大豆连作障碍及调控技术研究进展

综述了近15年来有关大豆连作引起的根分泌物及残茬腐解物的自毒作用、植株营养失调、病虫危害加重、土壤微生物种群数量和生物肥力及土壤某些理化性质改变等障碍因素方面的研究，总结了提高连作大豆产量品质的主要调控措施。在此基础上，对有关研究需进一步关注的几个问题进行了讨论。     

大豆专用肥对轮作、连作大豆土壤酶活性和有效养分的影响

采用盆栽、田间小区控制试验及室内分析相结合的方法 ,研究了施用大豆专用肥对连作、轮作大豆土壤酶活性和有效养分的影响。结果显示施用大豆专用肥后 ,土壤酶活性和有效养分总体均能达到或高于轮作土壤常规施肥水平 ,这表明大豆专用肥能调控大豆连作所引起的土壤酶活性和养分恶化 ,最终使得大豆专用肥能克服大豆连作所引起的大幅度减产     

大豆专用肥对轮作、连作大豆土壤酶活性和有效养分的影响

采用盆栽、田间小区控制试验及室内分析相结合的方法，研究了施用大豆专用肥对连作、轮作大豆土壤酶活性和有效养分的影响。结果显示施用大豆专用肥后，土壤酶活性和有效养分总体均能达到或高地轮作土壤常规施肥水平，这表明大豆专用肥能调控大豆连作所引起的土壤酶活性和养分恶化，最终使得大豆专用肥能克服大豆连作所引起的大幅度减产。     

东北黑土区长期不同种植模式下土壤碳氮特征评价

土壤碳氮是衡量土壤肥力的重要指标,阐明农田管理措施对土壤碳氮特征的综合影响,可为农田地力培育和土地可持续利用提供理论与技术支撑。该研究借助在吉林公主岭建立的长期定位试验,选择休闲处理与增施有机肥条件下的玉米连作、玉米-大豆轮作、大豆连作等处理,系统评价了种植模式对土壤不同形态碳氮的影响及其相互关系。经过21 a的增施有机肥,玉米连作、玉米-大豆轮作、大豆连作3个处理的耕层(0~20 cm)土壤有机碳、全氮和有效氮比休闲处理分别提高23.5%~46.8%、4.9%~64.3%和35.4%~121.9%,其中以玉米连作处理最高(P0.05);有机碳与全氮、有效氮呈极显著的相关关系(P0.01),表明较高的有机碳会促进氮素有效性。玉米连作处理的耕层土壤微生物量碳分别比玉米-大豆轮作和大豆连作处理高23.1%和41.4%,而土壤微生物量氮则分别高37.8%和135.3%,差异显著(P0.05)。玉米连作处理下耕层2 000μm、≥250~2 000μm、≥53~250μm以及53μm的土壤团聚体结合有机碳均为最高(P0.05)。此外,玉米连作处理的高活性有机碳组分显著(P0.05)高于其他处理,其化学活性指数也显著(P0.05)高于玉米-大豆轮作处理,表明玉米连作处理下的土壤有机碳对外界环境变化较为敏感。上述研究表明,在施用有机肥的条件下,长期玉米连作可提高土壤有机碳质量分数,促进土壤氮素有效性,但应配合采用合理的耕种措施,以降低有机碳分解风险。     

大豆连作障碍及产生机理

选择不同连作年限的地块设置试验小区，定期调查大豆根腐病发病程度，大豆收获后测产，并采用稀释平析以法测定大豆根际土壤中微生物组成及密度结果表明：连作导致大豆产量降低，根腐病加重，形成了明显的连作障碍现象，连作障碍产生的原因初步认为系由于大奶际病原真菌种类增加，有益真菌数量减少而致。同时连作导致大豆根际细菌放线菌密度下降，由此造成大豆根腐病加重。     

土层置换对大豆土壤酶活性及根腐病病情指数的影响

大豆连作导致土壤养分失衡,土壤酶活性降低,以及大豆病害加剧、品质和产量降低等问题。采用田间小区试验方法,通过对土层置换及大豆种衣剂拌种等措施对大豆土壤不同土层土壤酶活性及根腐病病情指数影响的分析,为消除大豆连作障碍提供科学的技术支撑。结果表明:土层置换处理及置换后增施磷肥或有机肥及大豆种衣剂处理,提高了大豆田间土壤脲酶活性、蔗糖酶活性和磷酸酶活性。与对照CK相比,T_2,T_3,T_4处理0—10cm土层脲酶活性均增加;土层置换并增施有机肥显著提高了土层中蔗糖酶活性;土层置换后增施磷肥或有机肥及大豆种衣剂拌种处理均可有效保持大豆土壤中磷酸酶的活性,并且可降低大豆根腐病病情指数;土层置换并增施磷肥处理提高了大豆产量,较CK处理产量提高20.42%,差异达到显著水平。     

三江平原岗地白浆土水解酶活性和动力学特性对不同连作农作物的响应

作物种植会对农田生态系统产生一定的影响。大田试验条件下,在黑龙江省853农场岗地白浆土上连续6年种植玉米、大豆、小麦、水稻,研究了土壤理化性质以及土壤中与碳、氮、磷、硫元素转化相关的9种水解酶活性和动力学特性的响应;同时研究了不同作物种植对土壤脲酶、磷酸单酯酶、磷酸二酯酶、芳基硫酸酯酶及β-葡糖苷酶动力学特性的影响。结果表明,大豆连作土壤的有效氮、总碳、总氮、总磷和总硫含量都稍高;大豆处理土壤pH值略低,但其它三种作物种植下的土壤均呈微酸性,差异不显著。土壤水解酶动力学参数对种植作物的反应与表观活性的反应不一致。玉米连作土壤蛋白酶和磷酸单酯酶活性高于其它处理;小麦处理的磷酸二酯酶和芳基硫酸酯酶活性最高,水稻连作土壤蛋白酶、磷酸二酯酶和磷酸三酯酶活性最低。连年种植小麦处理的土壤脲酶、磷酸二酯酶以及芳基硫酸酯酶Vmax显著高于其它处理,小麦连作土壤β-葡萄糖苷酶、脲酶、磷酸二酯酶和芳基硫酸酯酶的Vmax/Km值显著高于其它处理,可以看出在此处理下土壤酶具有较强的催化潜势。     

烤烟连作对耕层土壤酶活性及微生物区系的影响

以烤烟品种"龙江911"为材料,在大田试验条件下分别测定了连作1年和5年的烤烟耕层土壤酶活性及微生物区系变化。结果表明:烤烟连作1年的耕层土壤酸性磷酸酶与脲酶活性高于正茬(大豆-小麦-烤烟),而烤烟连作5年的土壤酸性磷酸酶与脲酶活性低于连作1年。在0~10 cm土层内,烤烟连作1年和连作5年的土壤过氧化氢酶活性均比正茬低,且连作5年土壤比连作1年土壤降低了35.47%。10~20 cm土层内,烤烟连作1年和5年的土壤蔗糖酶活性分别比正茬降低了30.27%和52.14%。烤烟连作减少了土壤细菌和放线菌数量,增加了真菌数量,细菌主要以土壤氨化细菌、好气性自生固氮菌和好气性纤维素分解菌降低为主。因此,烤烟连作破坏了微生物种群的平衡及降低土壤酶活性可能是引起烤烟连作障碍的主要原因之一。     

长期轮作和连作对白浆土中氮素的影响

对轮作及大豆、玉米、小麦长期连作白浆土中氮含量及有机态氮组分变化进行研究。结果表明，在不施肥情况下，小麦连作区土壤由全氮、碱解氮降幅最大，酸解总氮、氨基酸态氮和氨基糖态氮降幅最小。在施有机肥情况下，土壤全氮、碱解氮及酸解总氮则以小麦连作区增幅最小，玉米连作区增幅最大；氨基酸态氮和氨基糖态氮在轮作区增幅最大。其他组分氮在轮作与连作小区间变化无规律。     

不同有机物料对连作大豆土壤养分含量及生物性状的影响

选取畜禽粪便、天然有机物料、有机肥类有机物料3大类共9种有机物料进行大田试验,设正茬和连作2种种植方式,主要研究不同类型有机物料对土壤养分和生物性状变化特征的影响。结果表明:有机物料的施入对提高土壤养分含量和改善土壤生物性状作用效果明显。正茬土壤pH为5.70~6.00,连作土壤pH为5.50~5.90,施用有机物料小区均高于CK处理。畜禽粪便类有机物料,对提高大豆土壤速效钾含量效果显著,对正茬和连作土壤分别平均提高12.73%和17.09%;猪粪对正茬土壤呼吸提高11.30%;鸡粪对连作土壤中微生物量氮提高13.85%。天然有机物料,对提高土壤中碱解氮作用明显,正茬和连作分别平均提高6.31%和3.30%。有机肥类有机物料,对大豆土壤中速效磷含量正茬和连作土壤分别提高2.13%和2.27%,有机质含量分别提高1.98%和4.20%;鸡粪型有机肥对正茬土壤微生物量碳提高3.45%。所有有机物料处理整体效果均好于CK处理,这表明有机物料的施入具有提高大豆土壤养分含量,改善土壤养分性状的作用。     

Developing suppressive soil for root diseases of soybean with continuous long-term cropping of soybean in black soil of Northeast China

Field experiments were set up in 1991 to test if suppressive soil to soybean root diseases could be developed with continuous long-term soybean cropping in black soil of Northeast China. Based on the field observation in 2007, 2009, and 2011, soybean root growth was promoted, and the severities of root disease were reduced in a field with continuous long-term cropping with soybean. Population densities of the pathogens (Fusarium spp. and Heterodera glycines) in the soybean cropping field were significantly (P < 0.05) lower than rotation of soybean with wheat or corn. Higher levels of biological control agents (Trichoderma harzianum, Pochonia chlamydosporia, or Paecilomyces lilacinus) also were found in the long-term soybean cropping field. Therefore, continuous long-term cropping of soybean in black soil of Northeast China could develop suppressive soil to soybean root diseases.     

Impact of long-term continuous soybean cropping on ammonia oxidizing bacteria communities in the rhizosphere of soybean in Northeast China

Continuous cropping can be a serious problem in Chinese soybean production. This can result in yield reduction, root diseases, and changes in microbial community structure. We studied community structure, clone libraries, and abundance of ammonia oxidizing bacteria (AOB) in soybean fields there were in continuous soybean production for up to 17 years (SC17). Results showed that the potential nitrification rate (PNR) and amoA gene abundance of soybean in continuous cultivation for seven years (SC7) was 0.34 µg NO₃^? g^?1 and 4.71 × 10^?5 amoA gene copies/g dry soil, respectively. These values were lower than other treatments. Phylogenetic affiliation analysis based on blast results of amoA gene clone sequencing showed that the sequences belonged to seven clusters: Cluster 1, Cluster 3b, Cluster 3a.1, Cluster 3a.2, Cluster 9, Cluster 10, and Cluster 4. Correlation of AOB community compositions with environmental factors was performed using canonical correspondence analysis (CCA). Results indicated that the composition of AOB communities in maize–soybean (MS) rotation and continuous cropping of soybean for two years (SC2) were positively related to the PNR of soil, soil moisture, and soil total nitrogen content. Soybean fields continuously cropped for 11 years (SC11) and SC7 fields had AOB community compositions that were negatively related to these factors. The AOB community composition of SC17 was positively correlated to the soil total carbon content of soil. The results in this study indicate that the potential activity and abundance of AOB community in soil significantly changed after seven years continuous cropping compared to other continuous cropping intervals. Cropping systems have important effect on the diversity of functional microorganisms and associated nitrogen cycles.     

不同农田植被条件下黑土坡耕地产流和产沙特征

[目的]研究不同农田植被条件下的水土侵蚀特征,为该区作物种类选择提供参考。[方法]2013年在位于东北典型黑土带上的黑龙江省红星农场径流小区内,开展了玉米、大豆、大豆—玉米间作3种农田植被条件下的地表径流和土壤侵蚀特征研究。[结果]玉米的径流拦蓄和土壤侵蚀控制的效果最好,间作次之,大豆位居最后;玉米和间作模式的地表径流分别较大豆减少了15.8%和10.7%,土壤侵蚀量亦分别减少了10.47%和5.35%。[结论]在较低降雨强度下玉米和间作的减流减沙效果差别不甚明显,在较高强度下玉米和间作减流减沙效果明显好于大豆。     

Effect of winter wheat cover cropping with no-till cultivation on the community structure of arbuscular mycorrhizal fungi colonizing the subsequent soybean

Winter cover crops increase the amount of indigenous arbuscular mycorrhizal fungi (AMF) in the soil, providing beneficial effects such as enhancement of phosphorus uptake by the subsequent crop. However, its impact on the AMF community structure is not well understood. In the present study, we aimed to reveal the effect of winter wheat cover cropping with no-till cultivation on the AMF community structures in soil and roots of the subsequent soybean. For this purpose, we conducted a field experiment consisting of two treatments, no-till soybean cultivation after winter wheat cover cropping (NTWC) and conventional soybean cultivation after winter fallow management as a control (CONT). At the flowering stage of soybean, higher AMF colonization of soybean roots was observed in the NTWC plots compared with the CONT plots. Additionally, aboveground biomass and phosphorus uptake of soybean in the NTWC plots were significantly higher than those in the CONT plots. Molecular community analyses based on PCR-denaturing gradient gel electrophoresis (DGGE) of AMF 18S rRNA genes indicated that the AMF community structures in the soil and soybean root of the NTWC plots were clearly different from those of the CONT plots. The DGGE profiles showed that the wheat cover cropping preferentially increased some phylotypes belonging to Glomeraceae and Claroideoglomeraceae. In addition, most of the phylotypes were characteristically observed in the subsequent soybean root of the NTWC plots, strongly suggesting that these phylotypes colonizing the cover crop wheat were taken over by the subsequent soybean. Our study revealed the significant effect of winter cover cropping with no-till cultivation on the structure of AMF community colonizing the subsequent soybean.     

东北黑土区典型县域种植模式遥感识别与空间格局分析

种植模式对黑土地的土壤肥力和作物产量有显著影响，建立合理的种植模式是养好用好黑土地的重要措施。目前，黑土区种植模式的类型及其空间格局仍缺乏系统的分析，而遥感技术结合地学信息图谱方法则是监测黑土区种植模式的有效手段，但应用较少。该研究基于2012－2017年遥感反演作物分类数据，采用地学信息图谱方法识别种植模式，并使用核密度分析方法测度了各类种植模式的空间分布特征。结果表明：1）克东县可识别出5类种植模式，其中，主要的种植模式为无序种植模式、大豆连作模式和两年轮作模式，三者面积总和占比为83.90%。2）县域西部和北部以大豆连作模式为主，县域中部、东部和南部以无序种植模式为主，玉米连作模式呈东北-西南向带状分布，三年轮作模式和两年轮作模式呈"局部集聚、全局分散"的分布形态。3）行政村尺度的种植模式结构大体可以分为5种类型，总体呈现以"无序种植-大豆连作-两年轮作"类型为主并以其他类型为辅的空间结构特征，属于主要类型的行政村数量占比为32.08%。     

Depth distribution of soil organic C and N after long-term soybean cropping in Texas

Crop management practices have potential to enhance subsoil C and N sequestration in the southern U.S., but effects may vary with tillage regime and cropping sequence. The objective of this study was to determine the impacts of tillage and soybean cropping sequence on the depth distribution of soil organic C (SOC), dissolved organic C (DOC), and total N after 20 years of treatment imposition for a silty clay loam soil in central Texas. A continuous soybean monoculture, a wheat–soybean doublecrop, and a sorghum–wheat–soybean rotation were established under both conventional (CT) and no tillage (NT). Soil was sampled after soybean harvest and sectioned into 0–5, 5–15, 15–30, 30–55, 55–80, and 80–105 cm depth intervals. Both tillage and cropping intensity influenced C and N dynamics in surface and subsurface soils. No tillage increased SOC, DOC, and total N compared to CT to a 30 cm depth for continuous soybean, but to 55 cm depths for the more intensive sorghum–wheat–soybean rotation and wheat–soybean doublecrop. Averaged from 0 to 105 cm, NT increased SOC, DOC, and total N by 32, 22, and 34%, respectively, compared to CT. Intensive cropping increased SOC and total N at depths to 55 cm compared to continuous soybean, regardless of tillage regime. Continuous soybean had significantly lower SOC (5.3 g kg⁻¹) than sorghum–wheat–soybean (6.4 g kg⁻¹) and wheat–soybean (6.1 g kg⁻¹), and 19% lower total N than other cropping sequences. Dissolved organic C was also significantly higher for sorghum–wheat–soybean (139 mg C kg⁻¹) than wheat–soybean (92 mg C kg⁻¹) and continuous soybean (100 mg C kg⁻¹). The depth distribution of SOC, DOC, and total N indicated treatment effects below the maximum tillage depth (25 cm), suggesting that roots, or translocation of dissolved organic matter from surface soils, contributed to higher soil organic matter levels under NT than CT in subsurface soils. High-intensity cropping sequences, coupled with NT, resulted in the highest soil organic matter levels, demonstrating potential for C and N sequestration for subsurface soils in the southern U.S.     

春小麦—向日葵复种对土壤水盐及农田生产力的影响

为充分利用自然资源,减轻土壤盐渍化,提高农田生产力,在内蒙古河套灌区以春小麦、玉米和向日葵单作为对照,监测春小麦—向日葵复种对土壤水分、盐分和农田生产力的影响。结果表明:春小麦收获前,春小麦—向日葵复种和春小麦单作0—100cm土层土壤水分低于玉米单作和向日葵单作;春小麦收获后春小麦—向日葵复种、玉米单作和向日葵单作耕层土壤水分高于春小麦单作,20—80cm土层土壤水分则低于春小麦单作。春小麦收获前不同种植模式的土壤盐分变化剧烈,春小麦收获后则变化平缓。不同种植模式主要影响0—40cm土层土壤盐分,对40cm土层以下的土壤盐分影响较小。复种向日葵收获期春小麦—向日葵复种耕层土壤盐分较春小麦单作、玉米单作和向日葵单作分别降低32.52%,16.70%和24.92%,0—100cm土层分别降低13.32%,8.88%和12.07%。春小麦—向日葵复种的等价产量较春小麦单作、玉米单作和向日葵单作分别高出126.01%,3.86%和3.21%。春小麦—向日葵复种可减少土壤盐分,提高农田生产力,在河套灌区具有一定的发展前景。     

连作土壤盆栽大豆的根际酸度和微生物数量变化

连作土壤条件下，不同抗性品种的根际微生物变化不同。盆栽试验结果表明，连作条件下，抗病品种绥农10号和抗线2号根际环境pH中性偏碱，不利病原真菌生长；感病品种合丰25号根际则处于偏酸环境，使作物易于感染根腐病。抗性大豆品种绥农10号和抗线2号的根际细菌数量增加，真菌数量减少；感病品种合丰25号的细菌和真菌数量变化不显著。