【作者】 雍太文；

【导师】 杨文钰；

【作者基本信息】 四川农业大学 ， 作物栽培学与耕作学， 2009， 博士

【摘要】 本研究于2005～2008年,应用根系分隔技术和同位素示踪技术等,采用大田小区试验和¹⁵N同位素标记盆栽试验,以“小麦/玉米/甘薯”三熟套作体系为对照,研究了“小麦/玉米/大豆”这一新的三熟套作体系中氮素利用的种间竞争促进作用、氮素的吸收利用特性及根际微生态效应。主要研究结果如下:1.采用双佳值法研究了“麦/玉/豆”套作体系的氮肥周年平衡施用技术,结果表明,“麦/玉/豆”套作体系在中产田的周年氮肥最佳施用总量为342.8kg/hm²,小麦、玉米和大豆适宜分配比例为33.76:35.71:30.54,各作物最佳施氮量为小麦115.73kg/hm²、玉米122.41kg/hm²、大豆104.69kg/hm²。2.采用¹⁵N土壤稀释标记法,通过2006年至2008年两年根系分隔盆栽试验,研究了“麦/玉/豆”套作体系对氮素的种间竞争作用及吸收利用特性,结果表明,“麦/玉/豆”体系中作物间对氮素的竞争与促进作用并存,小麦、玉米为套作优势作物,大豆为套作劣势作物(A_WC＞0、NCR_WC＞1;A_CS＞0、NCR_CS＞1),“麦/玉/薯”体系则表现出较强的种间竞争作用,种间促进作用相对较弱,小麦为套作优势作物(A_WC＞0,NCR_WC＞1),玉米和甘薯为套作劣势作物(A_CS=0.191＞0;NCR_CS=1.01＞1)。不分隔与完全分隔相比,“麦/玉/豆”与“麦/玉/薯”体系中的小麦籽粒产量、地上部总生物量、籽粒吸氮量、地上部总吸氮量、籽粒¹⁵N吸收量、¹⁵N总吸收量和¹⁵N植株总回收率均得到提高,土壤残留¹⁵N%丰度及总N含量降低,其中籽粒产量分别提高25.594%和24.811%,籽粒¹⁵N吸收量分别提高67.194%和53.859%,¹⁵N植株总回收率分别提高38.069%和38.727%;提高了“麦/玉/豆”中玉米的籽粒产量、地上部总生物量、籽粒吸氮量、地上部总吸氮量、¹⁵N籽粒吸收量、¹⁵N植株总回收率、土壤残留¹⁵N%丰度及土壤总N含量,“麦/玉/薯”则降低;降低了大豆的籽粒产量、籽粒吸氮量、¹⁵N总吸收量和¹⁵N植株回收率降低,但土壤总N含量提高7.284;降低了甘薯的块根产量、块根吸氮量和土壤总N含量,但¹⁵N植株总吸收量和¹⁵N植株回收率提高47.958%和47.957%。“麦/玉/豆”体系的小麦、玉米土壤NO₃-N含量及无机氮（NO₃-N、NH₄-N）总量降低,“麦/玉/薯”体系则升高,且高于“麦/玉/豆”体系;两种体系的大豆、甘薯土壤NO₃-N含量均升高,且大豆高于甘薯;两种体系均吸收利用了前茬小麦、玉米及大豆（甘薯）作物的残留¹⁵N,并发生了¹⁵N的转移,但“麦/玉/豆”体系的¹⁵N吸收量、¹⁵N回收率和¹⁵N转移强度高于“麦/玉/薯”。3.采用叶片¹⁵N富集标记法,在不同氮素水平下,研究了“麦/玉/豆”套作体系的氮素转移,结果表明,“麦/玉/豆”体系在相同施氮水平下的产量、吸氮量与土壤总N含量均高于“麦/玉/薯”,“麦/玉/豆”体系较“麦/玉/薯”更具有产量优势和氮素营养优势。两种体系的小麦和大豆（甘薯）的籽粒（块根）产量与吸氮量随施氮量的增加呈先增加后降低趋势,以A3（300Nkg/hm²）处理最高,玉米籽粒产量和吸氮量随施氮量的增加而增加,以A4（450Nkg/hm²）处理最高;两种体系中小麦、玉米和甘薯土壤总N含量以A3处理最高,大豆土壤总N含量随施氮量的增加而降低,以A1（0Nkg/hm²）处理最高。两种体系中各作物的土壤NO₃-N含量随施氮量的增加而增加,但“麦/玉/豆”体系低于“麦/玉/薯”。两种体系均存在氮素的双向转移,转移量随土壤肥力及施氮量的提高而降低,“麦/玉/豆”体系的¹⁵N净转移量和转移强度高于“麦/玉/薯”。以小麦为¹⁵N供体植物时,两种体系向玉米的氮素转移量和转移率差异不大。以玉米为¹⁵N供体植物时,玉米向小麦和大豆（甘薯）转移了氮素,以300kgN/hm²供氮水平下的转移量和转移率最高,且以向小麦的转移为主,两种体系中向小麦的转移量分别是大豆和甘薯的2.902倍～9.402倍、1.338倍～2.187倍;两种体系中玉米向甘薯的转移率是玉米向大豆转移率的1.001倍～2.203倍。以大豆（甘薯）为¹⁵N供体植物时,大豆、甘薯向玉米转移了氮素,大豆向玉米的转移率比甘薯向玉米的转移率高21.266%～52.003%。两种体系中小麦的¹⁵N净转移量＞0,玉米和大豆（甘薯）的¹⁵N净转移量＜0;“麦/玉/豆”体系中小麦、玉米和大豆的¹⁵N净转移量分别比“麦/玉/薯”中的小麦、玉米、甘薯高3.256%～12.083%、26.993%～166.209%和26.242%～78.694%。4.在大田试验条件下,通过两年试验研究了不同种植方式的根际微生态效应及根际土壤环境与作物对氮素吸收的关系,结果表明,与净作和“麦/玉/薯”相比,“麦/玉/豆”体系表现出明显的套作优势(LER＞1、A_WC＜0、A_CS＞0、NCR_WC＜0、NCR_CS＞1);降低了玉米、大豆土壤的PH和小麦土壤的湿度、PH,提高了玉米和大豆的土壤湿度;提高了开花期（吐丝期）和成熟期小麦、玉米和大豆的生物量、吸氮量、根系活力和根干重;提高了各作物土壤中细菌、真菌、放线菌三种微生物的数量,以及各作物土壤总N含量和脲酶、蛋白酶的酶活性,降低了各作物土壤NO₃-N含量及硝酸还原酶活性。DGGE分析表明,“麦/玉/豆”套作系统中各作物的多样性指数（H′）高于净作与“麦/玉/薯”体系,相似性指数（Cs）方面,套作与套作之间的Cs高于套作与净作间的Cs,套作边行与净作之间的Cs相对较小,套作中行与净作的Cs相对较高。相关分析表明,小麦、玉米和大豆（甘薯）的吸氮量与土壤中脲酶、蛋白酶、细菌数量、真菌数量、放线菌数量和根系活力呈显著或极显著正相关,与硝酸还原酶、NO₃-N、NH₄-N呈极显著负相关。更多还原

【Abstract】 From 2005 to 2008 year,through ¹⁵N isotopic tracer method and root barriers technique,field experiment and ¹⁵N labeling pot experiment were carried out to investigate nitrogen source uptake and utilization mechanics,interspecific competition and facilitation for nutrients,and rhizosphere micro ecology effect in the relay-planting system of wheat/maize/soybean,contrasting by the relay-planting system of "wheat/maize/sweet potato".The results showed as fellows.1.Applying the double optimal value method,the annual optimal amount of nitrogen fertilizer and the ratio of nitrogen fertilizer distributed among crops in the relay-planting system of "wheat/maize/soybean" were studied.The results showed that the annual optimal total amount of nitrogen fertilizer applied in this system was 342.8kg.hm^-2 in the medium-yield cropland.The suitable distributive proportion of nitrogen fertilizer was 33.76:35.71:30.54 among the three crops,and the applying amounts for wheat,maize and soybean were 115.73kg.hm^-2,122.41kg.hm^-2,and 104.69kg.hm^-2 respectively.2.From 2006 to 2008 year,the methods of root barrier and ¹⁵N-isotope dilution were used to investigate the interspecific nitrogen competition and facilitation,nitrogen uptake and utilization in the relay-planting system of "wheat/maize/soybean".The results showed that there were coexisted the nitrogen competition and facilitation in the relay-planting system of "wheat/maize/soybean",wheat and maize had competing advantage,and soybean had competing disadvantage（Awc＞0,NCRwc＞1;Acs＞0, NCRcs＞1）.There were strong interspecific nitrogen competition and infirm facilitation in the system of wheat/maize/sweet potato.Wheat had competing advantage（Awc＞0, NCRwc＞1）,and maize and sweet potato had competing disadvantage（Acs=0.191＞0; NCRcs=1.01＞1）.In the relay-planting systems of "wheat/maize/soybean" and "wheat/maize/sweet potato",comparing the no barrier with solid barrier,the grain yield,total biomass above ground,grain nitrogen uptake,the total nitrogen uptake above ground,¹⁵N grain uptake, ¹⁵N total uptake and ¹⁵N crop recovery rate of wheat increased remarkably,and ¹⁵N% abundance and N%content of soil reduced obviously.The grain yield increased by 25.594%and 24.811%respectively,¹⁵N grain uptake increased by 67.194%and 53.859% respectively,¹⁵N crop recovery rate increased by 38.069%and 38.727%respectively.In the relay-planting system of "wheat/maize/soybean",the grain yield,the total biomass above ground,grain nitrogen uptake,the total nitrogen uptake above ground,¹⁵N grain uptake,¹⁵N crop recovery rate of maize,and the ¹⁵N%abundance of soil and total N content increased by 14.402%,9.763%,44.926%,31.129%,37.8492%,25.157%,13.896 and 10.145 respectively.But in the "wheat/maize/sweet potato" system with no barrier, the value of above index reduced by 20.007%,10.094%,6.786%,2.978%,25.366%, 15.988%,17.366%and 5.195%respectively.For soybean,grain yield,the ¹⁵N crop uptake,¹⁵N grain uptake,and ¹⁵N crop recovery rate reduced,but the soil N%content increased by 7.28%.For sweet potato,earthnut yield,the ¹⁵N total uptake,and total N content of soil reduced,but ¹⁵N crop uptake and crop recovery rate increased by 47.958% and 47.957%.In the relay-planting system of "wheat/maize/soybean",the content of NO₃-N and the total amount of inorganic nitrogen（NO₃-N、NH₄-N） in soil reduced,but that of the wheat/maize/sweet potato system increased,and the values were higher than wheat/maize/soybean system.In the two relay-planting systems,the NO₃-N content of soil increased for soybean and sweet potato,and that of soybean was higher than sweet potato.Soybean or sweet potato utilized soil rudimental ¹⁵N from wheat,maize and soybean（sweet potato） stubble.There existed ¹⁵N transfer between crops in the two relay-planting systems,but the ¹⁵N uptake and recovery rate,and the intensity of ¹⁵N transfer in the relay-planting system of "wheat/maize/soybean" were higher than that of "wheat/maize/sweet potato".3.Pot experiment was carried out to study the nitrogen transfer occurring in the relay-planting system of "wheat/maize/soybean" at three different nitrogen fertilizer application rates（150kg/hm²,300kg/hm²,450kg/hm²） using ¹⁵N foliar labeling method. The results showed that,the grain yield,total nitrogen uptake above ground,and total N content of soil in the relay-planting system of wheat/maize/soybean,were higher than that of the relay-planting system of wheat/maize/sweet potato at the same nitrogen fertilizer application rate.The wheat/maize/soybean system had obvious advantage of yield and nitrogen nutrition,comparing for wheat/maize/sweet potato system.In the two systems,the grain（or earthnut） yield and nitrogen uptake of wheat and soybean（or sweet potato） increased first and then reduced with the nitrogen fertilizer application rate increasing,the indices values of the A3 treatment（300Nkg/hm²） was highest.The grain yield and nitrogen uptake of maize were increasing with the nitrogen fertilizer application rate increasing,the values of the A4（450Nkg/hm²） treatment was highest. The soil total nitrogen content of the wheat,maize and sweet potato was highest in A3 treatment.But the soil total nitrogen content of the soybean reduced with the nitrogen fertilizer application rate increasing,the value of Al（0Nkg/hm²） treatment was highest. NO₃-N content of crops in the two relay-planting systems increased with the nitrogen fertilizer application rate increasing,and the value of NO₃-N content of wheat/maize/soybean system was higher than that of wheat/maize/sweet potato system.There existed bi-directional N transfer in the two relay-planting systems,and the amounts of N transferred reduced with the soil fertility and nitrogen fertilizer application rate increasing.The amount of net ¹⁵N transferred and transfer intensity in the relay-planting system "wheat/maize/soybean" were higher than that of "wheat/maize/sweet potato".When wheat functioned as ¹⁵N donor plant,the ¹⁵N% abundance in maize shoot was consistently higher than the ¹⁵N%nature abundance.It indicated that the ¹⁵N transfered from wheat to associated maize,but the amounts of N transferred and the proportion of ¹⁵N transferred were small difference between the two relay-planting systems.When maize functioned as ¹⁵N donor plant,there existed the ¹⁵N transfer from maize to associated wheat and soybean（sweet potato）.The amount of transferring N of A2（300Nkg/hm²） treatment was highest.In the two systems,the amounts of N transferred from maize to wheat was higher 290.2%～940.2%and 133.8%～218.7%than that of N transferred from maize to soybean（or sweet potato）,but the amounts of N transferred from maize to sweet potato was higher 100.1%～220.3% than that of N transferred from maize to soybean.When soybean or sweet potato functioned as ¹⁵N donor plant,there existed the ¹⁵N transfer from soybean（sweet potato） to associated maize,and the proportion of ¹⁵N transferred from soybean to maize was higher 21.266%～52.003%than that of the ¹⁵N transferred from sweet potato to maize. The amount of net ¹⁵N transferred＞0 for wheat,but that of maize and soybean（sweet potato）＜0.Amounts of net ¹⁵N transferred of wheat,maize,and soybean in the wheat/maize/soybean system were higher 3.256%～12.083%,26.99%～166.209%,and 26.242%～78.694%than that of the wheat/maize/sweet potato system.4.Two-year field experiment was carried to study the effect of different planting systems on rhizosphere mic-ecology,and the relation between rhizosphere soil environment and nitrogen uptake and utilization.The results showed,comparing the single cropping condition and the relay-planting system of "wheat/maize/sweet potato"with the relay-planting system of "wheat/maize/soybean",wheat/maize/soybean system indicated obvious relay-planting advantage（LER＞1,Awc＜0,Acs＞0,NCRwc＜0, NCRcs＞1）,soil PH of maize and soybean,and soil humidity of wheat reduced,but the soil humidity of maize and soybean increased.On the florescence date and maturity date of crops,the biomass,nitrogen uptake,root activity and root dry matter weight of wheat, maize,and soybean increased,and also the amounts of bacterium,the fungus,and ray fungi of soil increased.Result of DGGE showed,shanon-wiener index（H’） of the relay-planting system of wheat/maize/soybean were higher than single cropping condition and the relay-planting system of wheat/maize/sweet potato,the similarity coefficient（Cs） between the relay-planting systems were higher than that of relay-planting system and single-planting system,and CS between fringe rows and single-planting system were low comparatively,but CS between middle rows and single-planting system were high comparatively.At the same time,the total N content, the activity of urease and proteinase enzyme of soil increased,and the nitrate reductase activity and NO₃-N content of soil reduced.Correlation analysis showed that the nitrogen uptake of wheat,maize and soybean（sweet potato） were significant positively correlated with root activity,and activity of urease and proteinase enzyme,and amounts of bacterium,fungus and ray fungi,but were significant negatively correlated with nitrate reductase activity,NO₃-N and NH₄-N content of soil.更多还原