC,ROOC and TOC.3.Soil organic N was fractionated by acid hydrolysis-distillation method.Total acid hydrolysable N（TAHN） accounted for 64%～92%of the TN in the paddy soils. Compared with CK,application of inorganic fertilizer or organic amendments increased amino acid N（AAN）,ammonium N（AN）,and amino sugar N（ASN） and decreased hydrolysable unidentified nitrogen（HUN） for most of sites.Several treatments had no significant effects. Soil soluble organic N（SON） accounted for 0.4%～0.9%of TN.NPK plus manure or straw significant increased the contents and percentages of SON.SON was closely correlated with the soil organic N fractions.4.Soil microbial biomass（MB） C and N were measured by the fumigation-extraction method.Compared with CK,application of inorganic fertilizers alone showed no significant effects on soil MB C and MB N.Application of manure or straw along with inorganic fertilizers also significantly increased soil MB C and MB N contents for all sites.In average,soil MB C represented 2.1%of TOC and MB N accounted for 2.5%of TN.MBC and MBN were closely correlated with the soil TOC and TN contents respectively.The tendency for a reduction in MB C:N ratio in all the treatments compared with CK.The soil microbial community functional diversity was detected by BIOLOG system. The Average Well Color Development（AWCD） in BIOLOG plates indicated the ability of carbon utilization of microbial community.All the treatments exhibited the elevation of AWCD during the period of incubation,but the differences among the treatments were obvious.Application of manure along with inorganic fertilizer caused the highest increase of the AWCD while applying straw-incorporation had less affection on the AWCD, which was even lower than the CK treatment.It implicated that long-term fertilization resuked in the variation of the carbon utilization efficiency of soil microbial communities.The indices of Shannon,Simpson and McIntosh were calculated to show the richness, dominance and evenness of the functional diversity,while the principal component analysis of substrate reactions reflected the main carbon sources utilized by microbial community.The treatments of manure along with inorganic fertilizer remarkably improved the richness,dominance and evenness of soil microbial community in comparison with CK.The treatment of straw-incorporation induced increase of the dominance,but had no significant effects on the richness and evenness.The principal components were extracted from the principal component analysis and their cumulative contribution of variance accounted to 85%～92%.The correlation coefficients between main substrates and PC1 or PC2 indicated that the main carbon sources for soil microbes were carbohydrates and amino acids in all treatments and there were significant differences of carbon substrate utilization patterns in different treatments.5.Dynamics of soil organic C and N mineralization affected by different treatments and its relationship with organic C fractions in paddy soils were investigated.Mineralization of soil organic C was estimated by using 58-d anaerobic incubation at 30℃.The cumulative amounts of mineralized CO₂ ranged from 448.64～1516.77μg/g and mineralized CH₄ ranged from 15.60～33.34μg/g.Total amounts accounted for 3.59～5.57%of soil TOC.The rates of CO₂ production were higher during the 13-day incubation for different treatments,then decreased and afterwards a little varied.The rates of CH₄ production presented a slowly increasing at first and then rapidly declined to low constant rates.The cumulative released C（CRC） in NPK plus manure or straw treatments were greater than that in NPK treatments.Significant correlations were found between CRC and different organic C fractions.However,the percentages of ROOC,HC,and FC in TOC were positively correlated with the CRC.The correlations of soil organic C fractions with the percentages of CRC in TOC were not significant.Mineralization of soil organic C was estimated by using 33-d aerobic incubation under 3 temperature regimes（10℃,20℃,30℃）.The rates of CO₂ production were higher during the earlier phase（0～13 d） for different treatments,then decreased and afterwards a little varied.Daily mineralization of soil organic C during incubation accords to relationship of logarithm.While the soil temperature increasing,the amounts of total mineralized C increased for each treatment of each site.The amounts of total mineralized C in NPK plus manure or straw treatments were greater than that in inorganic fertilizers treatments.The correlations of different soil C fractions with total mineralized C were significantly correlated at 10℃,20℃and 30℃.The Q₁₀ values of paddy soils for different treatments ranged from 1.01～1.53.Significant correlations were found between qCO₂,enzyme activities and Q₁₀,while there were negative correlations between C/N ratios,Kos and Q₁₀.Mineralization of soil organic C was estimated by using 21-d incubation under 4 temperature regimes（10℃,20℃,30℃,45℃） and 2 water contents（submerged and 65% water-filled pore spaces）.Mineralization enhanced gradually with temperature in the range of 10-30℃.Compared with submerged incubation,the condition of 65% water-filled pore spaces was more beneficial to soil N mineralization.Mineralization of soil organic N was estimated by using 98-d anaerobic incubation at 30℃.The amounts of net mineralized N（NMN） increased with the prolongation of incubation time.The rates of N mineralization were highest about at the 4th week incubation for different treatments.The rate of mineralization and the ratio of NMN to TN in NPK plus manure or straw treatments are greater than that of inorganic fertilizers treatments.Significant correlations were found between NMN and TN and MBN.The data obtained show that the soil organic matter and microbial activities in paddy soils was improved by application of manure along with inorganic fertilizers when compared to inorganic fertilizers alone.It is therefore important that the traditional use of manure should be strongly promoted in order to maintain long-term soil productivity even where inorganic fertilizers are being used to achieve high yields.Not only will this improve the soil organic matter but it will also reduce the rates of inorganic fertilizers required since nutrients will be released from the manures.The incorporation of rice straw is another important way of promoting soil organic matter accumulation,so the importance of straw retention also needs to be stressed.更多还原