Effect of different fertilization modes on soil organic carbon sequestration in paddy fields in South China: A meta-analysis

Evidences have shown that fertilizer application could affect soil organic carbon (SOC) content in cropland. South China is the main production region of rice, in which many different fertilization practices have been widely used during the last several decades, but the effect of different fertilization modes on SOC sequestration in paddy fields in this region was scarcely studied. Based on 274 samples taken from 44 paddy field experimental sites in South China, a meta-analysis was performed to quantify the relative annual change of SOC content (RAC) and SOC sequestration duration in paddy fields under five fertilization modes (inorganic nitrogen fertilization, N; inorganic nitrogen and phosphorus fertilization, NP; inorganic nitrogen, phosphorus, and potassium fertilization, NPK; organic fertilization, O; and inorganic combined with organic fertilization, OF). The results showed that the RAC under the five fertilization modes was 0–0.4 g kg⁻¹ yr⁻¹, with increments of 0.19 and 0.23 g kg⁻¹ yr⁻¹ in double cropping systems and triple cropping systems, respectively. The RAC under the O and OF treatments was higher than that under the N, NP and NPK treatments and was the highest (0.32 g kg⁻¹ yr⁻¹) under OF among the five treatments. The SOC accumulation rate decreased with time, and the SOC sequestration duration under N, NP, NPK, O and OF was approximately 23, 28, 46, 64 and 55 years, respectively. The accumulation enhancement rate of SOC over the whole SOC sequestration period under the N, NP, NPK, O and OF treatments was approximately 12.9%, 23.4%, 29.3%, 47.2% and 55.1%, respectively. The OF treatment performed the largest potential for SOC sequestration in paddy fields in South China under long-term conditions.     

平衡施肥对缺磷红壤性水稻土的生态效应

为了研究平衡施肥对缺磷水稻土的生态效应,对长期缺施磷肥水稻土进行了3.5年平衡施肥试验。试验采取盆栽水稻的方式,在长期缺施磷肥的红壤性水稻土上比较不施磷肥（NK）、平衡施用氮磷钾无机肥（NPK）、无机氮磷钾肥配施硅肥（NPKSi）、无机氮磷钾肥配施有机肥（无机肥占3/5）、NPK基础上增施磷肥（NKhP）、NPKM基础上增施磷肥（NKhPM）处理的土壤肥力、土壤微生物特性、土壤磷的渗漏量以及地上部水稻产量、养分利用率、磷肥利用率的变化。试验表明,平衡施肥处理NPK、NPKSi、NPKM、NKhPM显著提高水稻产量,比不施磷肥（NK）平均增产147%,其中NPKM提高152%;能提高土壤肥力,比不施磷肥土壤有机质含量平均提高18.5%,其中NPKM提高30.1%;显著提高土壤微生物生物量,比不施磷肥土壤微生物生物量碳（MBC）平均提高57.2%,其中NPKM提高87.1%;提高氮素、钾素养分利用率,比不施磷肥平均分别提高120.3%、33.6%,其中NPKM分别提高152%、43%。而长期重施无机磷肥处理（NKhP）虽然水稻产量比不施磷肥处理提高125.1%,但因土壤中磷酸根离子含量过高影响土壤微生物正常生长,土壤微生物活度比不施磷处理降低9.4%,土壤微生物量碳（MBC）降低2.4%,稻田土壤微生物生态系统质量劣化。此外,重施磷肥处理（包括NKhP、NKhPM）易导致稻田水体的磷污染。各处理比较,NPKM综合生态效应最佳,以下依次是NKhPM、NPKSi、NPK,NKhP,NKhP对稻田土壤微生物生态系统产生负效应。根据试验结果,平衡施肥是恢复缺磷水稻土的有效措施,其中在平衡施用氮磷钾化肥的基础上增施有机肥或硅肥效果较好。     

长期不同施肥制度下几种土壤微生物学特征变化

 为阐明土壤微生物对土壤健康的生物指示功能, 以国家褐潮土肥力与肥料效益监测基地的长期肥料试验为平台, 应用BIOLOG ECO微平板培养法与常规分析法研究了长期施肥15年后不同施肥制度对土壤微生物生物量、活性、群落代谢功能多样性及土壤肥力的影响。研究结果表明, 与对照(CK)相比, 长期化肥与有机肥配施土壤中土壤有机质(SOM)、全氮(STN)、全磷(STP)含量升高, 土壤C/N与pH值降低, 土壤微生物量碳(Soil microbial biomass carbon, SMBC)、生物微生物量氮(Soil microbial biomass nitrogen, SMBN)、微生物商(qMB)及脲酶(Urease)活性升高, BIOLOG ECO微平板平均颜色变化率(Average well color development, AWCD)、土壤微生物代谢功能多样性指数变化不明显。和长期单施化肥处理(NPK)相比, 长期化肥与有机肥配施处理中上述几种微生物学特征(SMBC、SMBN、qMB、Urease及AWCD、代谢功能多样性指数)均呈极显著增加。NPK处理与CK相比虽然SOM、STN、STP含量稍有升高, 土壤C/N与pH值降低, SMBC、SMBN、qMB及Urease活性增高, 但是AWCD、土壤微生物代谢功能多样性指数却显著下降。过氧化氢酶活性(Catalase)在各处理土壤中的差异不显著。土壤微生物碳源利用的主成分分析表明, 长期不同施肥各处理在土壤微生物利用碳源的种类和能力上有差异。此试验说明, 土壤微生物受农业管理措施和多种环境因素的影响, 土壤微生物学特征可作为土壤质量的敏感指标, 为提高作物产量、增强肥力提供理论参考。     

不同施肥措施对红壤稻田氮磷平衡及生态经济效益的影响

应用始于1982年的长期定位试验,研究了单施化肥、单施有机肥及化肥与有机肥不同配比等处理下红壤区稻田的氮磷平衡,并评价了不同处理的生态经济效益,以期筛选出生态经济效益最优的施肥配比,减少红壤区稻田氮磷损失.结果表明: 不施肥处理(CK)下稻田氮素略有盈余(27.10 kg·hm^-2)、磷素亏缺(-6.85 kg·hm^-2),其他处理下氮磷均出现盈余,氮盈余量达110.94～243.98 kg·hm^-2,磷盈余量达19.06～67.49 kg·hm^-2.单施化肥(NPK)或有机肥(M)对稻田中氮磷平衡并无影响.在相同施肥量下,化肥配施有机肥(NPKM)比NPM和NKM的氮素盈余量分别低6.3%和12.9%,磷盈余量比NPM和PKM分别低3.7%和13.8%,能较好地维持农田的氮磷平衡.有机肥和化肥配施不同组合下均能提高0～20 cm土层全氮、全磷、碱解氮和速效磷含量.高施磷量处理稻田20～40 cm土层的速效磷含量较高.NPKM处理的生态经济效益综合评价得分值最高(0.762),是兼顾经济和生态效益的最优施肥配比,而CK处理的得分最低(0.560).根据本研究结果,在试验所处立地条件下,保持红壤稻田氮磷平衡的氮磷施肥量应分别为:N 157.71 kg·hm^-2,P₂O₅ 112.18 kg·hm^-2.     

Energy budgeting and emergy synthesis of rainfed maize–wheat rotation system with different soil amendment applications

Soil is a non-renewable resource and its preservation is essential for food security, ecosystem services and our sustainable future. Simultaneously, it is a major challenge to substitute non-renewable fossil based resources with renewable resources to reduce environmental load. In order to check soil erosion vis-a-vis degradation of sloppy lands of rainfed maize–wheat rotation system, fertilization with organic manure supplemented with inorganic fertilizers is required. In order to address these issues, substitution of 50% NPK through four organic manures viz. farmyard manure (FYM), vermicompost (VC), poultry manure (PM) and in situ green manuring (GM) of sunnhemp (Crotalaria juncea L.) were evaluated against 100% NPK through inorganic fertilizers and through FYM for energy budgeting and emergy synthesis during 2009–2014. Integrated use of FYM along with 50% NPK fertilizers could maintain the highest energy ratio (7.3), human energy profitability (142.4), energy productivity (0.22 kg MJ⁻¹), and energy profitability (6.3 MJ ha⁻¹) over other treatments. However, GM and inorganic fertilizers on equal NPK basis maintained the highest energy intensiveness (24.61 MJ US $⁻¹) and exhibited higher emergy yield ratio (2.66) and lower emergy investment ratio (0.60) and environmental loading ratio (3.74) which resulted into higher environmental sustainability index (0.71) over other treatments. Fertilization with organic manure (FYM) alone could not compete with other fertilized options to energy budgeting and emergy synthesis except specific energy. The study demonstrated that innovative integrated nutrient management of chemical fertilizers and organic manures particularly FYM for energy budgeting and GM for emergy synthesis may be considered as feasible and environment-friendly options for soil conservation, thereby benefiting a 50% saving on costly chemical fertilizers in non-OPEC countries which import most of its phosphorus and potassium fertilizers.     

黄泥田土壤真菌群落结构和功能类群组成对施肥的响应

研究长期不同施肥黄泥田土壤真菌群落组成和功能特性,深入认识真菌对不同施肥的响应机理,可以为合理施肥和保证农田土壤健康发展提供科学依据.设置不施肥(CK)、单施无机肥(NPK)、无机肥配施农家肥(NPKM)、无机肥加秸秆还田(NPKS)4个处理,采用Illumina高通量测序和FUNGuild对不同施肥处理下黄泥田土壤真菌群落结构和功能群进行分析.结果表明:从门水平上看,土壤真菌群落主要由子囊菌、担子菌和接合菌构成,且以子囊菌为主(47%~74%).NPKM和NPKS处理中子囊菌的相对丰度分别为49%和47%,显著低于CK(71%)和NPK(74%)处理,从目水平上看,减少的主要为肉座菌、格孢腔菌和散囊菌.NPKM和NPKS处理担子菌相对丰度分别为18%和28%,高于CK(14%)和NPK(10%)处理,从目水平上看,增加的主要为银耳菌、糙孢伏革菌和伞菌.与CK相比,单施无机肥降低了担子菌含量.不同施肥处理均在一定程度上增加了接合菌门的丰度,从目水平看,以内囊霉菌和粪蛙霉菌为主.NPK处理真菌α多样性指数显著低于其他处理,NPKM和NPKS处理的丰富度指数(Chao1和ACE)高于CK和NPK处理.不同处理之间真菌的营养类型以腐生营养型为主(48%~57%),NPKM和NPKS处理的共生营养型真菌相对丰度为17%,显著高于CK和NPK处理,增加的以丛枝菌根真菌、外生菌根真菌为主.NPK处理动物病原菌含量(10%)显著高于其他处理.冗余分析(RDA)结果表明,土壤含水量、孔隙度和盐度是影响真菌群落结构和功能类群组成的主要因子,其次为有机质和总氮.长期单施无机肥降低真菌种群多样性,增加致病菌含量,不利于土壤健康,而有机无机肥配施可在一定程度上提高真菌种群丰富度指数和共生真菌比例,有利于保持黄泥田稻田土壤健康的生态环境和真菌群落的多样性.     

鄱阳湖流域长期施肥下双季稻田的土壤基础地力

为探讨鄱阳湖流域不同施肥措施的土壤基础地力变化规律,基于长期施肥定位试验(始于1981年),采集定位30年时的不施肥(CK)、施用氮磷钾肥(NPK)和氮磷钾肥与有机肥配施(NPKM)土壤,于2012—2014年进行连续3年的施肥和不施肥试验,分析水稻产量和土壤基础地力贡献率的差异及关键影响因子.结果表明:不论施肥与否,3年的水稻产量均表现出NPKM处理显著高于NPK和CK处理,尤其是在不施肥条件下,NPKM处理的年产量分别比CK和NPK处理增加37.7%～143.9%和20.8%～66.7%.3年间,CK、NPK和NPKM处理的土壤基础地力贡献率分别为41.8%～53.1%、45.2%～62.6%和59.1%～88.1%,且NPKM处理的土壤基础地力贡献率均显著高于NPK和CK处理.进一步分析发现,土壤有机质和有机碳平衡量与土壤基础地力贡献率呈显著正相关.总之,在鄱阳湖流域的双季稻田,长期有机无机肥配施有利于该地区土壤基础地力的提升,且土壤有机质和有机碳平衡是土壤基础地力变化的关键因子.     

长期不同施肥下水稻产量及土壤有机质和氮素养分的变化特征

利用开始于1982年的湖南祁阳官山坪水稻长期(1982-2010年)定位试验,研究不同施肥条件下水稻产量及土壤有机质、氮素养分的动态变化特征,试验设置NPK、NPKM(M为牛粪)、 NPM、NKM、PKM、M和CK等7个处理.28年长期不同施肥处理结果表明：肥料的施用均能提高土壤有机质、全氮、碱解氮含量和水稻产量.氮、磷、钾化肥+有机肥(NPKM)处理的水稻产量一直保持最高水平,氮、磷、钾化肥(NPK)处理随着试验年限的延长呈下降趋势,其水稻产量逐渐低于其他施肥处理.单施有机肥或有机无机肥配施各处理土壤有机质含量在试验开始后的前16年有一个快速增加的过程,之后略有下降,然后仍保持增长趋势;NPK化肥处理土壤有机质含量仅在试验开始后的前8年增加较快,之后在一个相对稳定的范围内波动.各施肥处理在试验开始后的前8年内土壤全氮含量均呈快速积累趋势,以NPKM处理增幅最大.各施肥处理土壤碱解氮含量在试验开始后的前12年增加较慢,平均每年增加0.66～2.25 mg·kg^-1,1994-1998年增加较快,平均每年增加6.45～32.45 mg·kg^-1;1998年之后,各施肥处理土壤碱解氮含量均略有下降,其中,有机无机肥配施处理增加较快,单施化肥处理增加较慢.表明有机肥的施用是红壤性水稻土有机质和氮素营养水平稳定提升的关键措施,是红壤稻田土壤可持续利用的重要保障.     

长期施肥对新疆灰漠土土壤微生物群落结构与功能多样性的影响

以20a新疆国家灰漠土土壤肥力与肥料效益长期定位试验为平台,采用常规培养法,结合Biolog技术对可培养微生物、生理菌群数量和碳源利用进行测定分析,研究撂荒(CK0)、耕作不施肥(CK)、不同化肥(N、NK、NP、PK、NPK)、化肥配施低量高量有机肥(NPKM1和NPKM2)和秸秆还田(NPKS)等10种处理土壤微生物特征,揭示长期施肥对土壤微生物群落结构与功能多样性的影响。结果表明:(1)可培养微生物:与CK处理相比,CK0处理显著提高了细菌、放线菌和真菌的数量(P0.05),NPKS处理微生物数量则显著降低(P0.05);不同化肥处理的细菌(除PK处理外)、放线菌(除PK和N处理外)数量也有所增加,增幅在8.14%—135.70%和15.30%—44.78%之间;真菌数量(除NK处理外)则有一定幅度的降低;NPKM1和NPKM2处理,微生物数量最高,细菌分别增加了162.20%和173.75%,放线菌增加了34.39%和39.37%,真菌增加了63.33%和488.33%;(2)生理菌群:与CK0相比,CK处理显著提高了自生固氮菌和亚硝化细菌数量(P0.05),显著降低了氨化细菌和纤维素分解菌数量(P0.05);与CK相比,NPKM1和NPKM2处理显著提高土壤中与氮素转化有关的生理菌群数量(P0.05),不同化肥处理和NPKS处理的影响不相同,NPK处理显著高于其余处理(P0.05);(3)微生物碳源利用:微生物活性表现为NK、NPKM1、NPKM2N、NPK、CKPK、NPKSCK0、NP;CK0处理3个多样性指数以及NPKM1、NPKM2和NK处理Shannon(H)指数最高,其余施肥处理差异不显著;糖类、氨基酸类、羧酸类和胺类是微生物利用的主要碳源。(4)聚类分析表明,除NP处理外,施氮处理土壤有较为相似的碳源利用,细菌和真菌与养分之间有较好的相关性,可培养微生物和生理菌群与微生物碳源利用的相关性较差。因此,长期不同施肥对新疆灰漠土土壤微生物群落结构和功能多样性产生了显著的影响,长期耕作不施肥降低了土壤微生物群落结构和功能多样性,不同化肥配合施用对微生物群落的影响不同,NPK及NPK配施有机肥可提高土壤微生物多样性。     

不同施肥制度土壤微生物量碳氮变化及细菌群落16S rDNA V3 片段PCR产物的DGGE分析

应用化学分析和变性梯度凝胶电泳（DGGE）技术分离PCR扩增的16S rDNA的方法,研究了不同施肥制度对土壤微生物量碳、氮变化及微生物多样性的影响。结果表明,连续15a长期试验下,土壤微生物量碳（SMB-C）和微生物量氮（SMB-N）的含量大小均为长期撂荒（CK0）土壤高于农田土壤,而在农田土壤中,长期施肥的处理（NPK、NPKM、NPKSt和NPKF）高于长期不施肥处理（CK）,不同的种植制度中,长期复种轮作（NPKF）高于长期复种连作（NPK）;各处理的SMB-C/SOC（土壤有机碳）和SMB-N/TN（全氮）的比值的变化趋势与SMB-C和SMB-N变化一致;从PCR-DGGE分析,长期氮磷钾化肥配施有机肥（NPKM）处理的微生物量碳、氮的含量最高,微生物丰度最高,细菌物种最多,其次为长期撂荒（CK0）,CK处理细菌物种最少。UPGMC聚类分析表明NPK和NPKF处理细菌的群落结构相似,CK和CK0处理细菌的群落结构相似,而NPKM和NPKSt处理细菌的群落结构相似。     

不同施肥措施下亚热带稻田土壤碳、氮演变特征及其耦合关系

在湖南省稻田生态系统长期定位监测点研究了不同施肥措施下稻田土壤碳、氮演变及其耦合特征.结果表明：1986—2003年,无肥处理（对照,CK）稻田土壤有机碳和全氮含量略呈下降趋势;化肥（NPK）处理有机碳和全氮含量基本保持稳定,而有机 无机肥配施处理有机碳和全氮含量均呈增加趋势.与对照相比,化肥处理的土壤有机碳和全氮含量分别提高13%和18%,低量有机肥（LOM）处理分别提高54%和45%,高量有机肥（HOM）处理分别提高89%和67%.统计分析表明,土壤有机碳和全氮含量呈显著正相关（P<0.01）.稻田土壤C/N为8.5～12.9,多数分布在10左右.研究表明,有机-无机肥配合施用能在一定程度上促进稻田土壤碳、氮的固定与积累;稻田土壤碳、氮具有较好的耦合关系.     

长期施肥下黄壤旱地玉米产量及肥料利用率的变化特征

选取贵州黄壤长期定位监测点中对照（CK, 不施肥）、单施全量有机肥（M, 30555 kg·hm^-2）、有机肥与化肥配施（NPKM,年施N 165 kg·hm^-2、P₂O₅ 82.5 kg·hm^-2、K₂O 82.5 kg·hm^-2、有机肥30555 kg·hm^-2）和氮磷钾化肥配施（NPK,年施N 165 kg·hm^-2、P₂O₅ 82.5 kg·hm^-2、K₂O 82.5 kg·hm^-2）4个处理的16年试验数据进行分析,研究了黄壤区长期不同施肥下作物产量及肥料效益的变化趋势,为评价和建立长期施肥模式、促进粮食持续生产提供依据.结果表明：长期施肥条件下玉米产量年际间变化较大,总体呈上升趋势.其中NPKM处理增产效果最好,可增产4075.71 kg·hm^-2,增产率高达139.3%.长期施肥可提高玉米肥料利用率,其中M处理对玉米氮肥和磷肥利用率的提升作用最显著,分别达35.4%和18.8%;而NPK处理在提高玉米钾肥利用率方面作用明显,提高了20%,远高于M处理的87%和NPKM处理的9.2%.可见,长期均衡施肥,尤其是有机肥与化肥配施对提高作物产量和肥料效益具有积极作用.     

Long-term field fertilization alters the diversity of autotrophic bacteria based on the ribulose-1,5-biphosphate carboxylase/oxygenase (RubisCO) large-subunit genes in paddy soil

Carbon dioxide (CO₂) assimilation by autotrophic bacteria is an important process in the soil carbon cycle with major environmental implications. The long-term impact of fertilizer on CO₂ assimilation in the bacterial community of paddy soils remains poorly understood. To narrow this knowledge gap, the composition and abundance of CO₂-assimilating bacteria were investigated using terminal restriction fragment length polymorphism and quantitative PCR of the cbbL gene [that encodes ribulose-1,5-biphosphate carboxylase/oxygenase (RubisCO)] in paddy soils. Soils from three stations in subtropical China were used. Each station is part of a long-term fertilization experiment with three treatments: no fertilizer (CK), chemical fertilizers (NPK), and NPK combined with rice straw (NPKM). At all of the stations, the cbbL-containing bacterial communities were dominated by facultative autotrophic bacteria such as Rhodopseudomonas palustris, Bradyrhizobium japonicum, and Ralstonia eutropha. The community composition in the fertilized soil (NPK and NPKM) was distinct from that in unfertilized soil (CK). The bacterial cbbL abundance (3–8?×?10⁸ copies g soil^?1) and RubisCO activity (0.40–1.76 nmol CO₂ g soil^?1 min^?1) in paddy soils were significantly positively correlated, and both increased with the addition of fertilizer. Among the measured soil parameters, soil organic carbon and pH were the most significant factors influencing the community composition, abundance, and activity of the cbbL-containing bacteria. These results suggest that long-term fertilization has a strong impact on the activity and community of cbbL-containing bacterial populations in paddy soils, especially when straw is combined with chemical fertilizers.     

长期施用不同无机肥对旱地红壤线虫群落的影响

红壤生态系统中土壤生物群落对于维持土壤功能的正常发挥具有重要作用.本研究基于持续25年的红壤旱地化肥定位试验,研究不同无机肥组合,包括氮磷钾(NPK)、氮磷钾补充石膏(NPKCaS)、氮磷(NP)、氮钾(NK)和磷钾(PK)对花生生长季土壤线虫群落的影响.结果表明： 土壤线虫总数、营养类群以及各生态指数在处理间差异显著(P<0.01).线虫总数由高到低的顺序为PK>NPKCaS>NPK>NP>NK.除5月外,NPK、NP、NK处理的线虫总数均显著低于NPKCaS和PK处理.NPKCaS处理的优势类群为食细菌线虫,平均丰度为42.1%,其他处理均以植食性线虫为优势营养类群,其平均丰度为38%~65%.NPKCaS处理线虫群落较高的成熟度指数、瓦斯乐斯卡指数和结构指数说明土壤食物网结构较为成熟和稳定,同时表明氮磷钾补充石膏通过缓解土壤酸化创建了良好的土壤健康状况.仅施氮钾的处理则相反.本研究证实了施用石膏和磷肥是改善红壤质量的有效措施,土壤线虫群落分析能较好地反映不同无机肥对红壤旱地生态系统的影响.
     

长期不同施肥处理对苹果产量、品质及土壤肥力的影响

通过连续7年(2003-2010年)的田间定位试验,研究了不同施肥处理\[不施肥对照,CK;不施N肥只施PK肥,PK;不施P肥只施NK肥,NK;不施K肥只施NP肥,NP;单施NPK化肥,NPK;单施有机肥(猪粪),M;化肥有机肥配施(化肥有机肥氮各占一半),NPKM\]对渭北旱塬富士苹果产量、品质及果园土壤养分含量变化的影响.结果表明: 施肥可以提高苹果产量,连续7年不同施肥处理苹果平均产量较对照提高14.4%～63.8%,各处理苹果年平均产量顺序为:NPKM＞NPK≥M＞NP≥NK＞PK＞CK.NPKM、M、NPK处理随着试验时间的推移,果实可溶性糖、维生素C、可溶性固形物含量呈上升趋势,NPKM、M处理不同年际间波动相对较小;NPKM处理糖酸比5年较对照提高了30.9%,维生素C含量提高了17.5%.长期合理施肥有利于提高土壤有机质,NPKM、M处理0～20 cm土层有机质含量提高幅度最大,分别提高了28.8%和29.3%. NPK、NPKM、M处理土壤各层速效氮、有效磷、速效钾含量较试验前均有显著提高,NPK处理0～20 cm、20～40 cm和40～60 cm土层速效氮含量分别提高了22.7%、37.3%和53.4%.与NPK处理相比,NPKM处理的土壤速效磷含量提高了18.7%,且不同处理土壤速效磷含量上层显著大于下层.
     

Contrasting soil microbial responses to fertilization and tillage systems in canola rhizosphere

Information regarding the simultaneous evaluation of tillage and fertilization on the soil biological traits in canola production is not available. Therefore, field experiments were conducted in 2007–2010 in a split plot based on randomized complete block design with three replications. Main plots consisted of conventional tillage (CT); minimum tillage (MT) and no tillage (NT). Six strategies of fertilization including (N₁): farmyard manure (cattle manure); (N₂): compost; (N₃): chemical fertilizers; (N₄): farmyard manure + compost; (N₅): farmyard manure + compost + chemical fertilizers and (N₆): control, were arranged in sub plots. Results showed that the addition of organic manure increased the soil microbial biomass. No tillage system increased microbial biomass compared to other tillage systems. The activities of all enzymes were generally higher in the N₄ treatment. The activity of phosphatase and urease tended to be higher in the no tillage treatment compared to the CT and MT treatments.     

Effect of stand age on soil microbial community structure in wolfberry (Lycium barbarum L.) fields

Soil physicochemical properties and microbes are essential in terrestrial ecosystems through their role in cycling mineral compounds and decomposing organic matter. This study examined the effect of stand age on soil physicochemical properties and microbial community structure in wolfberry (Lycium barbarum L.) fields, in order to reveal the mechanism of soil degradation due to long-term stand of L. barbarum. The objective of the study was achieved by phospholipid fatty acid (PLFA) biomarker analysis of soil samples from L. barbarum fields in Zhongning County, Ningxia Province—the origin of L. barbarum. Five stand ages of L. barbarum were selected, < 1, 3, 6, 9, and 12 years (three plots each). The results showed that soil bulk density increased slightly with increasing stand age, while no clear trend was observed in soil pH or total salinity. As the stand age increased, soil organic matter and nutrients first increased before decreasing, with the highest levels being found in year 9. There was an amazing variety of PLFA biomarkers in soil samples at different stand ages. The average concentrations of total, bacterial, fungal, and actinomycete PLFAs in the surface soil initially decreased and then increased, before decreasing with the stand age in summer. The PLFA concentrations of major microbial groups were highest in year 9, with the total PLFA concentrations being 32.97% and 10.67% higher than those in years < 1 and 12, respectively. Higher microbial PLFA concentrations were detected in summer relative to autumn and in the surface relative to the subsurface soil. The highest ratios of Gram-positive to Gram-negative bacterial (G^?/G⁺) and fungal to bacterial (F/B) PLFAs were obtained in year 6, on average 76.09% higher than those at the other four stand ages. The soil environment was most stable in year 6, with no differences between other stand ages. Therefore, soil microbial community structure was strongly influenced by the stand age in year 6 only. The effect of stand age on soil G^?/G⁺ and microbial community structure varied with season and depth; there was little effect for F/B in the 20–40 cm soil layer. Principal component analysis revealed no correlations between microbial PLFA concentrations and total salinity in the soil; negative correlations were noted between soil pH and F/B in summer (P < 0.01), as well as between soil pH and fungal PLFA in autumn (P < 0.05). Moreover, microbial PLFA concentrations were correlated with soil organic matter (mean R = 0.7725), total nitrogen (mean R = 0.8296), total phosphorus (mean R = 0.8175), available nitrogen (mean R = 0.7458), and available phosphorus (mean R = 0.7795) (P < 0.01). On the whole, the soil ecosystem was most stable in year 6, while soil organic matter, nutrients, and microbial PLFA concentrations were maximal in year 9; thereafter, soil fertility indices and microbial concentrations decreased and soil quality declined gradually as the stand age increased. Therefore, farmers should reduce the application rate of fertilizers, especially compound or mixed fertilizers, in L. barbarum fields; organic or bacterial manure can be applied increasingly to improve the soil environment and prolong the economic life of L. barbarum.     

长期施肥对土壤微生物量及土壤酶活性的影响

 该文以北京国家褐潮土土壤肥力与肥料效益长期监测基地的长期肥料定位试验为平台,研究了长期不同施肥制度对土壤的生物学特性及其土壤酶的影响。主要研究结果：长期撂荒土壤(15年)的有机质和全氮(TN)的含量、微生物量碳(SMB-C)和氮(SMB-N)、土壤的蔗糖酶、磷酸酶和脲酶活性以及SMB-C/SOC(土壤有机碳)和SMB-N/TN比值都高于种植作物的农田土壤;而其代谢商和容重值低于农田土壤。长期施肥的农田(NPK、NPKM 、NPKS和NPKF),其土壤养分含量、微生物量碳和氮以及土壤蔗糖酶、磷酸酶和脲酶活性均高于不施肥的农田(CK);而小麦(Triticum aestivum)-玉米(Zea mays)→小麦-大豆(Glycine max)复种轮作(NPKF)的农田又高于长期复种连作(NPK)的农田;在施肥处理中(NPK、NPKM、NPKS和NPKF),长期化肥与有机肥配合施用的处理(NPKM )的土壤上述指标高于其它施肥处理(NPK、NPKS和NPKF),但其土壤的代谢商、pH值和容重值较低。     

稻草还田对水稻土固氮基因(nifH)组成结构和多样性的影响

以中国科学院桃源农业生态试验站长期定位施肥试验为平台,选取稻草还田(C)、氮磷钾(NPK)、氮磷钾加稻草还田(NPK+C)和不施肥对照(CK)4个处理,在晚稻的分蘖期、孕穗期和成熟期分别采集土样,利用实时定量PCR(Q-PCR)和末端限制性片段多态性(T-RFLP)等分子生物学方法研究长期稻草还田对水稻土含nifH基因固氮微生物群落丰度、组成和多样性的影响.结果表明：与对照相比,稻草还田和单施化肥处理均显著增加nifH基因的丰度(分蘖期除外),NPK+C处理中含nifH基因的微生物数量最高;nifH基因组成也受到长期施肥的影响,其中CK处理nifH基因组成与各施肥处理明显不同,C与NPK处理间nifH基因组成存在一定差异,而NPK与NPK+C处理间无显著差异.长期施肥不会引起含nifH基因微生物群落多样性的显著改变.可见,稻草还田不仅引起nifH基因群落的组成发生变化,而且导致其数量显著增加,因而可增加土壤的固氮能力.     

Long‐term balanced fertilization increases the soil microbial functional diversity in a phosphorus‐limited paddy soil

The influence of long‐term chemical fertilization on soil microbial communities has been one of the frontier topics of agricultural and environmental sciences and is critical for linking soil microbial flora with soil functions. In this study, 16S rRNA gene pyrosequencing and a functional gene array, geochip 4.0, were used to investigate the shifts in microbial composition and functional gene structure in paddy soils with different fertilization treatments over a 22‐year period. These included a control without fertilizers; chemical nitrogen fertilizer (N); N and phosphate (NP); N and potassium (NK); and N, P and K (NPK). Based on 16S rRNA gene data, both species evenness and key genera were affected by P fertilization. Functional gene array‐based analysis revealed that long‐term fertilization significantly changed the overall microbial functional structures. Chemical fertilization significantly increased the diversity and abundance of most genes involved in C, N, P and S cycling, especially for the treatments NK and NPK. Significant correlations were found among functional gene structure and abundance, related soil enzymatic activities and rice yield, suggesting that a fertilizer‐induced shift in the microbial community may accelerate the nutrient turnover in soil, which in turn influenced rice growth. The effect of N fertilization on soil microbial functional genes was mitigated by the addition of P fertilizer in this P‐limited paddy soil, suggesting that balanced chemical fertilization is beneficial to the soil microbial community and its functions.